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The purpose of this workshop is to spread the vast amount of information available on semiconductor physics to every possible field throughout the scientific community. As a result, the latest findings, research and discoveries can be quickly disseminated. This workshop provides all participating research groups with an excellent platform for interaction and collaboration with other members of their respective scientific community.

This workshop’s technical sessions include various current and significant topics for applications and scientific developments, including

• Optoelectronics

• VLSI & ULSI Technology

• Photovoltaics

• MEMS & Sensors

• Device Modeling and Simulation

• High Frequency/ Power Devices

• Nanotechnology and Emerging Areas

• Organic Electronics

• Displays and Lighting

Many eminent scientists from various national and international organizations are actively participating with their latest research works and also equally supporting this mega event by joining the various organizing committees.

Inhaltsverzeichnis

Frontmatter

Erratum to: An Intense Green Emission From ZnO Nanoparticles Coated with MgO

K. Sowri Babu, A. Ramachandra Reddy, K. Venugopal Reddy

VLSI and ULSI Technology

Frontmatter

Co-existence of Multiferroic Memories in CoFe2O4/Bi3.4Sm0.6Ti3O12 Composite Structures

CoFe

2

O

4

/Bi

3.4

Sm

0.6

Ti

3

O

12

/bilayer films were synthesized by chemical solution route and deposited by spin coating on Pt (Pt/TiO

2

/SiO

2

/Si) substrate. X-ray diffraction of the bilayer and multilayer structures revealed the composite-like structure. Dielectric spectroscopy shows relaxation in dielectric loss and reaches ~1 % at 10

6

Hz. CoFe

2

O

4

/Bi

3.4

Sm

0.6

Ti

3

O

12

system shows the co-existence of ferroelectric polarization Pr > 40 μC/cm

2

and magnetization Mr = 52 emu/cm

3

for bilayer, and Pr = 60 μC/cm

2

Mr = 72 emu/cm

3

, respectively, for four alternate layers, has been achieved at room temperature. Different permittivity and permeability may affects the coupling parameters may give rise to simultaneous ferromagnetic and ferroelectric responses.

A. Charris-Hernandez, A. Kumar, M. S. Tomar

Impact of Fin Sidewall Taper Angle on Sub-14 nm FinFET Device Performance

Recent advances in FinFET technology include fins with tapered sidewalls in addition to conventional vertical sidewall fins. Our 3-D TCAD simulation results suggest that for low to moderately doped fins, vertical sidewall fins have superior electrical performance. Only at extremely high fin doping concentrations could tapered sidewall fins be electrically beneficial.

Abhisek Dixit, Terence B. Hook, Jeffrey B. Johnson, E. J. Nowak, Kota V. Murali

Capacitance-Voltage Measurement of SiO2/GeOxNy Gate Stack on Surface Passivated Germanium

Germanium (Ge) based MOS transistors is possible alternative to silicon based MOS transistors due to high mobility of carriers in Ge. Extensive research is going on for fabrication of high mobility MOS devices worldwide. Here, we have studied the c-v characteristics of Ge based surface passivated MOS structure such as dielectric constant of gate stack, effective oxide charges, density of interface charges at semiconductor oxide interface etc. The interface trap density extracted from the C-V/G-V measurement showed the lowest interface trap density of 7.82 × 10

11

cm

2

eV

−1

. The minimum leakage current density for SiO

2

/Ge

x

ON

y

gate dielectric stack is 1.35 × 10

−7

A cm

−2

at gate bias of 1 V.

Anil G. Khairnar, Vilas S. Patil, Ashok M. Mahajan

Effect of Supercritical Drying on Sol-Gel Deposited Silica Aerogel Thin Films at Different Temperatures

Now a days silica aerogel thin films are attracted more attention as an interlayer dielectric (ILD) application in ULSI technology due to the lowest dielectric constant. In present work, we report the successful deposition of silica aerogel thin films on Si wafer by sol-gel technique. Further, in order to introduce porosity the deposited thin films were dried at supercritical condition with different temperatures. Elipsometric study shows that the refractive index (RI) of as deposited film is observed to 1.44 whereas RI of super critically dried thin films is observed to be decreased to 1.29 for the film dried at 40 °C. The film thickness observed to be decreased from 200 to 129 nm with increase in supercritical drying temperature. The dielectric constant of the films is observed to be lowered to 2.8 for the film dried at 40 °C temperature. The pore volume and porosity of the films increased up to 0.25 and 37 % respectively with increase in drying temperature while the density of the films is decreases with increasing temperature

Anil Gaikwad, Yogesh Mhaisagar, Jigar Bhavsar, Ashok Mahajan

Stress-induced Degradation and Defect Studies in Strained-Si/SiGe MOSFETs

Effect of threading dislocations contributing to the increased 1/

f

noise in strained-Si MOSFETs is studied. Results of low-frequency noise study of strain-engineered MOSFETs are presented including 1/

f

and random telegraph noise (RTN). From the bias dependency of 1/

f

noise the correlated mobility fluctuation model (in NMOSFETs) is identified as the dominant noise mechanism. The low-frequency noise study reveals electrical stress-induced device degradation shown by the increased 1/

f

noise and complex RTN indicating reliability issues. A detailed low-frequency noise study in highly-scaled, strained MOS devices is presented indicating the capabilities of LF noise study for assessing device quality and lifetime essential in reliability analysis.

Chhandak Mukherjee, C. K. Maiti

T-CAD Design Simulation and Comparative Performance Analysis of 6-T SRAM Cell with Nanoscale SOI and MOS Technology

During last few decades, either memory or processor, VLSI circuit efficiency, has been significantly improved through a combination of device scaling, new device structures and material property improvement. In nano-meter region, conventional silicon technology has been suffered from the fundamental physical limitations so some alternative device technologies like Silicon-on-Insulator (SOI) technology has been emerged. Experimentally or theoretically, SOI technology has shown better short channel effect immunity and thus transistor scalability and circuit performance has been improved. In last decade, intense interests have been paid in practical fabrication and compact modelling of SOI MOSFET but little attention has been paid to understand the SOI based circuit performance analysis and improvement. In the present analysis, using TCAD Simulator, six transistors SRAM cell has been designed with SOI and conventional MOSFET nano-structures. SRAM effective reading and writing operations have been compared to implicate the improvement in efficiency with SOI technology. Time delay and power dissipation for both SOI SRAM and MOS SRAM cell has been compared also. It has been observed that nano-SOI SRAM cell shows better reading sensitivity as well as better power efficiency but with little higher delay effect compared to nano-MOS SRAM cell.

P. Deepika, E. Subhasri, Sanjoy Deb

Investigation of Current Conduction Mechanism in HfO2 Thin Film on Silicon Substrate

In this work, we have investigated current conduction mechanisms in HfO

2

thin film deposited on silicon substrate by RF sputtering technique. The thin films of HfO

2

were deposited on p-type silicon substrates. FTIR measurement shows the presence of hafnium in the film. Among the various conduction mechanisms the 13.7 nm thin HfO

2

film on Si follows the Fowler–Nordheim (FN) tunneling. The Poole–Frenkel (PF) emission, Schottky emission (SE) and Direct Tunneling (DT) also studied. The barrier height (ϕ

B

) of 0.74 eV is calculated from experimental work through Fowler–Nordheim tunneling mechanism.

Anil G. Khairnar, Khushaboo S. Agrawal, Vilas S. Patil, Ashok M. Mahajan

Resistive Switching in MIM Capacitors Using Porous Anodic Alumina

Bipolar resistive switching phenomena have been observed in TiN/AAO/TiN structures. Porous anodic aluminium oxide (AAO) membranes with pore diameters ranging from 15 to 50 nm were prepared by two step anodization in oxalic acid under specific reaction condition on TiN layer. The nanochannel arrays of AAO membranes were characterized with field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). AAO membrane was sandwiched between two conducting TiN layers to fabricate MIM structures. Good stability in resistive switching behaviour up to several cycles and a ~ 2x resistance ratio has been achieved.

K. Mukherjee, S. Upreti, A. Bag, S. Mallik, M. Palit, S. Chattopadhyay, C. K. Maiti

Process Model Accuracy Enhancement Using Cluster Based Approach

Full chip resist simulation is a critical step in the lithography simulation of advanced CMOS technology nodes. The semi-empirical compact models (such as compact model 1, also known as CM1) are generally used in the semiconductor industries for resist simulation since the physical models are computationally expensive. The CM1 model considers physical effects of the resist process and uses a constant threshold on a two dimensional resist surface to extract the critical dimension (CD). However, the required threshold for different samples may vary over a range and therefore a constant threshold value may not hit an optimal solution for all the samples. In this paper, we propose a clustering based approach to enhance the accuracy of CM1 model and resist simulation. In this proposed approach, various attributes of the lithographic samples such as aerial image and pattern density are used to bin the samples into different groups (clusters). The CM1 model is then used to calibrate parameters individually for each group. This approach is verified by doing the resist simulation on one of the layers of 14 nm CMOS technology and the results show good improvement in model accuracy.

Pardeep Kumar, Samit Barai, Babji Srinivasan, Nihar R. Mohapatra

Room Temperature-Processed TiO2 MIM Capacitors for DRAM Applications

We report the room temperature fabrication of Ta/TiO

2

/Ta metal–insulator-metal (MIM) capacitors (mainly, for DRAM applications). The fabricated devices show high capacitance density (~15 fF/μm

2

), and low leakage current density of 6.4 × 10

−8

A/cm

2

(27 °C) and 3.3 × 10

−6

A/cm

2

(125 °C) at −1 V. We analyze the electrical and material characteristics of the fabricated capacitors, and compare the device performance of these capacitors with other TiO

2

and TiO

2

-based MIM capacitors reported in recent literature.

Revathy Padmanabhan, Navakanta Bhat, S. Mohan

Two Input Multiplexer Based on Single-Electronics

The design of capacitive single-electron transistors (C-SETs) based two-input multiplexer is reported in this paper. Voltage state logic is employed to design the circuit and SIMON 2.0 was used for simulation. Truth table of the designed two input multiplexer was verified for all the possible input vectors. Additionally, the stability of the circuit was checked by plotting stability and free energy history diagrams. The average power consumtion of the designed circuit is ~31.4 PicoWatts.

P. Vishnu Chaitanya, Pankaj B. Agarwal

High Frequency and Power Devices

Frontmatter

Advancements in SiC Power Devices Using Novel Interface Passivation Processes

For the next generation 4H-SiC MOSFET devices it is very critical to have a good 4H-SiC/SiO

2

interface. In this paper we reported two new passivation processes - thin phosphorous (P) passivation and nitrogen plasma (N2P) passivation. With thin P passivation the mobility of ~75 cm

2

/V·s can be achieved with improved threshold voltage stability. N2P passivation gives an alternative to introduce nitrogen (N) at the interface in minimum oxygen (O) ambient during passivation. With this new N2P process we can introduce more N at the interface, almost two times compared to standard NO (nitric oxide) passivation.

Y. K. Sharma, A. C. Ahyi, T. Issacs-Smith, A. Modic, Y. Xu, E. Garfunkel, M. R. Jennings, C. Fisher, S. M. Thomas, L. Fan, P. Mawby, S. Dhar, L. C. Feldman, J. R. Williams

Planar Schottky Varactor Diode Characterization for MMIC Voltage Controlled Oscillator Applications

A technique for characterization and modeling of planar varactor diodes is presented. The diode structures were fabricated on a low cost GaAs process, measured in a shunt configuration, and subsequently modeled. The simulations are in good agreement with the measured data. The planar device was integrated in an MMIC VCO and the measured performance conforms to the design objectives.

Vijesh Arora, C. P. Kulkarni, Sangam Bhalke, Ashok Kumar

Optically-Switched Wide-Bandgap Power Semiconductor Devices and Device-Transition Control

In this paper, a top-level outline on the work related to optically-switched power semiconductor devices that have been carried out at the University of Illinois, Chicago (UIC) or those in which UIC has been involved has been outlined. In addition, an outline on optical control that affects the switching dynamics of the power semiconductor devices is provided.

S. K. Mazumder, A. Mojab, H. Riazmontazer

Study on Temperature Dependence Scattering Mechanisms and Mobility Effects in GaN and GaAs HEMTs

GaN and GaAs materials are the preferred materials of choice of worldwide researchers for High Electron Mobility Transistor (HEMT) due to suitable material properties. In this paper temperature dependence scattering effects are discussed. The degradation of mobility from different scattering mechanisms and its effect on drain current is also shown. The total mobility in bulk GaN and GaAs semiconductors are compared. The variations in electronic concentration with temperature are also presented in these types of HEMTs. The mobility degradation and its effect on drain current are also portrayed for AlGaAs/AlGaN HEMT’s.

D. Pandey, A. Bhattacharjee, T. R. Lenka

Study of Oxygen Implantation in GaN/Sapphire

This paper presents the effect of oxygen implantation in MOCVD grown GaN epitaxial layer on sapphire substrate. Oxygen implantation was done on three different energies with different dose, namely 3 × 10

14

cm

−2

at 30 keV, 5 × 10

14

cm

−2

at 60 keV and 1.2 × 10

15

cm

−2

at 100 keV in the same GaN sample to get a flat impurity doping profile. Implanted sample was characterized by High Resolution X- ray Diffraction (HRXRD), Field Emission Scanning Electron Microscopy (FE-SEM) and wet chemical etching. Sample was also annealed at 800 °C, in air, for 5 min duration to reduce the implantation damage. Break down voltage of the sample was also measured before and after annealing to see the suitability of implantation process for device isolation. The breakdown voltage showed an increase after the implantation and annealing. The increase in the breakdown voltage has been explained in terms of the increase in the defect density as a result of the implantation. Increasing the breakdown voltage is attributed to trapped charge carrier by the defective region thereby increasing resistivity. Wet chemical etching of the samples were done to determine the dislocation density before and after implantation. Increase in the dislocations is also inferred to increase the resistivity in the sample.

Akhilesh Pandey, S. P. Chowdhury, Sandeep Dalal, Anand Kumar, Shankar Dutta, R. Raman, A. K. Kapoor

GaN HEMT Based S-Band Power Amplifier

In this paper, Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) based S-band power amplifier design, simulation, fabrication, assembly and RF testing have been discussed. This power amplifier is capable of giving an output power ~8 watts in 3.3–3.5 GHz frequency range with a PAE greater than 90 %.

Archana Ahirwar, Poonam Singh, S. K. Tomar, Meena Mishra, Ashok Kumar, B. K. Sehgal

Structural and Optical Characterization of β-Ga2O3 Thin Films Grown by Pulsed Laser Deposition

Polycrystalline β-Ga

2

O

3

thin films were grown on sapphire substrate (0001) by pulsed laser deposition (PLD) technique. The crystalline structure and optical band gap were studied as a function of growth temperature, laser beam energy, annealing temperature and time. To tailor the band gap of β-Ga

2

O

3

thin films by Al diffusion from the sapphire substrate the films were annealed for 24 h at different temperatures. The amount of Al diffusion was different for different temperatures of annealing which resulted in the increase of band gap as well as the shift of diffraction peaks to higher angles with increasing temperature. The annealed films showed high transparency in the deep UV region of the spectrum.

Anshu Goyal, Brajesh S. Yadav, O. P. Thakur, A. K. Kapoor

Effect of Vertical and Longitudinal Electric Field on 2DEG of AlGaN/GaN HEMT on Silicon: A Qualitative Reliability Study

Effect of both vertical and longitudinal electric field on AlGaN/GaN HEMT 2DEG channel is studied under long pulses with different duty cycles at two separate V

GS

(i.e. at +2 and -2 V). The duty cycles of applied pulses are of 100, 50, 5 and 0.5 %. Separate responses are being observed to confirm different non-ideal reliability issues like scatterings, effects of surface states and trapped electrons. It also raises an optimization scenario between available 2DEG concentration in channel and its various scattering and depletion phenomenon.

Ankush Bag, Partha Mukhopadhyay, Saptarsi Ghosh, Palash Das, Rahul Kumar, Sanjay K. Jana, Sanjib Kabi, Dhrubes Biswas

Electrical Characterization of Interface States in In/p-Si Schottky Diode From I–V Characteristics

Interfaces state density of In/p-Si Schottky diode has been determined using experimental non ideal forward bias current –voltage (I–V) characteristics. The diode showed non ideal I–V behavior with an ideality factor of 1.91 and was thought effects of interfacial oxide layer. Considering that the interface states localized at the interfacial layer-semiconductor interface are in equilibrium with the semiconductor, the energy distribution of the interface states was exactly determined from the forward bias I–V characteristics by taking account voltage dependence barrier height. The I–V characteristics were used for determining the voltage dependence barrier height. Although the change in barrier height with applied bias is small, it is important for exactly determining the shape of the interface state density distribution curve.

B P Modi, J M Dhimmar

Temperature Dependence Junction Parameters: Schottky Barrier, Flatband Barrier, and Temperature Coefficients of Schottky Diode

The variation in electrical characteristics In-pSi Schottky diode have been systematically investigated as a function of temperature by using forward bias current–voltage measurement. The main diode parameters, ideality factor and zero bias barrier height (Ф

bo

) were found strongly temperature dependent. The zero bias barrier increases and the ideality factor decreases with increasing temperature while the flat band barrier (Ф

bf

) values increase with decreasing temperature. The temperature coefficient of the barrier height is found to be around −0.7 meV/

o

K, very closed agreement with platinum silicide contact on p-silicon and can be suitably understood on Tersoff’s model.

J. M. Dhimmar, B. P. Modi

Characterization of AlGaN Thickness and Sheet Carrier Concentration of AlGaN/GaN Based HEMT Using Electrical Measurement

We present a simple non-destructive technique to characterize the AlGaN barrier layer thickness and sheet carrier concentration for AlGaN/GaN heterostructure. Characterization of AlGaN thickness and sheet carrier concentration has been carried out for AlGaN/GaN HEMT structure using the capacitance–voltage characterization of FATHEMT (dimension Lg = 20 µm, Wg = 150 µm). The estimated values for AlGaN thickness and the sheet carrier concentration (n

s

) were ~23.2 nm and ~1e13/cm

2

respectively for MBE grown structure. The estimated values of AlGaN thickness are fairly matching well with measured data of HRXRD within variation of ±5 % and the estimated sheet carrier concentration values are also of the same order as evaluated using Hall Measurement.

Henika Arora, D. S. Rawal, B. K. Sehgal

Effect of Junction Temperature on the Microwave Properties of IMPATT Diodes

The microwave characteristics, with respect to two different operating junction temperatures, are simulated for the IMPATT diodes based on Si, GaAs and 4H-SiC semiconductor material. With the rise in junction temperature, a general trend of decrease in device efficiency and increase in device negative conductance are observed for all the diodes under consideration. It is also interesting to note that noise measure reduces significantly with rise in junction temperature.

J. Pradhan, S. R. Pattanaik, S. K. Swain, G. N. Dash

On the Determination of Electron Effective Mass in 2DEGs in Gallium Nitride HEMT Structures

Temperature dependence of the Shubnikov de Haas oscillation observed in the temperature range of 1.8–6 K due to doubly occupied subbands in the two-dimensional electron gas (2DEG) in AlGaN/GaN HEMT structures grown by MBE inhouse has been used to determine the effective mass m* using a novel method of nonlinear curve fitting method which is assigned to be more accurate which is reflected by the R-squared value of the fitting than discussed by previous workers using conventional approximation in linear-curve fitting model. Also the range in which the approximation of the conventional method is valid has been found out.

Manna Kumari Mishra, Rachna Manchanda, Sushil Lamba, O. P. Thakur, R. K. Sharma, R. Muralidharan

Observation of Negative Magnetoresistance in Gallium Nitride HEMT Structures

Negative Magnetoresistance (NMR) was observed in GaN HEMT structures grown by MOCVD and was studied in the temperature range of 1.9–77 K and under magnetic field from 0—8T. The presence of NMR is directly related to disorder in the structures and is likely due to the simultaneous presence of short-range (strong) scattering centres due to interface roughness and/or alloy disorder and smooth disorder(random potential due to remote impurities). Moreover the low values of quantum scattering time glean an insight to the presence of interface roughness in all the samples. The degree of disorder can be ascertained qualitatively through values of NMR in conjecture with quantum scattering time, mobility and carrier concentrations values.

Manna Kumari Mishra, Rachna Manchanda, Premila Mohan, Renu Tyagi, O. P. Thakur, R. K. Sharma, R. Muralidharan

Large-Signal Analysis of III-V Nitride Based DD-Transit Time Device: A New Source for THz Power Generation

Performance of GaN based Double Drift Avalanche Transit Time device is proposed in this paper, for the first time, for useful application in THz-imaging. The device is designed and analyzed by developing a generalized non-linear large-signal simulator that includes effects of elevated temperature, phonon-bottle-necking, scattering limited mobility-velocity and parasitic resistance. The study reveals that the proposed device is capable of generating a pulsed power ~ 0.4 W with an efficiency of 8 % at 1.4 THz under 50 % large signal modulation.

Moumita Mukherjee, D. N. Bose

A Comparison of Hot Carrier and 50 MeV Li3+ Ion Induced Degradation in the Electrical Characteristics of Advanced 200 GHz SiGe HBT

The degradation in the electrical characteristics of advanced 200 GHz SiGe HBTs were studied by mixed mode electrical stress up to 10,000 s. The degradation in the electrical characteristics of SiGe HBTs was also studied by exposing the SiGe HBTs to 50 MeV lithium [Li

3+

] ions. The electrical characteristics were measured before and after every total dose and after fixed stress time. The normalized peak h

FE

of the stressed and irradiated SiGe HBTs are compared to estimate the equivalent stress time for a particular total dose. These correlations are drawn for the first time and the results will establish a systematic relation between stress time and irradiation time.

K. C. Praveen, N. Pushpa, M. N. Bharathi, John D. Cressler, A. P. Gnana Prakash

Growth and Characterization of AlInGaN/AlN/GaN Grown by MOCVD

Al

x

In

y

Ga

1-x-y

N epilayers have been grown by metal organic chemical vapor deposition (MOCVD) at different temperatures from 740 to 940 °C. The incorporation of indium increases with decreasing growth temperature, while the incorporation of Al composition was 30–40 %. The optical properties of the samples have been investigated by photoluminescence (PL). The results show that the sample grown at 890 °C exhibits the best crystalline and optical quality.

Ravi Loganathan, Mathaiyan Jayasakthi, Kandhasamy Prabakaran, Raju Ramesh, Ponnusamy Arivazhagan, Boopathi kuppulingam, Subramanian Sankaranarayanan, Manavaimaran Balaji, Shubra Singh, Krishnan Baskar

Structural Optical and Electrical Studies of AlGaN/GaN Hetrostructures with AlN Interlayer Grown on Sapphire Substrate by MOCVD

In the present study of AlGaN/GaN heterostructures with high quality AlN interlayer (AlN-IL) were grown by metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrate. The AlN inter-layer thickness was varied as 1, 2 and 3 nm. The High-resolution X-ray diffraction (HRXRD) FWHM for (002) plane of GaN was measured for AlGaN/GaN with different AlN-IL thickness. The surface roughness was measured using Atomic Force Microscope (AFM). The Photoluminescence (PL) band edge emission, the room temperature and low temperature hall measurement show the enhancement of two-dimensional electron gas (2DEGs) sheet carrier density due to AlN-IL. The results have been discussed in detail.

Raju Ramesh, Ponnusamy Arivazhagan, Mathiyan Jayasakthi, Ravi Loganthan, Kandhasamy Prabakaran, Boopathi Kuppuligam, Manavimaran Balaji, Krishnan Baskar

Effect of Ni Ions Irradiation on GaAs pHEMT Materials and Devices

GaAs/AlGaAs heterostructure based pHEMT material and fabricated pHEMT devices characteristics were studied with Ni ions irradiation at different fluences. The structural, electrical and optical characteristics were compared before and after irradiation. The structural property of the material was found unchanged while optical and electrical deterioration was observed for used fluences.

Rupesh K. Chaubey, Akhilesh Pandey, A. A. Naik, Seema Vinayak, B. K. Sehgal, P. C. Srivastava

Design and Fabrication of GaN HEMT Based Power Amplifier

This paper discusses the design and measurement of highly efficient GaN HEMT based power amplifier at L Band. Large signal parameters including PAE and power output are presented at an operating frequency of 1 GHz. High efficiency >82 % is achieved by terminating the harmonics at the input as well as at the output and a high output power of 5.2 W is achieved by impedance matching or tuning technique.

Sanjay Kumar Tomar, Meena Mishra, Ashok Kumar, B. K. Sehgal

Electron Beam Lithography for Fabrication of Sub 250 nm T Gates for AlGaAs/InGaAs PHEMT Based MMICs

MMICs operating at 40 GHz and above require PHEMTs with T gates of dimensions 250 nm or less. We are presenting here a process to fabricate T gates using single step electron beam lithography process on a bilayer resist stack of PMMA and its methacrylic acid co-polymer P(MMA-MAA). Using this process we have fabricated T gates of dimensions up to 150 nm. One of the PHEMTs fabricated with 250 nm T gate have demonstrated cut off frequency of 53 GHz.

R. K. Khatri, S. S. Sarkar, A. Rudra, Mahadev Bhat, A. A. Naik, Ashok Kumar, B. K. Sehgal, R. Muralidharan

L Band to 140 MHz Frequency Converter for Wide Dynamic Range Receiver

This paper describes a L-band to 140 MHz frequency converter. It has attractive features like wide dynamic range (−75 dBm to −5 dBm), low spurious levels, low LO leakage, EMI/EMC Compatibility, optimum output power level and compact size (78 mm × 43 mm × 1.6 mm).

Seema Tomar, Sushil Kumar Singh

Ohmic contacts to AlGaN/GaN HEMTs: A Comparison of Two Different Ti/Al Metaletal Ratios

Ohmic contacts formed with two different metal stacks; by varying the Ti/Al thickness ratio were rapid thermal annealed in the temperature range 740–820 °C for 30 s in N

2

ambience. The ohmic contact formed with Ti/Al metal thickness ratio 1/5 showed lower R

c

values and smoother surface morphology compared to the contact with Ti/Al metal thickness ratio 1/1.5. The difference in behavior for both the contacts was corroborated with the outcome of different metallurgical reactions as observed by X-ray diffraction (XRD) and Energy dispersive X-ray analysis (EDX).

Somna S. Mahajan, Robert Laishram, Sonalee Kapoor, Anshu Goel, Seema Vinayak, B. K. Sehgal

Development of GaAs Hyperabrupt Schottky Varactor Diode using Ion-Implanted Active Layer on SI GaAs

We report here the fabrication of ion implanted GaAs hyperabrupt varactor diode that can be integrated in MMIC process. Varactor diodes with constant sensitivity γ of 0.55–0.65 with C

max

/C

min

varying from 2.5 to 3.5 have been fabricated. Varactors diode geometries with different anode lengths, anode width, single and multiple finger anodes with device area varying from 50 to 6,000 μm

2

were fabricated. The breakdown voltage of >10 V have been obtained for all the different value capacitors ranging from 0.16 to 11.2 pF.

S. Dayal, S. Mahajan, D. S. Rawal, B. K Sehgal

Passivation of AlGaN/GaN HEMT by Silicon Nitride

We report here the passivation of AlGaN/GaN HEMT devices with silicon nitride films deposited by inductively coupled plasma chemical vapour deposition (ICPCVD). With low power ammonia plasma pretreatment and silicon nitride film passivation having refractive index of 2.01 and 2,000 A

0

thickness, 80–95 % current recovery and minimum knee walkout have been achieved on different samples.

S. Dayal, Sunil Kumar, Sudhir Kumar, H. Arora, R. Laishram, R. K. Chaubey, B. K. Sehgal

Gate Leakage Current Suppression in AlGaN/GaN HEMT by RTP Annealing

Ni/Au Schottky contacts to AlGaN/GaN HEMT were formed by E-beam evaporation technique and lift-off process. The contacts were Rapid thermal annealed at 300 °C for duration of 2–10 min. A significant suppression in gate leakage current was observed at 2 and 4 min annealing. At further higher annealing duration deterioration in the reverse gate characteristics was observed.

Somna S. Mahajan, Anushree Tomar, Robert Laishram, Sonalee Kapoor, Amit Mailk, AA Naik, Seema Vinayak, BK Sehgal

A Method to Characterize Microstrip Lines for Design of MMICs up to 40 GHz

This paper presents the characterization method for microstrip lines of different characteristic impedance used for design of Microwave Monolithic Integrated Circuits (MMIC) up to 40 GHz. This characterization method is based on extracting the T-matrix of coplanar waveguide-to-microstrip (CPW-M) transitions the S-parameters of two microstrip lines of different lengths, each of which includes CPW-M transitions on either-side. The T-matrix of CPW-M is then subtracted from the S-parameters of microstrip line with CPW_M transitions to obtain the S-parameters of only the microstrip line without CPW-M. To validate the proposed method the extracted S-parameter matrix of microstrip lines have been compared with the electromagnetic simulation results of microstrip lines without CPW-M transition. This exercise has been carried out on GaAs (Gallium Arsenide) of 100 um thickness, but the method is applicable to other substrates as well.

Samuder Gupta, Subhash Chander, Ashok Kumar

Small-Signal RF and Microwave Characteristics of Sub-Micron AlGaN/GaN HEMT

AlGaN/GaN high electron mobility transistors (HEMTs) have tremendous applications as high-power, high-temperature and high-frequency devices due to some unique material properties of GaN. Looking at the prospects of AlGaN/GaN material system in ultra high-frequency applications, we discuss the small signal RF and Microwave characteristics of sub-micron (0.25 μm gate-length) recessed gate AlGaN/GaN HEMT in this paper. The RF and Microwave characteristics discussed in this paper include max-frequency of oscillation (f

max

), cut-off frequency (f

t

), current-gain (h

21

), Masons unilateral gain (MUG) and Maximum Stable Gain (MSG). We have also included the stability analysis by Rollett stability factor (K), followed by Smith Chart and Polar plots within the scope of this paper. The f

max

and f

t

are compared with the available experimental results from the literature.

T. R. Lenka, G. N. Dash, A. K. Panda

Design and Development of an S-band 6 bit MMIC Attenuator with Low Insertion Loss

A monolithic S-band 6 bit digital attenuator with dynamic range of 31.5 dB and with low insertion loss and compact size has been designed, fabricated and tested. Result shows the exceptional performance with reference state insertion loss as low as 2.8 dB at 3.2 GHz and VSWR better then 15 dB over all attenuation state and frequencies. The chip has a total size of 5.0 × 2.5 mm

2

and the technology used is 0.7 um GaAs MESFET (G7S) switch process.

Umakant Goyal, Ashok Kumar

Device Modelling and Simulation

Frontmatter

Monitoring Parameters for Optimization of Power & Efficiency and Minimization of Noise in High Frequency IMPATT Diodes

Studies on Impatt Diodes, as the premier class of Solid State Power Sources covering frequencies from 10 to 500 GHz, reveal various ways and means for pushing Frequency, Power and Efficiency and lowering avalanche noise through monitoring of Structural, material and operating parameters. Enhancement of efficiency through incorporation of charge bump, choice of WBG semiconductor like ZnS, use of new structure (DAR) and new junction type (Hetero junction/Hetero structure junction; pushing rf power by increasing bias current, using different WBG semiconductors (SiC, GaN, ZnS); moving to high frequency band through increase of bias current with doping modulation for compensating performance deterioration, harmonic operation and width modulation and lowering of noise by selection of proper semiconductor, diode structure and type of junction can be realized.

S. P. Pati, P. R. Tripathy

Bipolar Attributes of Unipolar Junctionless MOSFETs

In this work, we present an analysis of bipolar effects in unipolar junctionless (JL) MOSFETs. The reason for dominant bipolar behavior in JL devices in comparison to inversion mode devices has been analyzed. Bipolar induced effects such as steep subthreshold slope, hysteresis in transfer and output characteristics, single transistor latch, and snapback are presented. Results will be useful for identifying advantages and challenges of JL transistors for dynamic memory applications.

Mukta Singh Parihar, Abhinav Kranti

Ambipolar Behaviour of Tunnel Field Effect Transistor (TFET) as an Advantage for Biosensing Applications

In this work, an analytical model for a dielectric modulated (DM) double gate (DG) Tunnel Field Effect Transistor (TFET) working as a biosensor for label free electrical detection of biomolecules has been proposed. It has been analyzed that the ambipolar behaviour of tunnel field effect transistor can also be used for sensing of the biomolecules when the negative voltage is applied to n-TFET. In this paper, the ON current (for both negative and positive gate voltage) of the TFET has been used as the sensing parameter. The characteristics trends are verified via ATLAS (SILVACO) device simulation results.

Ajay Singh, Rakhi Narang, Manoj Saxena, Mridula Gupta

Analytical Expression of Barrier Layer for Enhancement Mode AlGaN/GaN HEMT

In this paper, we have investigated analytically the required thickness of barrier layer for the enhancement mode of AlGaN/GaN high electron mobility transistor (HEMT). A mathematical expression is derived for barrier layer of AlGaN/GaN high electron mobility transistor (HEMT) so that the device can work in enhancement mode. This critical value of barrier layer is fixed for a particular Al composition, gate barrier height and relaxation factor. The device will work in enhancement mode if the barrier layer thickness is below the critical value. This critical value of barrier layer is a function of polarization charge. It is seen from derived result that critical value of barrier layer increases if the polarized charge is reduced. Threshold voltage is calculated to show the dependence of critical barrier layer thickness and the gate barrier height.

Apurba Chakraborty, Saptarshi Ghosh, Ankush Bag, Palash Das, Dhrubes Biswas

Modeling and Simulation of Package Inductance for Pulsed IMPATT Diodes with Integrated Beam Lead Structure

High Power Pulsed IMPATT diodes are now being fabricated with Integrated Beam Lead Structure for top electrical contact inside diode package to obtain higher output power, greater bondability and better Thermal Dissipation. Relatively lower package Impedance of Beam lead structure ensures better device circuit interaction. The authors have introduced a novel analytical method based on HFSS software to predict the value of Package Impedance of a Beam Lead Structure as well as its dependence on dimensional parameters.

Arijit Das, Diptadip Chakraborty, Nabin Chandra Mandal

Memristor-based Memory Cell with Less Noise Margins and Storing Non-Binary Data

Memristor has been realized as a non-linear, two terminal physical device recently by HP labs. Memristor is considered as the fourth fundamental circuit element. Technologies using memristor provides much better scalability, higher utilization as memory storage, non-volatility and overall lower power consumptions as compared to conventional CMOS technology. A detailed study of the non-linear model of the memristor has been done. The time and the voltage characteristics of stable read and write operations, and the tradeoffs between the various design parameters such as voltage, frequency, noise margin, and area are included in this paper. Based on this modeling we compare a generic hybrid CMOS-Memristor memory cell and a memristor-SRAM cell with less noise margins and very low power. We also extend the notion of binary storage of the memristor to other number systems as well. The memristor can be used to represent number system by the virtue of different memory states it possess i.e. non-binary storage using memory array.

Priya Yadav, B. K. Das

Reduction of Electron Overflow Problem by Improved InGaN/GaN Based Multiple Quantum Well LEDs Structure with p- AlInGaN/AlGaN EBL Layer

InGaN/GaN-based Multi Quantum Well (MQW) LEDS with p-AlInGaN/AlGaN electron blocking layers (EBL) are studied using the SimuLED simulator. The simulation results specify the importance of p-AlInGaN/AlGaN electron blocking layers to suppress the electron overflow problem in the InGaN based MQW LED device structure for the further improvement in the optical and electrical performance of the device. The designed AlInGaN/AlGaN EBL was investigated by changing different Al and In concentrations and was analyzed. It shows a reduction in electron overflow and subsequent increase in Internal Quantum Efficiency by insertion of Al

X

In

Y

Ga

1-X-Y

N-Al

0.15

Ga

0.85

N(X = 0.1, Y = 0.15) EBL instead of conventional AlGaN EBL. Structure shows a significant reduction in efficiency droop and aiding a supportive barrier for electron overflow.

Dipika Robidas, D Arivuoli

Two Dimensional Model for Threshold Voltage Roll-Off of Short Channel High-k Gate-Stack Double-Gate (DG) MOSFETs

In this paper a two-dimensional (2D) model of threshold voltage roll-off of uniformly doped high-k gate stack double-gate (DG) metal–oxide–semiconductor field-effect transistors (MOSFETs) is presented. The surface potential is obtained by solving the 2D Poisson’s equation using evanescent mode analysis and then it is used to model the threshold voltage roll-off. Threshold voltage roll-off variations against device channel length for different values of gate dielectric constant and silicon film thickness are shown. The modeling results show a good agreement with the numerical simulation data obtained by ATLAS™, a 2D device simulator from SILVACO.

Ekta Goel, Sanjay Kumar, Gopal Rawat, Mirgender Kumar, Sarvesh Dubey, S. Jit

A Quantum Analytical Model for Inversion Current in Short Channel DMDG SON MOSFET

DMDG MOSFET, a promising alternative to conventional CMOS devices, has evolved from extensive research in the present era. In our present work we have incorporated quantum mechanical effects on DMDG SON MOSFET because these effects became significant factors in deca-nanometer scale. Here, we have studied the current voltage characteristics of DMDG SON MOSFET incorporating the quantum mechanical effects. For maximum charge inversion in the channel, minimum value of surface potential is considered to calculate charge and corresponding current along the channel.

Gargee Bhattacharyya, Sharmistha Shee, Pranab Kishore Dutta, Subir Kumar Sarkar

An Analytical Study of Ion Implanted Strained-Si on SOI MOSFETs for Optimizing Switching Characteristics

In this paper, surface potential based analytical model of subthreshold swing of ion implanted strained-Si-on-Insulator (SSOI) MOSFETs have been presented. A comprehensive evaluation is presented to optimize the switching characteristics for this MOS structure. The modeling results are validated by comparing with the simulation data obtained by the two dimensional (2D) device simulator ATLAS™.

Gopal Rawat, Mirgender Kumar, Sarvesh Dubey, S. Jit

Statistical Compact Model Extraction for Skewed Gaussian Variations

A technique for extracting Statistical Compact Model (SCM) parameters for skewed Gaussian parameters is proposed. Existing techniques handle non-Gaussian variations through non-linearity in model equations. However, hardware data on certain technologies suggest that non-Gaussian variations are observed even on linear parameters like Idlin/Idsat. We propose to model such variations through skewed Gaussian random variables. Analytical expressions for the statistics of the skewed Gaussian process and performance parameters are derived. SCM parameters are extracted by setting up a skewed back propagation of variance (SBPV) algorithm.

V. Janakiraman, Shrinivas J. Pandharpure, Josef Watts

On the Voltage Transfer Characteristics (VTC) of some Nanoscale Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs)

The voltage transfer characteristics (VTC) of a complementary metal-oxide-semiconductor (CMOS) inverter provides necessary information about some of the most important performance parameters, such as noise margin (low/high), inverter logic threshold voltage, and so on. Over years, there has been an increasing trend to use various commercially available Technology Computer Aided Design (TCAD) tools and circuit simulators to study such performance parameters. The emergence of novel devices has forced the theoretical research community to refine TCAD tools and simulators. We have developed a simulator that can plot the VTC curve of strained/unstrained nanoscale MOSFET based CMOS circuits. Our algorithm can faithfully reproduce the VTC curve of nanoscale MOSFET based CMOS inverter with an average deviation of less than 2 %. We have also shown the dependence of VTC curves of nanoscale strained Si/SiGe and multi channel (MC) gate-all-around (GAA) MOSFET based CMOS inverters on some important device parameters.

Jhuma Saha, Amrita Kumari, Shankaranand Jha, Subindu Kumar

Influence of Interface Deep Traps on Capacitance of AlGaN/GaN Heterojunctions

We have studied by modeling and simulation dependence of capacitance of AlGaN/GaN heterostructures by the presence of deep traps localized at the AlGaN and GaN interface. For low frequency capacitance the deep traps cause voltage shift of capacitance curves when the traps concentration is relatively low. With increasing traps concentration the voltage shift increases and above some critical traps concentration the new capacitance peak is observed in the

C

V

curve. We expect that in experimental structures only traps located close to the conduction band minimum can follow external signal.

Jozef Osvald

Effect of Ge-composition on the Gain of a Thin Layer Si 1-y Ge y Avalanche Photodiode

Gain calculation of Si

1

-

y

Ge

y

n

+

-i-p

+

avalanche photodiode (APD) is described for multiplication layer down to tens of nanometers considering dead-space effect. Carrier diffusion from undepleted regions is considered to study the effect of low bias. The computed results are used to investigate the effect of Ge-composition

(y)

on the gain of a Si

1

-

y

Ge

y

APD having thin multiplication layer. Results show that gain increases with bias more rapidly with the increase in Ge-content. It is also seen that thinner multiplication layer is required for APD having lower Ge-content to achieve the same gain at a given bias.

Kanishka Majumder, N. R. Das

Prformance Investigation of Dual Material Gate Stack Schottky-Barrier Source/Drain GAA MOSFET for Analog Applications

This paper presents the analog performance of the Dual Material Gate Stack (DMGS) Schottky–Barrier (SB) Source/Drain (S/D) Gate All Around (GAA) MOSFET. A comprehensive comparative analysis has been carried out with doped source/drain by using ATLAS device simulator. Impact of gate material engineering such as dual material gate and the high-k dielectric has been carried out in detail. The analysis reveals that new structure exhibits superior analog performance. The DMGS-SB-S/D GAA has a number of desirable features, i.e. high on-state current I

on

, increased current gain, improved transconductance g

m

, improved output conductance g

d

, high unity-gain frequency f

T

, and maximum transducer power gain. MOSFET with metal S/D shows the faster performance due to low parasitic S/D resistance offered by SB-S/D. So it can be used for faster switching and high frequency applications.

Manoj Kumar, Subhasis Haldar, Mridula Gupta, R. S. Gupta

Large Signal Physical Operation of a III–V Nitride Based Double Velocity Transit Time Device: A Potential Source For THz Imaging

Performance of GaN/AlGaN based Double Velocity Avalanche Transit Time device is proposed in this paper, for the first time, for useful application in THz-imaging. The device is designed and analyzed by developing a generalized non-linear large-signal simulator that includes effects of elevated temperature, phonon-bottle-necking, scattering limited mobility-velocity and parasitic resistance. The simulation reveals that the proposed device is capable of generating a considerable pulsed power ~8 × 10

10

W/m

2

with an efficiency of 8 % at 1.4 THz under 50 % large signal modulation. Dc characterization of the fabricated diodes is in agreement with simulation results.

Moumita Mukherjee

Influence of Source-Gate and Gate Lengths Variations on GaN HEMTs Based Biosensor

AlGaN/GaN has been considered as a promising candidate for bio-sensing applications due to their outstanding properties. Scaling of gate length and source to gate length plays a key role in the performance of biosensor as it directly influences the device transconductance and hence the sensitivity and response time of biosensors. In this paper, we investigated the effect of variations in gate lengths (1–5 μm) and source to gate length (1–3 μm) to choose the most suitable one for bio sensing applications. Downscaling of gate length (L

G

) and source to gate length (L

SG

) improve the device performance, enhancing the drain-current (I

ds

) and device transconductance. The results of simulations indicate that L

G

1 μm_L

SG

1μm with constant L

SD

configuration shows highest output current 1.01 A/mm, transconductance (g

m

) 211 mS/mm with lowest value of gate leakage current. Irrespective of L

SG

, effect of variation in L

G

follows same trend.

Niketa Sharma, Diksha Joshi, Nidhi Chaturvedi

Effect of Intersubband Interaction on Multisubband Electron Mobility in a Parabolic Quantum Well Under Applied Electric Field

We study the effect of external electric field

F

on the multisubband electron mobility μ of a barrier delta doped Al

x

Ga

1−x

As parabolic quantum well structure. We show that by applying the electric field a transition from double subband to single subband occupancy can be made leading to enhancement of mobility due to supression of intersubband effects. We analyse the variation of mobility as a function of

F

by changing the well width and surface electron density which shows interesting results.

N. Sahoo, A. K. Panda, T. Sahu

Prospects and issues of Diamond based IMPATT Diode at MM-Wave Frequency

We study the effect of external electric field

F

on the multisubband electron mobility μ of a barrier delta doped Al

x

Ga

1−x

As parabolic quantum well structure. We show that by applying the electric field a transition from double subband to single subband occupancy can be made leading to enhancement of mobility due to supression of intersubband effects. We analyse the variation of mobility as a function of

F

by changing the well width and surface electron density which shows interesting results.

N. Sahoo, A. K. Panda, T. Sahu

The Application of Level Set Method for Simulation of PECVD/LPCVD Processes

In this study we present a Chemical Vapor Deposition (CVD) process simulator based on the sparse field method for solving the level set equations. An accurate and efficient tool for tracking the CVD profile evolution is developed, which includes different physical effects of direct deposition and angle dependent ion-induced deposition as well as re-deposition. The simulation results shows that the deposition profiles agree well with the experiment for different opening sizes and various micro structures. It also provides the evidence that this approach is able to describe the complex topographical evolution for PECVD/LPCVD processes.

Sajal Sagar Singh, Yuan Li, Yan Xing, Prem Pal

Doping Concentration Dependence of Pinch-Off Effect in Inhomogeneous Schottky Diodes

The Poisson’s equation along with drift diffusion equations have been used to simulate the current–voltage characteristics of inhomogeneous Schottky diodes with different doping concentration. Firstly, the potential variation inside the bulk semiconductor is calculated and then the current as a function of bias through the Schottky diode for various doping concentration are calculated. From the simulated current–voltage characteristics the diode parameters are extracted by fitting of current–voltage data into thermionic emission diffusion current equation. The derived barrier parameters are analyzed to study the effect of different barrier patch size and different doping concentration on the current–voltage characteristics of inhomogeneities Schottky diodes. Pinch-off effect is brought to light by this numerical simulation which indicate that regions of low-SBH regions are blocked (get vanish) when the size of these patch regions is less than the average depletion width For normal doping there exists a peak in ideality factor plot at certain spacing. However the peak in ideality factor slowly diminishes as the doping decreases. No such distinct feature is seen in barrier height plots.

Subhash Chand, Priyanka Kaushal

Gate Leakage Current Modeling in Ferroelectric FET

A gate leakage current model is proposed for a negative capacitance or ferroelectric Field Effect Transistor (Fe-FET). A simple gate structure containing a ferroelectric, Lead Zirconate Titanate (PZT) mounted on silicon substrate without any buffer layer between the two is considered. This model is based on Schottky and Poole–Frenkel current conduction mechanisms. It has been found that Poole–Frenkel current conduction mechanism takes place in ferroelectrics and the gate leakage currents in the gate stack containing ferroelectric as dielectric can be modeled using a unified Schottky Poole–Frenkel model.

Raheela Rasool, Najeeb-Ud-Din

A New Superjunction Power MOSFET with Oxide-Pillar-in-Drift Region

In this paper, we propose a new SJMOSFET with oxide pillar in its drift region that shows an improvement in its breakdown performance and relation between the B

v

and R

on

become more linear as compared to the conventional SJMOSFET due to a reduction in the vertical electric field. Simulations has been done using PISCES-II device simulator. The effect of oxide pillar width has also been done and analyzed.

Deepti Sharma, Rakesh Vaid

Electron mobility Enhancement in Barrier Delta Doped Asymmetric Double Quantum Well Structures

We analyze the electron mobility in asymmetric double quantum wells by introducing different doping concentrations in the barriers and also by taking different well widths. We show that the asymmetry induced changes in the subband wave functions, energy levels and occupation of subbands lead to enhancement in subband mobility in a multisubband occupied system through the intersubband interactions.

S. Das, R. K. Nayak, T. Sahu, A. K. Panda

A Simplified Approach for Automatic Extraction of Model Parameters of Spiral Inductors for Design of MMICs

A simplified parameter-extraction technique is presented for accurately modeling on-chip spiral inductors in microwave monolithic integrated circuits (MMICs) and radio frequency integrated circuits (RFICs). The proposed model is a pi-circuit with

RC

network connected with both vertical branches to account for substrate coupling. The extraction process starts with series inductance and resistance at low frequencies. Then, the feedback capacitance between two metal layers on which inductor is fabricated is evaluated. Afterward, the substrate resistance and capacitance, is extracted at higher frequencies. All circuit element values of the network are analytically determined from simulated S- parameters obtained from momentum and validated with the measured

S

- parameters of a 2 turn inductor fabricated on 200 um GaAs (Gallium Arsenide) substrate for frequency up to 26 GHz. The extraction of equivalent network for 1–6 turns of inductor has also been carried out with S-parameter input from momentum simulator.

Samuder Gupta, Subhash Chander, Ashok Kumar, B. K. Sehgal

Threshold Voltage Modeling of Short-Channel DG MOSFETs with Non-Uniform Doping in the Vertical Direction

Two-dimensional (2D) modeling of threshold voltage of short-channel double-gate (DG) metal-oxide-semiconductor field-effect transistors (MOSFETs) with a vertical Gaussian-like doping profile is proposed in this paper. The parabolic approximation method has been used to solve the 2D Poisson’s equation to obtain the channel potential function of the device. The minimum surface potential thus obtained, has been used to model the threshold voltage of the device. Threshold voltage variations against channel length for different device parameters have been demonstrated. The validity of proposed model is shown by comparing the results with the numerical simulation data obtained by using the commercially available ATLAS

TM

, a 2D device simulator from SILVACO.

Sanjay Kumar, Ekta Goel, Gopal Rawat, Kunal Singh, Mirgender Kumar, Sarvesh Dubey, S. Jit

Improved Underlap FinFET with Asymmetric Spacer Permittivities

A much higher performance can be achieved by the use of a high-K spacer for only the SE region of the Underlap FinFET. We explain this effect using a 3-transistor equivalent circuit in the FinFET device. Our new device design does not increase OFF state current.

Saurabh K. Nema, M. SaiKiran, P. Singh, Archana Pandey, S. K. Manhas, A. K. Saxena, Anand Bulusu

Comprehensive Analytical Modeling of N-polar GaN/AlGaN Insulated Gate HEMTs with and without Polarization Neutralization Layer

Electrical characteristics of N-polar GaN/Al

x

Ga

1-x

N insulated gate (MIS) HEMTs are theoretically analyzed. Threshold voltage models are developed for both the generalized and the polarization neutralized structures. Based on these developments, the drain current and transconductance are formulated after incorporation of an appropriate Monte-Carlo simulation based mobility model for GaN. Non-idealities such as imaging charges in the interface/buffer, source drain resistances, and velocity saturation are taken into account in the present model. The analytical results on the transport characteristics of the device are compared with experimentally measured data and are in close agreement.

Saptarsi Ghosh, Syed Mukulika Dinara, Ankush Bag, Apurba. chakraborty, Partha Mukhopadhyay, Sanjib Kabi, Dhrubes Biswas

Microwave Characteristics of SiC IMPATT Diodes at 220 GHz

The microwave characteristics of SiC IMPATT diodes at 220 GHz are simulated in this paper. In our simulation study, we have considered both the SDR and DDR structures of IMPATT diode based on 4H-SiC and 6H-SiC materials. The simulation of these diodes reveals that 4H-SiC is a promising material for IMPATT applications based on DDR structure with a minimum noise measure as compare to 6H-SiC semiconductor. It is also interesting to note that n-type 4H-SiC SDR IMPATT diode outperforms the other SDR IMPATT diodes in terms of noise measure.

S R Pattanaik, J Pradhan, S K Swain, G N Dash

Spectral Peak Shift in One-Dimensional Nonlinear Photonic Crystal

We present a numerical study of the pulse propagation inside a one-dimensional nonlinear photonic crystal (PC) in which the nonlinear layer is a Kerr medium. The Transfer matrix method is used to study the nonlinear propagation in the structure. We observe shift in the peak spectral wavelength induced by self-phase modulation as a result of high Kerr nonlinearity.

Shereena Joseph, Aurangzeb Khurram Hafiz

Investigation on Hybrid Green Light-Emitting Diode

We propose a hybrid light-emitting diode (LED) design comprising of p-GaN/ p-MgZnO/ InGaN/ n-MgZnO/ n-ZnO emanating green electroluminescence centered around 560 nm. We compare the performance of proposed LED with ZnO and GaN based green LEDs through 2-D numerical simulation. It is found that hybrid LED shows highest IQE of 93.2 % with added advantage of least efficiency droop at high injection current.

Shruti Verma, Shaibal Mukherjee

Advanced AlGaN/GaN Resonant Tunneling Diode on Silicon Substrate for Negligible Scattering and Polarization effects

In this work we have proposed an advanced AlGaN/GaN resonant tunneling diode (RTD) structure on silicon substrate which introduces modulation doped emitter collector regions and graded spacer layers. An analytical model has been presented to predict the variation of transmission coefficient (Tc) with different scattering phenomena. The physical interpretations of this structure define negligible scattering effects and polarization induced field. Simulated results show an improved current voltage (I–V) characteristics as well as high peak to valley current ratio (PVCR).

Subhra Chowdhury, Anirban Santara, Partha Mukhopadhyay, Dhrubes Biswas

Improved Performance of Junctionless Tunnel FETs with Source/Channel Heterostructure

We propose a junctionless tunnel FET architecture with a heterostructure at the source/channel interface. We show that the use of a low bandgap material in the source of this device results in significant ON current improvement. We further show that ON current improvement can also be achieved by using a low-k isolation dielectric. The proposed device architecture which combines the merits of both junctionless FETs and Tunnel FETs can be a potential candidate for sub-20 nm technology node.

Suresh Gundapaneni, Aniruddha Konar, Mohit Bajaj, K. V. R. M. Murali

Modeling Charge Control in Heterostructure Nanoscale Transistors

We present a multi-scale methodology for the modeling of charge control in multigate field-effect-transistors (MuGFETs) comprising alternative channel materials, including heterostructures. Using SiGe and Ge as examples, we will show how bandstructure calculations for material parameters may be connected to technology-computer-aided design (TCAD) simulations for the ideal charge–voltage characteristics. Lastly, we outline a custom simulation tool that includes interface and border trap effects in addition to usual electrostatics and quantization.

Dhirendra Vaidya, Saurabh Sant, Arjun Hegde, Saurabh Lodha, Udayan Ganguly, Swaroop Ganguly

Surface Potential Based Analytical Model for Hetero-Dielectric p-n-i-n Double-Gate Tunnel-FET

In this work a piecewise Surface Potential based analytical model for a Hetero-Dielectric p-n-i-n Double Gate Tunnel FET has been developed which captures the device performance in all regions of operation i.e. Accumulation, Depletion and Inversion Region. Moreover, a comparative study among single High-k dielectric, single Low-k dielectric and Hetero-Dielectric TFET has been done. Here V

gs

and V

ds

dependent explicit equations for surface potential have been derived which are subsequently been made to be channel length dependent. Furthermore, the electrostatic behavior of the device is studied in terms of Lateral Electric Field and Energy Band Diagram. The efficacy of the model has been validated through simulated results obtained using ATLAS device simulation software.

Upasana, Rakhi Narang, Manoj Saxena, Mridula Gupta

Hot Carrier Reliability Issues of Junctionless Transistor due to Interface Trap Charges for Analog/RF Applications

This paper investigates the analog/RF performance of Junctionless Transistor (JLT) by employing temperature variations, ranging from 200 K to 500 K, along with the influence of interface trap charges. The objective of the present work is to study the performance degradation of junctionless transistor due to interface/fixed trap charges present at the semiconductor/oxide interface of the device at wide temperature ranges. Analog/RF performance distortion in terms of figure of merit (FOM) metrics: intrinsic gain, transconductance, I

on

/I

off

ratio, parasitic capacitances, cutoff frequency, current gain, power gain and Gain Transductance Frequency Product (GTFP) has been carried out using ATLAS 3D device simulator. Simulation results reveal that the density of localized charges has strong affects on the device performance and effectively changes the sensitivity of device. It is also analysed that performance degradation is more egregious at low temperature ranges and subthreshold region. This study is beneficial to design and optimization of junctionless device for analog/RF applications.

Yogesh Pratap, S. Haldar, R. S. Gupta, Mridula Gupta

Photovolatics

Frontmatter

Tuning of Plasmonic Nanoparticles for Enhancing Solar Cell Efficiency

Plasmonic nanoparticles based thin film solar cells plays a crucial role in designing the current breed of third generation solar cells. To decrease the material cost for economic viability without compromising on absorption efficiency, it is necessary to use the light scattering and trapping properties of such kind of solar cells. In our recent work, we analyzed the optical properties of silver nanoparticles formed using Rapid Thermal Annealing (RTA) and compared the experimental results with Mie scattering theory.

Somik Chakravarty, Lingeswaran Arunagiri, Shiv Chaudhary, Abhishek Verma, V. K. Jain

Enhancement of Performance of Crystalline and Amorphous Silicon Solar Cells through Optical Engineering by Nanostructured Materials

Optical engineering of solar cells by nanostructured materials has recently emerged as a new frontier of photovoltaic research. Noble metal and dielectric nanostructures that can scatter and guide light have shown great capability for significantly improving the energy conversion efficiency of both crystalline and amorphous silicon solar cells, indicating a direction towards an innovative pathway for the advancement of solar industry. Silver nanoparticles applied on the front and rear surfaces of solar cells have dominated theoretical and experimental research as their high polarizability leads to large plasmonic scattering of the incident electromagnetic spectrum resulting in a reduction of reflectivity of the front surface as well as light trapping due to scattering. However, the joule loss of incident power in metal nanoparticles becomes very critical while designing high efficiency silicon solar cells. The use of lossless dielectric therefore emerges as an alternate solution to metal nanoparticles. Dielectric nanoparticle array helps to reduce the reflection losses by grading the refractive index mismatch in between silicon substrate and air along with omni-directionality. With a proper choice of design, photon transmission of more than 97 % of the incident photons in the solar AM 1.5 spectrum can be achieved which is comparable to the photon transmission by conventionally textured and ARC silicon surface. Further enhancements can be obtained by embedding lossless dielectric nanoparticles in the active absorber silicon layer to enhance scattering and corresponding light trapping. Optical simulations combined with the electrical model of a solar cell shows that a relative improvement in efficiency of about 6 % is obtained when 200 nm radius voids having 30 % coverage are embedded in a 20 μm thick solar cell to be pronounced in thinner cells (25 % for a thin cell 2 μm thick). For amorphous silicon solar cells also, optical engineering of the front glass surface by texturing and/or suitable coverage of silica nanoparticles have shown significant reduction in reflectivity and greater angular scattering of light leading to a large enhancement (about 6 %) in efficiency. The research work leading to possible performance enhancement in silicon solar cells through optical engineering by nanostructured will be discussed.

H. Saha, Swapan K. Datta

Single-Pot Rapid Synthesis of Colloidal Core/Core-Shell Quantum Dots: A Novel Polymer-Nanocrystal Hybrid Material

Colloidal core and core shell Quantum Dots (QD’s) are unique and important optoelectronic materials because properties of these QD’s can be tailored by configuring core and optimizing shell thickness. In this research work, lead selenide (PbSe) core and PbSe-CdSe (Core-shell) QD’s are synthesized using oleic acid as a capping ligand by colloidal route. This simpler, cost-effective and rapid single pot synthesis route for colloidal core-shell quantum dots unlike conventional double-pot approach like cation-exchange and SILAR process has been reported for the very first time. Phase formation of prepared quantum dots is confirmed by XRD analysis, capping ligand presence by IR spectroscopy and morphological information by Scanning electron microscopy respectively. These synthesized inorganic quantum dots are dispersed in Poly (3-hexyl thiophene) polymer for formation of their respective nanocomposites. From PL quenching studies, it was inferred that PbSe-CdSe core-shell quantum dots showed enhanced rate of PL quenching and hence higher value of Stern-Volmer constant (K

SV

) than PbSe Core QD’s. This confirms that CdSe shell formation on PbSe core significantly passivates the core-surface, increases the stability and enhances the charge transfer mechanism for its potential application in Hybrid Solar cells.

Aarti Mehta, Shailesh N. Sharma, Kanchan Sharma, Parth Vashishtha, S. Chand

Study of Al and Ga Doped and Co-Doped ZnO Thin Film as front Contact in CIGS Solar Cell

Zinc Oxide (ZnO) is a group II-VI semiconductor material widely applied in optoelectronic because of its wide band gap (~ 3.3 eV), high chemical stability, high order transmittance and piezoelectric properties. In the present study Al doped ZnO, Ga doped ZnO and Al and Ga (1:1) co-doped ZnO thin films were grown on glass substrates by DC sputtering at room temperature. The thickness for all the deposited film was kept constant. The transmission of Al doped ZnO and Al and Ga co-doped ZnO the films shows more than 80 % of transmittance in the visible region of light where as for Ga doped ZnO thin film around 75 % of transmittance was observed. The XRD pattern of the films shown a preferable growth orientation in (002) phase, except this main peak some weak peaks were also appeared at (102) and (103). It shows the films are polycrystalline in nature. Also from the XRD result the crystallite size of Al doped ZnO, Ga doped ZnO and Al and Ga co-doped ZnO were determined and found to be 63.2, 73.3 and 85.5 nm respectively. Also from FTIR, the increase in crystallanity is observed in case of Al doped ZnO and Al and Ga (1:1) co-doped ZnO thin film. The electrical properties such as mobility, carrier concentration and resistivity were measured using Hall Effect Measurement system. Both carrier concentration and mobility values were increased in case of Al and Ga co-doped ZnO thin film compared to that of doped ZnO thin films. In case of Al and Ga co-doped ZnO thin film the lowest resistivity value of 5.46 × 10

−4

Ω cm was observed. It was observed that Al and Ga co-doped ZnO thin film showed the resistivity in the range of 10

−4

Ω cm with enhanced optical transmittance. Such a transparent and conducting zinc-oxide thin film can be used as front contact in CIGS solar cell.

Chandan Ashis Gupta, Abhisek Mishra, Sutanu Mangal, Udai P. Singh

Charge Transport Studies in Pure and CdS Doped PBDTTPD:CdS Nanocomposite for Solar Cell Application

The recent trends in organic photovoltaic is towards the development of hybrid solar cells using the active absorption layer of a nancomposite layer having conjugated polymer incorporated with inorganic quantum dots, nanorods, nanoparticles, etc. The dispersion of nanomaterials in polymer matrix leads to inadequate charge transfer, agglomeration etc., which is a hindrance towards achieving high efficiency in the hybrid solar cells. On the other hand if nanomaterials are grown in situ into polymer matrix, it may enable to overcome the above disadvantage. Keeping this in view, we have synthesized a nanocomposite of PBDTTPD:CdS by in situ growth of CdS nanorods into polymer matrix. The charge transport mechanism was studied and the nanocomposite showed improvement in charge carrier mobility over the pure polymer which has been attributed to improvement in inter-chain charge transport by the presence of inorganic nanocrystals in polymer matrix.

Dibyajyoti Mohanty, Vishal Bharti, Jitender Gaur, Ramil Bhardwaj, G. D. Sharma, Suresh Chand

Encapsulation of SiNWs Array with Diamond-like Nanocomposite Thin Film for Ultra-low Reflection

Silicon nanowire (SiNW) arrays were synthesized using single step metal assisted chemical etching (SSMACE) method on n-type mono crystalline silicon. The effect of encapsulation of SiNW arrays with diamond-like nanocomposite (DLN) deposited by plasma assisted chemical vapor deposition (PACVD) method has been investigated. The structural and optical properties of SiNW and DLN thin film has been studied using FESEM, FTIR and UV–VIS-NIR spectroscopy. A very low (3–4 %) and high broadband (300–1,000 nm) reflection has been achieved from SiNWs array. However, after deposition of DLN thin film on nanowire array, the reflection further reduces significantly to 1.7 %. The SiNW arrays encapsulated with DLN thin film has a great potential to use in solar cell.

S. Jana, S. Das, D. De, S. Garain, S. Ray, U. Gangopadhyay, P. Ghosh, A. Mondal

In-Situ Growth of CdS Nanorods in PTB7 by Solvothermal Process for Hybrid Organic Inorganic Solar Cell applications

We demonstrate a high yielding, green approach using solvothermal, in situ growth of CdS nanorods (NRs) in a low band gap polymer, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7). The use of chloroaniline dithiocarbamate and chloroaniline as ligands to functionalize the Cd (II) ions provides a new path for solubilization of Cd (II) complex in the chlorobenzene solvent. It removes use of volatile and hazardous chemicals such as pyridine as ligand which are conventionally used to enhance solubility of such complexes. It is the first example of solvothermal process used for in situ growth of CdS NRs in a polymer matrix. This nanocomposite is used to fabricate hybrid-organic–inorganic-solar cells (HOISC) as donor–acceptor combination in the bulk hetrojunction (BHJ) geometry. The incorporation of CdS NRs shows significant decrease in the band gap of PTB7 from 1.71 eV to 1.59 eV and the photoluminescence (PL) studies show significant quenching in the PL of PTB7 by the addition of CdS NRs. This suggests that the PTB7:CdS NRs is a potential nanocomposite for the bulk heterojunction active layer in the HOISCs. The HOISCs fabricated using the PTB7:CdS as donor–acceptor combination give power conversion efficiency of the order of 1.16 %. This work has implication in the development of green economical and efficient HOISC by using highly controlled synthetic process.

Ramil K. Bhardwaj, Vishal Bharti, Jitender Gaur, Abhishek Sharma, Annu Sonania, Dibyajyoti Mohanty, Shilpa Jain, Gauri D. Sharma, Neeraj Chaudhari, Suresh Chand, Kamalika Banerjee

Synthesis of AgInS2 Nanoparticles Directly in Poly (3-hexyl thiophene) (P3HT)Matrix: Photoluminescence Quenching Studies

Inorganic semiconductor AgInS

2

nanoparticles and P3HT/AgInS

2

composite was synthesized by decomposition of silver indium xanthate. The synthesized nanoparticles and composite were characterized by XRD and UV–Vis spectroscopy. PL quenching of the composite demonstrate that the electron transfer from polymer to inorganic NPs through ex-situ solution blending is less efficient in PL quenching as compared to in situ synthesis.

Nitu Chhikara, Poonam Gupta, B. K. Gupta, Kiran Jain, S. Chand

Role of Plane and Textured TCO Surfaces in Enhancing the Efficiency of Thin Film Amorphous Silicon Solar cell: A Theoretical Approach

In the present work, comparison is made between ITO indium tin oxide) and ZnO (zinc oxide) as TCO layer for the amorphous silicon (a-Si:H) solar cell applications using AFORS-HET simulation software. In order to improve the efficiency of a-Si:H solar cell optimization of band gap of p layer was done along with suggesting the effective light trapping measures which can be adopted in this regard. The optimized value of band gap for p layer 2.1 eV was found for obtaining maximum efficiencies of 14.91 % with ITO and 17.02 % with ZnO as front contact. The further study explored the use of textured TCO surfaces instead of the plane surfaces. The use of textured surfaces of ITO and ZnO enhanced the efficiencies to 15.85 % and 18.10 % respectively at optimized values of the band gap of p, i, and n layers. Hence the overall investigation of a-Si:H solar cells with the idea of maximizing the light trapping using plane as well as textured surfaces of TCO coatings suggests the possibilities for fabrication of efficient a-Si:H solar cells. Our simulation results reveals ZnO as suitable TCO material in order to enhance the efficiencies of solar cell compared to ITO.

Mansi Sharma, Arti Rawat, S. Sudhakar, Sucheta Juneja, Sushil Kumar

Thermal Sintering Improves the Short Circuit Current of Solar Cells Sensitized with CdTe/CdSe Core/Shell Nanocrystals

Aqueous colloidal solution of CdTe/CdSe core/shell nanocrystals used in this sensitized solar cells were synthesized using a wet chemical method. These colloidal nanocrystals were capped with Mercapto-Succinic Acid, which is a bi-functional linker molecule. The nanocrystal sensitized TiO

2

electrodes were prepared by pipetting aqueous solution of MSA capped CdTe/CdSe nanocrystal onto the mesoporous TiO

2

followed by making a ZnS window layer. We found that, presence of Mercapto-Succinic Acid significantly affects short circuit current and thereby the overall efficiency of solar cell as it is insulating in nature. Sintering at 400

O

C seems to help in increasing charge transfer from nanocrystals to TiO2. This in turns actually shows up as a large increase in short circuit current density by 186 % and efficiency by 216 % compared to non-sintered cells. Parameters for the highest efficiency cell are J

sc

= 8 mA/cm

2

, V

oc

= 0.53 V and η = 1.74 %.

Padmashri Patil

Effect of Cd/S Molar Ratio on the Optical and Electrical Properties of Spray Deposited CdS Thin Films

Cadmium sulphide thin films were deposited from the solutions containing precursor materials with different Cd/S molar ratios on glass substrates by spray pyrolysis. The grown CdS thin film show hexagonal structures as indicated by powder XRD studies. Surface morphology and elemental composition in the films were obtained from FESEM and EDX measurements, respectively. The optical properties of CdS films were less influenced by Cd/S molar ratio in the solution where as resistivity is found to be sensitive to precursor molar ratio. Transmittance of the films was found to be above 80 %. The lowest resistivity of 1.04 × 10

2

Ω cm were obtained for the films deposited from solution with Cd/S molar ratio equal to 0.5. The properties of the CdS thin films grown with Cd/S molar ratio equal to 0.5 appears suitable for window layer in heterojunction thin film solar cells.

P. M. Parameshwari, K. Gopalakrishna Naik

Comparison of Incorporation of Na via In-situ and Ex-situ Modes for the Realization of Device Quality CIGSe Thin Films

Essentiality of Na incorporation into the CIGSe films is required in order to have highly crystalline films along with grain boundaries’ passivation. Our work focuses on comparison of two different methods to ensure the optimized sodium incorporation into the film to obtain device-quality material and thus high conversion efficiencies.

Parul Chawla, Son Singh, Parth Vashishtha, Suresh Chand, Shailesh N. Sharma

A Method of Estimating Indium Bump Integration Yield in Hybrid IRFPA of HgCdTe Photodiodes

Hybrid IRFPAs are comprised of photo detector array and readout integrated circuit (ROIC) made of different materials best suited for their purposes, interconnected by flip-chip bonding using indium bumps. Typically, array operability of >99.9 % is required in several high-end applications of IRFPAs. Therefore, one cannot afford any operability loss due to failure of bump connectivity. To ensure high yield of bump connectivity, some iteration in flip chip process is usually needed. This requires the correct estimation of the connectivity after all iterations, so that even the single unconnected pixel may be identified and corrected. In this paper, we demonstrate a reliable method of estimating the bump connectivity of the ROIC and HgCdTe photodiode array by prober level room temperature measurements. The charge integrated on the integration capacitor in various modes of operation has been used to estimate the connectivity. This method is useful for initial IRFPA technology development.

Raghvendra Sahai Saxena, Sushil Kumar Semwal, R. K. Bhan, R. Pal, R. K. Sharma

Current–Voltage and Capacitance–Voltage Characteristics of Ni/p-Si (100) Schottky Diode Over a Wide Temperature Range

In this study the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of metal semiconductor Ni/p-Si(100) based Schottky diode on p- type silicon measured over a wide temperature range (60–300 K) have been studied on the basis of thermionic emission diffusion mechanism and the assumption of a Gaussian distribution of barrier heights. The parameters ideality factor, barrier height and series resistance are determined by performing plots from the forward bias current–voltage (I–V) and reverse bias capacitance–voltage (C–V) characteristics. Thus, the barrier height for Ni/p-Si(100) Schottky diode obtained between 0.2053 and 0.513 eV, and the ideality factor (η) between 8.8792 and 2.4351 for 60–300 K range. A simple method, involving the use of

ϕ

b versus 1/T data, is suggested to gather evidence for the occurrence of a Gaussian distribution of barrier heights and obtain value of standard deviation 0.06402 (60–300 K).

Rajender Kumar, Subhash Chand

Effect of Substrate Temperature on the Structural and Optical Properties of CdTe Films Prepared by Thermal Evaporation

CdTe thin films are prepared on corning 1,737 glass using simple thermal evaporation technique at three different substrate temperatures, viz., room temperature, 100 and 200 °C. The dependence of the structural and optical properties of the prepared films on the substrate temperature at the time of deposition is studied using X-ray diffraction, UV–Vis–NIR spectroscopy and Raman spectroscopy. The prepared films at higher substrate temperature are having larger grain size and also improved crystallinity. Small changes in the optical band gap and the refractive index are observed. The films prepared at 200 °C have the lowest energy band gap of about 1.45 eV and also highest refractive index. Three phonon modes, i.e., Te–Te A1, LO and TO modes are observed in all the samples. The phonon band centers of the observed modes are slightly blue shifted with increase in substrate temperature. Observed significant broadening in the phonon modes in comparison to the bulk values could be due to the confinement effect in nanocrystals. The surface morphology of the films is studied using field emission scanning electron microscope.

Lalhriatzuala, Ramakrishna Madaka, Pratima Agarwal

Study of Schottky Barrier Contact in Hybrid CdSe Quantum Dot Organic Solar Cells

The hybrid organic solar cell devices are fabricated from P3HT:PCBM with Quantum dot CdSe materials.The Schottky barrier built-in potential of 0.45 V was calculated from C–V measurements. The photo current (J

Light

− J

Dark

) equals to zero at compensation voltage of 0.61 V. The depletion width (W) of an abrupt Schottky junction is calculated using carrier density. The Cole–Cole plot of the device is also determined from different bias voltage in the range of 10–1 MHz. The device can be modeled as the combination of RC parallel circuit.

M. Ramar, R. Manimozhi, C. K. Suman, R. Ahamad, Ritu Srivastava

Measurement of Variation of Minority Carrier Lifetime in 8 MeV Electron Irradiated c-Si Solar Cells Using RRT Method

The variation of minority carrier lifetime in c-Si solar cells due to the irradiation of 8 MeV electrons of various doses ranging from 5 to 100 kGy was studied. The minority carrier lifetime and diffusion length of c-Si solar cells were determined before and after irradiation using the reverse recovery transient (RRT) method. The minority carrier lifetime is found to decrease with increasing electron dose, which is interpreted as due to the creation of non-radiative recombination centers which affects the diffusion current. The minority carrier diffusion length decreases exponentially with electron dose. The reduction in diffusion length due to electron irradiation will reduce the conversion efficiency of solar cells.

Sathyanarayana Bhat P, Asha Rao, Sheeja Krishnan, Ganesh Sanjeev, Suresh E. Puthanveettil

Front Surface Glass Texturization for Improved Performance of Amorphous Silicon Solar Cell

Texturization of the front glass of superstrate type single junction amorphous silicon solar cells has been carried out in order to achieve the dual role of reducing reflectivity as well as increasing the angular scattering of light leading to more light trapping. Glass texturization has been carried out chemically using an aqueous solution of HF. To achieve a controlled etch rate (a) KOH or (b) AgNO

3

is added to the aqueous solution of HF for selectively masking the front surface of glass with K

2

SiF

6

or Ag nano-islands respectively. It may be noted that such texturing also increases the parasitic absorption due to larger light paths in the absorbing thin conducting oxide layer present in such superstrate type single junction amorphous silicon solar cells. Thus, an optimization is necessary for the top glass surface texturing for enhancement of the efficiency of the solar cell. It is found that the reflectivity reduces by about 3 % in both the cases from the reference value of about 9.5 %. Moreover, it is seen that the diffused transmission characteristics of the textured glass surface increases significantly (~30 %) which is expected to improve the overall short circuit current and efficiency of the solar cell. The present method of texturing the glass superstrate for anti reflection and light trapping in thin-film solar cells appears to be a promising method amenable for large scale applications.

Sonali Das, Avra Kundu, Chandan Banerjee, Prasenjit Dey, Swapan K. Datta, Hiranmay Saha

Study of Light-Induced Structural Changes Associated with Staebler-Wronski Photo-Degradation in Micro-Crystalline Silicon Thin Films

Hydrogenated amorphous silicon based devices lacks behind in their fruitful applications as it suffers from major drawback i.e. light induced degradation or S–W effect. Various theories or literature have been discussed so far, but exact mechanism is still an open challenge in research community. We report on light-induced structural changes in amorphous and micro/nano crystalline silicon by performing light soaking experiments for nearly 8 h. Under vacuum accompanied with the effect of annealing on these films. The electrical, structural and optical properties were analyzed with the use of dark and photo conductivity measurements, Raman spectroscopy, Scanning electron microscopy (SEM) and Photoluminescence studies. Using Raman spectroscopy, we estimated the bond distortion w.r.t degradation percentage in samples. We observed that crystallinity as well as particle size are responsible for increase or decrease in degradation of photoconductivity. Having 72.25 % crystallinity highly stable microcrystalline silicon films showed 1.44 % photo-degradation.

Sucheta Juneja, S. Sudhakar, Kalpana Lodhi, Srishti Chugh, Mansi Sharma, Sushil Kumar

Phosphorous Doped Hydrogenated Amorphous Silicon Carbide Films Deposited by Filtered Cathodic Vacuum Arc Technique

In the present work, we report the growth and characterization of phosphorous doped hydrogenated amorphous silicon carbide (a-SiC: H) films deposited by filtered cathodic vacuum arc technique using solid silicon target as cathode in presence of acetylene gas. The films have been characterized by x-ray diffraction, dark conductivity, activation energy, optical band gap, scanning electron microscopy, energy dispersive x-ray analysis and residual stress. The effect of arc current on the properties of P doped a-SiC: H films have been studied.

R. K. Tripathi, O. S. Panwar, Ajay Kumar Kesarwani, Sreekumar Chockalingam

Silicon Surface Passivation by Al2O3 film using Atomic Layer Deposition

Silicon surface passivation is studied using Al

2

O

3

thin film deposited by thermal process using atomic layer deposition (ALD) method. Minority carrier lifetime measurements showed that the film passivate the silicon surface effectively. Capacitance–voltage measurement confirms the activation of negative fixed charges after sintering at 400 °C.

P. K. Singh, Vandana, Neha Batra, Jhuma Gope, CMS Rauthan, Mukul Sharma, Ritu Srivastava, S. K. Srivastava, P. Pathi

Estimation of Photovoltaic Cells Model Parameters using Particle Swarm Optimization

Swarm intelligence based technique has been used in this work for the estimation of parameters of photovoltaic cells using the two-diode model of the photovoltaic cell. Particle Swarm Optimization algorithm was used to fit the calculated current–voltage characteristics of the photovoltaic cells to the experimental one. The estimated parameters were the generated photocurrent, saturation currents, series resistance, shunt resistance and ideality factors. The proposed approach was validated using industrial photovoltaic cells.

Vandana Khanna, B. K. Das, Dinesh Bisht, Vandana, P. K. Singh

Sustainable Organic Polymer Solar Cells Using TiO2 Derived From Automobile Paint Sludge

We demonstrate green synthesis of TiO

2

nanoparticles (Nps) derived from automobile paint sludge (APG) and its application in the development of sustainable and solution processable polymer solar cells (PSCs). The APG contains TiO

2

> 35 % of its weight with several surfactants, organic polymers and ~ 2 to 10 % inorganic matter depending on the type of paints used. The TiO

2

is generally present as micro sized particles in the APG which on hydrothermal treatment transform into nano sized particles. These organic matter is thermally extracted by a specially designed reaction vessel, where as the inorganic impurities are removed by repeated washing with dilute acids and bases. The TiO

2

Nps are characterized by SEM imaging, EDX analysis, powder XRD, TG/DTA and FTIR, spectroscopy techniques. The TiO

2

Nps are re-suspended in methanol for application in PSCs as an efficient electron transport layer. The TiO

2

layer was spin coated on bulk hetero junction active layer of low band gap donor polymers P3HT with PCBM as electron acceptor. The performance of the TiO

2

Nps is analyzed by fabricating devices in ITO/PEDOT:PSS/active layer/TiO

2

/Al configuration. The present work has implication for ultra low cost and sustainable PSCs with advantage of recycling of a highly hazardous industrial waste.

Jitender Gaur, Vishal Bharti, Shilpa Jain, Annu Sonania, Dibyajyoti Mohanty, Gauri D Sharma, Suresh Chand

CIGS thin film Deposition by Dual Ion Beam Sputtering (DIBS) system for Solar cell Applications

Currently in solar cell market the cost effective Copper Indium Gallium Selenide (i.e. Cu(In,Ga)Se

2

or CIGS) thin film solar cells are showing most promising result among all other thin film solar cell technology. Typically, CIGS thin films for photovoltaic devices are deposited by co-evaporation or by deposition of the metals with or followed by treatment in a selenium environment. These methods have several disadvantages and complications. In this article, we describe an alternative of the same. We described the CIGS thin films of 1 μm thickness grown onto soda lime glass substrates by Dual Ion Beam Sputtering (DIBS) system from a single quaternary target with the composition of Cu (In

0.70

Ga

0.30

)Se

2

in a single step route without any additional selenization at different temperatures from 100 °C to 400 °C. These CIGS thin films are characterized for the solar cell application. The effects of the substrate temperature, on the structural and optical property of the CIGS layers were studied at room temperature using X-Ray Diffraction and UV–Vis-NIR spectrophotometer. The obtained results of the thin films includes the crystallinity, grain size, absorption coefficient and band gap energy etc. In structural property the preferred orientation of grains along highly oriented the (112) plane is observed. Crystallinity of the films improved with increasing substrate temperature as evidenced by the decrease of FWHM from 0.64 °C to 0.29 °C The strong influence of growth temperature on these properties were observed. We demonstrated that growth temperature can be varied in order to optimize the film properties and improve device performance.

Shaibal Mukherjee, Vishnu Awasthi, Sushil K. Pandey, Saurabh K. Pandey, Shruti Verma, Mukul Gupta, Uday P. Deshpande

MEMS and Sensors

Frontmatter

Study of Fluid Flow in Micro-channel Based Devices

Microfluidic technology has contributed significantly to the advancement of Bio-MEMS, flow sensors, micromixers and heat sinks for chip cooling. Micro-channels play an important role in development of small scale fluid flow devices and are one of the essential parts of micromachined fluid systems. In addition to connecting different devices, micro-channels and micro-chambers are used in many other fields including biochemical, genetics, physics and industrial applications. In order to design micro-channel, it is very important to understand the mechanism and fundamental differences involved at micro scale fluid flow. This paper presents an analytical study of flow mechanism in micro channels, with a focus on effect of geometric dimensions and flow rate on the various micro-hydrodynamics parameters of trapezoidal shaped micro-channel. Pressure drop, friction-factor and Reynold number calculations for microchannel of different geometrical dimensions are presented. The channel width are in the range of 100–1,000 µm, where as the depth of the channel is taken as 50 microns. Water is used as the working fluid. The study of entrance and exit effects on pressure drop across micro-channel has also been considered. The study provides vital information for design and analysis of micro-channel devices, and is helpful in selection of the possible channel configuration for a specific application.

Renuka Saxena, Shailesh Kumar, Amita Gupta

Graphite Based Sensor for LPG and CO Detection

One of the top design priorities for gas sensors is developing simple, low-cost, sensitive and reliable sensors to be built in handheld portable devices. The present paper deals with the fabrication technique and sensing mechanism of a novel room temperature sensor for detection and quantification of highly inflammable Liquefied Petroleum Gas (LPG) and Carbon monoxide gas at room temperature. The detection of the presence of LPG and CO gas is based on the fact that the resistance of the sensing material of the device changes drastically when exposed to LPG and CO uniquely. This sensor is highly sensitive, repeatable, cost effective, portable, flexible and water proof; very less response as well as degassing time, simple fabrication technique, requires no extra dopants and can easily measure the leakage of LPG and CO as low as 80 ppm at ambient conditions. The fabricated graphite film sensors for the detection of LPG and CO gas have several advantages over conventional metal oxide sensors such as reduced size, low power consumption, room temperature operation and flexibility.

Prashant Shukla, Nitin Bhardwaj, Vasuda Bhatia, Vinod Kumar Jain

Development of Lactate Biosensor Based on Electro Statically Functionalized Graphene Oxide Bound Lactate Oxidase

The search for new advanced materials is an important area of contemporary research in numerous disciplines of science and the development of many new technologies. Great attention has been paid in recent years to nano-structured materials of different chemical composition, produced as nanoparticles, nanowires or nanotubes. In various fields of chemical analysis, there have been an increasing number of applications of graphene based material. In the present work Lactate oxidase has been immobilized onto the surface of graphene oxide polymeric film through glutraldehyde coupling. This film acted as a working electrode. The resulting biosensor was characterized electrochemically and detection performances were evaluated. It can keep more than 80 % of its initial activity after continuously using for three months. The sensor is also unaffected by the various serum interfering agent. The present lactate biosensor showed excellent properties for the sensitive determination of lactic acid with good reproducibility and remarkable stability.

Meeta Gera, V. K. Jain, N. Suman

Humidity Sensing Response of Poly (3, 4-ethylene dioxythiophene)-poly (styrene sulphonate) and Its Nanocomposites

Poly (3, 4-ethylene dioxythiophene)-poly (styrene sulphonate) (PEDOT:PSS) is the most commonly used conducting polymer in organic LEDs, photovoltaics and sensor applications. We studied the humidity sensing properties of this polymer and its nanocomposites. It has been found that chemically treated single walled carbon nanotubes and PEDOT:PSS polymer nanocomposites shows good humidity sensing properties.

Kanchan Saxena, Omita Nanda, Nidhi Gupta, Pramod Kumar, V. K. Jain

PECVD Grown SiC Cantilevers with Dry and Wet Release

Cantilevers made out of PECVD grown SiC films are reported here. The cantilevers were realized in two different methods—isotropic etch (Dry release) and combination of wet etch and critical point dry release. The dry release process for Silicon isotropic etch results in excellent etch selectivity against SiC, to provide released structures. The optimized wet release process is able to overcome stiction issues to provide excellent SiC cantilevers.

Adithi Umamaheswara, Smitha Nair, Lavendra, Suman Gupta, M. N. Vijayaraghavan, Navakanta Bhat

MEMS Mirrors for Optical Switching Applications

MEMS based optical switches are being developed for application in communication networks. Although, very useful, most of them have relatively simple functionality. Many of these systems are now at a commercialization stage. Silicon based optical switches with electrostatic actuating are proving to be very attractive due to their application in fiber optics telecommunication. In this paper, a study of 2 × 2 optical switch is presented. The analytical and FEM results are discussed.

Aklesh Kumar Meena, Ranvir Singh, Vinita Gond, Amita Gupta

Design Aspects of a MEMS Based Bi-axial Mirror

MEMS based bi-axial mirrors have become important because of their application in the field of projection display systems. Here, design aspects of a MEMS based bi-axial mirror are presented and discussed.

Aklesh Kumar Meena, Ranvir Singh, Yashoda Parmar, Vinita Gond, M. Islam, Amita Gupta

Electrochemical Synthesis of p-CuO Thin Films and Development of a p-CuO/n-ZnO Thin Film Hetero-Contact for Gas Sensing

Thin films of p-CuO has been synthesized using a simple electrochemical technique (Galvanic deposition) on Indium Tin Oxide (ITO) coated glass substrates and on ZnO/ITO coated glass substrates. The films were characterized using X-ray Diffraction Technique (XRD) and UV–VIS spectroscopy. The surface morphology of the films was studied using FESEM. Measurements of electrical properties of the n-ZnO/p-CuO heterojunction were carried out to understand its suitability for gas sensing application.

Amrita Ghosh, Bibhuti Bhusan Show, Nillohit Mukherjee, Swapan K. Datta, Gautam Bhattacharya, Anup Mondal

Optical Characterization of Anodically Grown Silicon Dioxide Thin Films

In silicon-based fabrication processes, silicon dioxide (SiO

2

) thin film is most widely used insulating film in the manufacture of integrated/discrete devices and microelectro-mechanical systems (MEMS). Various techniques have been established for the synthesis of silicon dioxide thin films. However, anodic oxidation method offers key advantages over the high temperature processes such as low cost, simple experimental set-up, low temperature, etc. In the present work SiO

2

thin films are developed on silicon using anodic oxidation technique at room temperature. Constant voltage mode is employed in order to investigate the effect of applied voltage and the electrolyte stirring on thickness, refractive index and chemical bonds of the as-grown oxide films. Spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR) are employed to characterize various properties of the as-grown oxide films. At the applied voltage of 250 V, the highest thickness of 134 nm is obtained. The oxides developed at higher voltages are slightly silicon rich. The present study is aimed to explore the applications of silicon anodic oxidation in MEMS/Microelectronics fabrication.

Ashok Akarapu, Prem Pal

Study on Design and Simulation of Zinc Oxide Based Film Bulk Acoustic Resonator for RF Filters

Film Bulk Acoustic Resonator (FBAR) technology is one of the enabling technologies which fulfill the two major needs of wireless industry i.e. high operating frequency range and miniaturization of RF components. This paper presents the design and simulation of a FBAR with zinc oxide as the piezoelectric layer. In the present work, FBAR has been designed and simulated for piezoelectric thickness of 0.75 and 1.25 μm. A thickness of 0.75 μm corresponds to a simulated frequency of 3.57 GHz and can be used for WiMAX applications whereas a 1.25 μm thick layer is suitable for GSM applications at 1.94 GHz. The suitability of the structure for RF filter applications has been observed in terms of electromechanical coupling coefficient.

Jyotirmoy Dutta, Atul Vir Singh, Sonal Singhal, Madhur Deo Upadhayay

Design and Analysis of RF MEMS Shunt Capacitive Switch for Low Actuation Voltage and High Capacitance Ratio

This paper presents the study of Radio-Frequency Micro-Electro Mechanical (RF MEMS) switches and is inspired by their superior performance over the contemporary solid-state devices (MESFET, PIN diode etc.) and their excellent performance in the field of communications for the past decade. The study focuses on the realization of electrostatically actuated capacitive shunt switches with the main emphasis being on low actuation voltage (or pull-down voltage) and high capacitance ratio of the switch. The beam used is meander based for low-spring constant and is suspended over a coplanar waveguide (CPW) transmission line. Low actuation voltage is achieved in the range of 2–6 V with a down-state capacitance of 5.53 pF and a reasonably high capacitance ratio of 117. The insertion loss (S

21

) of the switches is less than 0.75 dB in the ON-state. During the OFF-state, the switches have isolation higher than 40 dB from 10–20 GHz. A Switching time of 11.47 μs was achieved.

Johnson Taye, Koushik Guha, Srimanta Baishya

Design and Development of MEMS Pressure Sensor Characterization Setup with Low Interfacing Noise by Using NI-PXI System

In this paper, we present a self-contained automated MEMS pressure sensor testing system. The system is controlled by LabVIEW software, with a custom-designed menu-driven user interface in the OPEN-WIN window environment. It is capable of performing multi-parameter measurements including linearity, hysteresis, sensitivity and operating temperature. The built-in software package allows the user to perform statistical analysis with image capability. This system is applicable for device research, where, the “statistical” testing data provides the reliable experimental information and device mass production, where the interfacing noise free testing data and the generated graph can help in product sorting, quality control, and further processing. Fabrication and packaging issues of MEMS pressure sensor are also discussed in terms of device performance.

Kulwant Singh, Sualeh Akhtar, Soney Varghese, J. Akhtar

Ag–ZnO Nanocomposite for Multi Gas Sensing Applications

Nanocomposites of Ag/ZnOnanorodswere prepared by a simple sonochemical method. The morphology and crystallinity of the nanocomposite were studied using SEM, AFM and X-Ray Diffractometer. XRD analysis shows a good crystalline property of both Ag nanoparticles and ZnO nanorods. Scanning electron microscopy (SEM) images of the Ag/ZnO films revealed the uniform distribution of Ag nanoparticles on ZnO nanorods. The effect of Ag on gas sensing properties was investigated. It was found that composite film provides good response to low concentrations of gases and shows excellent selectivity in the presence of interfering gases like NH

3

and NO

2

at room temperature.

Monika Joshi, Vidur Raj, S. Pranauv Balaji, Ayushi Kaushik

Effect of Cu3N Layer Thickness on Corrosion and Ni Release Properties of Cu3N/NiTiCu Shape Memory Thin Films

In the present study Cu

3

N/NiTiCu/Si thin films were successfully grown using magnetron sputtering technique. The thickness of nanocrystalline Cu

3

N was varied from 200 to 415 nm and effect of Cu

3

N layer thickness on structural, phase transformation, morphological, corrosion and Ni release properties of Cu

3

N/NiTiCu/Si was studied. The NiTiCu/Si thin films exhibit shape memory effect even after depositing Cu

3

N protective layer. Cu

3

N(200, 305 nm)/NiTiCu/Si thin films possess low corrosion current density with higher corrosion potential and therefore exhibit better corrosion resistance as compared Cu

3

N(415 nm)/NiTiCu/Si film. The amount of Ni ions released in SBF solution was almost not detectable in case of 200, 305 nm thin Cu

3

N layer but increased significantly on increasing the thickness of Cu

3

N layer to 415 nm. Cu

3

N(415 nm)/NiTiCu/Si exhibit much reduced corrosion resistance and Ni ion release impeding capability. This can be explained by decrease in adherence of Cu

3

N(~415 nm) layer on NiTiCu/Si thin film due to its increased thickness. This work is of immense technological importance due to its variety of its BioMEMS applications.

Navjot Kaur, Davinder Kaur

Design of a Piezoresistive MEMS Resonator Operating Beyond 1 GHz

This paper focuses on design of Piezoresistive MEMS resonator for operation beyond 1 GHz, using FEM simulations. A method for simulation of transconductance of MEMS resonator is presented for first time. Lateral bulk acoustic mode of Twin beam resonator is simulated using the proposed method to get transconductance-frequency plot. Dimensions of the structure are optimized for best operation near 1.3 GHz. Design aspects of resonator including biasing effects, damping effects and anchoring variations are studied.

Vikrama Vamshi Pasula, Deleep R. Nair, Amitava DasGupta

A Novel Test Structure for Testing of ROIC for 2D Bolometric IR FPA

We propose a novel test structure and the technique for testing the readout integrated circuit (ROIC) without fabricating microbolometers on it. In general, each ROIC cell has two ends that are connected with a microbolometer. We propose to use two additional metal lines in row-column configuration in such a way that all the ROIC cells have one of their ends connected to a row metal line and other end to the column metal line. With this configuration, an M × N test array will have only M + N nodes and easy testability of all MN cells by simply wire bonding M row pads with the M microbolometers fabricated separately as M × 1 linear array. Also, the non-uniformity within the row will represent the non-uniformity contributed only by the ROIC. Therefore, fixed pattern noise (FPN) in the ROIC alone may also be tested by this method.

Raghvendra Sahai Saxena, Sushil Kumar Semwal, Nilima Singh, R. K. Bhan

Thick PECVD Germanium Films for MEMS Application

Plasma enhanced chemical vapour deposition (PECVD) of thick germanium (Ge) films (~1 m) on silicon di-oxide (SiO

2

) at low temperatures is described. A diborane pre-treatment on SiO

2

films is done to seed the Ge growth, followed by the deposition of thick Ge films using germane (GeH

4

) and argon (Ar). Further, the effect of hydrogen (H

2

) dilution on the deposition rate is also investigated. The film thickness and morphology is characterized using SEM. Use of high RF power and substrate temperature show increased deposition rate. EDS analysis indicates that these films contain 97–98 atomic percentage of Ge. A recipe for anisotropic dry etching of the deposited Ge films with 10 nm/min etch rate is also suggested.

B. Rashmi Rao, Navakanta Bhat, S. K. Sikdar

Design and Fabrication of Wafer-Level Package for RF MEMS Switch Using BCB

RF MEMS devices like switches are made up of movable fragile structures that need to be encapsulated in microcavities to protect them from contamination or damage during the subsequent wafer dicing and packaging process steps. This packaging method is referred to as wafer-level or zero- level packaging and enables the whole MEMS wafer to be packaged in the controlled environment of the clean room. This paper reports the design and fabrication of a packaging solution based on micromachined high resistivity silicon and BCB sealing. Theoretical studies have been carried out to study the effects of the cavity height and the width of the BCB sealing ring on the coplanar transmission line up to 40 GHz. Fabrication of the package has been demonstrated and RF measurements have been done on a 50 Ω line to validate the simulations. It is found that BCB has a negligible effect on the insertion loss of the CPW line.

Renu Sharma, Isha Yadav, Anupriya Katiyar, Milap Singh, Shaveta, Tulana Saha, Mohd. Imran, Praveen Kumar, K. K. Jain, R. K. Bhan, P. Dutta

Anisotropy and Surface Roughness of Silicon Etched by TMAH in Presence of Potassium Persulfate: A Comparison with Ammonium Persulfate

In this work the effects of adding potassium persulfate during anisotropic etching of silicon using Tetra Methyl Ammonium Hydroxide (TMAH), on the ratio of {100}: {111} etch rates, oxide etch rate and surface roughness, in comparison with adding ammonium persulfate, are studied. The amount of potassium persulfate added was varied to understand the effect of potassium ions on anisotropy and surface roughness in presence of persulfate ions, which is used to obtain smooth surfaces. It is experimentally demonstrated that the addition of Potassium persulfate increases the etch rates and anisotropy of the Silicon etching with TMAH solution without increasing the surface roughness, compared to the usually used ammonium persulfate.

Madhuri Suresh, Radha Bhaskar, P. Savitha, K. N. Bhat

A Novel Room Temperature Ammonia Gas Sensor Based on Diamond-Like Nanocomposite/c-Silicon Heterojunction

Thin amorphous diamond-like nanocomposite (a-DLN) films are deposited on p-type crystalline silicon (c-Si) by plasma assisted chemical vapour deposition (PACVD) technique to use it as an ammonia (NH

3

) gas sensor operable at room temperature. The non-linear current–voltage (I–V) characteristic of a-DLN/c-Si heterojunction shows a very good rectifying property of the junction in air and quick sensitivity in NH

3

gas at room temperature. The current output in reverse biased condition of the a-DLN/c-Si heterojunction is ~ 15 times higher in NH

3

than in air. Sensor also shows a good recovery property to the original state, even at room temperature. Sensing material is characterized by using Field Emission Scanning Electron Microscope (FESEM), Fourier Transform Infrared Spectroscopy (FTIR) and UV–VIS Near-IR Spectroscopy, to understand the sensing behaviour.

S. Das, S. Jana, D. De, U. Gangopadhyay, S. Garain, S. Ray, A. Mondal, P. Ghosh

Fabrication of High Density Silicon Microprobe Array

High density microprobe arrays have been widely used for several applications. In this work, we are presenting a simple one mask fabrication process of silicon based high density microprobe array (20 × 20) with an array pitch of 20 μm. The dimension of single microprobe structure is: 20 μm × 20 μm × 120 μm. Here, photoresist of 2.5 μm thickness is used as masking layer during the fabrication of microprobe array. The microstructure array is fabricated by using deep reactive ion etching (DRIE). Fabrication aspects of silicon based high density microprobe array are discussed.

Shankar Dutta, Isha Yadav, Praveen Kumar, Anand, Ramjay Pal

Study of PDMS as Dielectric Layer in Electrowetting Devices

An electrowetting-on-dielectric (EWOD) device by using Polydimethylsiloxane (PDMS) as dielectric layer has been fabricated. Aluminium metal film is used for EWOD electrode fabrication. Teflon AF 1600 thin film is coated to improve hydrophobicity and reduce liquid sticking (found in PDMS surface). Both PDMS and Teflon layer is deposited by spin coating. Direct coating of Teflon, on top of PDMS layer, results in poor quality film, because of inherent hydrophobic nature of PDMS. So, Oxygen plasma treatment of PDMS surface is carried, before Teflon coating. Movement of water droplet (conductivity: 250 μ S/m) is obtained at 150 V DC voltage supply. Present study demonstrates a simple, cost and time effective fabrication procedure for EWOD device.

Shiraz Sohail, Debanjan Das, Soumen Das, Karabi Biswas

Stress Engineering Using Si3N4 for Stiction Free Release of SOI Beams

We report on the effect of thin silicon nitride (Si

3

N

4

) induced tensile stress on the structural release of 200 nm thick SOI beam, in the surface micro-machining process. A thin (20 nm/100 nm) LPCVD grown Si

3

N

4

is shown to significantly enhance the yield of released beam in wet release technique. This is especially prominent with increase in beam length, where the beams have higher tendency for stiction. We attribute this yield enhancement to the nitride induced tensile stress, as verified by buckling tendency and resonance frequency data obtained from optical profilometry and laser doppler vibrometry.

Suman A. Gupta, Apoorva Shenoy, Monisha, V. Uma, M. N. Vijayaraghavan, Navakanta Bhat

Comparative Study on Temperature Coefficient of Resistance (TCR) of the E-beam and Sputter Deposited Nichrome Thin Film for Precise Temperature Control of Microheater for MEMS Gas Sensor

Nichrome (Ni–Cr 80/20 wt %), alloy of Ni and Cr is used as a microheater element of the MEMS microhotplate embedded in the metal oxide based gas sensor. Nichrome is used as a heater element for its unique properties like high resistivity, low cost, low Temperature Coefficient of Resistance (TCR), anti oxidant, anti corrosive nature, no need for extra adhesive layer as required for Pt or Au and also compatibility with standard silicon fabrication technology. Microheater with low TCR is the very important property to avoid localized hotspot and precisely controlling the active area temperature of the microhotplate for sensing the gases at different temperature. In this paper, Temperature Coefficient of Resistance (TCR) of the thin film of nichrome was studied by depositing two popular physical vapor deposition (PVD) methods one is Electron Beam Evaporation and other is DC Sputtering. The TCR parameter was extracted by placing the resistor in wafer level on the thermal chuck and measurement was done by varying the temperature of the thermal chuck using ATT System from room temperature up to 200 °C and measuring the resistance of the microheater using Agilent 4284A LCR meter. The structural characterization was carried out for finding the grain size and elemental composition of Ni/Cr of the as-deposited thin film using FESEM and EDX respectively. The effect of annealing at 300 °C temperature in N

2

ambient of the e-beam deposited nichrome thin film on the TCR was also analyzed.

Surajit Das, Jamil Akhtar

Enhanced TCR with Room Temperature TMI for Potential Application in Microbolometer

Polycrystalline samples Nd

0.5

La

0.2

Sr

0.3

MnO

3

(NL) and Nd

0.5

La

0.2

Sr

0.3

MnO

3

+ 0.2Ag (NL + Ag) are prepared by solid state reaction technique. These compounds are found to be crystallized in orthorhombic structural form. On addition of silver (Ag), the temperature coefficient of resistance (TCR) is significantly improved near the metal–semiconductor/insulator transition (T

MI

) temperature. The T

MI

is increased from 288 K (for NL) to 302 K (for NL + Ag). Enhancement in TCR is explained on the basis of the grain growth and their connectivity. The reduction in grain boundaries between grains improved the conduction process. High TCR (5.1 %) and room temperature T

MI

of NL + Ag sample are useful characteristics for MEMS-based uncooled microbolometer for infrared detection.

Sudarshan Vadnala, Saket Asthana, Prem Pal

High Resolution Quadrant Detector Based Tip-tilt Sensor for Adaptive Optics

A high resolution Quadrant Detector (QD) based tip-tilt sensor for adaptive optics system is tested with a 4 mm laser beam. The laser beam is made to displace by a nano-positioning stage with 30 nm resolution. The sensor is found to respond at the displacement (min.) of 1 μm. The corresponding error signal is found to be 4 mV. The sensor is also tested for minimum power requirement with corresponding bandwidth.

Awakash Dixit, Vikash Porwal, Aditya K. Mamgain, S. K. Mishra

Nanotechnology and Emerging Areas

Frontmatter

Raman Spectroscopy and Molecular Dynamics Simulation Studies of Carbon Nanotubes

Carbon Nanotubes (CNTs) are honey-combed lattices rolled up into cylinders with nanometer-sized diameters and lengths on the order of microns. Actively studied for over thirty years, and with now greater availability, single-walled nanotubes are predicted to significantly impact semi-conductor physics, owing to their unique electronic properties and reduced dimensionality. Some of the semi-conductor technologies in which CNTs are expected to hold significant promise are in super-capacitors, hydrogen storage materials, nanoprobes, and bio-chemical sensors. Necessary to many future CNT applications is a clear understanding of their thermal properties, as nano-devices based on single-walled and/or multi-walled nanotubes may have to experience high temperatures during the manufacturing process while being operated. This, in turn, affects the reliability due to thermal expansion and the ensuing strain in the electronic devices. The coefficient of thermal expansion (CTE) of CNTs is a key property for nano-electronic applications. In this paper we will present Raman Spectroscopy measurements of single-walled carbon nanotubes as a function of temperature in the range 25–200 °C, as well as Molecular Dynamics (MD) simulations that incorporate current state-of-the-art models of Carbon–Carbon interactions associated with the thermal expansion of carbon nanotubes.

Prabhakar Misra, Daniel Casimir, Raul Garcia-Sanchez

Equilibrium and Nonequilibrium Carrier Statistics in Carbon Nano-Allotropes

The integrated carrier statistics of Dirac Fermions in carbon allotropes comprising graphene nanolayer, graphene nanoribbons (GNR) and carbon nanotubes (CNTs) is described. Nonequilibrium Arora’s Distribution Function (NEADF) is the basis of transformation of randomly oriented to directed moments in the presence of an electric field, leading to saturation that is limited to the intrinsic Fermi velocity

$$ v_{Fo} \approx 10^{6} m/s $$

for carbon-based devices. In the semiconducting state, the intrinsic velocity is the saturation velocity that is substantially below

$$ v_{Fo} $$

depending on the carrier concentration. Velocity-field relation arising from NEADF is elaborated by a tanh function as a result of degeneracy temperature that rises linearly with carrier concentration in the strongly degenerate regime. Current–voltage characteristics and high-field-initiated resistance surge indicate the transformed nature of existing paradigms.

Vijay K. Arora, Arkaprava Bhattacharyya

Power Generation Using Graphene and Silver Nano Composite Based Paper Battery

This paper gives a detailed insight on a revolutionizing and gratifying solution of energy storage through Paper Batteries and provides an in-depth analysis of the same. A Paper Battery is a flexible, ultrathin energy storage and production device formed by combining grapheme/silver nano-particles with a conventional sheet of cellulose-based paper. A Paper Battery can function both as a high-energy battery and super capacitor, combining two discrete components that are separate in traditional electronics. The promising fabrication technique allows the Paper Battery to provide both long-term steady power production and self-life. Being environment friendly, flexible, biodegradable, light-weight and non-toxic, flexible Paper Batteries have impending adaptability to power the next generation of electronics, medical devices and hybrid vehicles, allowing for radical new designs and medical technologies. This paper is aimed at understanding and analyzing the electrical properties and physical characteristics of Paper Batteries; to study its advantages, potential applications, limitations and disadvantages. This paper also aims at highlighting the construction and method of fabrication of Paper Battery and look for alternative means of massproduction.

Suman, Prashant Shukla, Meeta Gera, Vinod Kumar Jain

Study of Forster’s Resonance Energy Transfer Between MWCNT and Phenoxazone 660

The laser induced fluorescence has been used to study the interaction between phenoxazone with multiwalled carbon nanotubes. The Phenoxazone P660–MWCNT pair shows Forster’s resonance energy transfer (FRET) from Phenoxazone P660 (donor) to MWCNT (acceptor). The FRET efficiency of this pair increases with the increase of the acceptor concentration. The Stern–Volmer plot indicates static as well as dynamic quenching with a maximum efficiency of 87 % observed in this pair. The result of the study indicate the possible applications of MWCNT-Phenoxazone pair as a spectroscopic nano-ruler.

Mohd. Shahid Khan, Javid Ali, Avshish Kumar, Mushahid Husain

How to Achieve High Quality Large Area Monolayer Graphene with Field Effect Mobility of 20,000 cm2/Vs

High quality graphene monolayers were grown using chemical exfoliation method by sonicating the highly ordered pyrolytic graphite in organic solvents. Properties of as exfoliated graphene layers were found to be strongly dependent on dielectric constant of the solvents. This was corroborated by confocal Raman spectroscopy and electrical measurements. Graphene samples exfoliated in solvents with low dielectric constant show diminutive D band intensities and excellent field effect mobility of 20,000 cm

2

/Vs and in solvents with high dielectric constant, D band intensity increases and mobility reduces to 11,000 cm

2

/Vs due to doping induced defects in graphene layers. Our results also show up shift in minimum conductivity point with doping level due to inhomogeneous potential induced by point defects near Dirac point.

Pawan Kumar Srivastava, Subhasis Ghosh

Field-Emission Study of Carbon Nanotubes Grown by Low Pressure Chemical Vapour Deposition on Single and Dual Layer of Catalyst

In the present research work, CNTs are synthesized by Low Pressure Chemical Vapor Deposition (LPCVD) method at 600 °C. The Si substrate is coated with Ni (single layer) in one sample and Ni over Cr layer (dual layer) as a catalyst on the other sample by using RF- sputtering method. Three precursor gases Acetylene (C

2

H

2

), Ammonia (NH

3

) and Hydrogen (H

2

) with flow rates 10, 50 and 50 sccm respectively are allowed to flow through the tube reactor for 20 min. Acetylene is used as source gas and Ammonia to etch the amorphous carbon and for the further reduction of catalyst size. The as grown CNTs sample was characterized by Scanning Electron Microscope (SEM) and Raman. Raman Spectra show the graphitic nature of CNTs grown on dual layer of catalyst. Field enhancement factor is increased in the dual layer coated samples.

Javid Ali, Avshish Kumar, Samina Husain, Shama Parveen, Sunny Khan, Harsh, M. Husain

A Novel Nanographite Based Non-enzymatic Cholesterol Sensor

This work reports a new non enzymatic cholesterol detection sensor using functionalized nanographite. This nanostructure was characterized by FTIR, SEM, TEM, XRD and EDX. Using nanographite as a working electrode, Ag/Agcl as a reference and platinum as a counter electrode a good non enzymatic cholesterol sensor was constructed. Under optimal detection conditions, the constructed sensor had a linear range of 50 to 500 mg/dl for cholesterol with a correlation co-efficient of 0.99784. Sensitivity of the developed cholesterol sensor is 1.0587 μA/mg. This biosensor showed good reproducibility, stability and low interferences.

Bhawana Singh, Nitin Bharadwaj, V. K. Jain, Vasuda Bhatia

Electron Beam Lithography Patterning of 50 nm Trenches and Islands on PMMA

Growth of patterned semiconductor nanostructures is important for development of semiconductor nanodevices. Nanostructures are fabricated using either top down or bottom up approach. In top down approach the nanostructures are obtained by trimming down a bulk semiconductor whereas bottom up approach selectively adds atoms to create nanostructures. Different type of patterning is required for both the strategies. For top down approach substrates are patterned using lithography in such a manner that islands of resist are created so that they can be used as masks whereas bottom up approach requires holes to be patterned on substrates so that nanostructures can be selectively grown in the holes. This paper discusses the processes both for patterning of 50 nm islands as well as trenches in PMMA using electron beam lithography.

S. S. Sarkar, A. Rudra, R. K. Khatri, R. Muralidharan

Lattice Specific Heat of Graphene Nanoribbons

The lattice specific heat,

C

L

, of graphene nanoribbons (GNRs) is studied, based on the elastic continuum model. An expression for

C

L

is obtained taking into account the modification of acoustic phonon dispersion due to spatial confinement. Considering the contributions from longitudinal, transverse, torsional and flexural acoustic phonon modes, numerical calculations of

C

L

, as a function of temperature, are presented for

T

< 3,000 K. With increase in temperature,

C

L

is found to increase up to

T

< 1,200 K and then tend to saturate to classical limit of 2,078 J/kgK at higher temperatures, the major contribution being from flexural modes. At low temperatures

C

L

is found to decrease with increase in GNR width.

A. S. Nissimagoudar, N. S. Sankeshwar

Catalytic Growth of 3C-SiC Nanorods: Structural and Optical Characterization

Cubic (3C)-silicon carbide (SiC) nanorods were grown in an inductively heated horizontal cold wall quartz tube reactor by atmospheric pressure chemical vapor deposition (APCVD). A single source precursor, hexamethyldisilane (HMDS) was used for both silicon and carbon and hydrogen (H

2

) as a carrier gas. A 10 nm thin film of nickel was used as a catalyst. As-grown nanorods were characterized by x-ray diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FESEM) to confirm the crystalline nature and the surface morphology of these nanorods. The room temperature photoluminescence (RTPL) spectrum showed the violet-blue emission from these nanorods.

Afzal Khan, Chacko Jacob

Synthesis and Characterization of Phosphorus Doped Hydrogenated Silicon Films by Filtered Cathodic Vacuum Arc Technique

Phosphorous doped hydrogenated silicon thin film has been deposited by filtered cathodic vacuum arc technique at different substrate temperatures at a fixed hydrogen gas pressure. X-ray diffraction, electrical conductivity and optical band gap and scanning electron microscopy have been used to characterize the properties of films.

Ajay Kesarwani, O. S. Panwar, R. K. Tripathi, Sreekumar Chockalingam

Room Temperature Ferromagnetism in ZnO Using Non-magnetic Ions

We report the growth and characterization of high quality Cu and Ag, doped ZnO thin films for different concentration from 0.1 to 10 % by RF magnetron sputtering. The X-ray diffraction study has shown single phase Wurtzite type ZnO thin films with no evidence of secondary phases. Room temperature ferromagnetism (RTFM) was observed in Cu and Ag doped ZnO thin films, in which magnetic moment decreases with increasing Cu and Ag content.

Zaheer Ahmed Khan, Anshu, Subhasis Ghosh

Stress Induced Degradation in Sputtered ZrO2 Thin Films on Silicon for Nano-MOSFET’s

This paper deals with stress induced degradation in reactively sputtered ZrO

2

/Si interface deposited in N

2

containing plasma and pure argon ambient. MOS C–V and I–V techniques were used for interface characterization. Leakage current and shift in flat band voltages were compared for ZrO

2

films deposited with and without N

2

containing plasma. The presence of nitrogen in the ZrO

2

films RF sputtered in nitrogen containing plasma was verified by glancing angle X-ray diffraction (XRD). The effect of post deposition annealing and current stress carried out on the samples deposited in different ambient was investigated. Electrical and reliability characteristics of annealed devices were found to be better than non annealed samples. The flat band voltage shifts towards negative value on being stressed, indicating positive charge trapping in the high k dielectric layer. The samples grown in pure argon ambient showed enhanced leakage as compared with samples grown in nitrogen ambient on application of stress.

Ashwath Rao, Joyline Dsa, Saurabh Goyal, B. R. Singh

Synthesis of Vertical Graphene by Microwave Plasma Enhanced Chemical Vapor Deposition Technique

Vertical graphene was synthesized on nickel substrate using microwave plasma enhanced chemical vapor deposition technique by varying gas pressure from 5 to 30 Torr under various mixing ratios of argon, hydrogen and methane. The Raman spectra show two major fingerprints of graphene, 2D peak at 2,700 cm

−1

and G peak 1,580 cm

−1

. Scanning electron microscopy microstructure revealed flower like graphene structure which could find applications in gas sensing and field emission due to high surface-to-volume ratio.

Atul Bisht, Sreekumar Chockalingam, O. S. Panwar, B. P. Singh, Ajay Kesarwani, Jagdish Chand

Raman Characteristics of Vertically Aligned Single Wall Carbon Nanotubes Grown by Plasma Enhanced Chemical Vapor Deposition System

Vertically aligned single wall carbon nanotubes (VA-SWCNTs) of diameter 0.8–1.5 nm suitable for semiconducting applications have been successfully grown on Iron catalyst film using Plasma Enhanced Chemical Vapor Deposition (PECVD) System. The Raman signal positions of the spectra in RBM, D and G bands confirm the existence of SWCNTs. The grown sample is excited with laser excitation wavelengths, 633 nm from He–Ne laser. The field emission study has been carried out in a vacuum chamber under a pressure of 10

−6

torr. Highly sensitive, capital intensive equipment such as Field Emission Scanning Electron Microscope (FESEM), has been used to identify the state and morphology of nanotube samples.

Avshish Kumar, Samina Husain, Shama Parveen, Javid Ali, M. Zulfequar, Harsh, M. Husain

A Novel of Synthesis of Iron Oxide Nanoparticles for Separation of Water–Oil, Water-Diesel, Water-Petrol

In the present investigation Fe

2

O

3

nanoparticles have been synthesized by chemical route. The characterization of crystallinity has been done using XRD. The morphology and bonding of Fe

2

O

3

NPs were investigated using SEM, Photolumiscence spectroscopy and FTIR. SEM analysis reveals that synthesized Fe

2

O

3

are cubical in shape with a size of 30–40 nm. It was also found that the nanoparticles are highly stable in nature.

Bharat Sharma, Monika Joshi, R. P. Singh

Electrical Characteristics of SWCNT Chemiresistor

This paper presents fabrication of microelectrode structure for SWCNT chemiresistor and its electrical characterization. SWCNT film was deposited over microelectrodes forming SWCNT chemiresistor. Its I–V characteristics have been measured and its dependency over temperature was studied.

D. Bala Sekhar, William R. Taube, A. Kumar

Studies on Nanostructured V2O5 Deposited by Reactive DC Magnetron Sputtering

Nanostructured V

2

O

5

thin films were deposited on to cleaned Si (100) substrates using reactive DC magnetron sputtering technique at various substrate temperatures (T

s

). The grain sizes of the films were around 140–210 nm. The field emission-scanning electron micrographs showed nanosheet like structure grown perpendicular to substrate. The optical bandgap energy of the films increased with increase in T

s.

The films deposited at 100 °C exhibited a temperature coefficient of resistance (TCR) value of −2.5 %/ °C.

P. Deepak Raj, Sudha Gupta, M. Sridharan

Surface Enhanced Raman Scattering on Anodized Alumina Templates for Bio-sensing Applications

SERS substrate was fabricated by depositing silver on anodized aluminum oxide (AAO) template. The thickness of the AAO template was 200 nm with 40 nm circular pore and 15 nm spacing. SERS effect was observed on these metal coated structures due to electric field enhancement around the edge of the pores. Para-Nitrophenol (pnp) solution of 10

−6

M concentration was detected which refers to an enhancement factor of 10

4

.

Deepak Ranjan Nayak, Navakanta Bhat, Siva Umapathy

Impact of Scaling Gate Oxide Thickness on the Performance of Silicon Based Triple Gate Rectangular Nwfet

Previously, simulations were carried out on the classical drift diffusion technique which no longer supports the present day criteria in a 3D domain. Now-a-days, we enhance our simulation capabilities by performing simulation at an atomistic level rather than bulk which gives us best result in a 3D domain. To fulfill this requirement, the first full-band quantum and atomistic transport simulator OMEN is designed for post CMOS devices. In this paper, we have investigated the effect of scaling gate oxide thickness of rectangular Si-NWFET on its device performance in terms of transfer characteristics, output characteristics, electron doping, drive current (I

on

), leakage current (I

off

), switching speed (I

on

/I

off

) and transconductance. We concluded that the conductivity of Si-NWFET and doping density of electrons in Si-NWFET enhances with the reduction in oxide thickness. Also, we have concluded that with the reduction in oxide thickness, drive current of the device increases and leakage current of the device decreases which is an improvement over CNTs and conventional MOSFETs. Further, the switching speed (I

on

/I

off

) of the device and transconductance (g

m

) enhances by reducing the oxide thickness.

Deepika Jamwal, Devi Dass, Rakesh Prasher, Rakesh Vaid

Characterization of Carbon Nanotube Field Effect Transistor Using Simulation Approach

As the size of the Si MOSFET approaches towards its limiting value, various short channel effects appear to affect its performance. Carbon nanotube field effect transistor (CNTFET) is one of the novel nanoelectronic devices that overcome those MOSFETs limitations. In this paper we have studied the effect of scaling carbon nanotube (CNT) diameter, insulator thickness and high-k dielectric materials on current-voltage characteristics of co-axial gated ballistic n-type CNTFET. The device metrics such as drive current (I

on

), leakage current (I

off

), I

on

/I

off

ratio, transconductance, subthreshold slope (S) and drain induced barrier lowering (DIBL) are also studied in this paper. The simulation results obtained are then compared with conventional nanoscale n-type MOSFET. It has been concluded that CNTFET seem to provide better performance than conventional nanoscale n-type MOSFET in term of high speed capability and lower switching power consumption.

Devi Dass, Rakesh Prasher, Rakesh Vaid

Electrical Characterization of n-ZnO Nanowires/p-Si Based Heterojunction Diodes

We report electrical characteristics of n-ZnO NWs/p-Si based heterojunctions diode fabricated by oxidation of thermally deposited metallic Zn on Al:ZnO coated p-Si substrates. The surface morphology of ZnO NWs has been investigated by atomic force microscopy (AFM). The carrier donor concentration of the ZnO NW films and barrier height of the heterojunction diode estimated from the

C

V

characteristics are 1.54 × 10

15

cm

−3

and 0.75 eV respectively. The estimated values of the barrier height and ideality factor from room temperature

I

V

characteristic are 0.73 eV and 2.13 respectively. As obtained value of barrier height from

C

V

characteristic is a bit higher then

I

V

characteristic, indicates presence of barrier inhomogeneity at the n-ZnONWs/p-Si interfaces. Furthermore, the value of series resistance

$$ \left( {{\text{R}}_{\text{s}} } \right) $$

has also been determined from forward bias I–V characteristics using Chueng’s function

Divya Somvanshi, S. Jit

Chalcogenide Micro/Nanostructures by Evaporation Condensation Method

Chalcogenide (As-S-Se) micro/nanostructures have been successfully synthesized using thermal evaporation-condensation method in evacuated glass ampoule. The nanowires have diameter ranging between 10 and 20 nm and they are few microns in length. The structures are characterized using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X Ray Diffraction (XRD) for their morphology, composition and structure respectively. These nanowires show promising applications in the field of nanoelectronics and nanophotonics.

Swati Raman, Ravi K. Kumar, M. Husain

Structural and Optical Characterization of ZnO Nanoparticles Synthesized Via Low Temperature Precipitation Method

ZnO nanoparticles were successfully synthesized via a low temperature and simple precipitation method. Crystallinity, phase purity and structural properties of as prepared material were analyzed by X-ray diffraction pattern (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) with 32 nm average crystallite size. Additionally, the optical properties of the sample were investigated by using Uv-Vis-NIR and Photoluminescence spectroscopy with an energy band gap at 3.09 eV. These results should be useful in developing optoelectronic devices such as UV-LEDs and laser diodes.

Mohammad Ramzan Parra, Fazila Syed, M. Husain, Fozia Z. Haque

Synthesis and Optical Properties of Pure and Eu+3 Ion Doped ZnO Nanoparticles Prepared Via Sol-Gel Method

Eu-doped Zinc Oxide nanoparticles, with wurtzite hexagonal phase have been successfully synthesized via simple sol-gel method. Crystallinity, morphologies and optical properties of the as-prepared nanoparticles were investigated by X-ray diffraction (XRD), Atomic Force microscopy (AFM) and photoluminescence spectroscopy (PL). XRD results indicated that trivalent europium ions were successfully doped into the crystal lattice of ZnO matrix with ~13 nm average crystallite size. X-ray peak broadening analysis was used to evaluate the average crystallite size and lattice strain by the Williamson-Hall (W-H) method. Photoluminescence spectroscopic results indicated that the emission peak located at ~610 nm was attributed to the 4f–4f intra-shell transition of

5

D

0

7

F

2

incorporated into wurtzite ZnO host by substitution on the Zn sub lattice.

Padmini Pandey, Mohammad Ramzan Parra, Rajnish Kurchania, Fozia Z. Haque

Synthesis of CNTs by Arc Discharge Method in Water Bath

Carbon nanotubes are very important class of carbon materials which have a variety of applications. Synthesis of these materials in bulk at low cost is of both industrial and academic interest at present. Presently, we have synthesized CNTs using dc-arc discharge between two graphite rods in water bath at different voltage and current conditions and characterized by SEM, RAMAN, TEM methods to optimize the appropriate growth conditions to achieve good quality and high yield CNTs.

G. B. V. S. Lakshmi, Saif Ahmad Khan

Comparative Study of SWNTs Dispersion in Organic Solvent and Surfactant Along with Observation of Multilayer Graphene

Organic solvents and surfactants both are used to disperse Carbon Nanotubes (CNTs), but the efficiency of both are different. Surfactant much efficiently disperse CNTs in comparison to organic solvent. As opposed to aqueous solutions, hydrophobic Single Wall Nanotubes (SWNTs) are easily wetted by organic solvent Di-Methyl Formamide (DMF) and therefore, to reduce self assembling of bundles and ropes of CNTs. Surfactants are effective at concentration 1 wt % for dispersion of SWNTs. Sodium Dodecyl Benzene Sulfonate (SDBS) effectively disperse aqueous solution of SWNTs at 0.5 mg/ml and further solution is diluted to concentration 0.3 mg/ml. Probe type sonication is used to make homogeneous solution and for initial exfoliation of CNTs. Small bundles and single SWNTs can be separated from bundles and amorphous carbon by using centrifugation. Atomic Force Microscopy (AFM) is employed to image the dispersed state of SWNTs by using organic solvent and aqueous solution of surfactant. Graphene presence and density difference of these are also observed at different concentration of SWNTs.

Geetika Kanwar, Pankaj B. Agarwal, Shriniwas Yadav

Hydrothermal Growth and Characterization of ZnO Nanomaterials

ZnO nanostructures are synthesised by hydrothermal method from zinc acetate dihydrate (Zn(CH

3

COO)

2.

2H

2

O) using water as a solvent. NaOH solution in water is used to adjust the pH of the growth solution. The ZnO nanostructures are synthesised from solution with pH varying from 7 to 12. The structural, morphology, and optical properties of the grown ZnO nanostructures are characterized by XRD, FESEM, EDS, UV-vis and photoluminescence spectroscopy. The growth of hexagonal shaped nanocrystals is observed at pH value of 7 and as the pH of the growth solution is increased the morphology of the nanomaterials changes from hexagonal rod shapes to hexagonal platelet shapes.

Shashidhara Bhat, B. V. Shrisha, K. Gopalakrishna Naik

Grafting of Ag Nanoparticles on GO Nano Sheets for Water Purification

In the present work we report a simple and effective method for the purification of water. The grafting of metallic Ag was done over hydrophilic nature of GO sheets. The morphology and crystallinity of the nanocomposite were studied using SEM and X-Ray Diffractometer. The metal-GO sheet exhibits excellent water treatment performance could be helpful in purifying water especially the control of bacteria and Total Dissolved Solid (TDS).

Jimmy Mangalam, Monika Joshi

Effect of ZnO Loading on the Electrical Characteristics of Graphene Oxide-ZnO Based Thin Film Transistors

Reduced graphene oxide based composites filled with metal oxide nanoparticles are emerging as active materials in transistor applications. Here we report fabrication of transistors on poly methyl methacrylate (PMMA) dielectric using graphene oxide-ZnO nanocomposite as channel layer with 5 wt % ZnO nanorods were loaded in graphene oxide. The transistors showed ambipolar conductivity with the value of hole and electron mobility as 0.74 and 0.67 cm

2

/Vs, respectively, on PMMA dielectric. This indicates that percolation threshold could not be achieved with 5 % ZnO though the low concentration of ZnO reduces the GO partially and the n-type conductivity slightly increases compared to the thermally or chemically reduced GO based TFTs.

S. Mahaboob Jilani, P. Banerji

Lattice Thermal Conductivity of Silicene

The lattice thermal conductivity,

κ

p

,

of suspended silicene is studied, using theoretical model and numerical calculations, over a wide temperature range (2 <

T

< 400 K). Explicit contributions from the in-plane longitudinal acoustic (LA) and transverse acoustic (TA) phonons and out-of-plane flexural (ZA) phonons are taken into account. Scattering of phonons by system boundaries, impurities and other phonons via umklapp process are considered. Numerical results presented show that, at low temperatures, the ZA phonon contribution is dominant, whereas at higher temperatures the LA and TA phonon contributions become important. A step-like behavior of

κ

p

at low temperatures is observed due to the dominance of the ZA phonons. The study highlights the relative importance of the three acoustic phonon modes in limiting

κ

p

, which could have important implications for the thermoelectric effect in silicene.

M. D. Kamatagi, James Elliott, N. S. Sankeshwar, A. Lindsay Greer

Gas Sensing Properties of Tin Oxide Nano-Powder Synthesized via Sol–Gel Route

In the present work SnO

2

nano-powder has been synthesized by a sol–gel method. Thick film pastes are then developed by using as-synthesized SnO

2

nano-powder with two different concentrations (0.5 and 1 wt %) of palladium (Pd). After that, the thick film sensor has been fabricated for the detection of various concentrations (1–5 vol %) of Liquefied Petroleum Gas (LPG). The investigations depict that sensing response of Pd-doped SnO

2

is size dependent and small particles are found to be enhance the sensitivity of the sensor. The mechanism for LPG sensing has been also described.

Meenakshi Choudhary, V. N. Mishra, R. Dwivedi

Structural and Optical Studies of Sol–Gel Deposited Nanostructured ZnO Thin Films: Annealing Effect

Zinc oxide (ZnO) thin films were deposited by sol–gel spin coating method on the glass substrate and then the film was annealed at 350, 450, 550 C for 1 h. Effect of annealing temperature on the structural and optical properties of the film was investigated. Annealed ZnO thin films are polycrystalline with (002) preferential orientation. The information on Crystalline size is obtained from the full width-at half- maximum (FWHM) of the diffraction peaks. The surface morphology of the films was investigated by atomic force microscopy (AFM). Surface roughness was found minimum (8.4 nm) for ZnO sample annealed at 450 C. The maximum transmittance of 87 % is observed for the film annealed at 450 C. The optical band gap value decreased and crystalline size increased with increasing the annealing temperatures.

Mohsin Ganaie, Shabir Kumar, Adam A. Bahishti, M. Zulfequar

Design of 2D Photonic Crystals for Integrated Optical Slow-Light Applications

2D photonic crystal waveguides have been designed in both GaAs/AlGaAs and SOI platforms for slow-light applications in planar lightwave circuits. The design parameters have been optimized using commercial FDTD tool. The extracted group velocity of a single-mode SOI photonic crystal waveguide has been shown to be 3–10 times slower than that of a photonic wire waveguide operating in third generation optical communication window (λ ~ 1,550 nm). This reduced group velocity has been exploited to design a plasma dispersion based compact SOI modulator with L

π

~70 μm.

Rashmi Joshi, Bijoy Krishna Das, Nandita DasGupta

Morphological and Optical Studies of Electrodeposited Selenium Nanowires

Selenium nanowires were fabricated by electrodeposition technique. Polycarbonate track-etched membrane with cylindrical nanopores was used as template. Scanning electron microscopy was employed to characterize the morphology and the size of fabricated selenium nanowires. The optical properties of the grown nanowires have been determined using UV–visible spectroscopy.

Narinder Kumar, Rajesh Kumar, Sushil Kumar, S. K. Chakarvarti

Effect of Metal Contact on CNT Based Sensing of NO2 Molecules

The electronic structure of Carbon Nanotubes (CNTs) is highly sensitive to the presence of foreign molecules. Also due to the large surface area of CNTs, there is a higher chance of them getting exposed to the surrounding gas molecules. This property is utilized in CNT based gas sensing applications. In this work, we have studied a zigzag CNT (Z-CNT) and simulated the transmission spectra and I–V characteristics using Density functional theory and Extended Huckel theory. Then the change in electrical properties of the Platinum (Pt) contacted Z-CNT on adsorption of NO

2

molecules was simulated. Exposure of NO

2

increases the conductance of the CNT by extracting electrons from the CNT making it p-type. Higher concentration of gas molecules results in larger change in the conductance due to the accumulated effects of individual gas molecules underlining its effectiveness in the formation of a gas sensor. Pt makes a schottky contact with the zigzag CNT and it was found that there is an appreciable change in the transmission spectrum as well as I-V characteristics making Platinum contacted zigzag CNT a good material for NO

2

detection. This study is aimed at understanding effect of adsorption of NO

2

and Pt contact on the I–V characteristics.

Neeraj Jain, S. Manhas, A. K. Aggarwal, P. K. Chaudhry

Synthesis of Zinc Oxide Nanostructures by Chemical Routes

Zinc oxide nanostructures were prepared by chemical route using Zinc nitrate and hexamethylenetetramine as starting material. Two different processes: simple chemical route with and without electrodeposition were carried out for obtaining thin films on glass substrates. Different structures were obtained using the two techniques. SEM images show that zinc oxide prepared by simple chemical route using a seed layer is in the form of uniform structure consisting of nanorods of very short length. On the other hand nano rods of larger dimensions were obtained by the electrodeposition technique on transparent conducting glass plates.

Nidhi Gupta, Omita Nanda, Pramod Kumar, V. K. Jain, Kanchan Saxena

Effect of Growth Temperature on the Diameter Distribution and Yield of Carbon Nanotubes

Growth of carbon nanotubes (CNTs) on iron sputtered Si substrate has been done by using self design Thermal Chemical Vapor Deposition (TCVD) at atmospheric pressure. Parameters of CNTs are highly dependent on the growth temperature. A strong relation between CNT’s diameter, yield and growth temperature was found. The experiments were done in the temperature range of 750–900 °C with an interval of 25 °C. It was found that at 750 °C there was no growth of CNT. However, at 775 °C, the horizontal network of CNTs having diameter range of 8–12 nm with sufficient yield was observed. As we increase the temperature, an increase in CNT’s diameter and decrease in yield was found. These results demonstrate that diameter and yields of CNTs can be controlled with the growth temperature.

Nishant Tripathi, Prabhash Mishra, Harsh, S. S. Islam

Growth and Characterization of MOCVD grown InP Quantum Dots on Si for Monolithic Integration

Integration of III-V based optoelectronics with Si microelectronics is one of the basic needs for next generation low cost monolithically integrated circuits. InP quantum dots (QDs) has been grown on Si substrate as a step for the integration of III-V based optoelectronics on Si. In this paper the growth details and the properties of the dots has been discussed. The luminescence property of the QDs has been analyzed with the help of the band alignment of the nano heterojunction. The carrier confinement mechanism has been discussed as well.

Nripendra N. Halder, Souvik Kundu, Rabibrata Mukherjee, D. Biswas, P. Banerji

Synthesis of Multilayer Graphene by Filtered Cathodic Vacuum Arc Technique

Filtered cathodic vacuum arc technique has been used to deposit amorphous carbon films of varying thickness on catalytic nickel thin film grown on SiO

2

/Si substrates. Subsequently these a-C films were annealed in vacuum at 650 °C. Raman spectroscopy together with optical microscopy and scanning electron microscopy has revealed multilayer graphene formation.

O. S. Panwar, Ajay Kesarwani, Atul Bisht, Sreekumar Chockalingam, S. R. Dhakate, B. P. Singh, R. K. Rakshit

Role of Coherent Nanostructures and Mass Fluctuation on Thermoelectric Properties in Iodine Doped PbTe0.5Se0.5

Further development to achieve high value of the figure of merit in existing high performance thermoelectric materials necessitates reduction in thermal conductivity near the amorphous limit without affecting the high values of Seebeck coefficient and electrical conductivity. In this study, we have demonstrated the effect of coherently embedded nanostructures of PbTe/PbSe and mass fluctuation of Te and Se atoms on the thermoelectric properties in iodine doped PbTe

0.5

Se

0.5

. Compared to the pristine PbTe, the combined effect of coherent nanostructures and mass fluctuations of Te and Se atoms is found to reduce the thermal conductivity significantly with slight decrease in electron mobility paving the path for a high figure of merit.

P. K. Rawat, P. Banerji

Structural and Elastic Properties of Cd1−xNixFe2O4 Ferrites

The structural and elastic properties of nickel substituted cadmium ferrites have been synthesized by solid state reaction method. The XRD pattern and FTIR spectral analysis confirms the formation of single phase cubic spinel structure of ferrite phase without any additional peaks. The linear variation of lattice parameter with nickel content it confirms the Vegard’s law. The structural parameters can be estimated through X-ray diffraction analysis. The estimated cation distribution of ferrite has been verified by comparing the observed and theoretical lattice parameters. The elastic parameters of ferrites such as longitudinal modulus, rigidity modulus, young’s modulus, bulk modulus and Debye temperatures were estimated through FTIR technique. The compositional dependence of structural and elastic properties of Cd-Ni ferrites has been reported in this article.

P. B. Belavi, L. R. Naik

Investigations on: How the Band Lineups, Band Offsets and Photoluminescences of an InxGa1−xN/GaN Quantum Well change with Biaxial Strain

Due to the large controversy regarding the material parameters of InGaN material systems, the band line up of In

x

Ga

1−x

N/GaN heterostructures still remains controversial. In this paper we calculate the band positions for strained and unstrained In

x

Ga

1-x

N/GaN interfaces considering the band gap of InN 0.7 eV, recently settled after long debate. Large changes of conduction band offsets and valance band offsets are pointed out when the previously reported band gap of InN, 1.9 eV is substituted by 0.7 eV.

Partha Pratim Bera, Siddhartha Panda, Dipankar Biswas

Effect of Dielectric Environment on Carrier Mobility in Chemically Exfoliated Graphene

We have studied the effect of dielectric environment on transport properties of graphene based field effect transistors where graphene layers were grown in various organic solvents with varying dielectric constant using chemical exfoliation. Electrical measurements of graphene transistors clearly indicate that dielectric constant of the solvents has no significant effect on charge carrier mobility in graphene.

Pawan Kumar Srivastava, Subhasis Ghosh

Fabrication of SWCNTs Based Flexible, Trace Level NO2 Gas Sensor Using Spray Coating Technique

Flexible nitrogen dioxide (NO

2

) sensor using thin-film single-walled carbon nanotubes (SWCNTs) was fabricated by spray coating on Polyethylene terephthalate (PET) substrate. The SWCNTs dispersed in deionized water using sodium dodecyl sulphate (SDS) as the surfactant. The uniformly dispersed SWCNTs were deposited on the PET film by using spray gun, and then SDS surfactant was removed from the sample for its proper gas sensing. This was done by dipping the sample into the HNO

3

and then washing with the deionized water followed by heat treatment at 110 °C for 1 h. The resultant devices were tested for sensing NO

2

molecules and a trace level NO

2

sensing was detected. The sensing mechanism was attributed by the electron transfer to the SWCNTs, as a result, the NO

2

reduced on the nanotube surface.

Prabhash Mishra, Neha Tabassum, Choksh Bhola, Vaibhav Sharma, Kamran Zaidi, Manish Gupta, Harsh, S. S. Islam

Growing Monolayer, Bilayer and Trilayer Reproducibly By Chemical Exfoliation

A prerequisite for the development of graphene based electronics is how to obtain the desired no. of graphene layers reproducibly. Here we present a method for the synthesis of monolayer, bilayer and trilayer of graphene via chemical exfoliation of HOPG in various solvents. The graphene monolayer, bilayer and trilayer were confirmed by Transmission Electron Microscopy, Raman spectroscopy and universal optical transmittance spectroscopy.

Premlata Yadav, Pawan Kumar Srivastava, Subhasis Ghosh

Electrical Characteristics of Si/ZnO Core–Shell Nanowire Heterojunction Diode

In this paper, we have presented the electrical characteristics of the silicon nanowire (SiNW)/Zinc oxide (ZnO) core–shell heterojunction diode. In this work ZnO thin film was conformally deposited by atomic layer deposition (ALD) method on vertically aligned SiNW arrays, fabricated by electroless metal deposition and etching method with the help of ultrasonication. The current–voltage and capacitance–voltage characteristics were measured to show the electronic properties of the device. The current–voltage characteristics show the nonlinear rectifying nature of the SiNW/ZnO core–shell heterojunction diode with ideality factor and barrier height of 3.2 and 0.68 eV respectively. The barrier height measured from C–V characteristics is 0.97 V. The difference between barrier heights calculated from both I–V and C–V characteristics show that barrier inhomogeneities can be present between the interface of Si and ZnO. However, the satisfactory performance of junction characteristics ideality factor and turn-on voltage of the Si/ZnO core–shell heterojunction diodes indicates their potential applications in optoelectronics and photonics.

Purnima Hazra, S. Jit

Novel Attributes in Scaling Issues of an InSb-Nanowire Field-Effect Transistor

Due to the inherently lower bandgap and larger permittivity of III–V materials, III–V MOSFETs are more susceptible to short-channel effects (SCE). They show promising improvement in drain-induced barrier lowering (DIBL), due to suppressed SCE. In this paper, we present a scaling study of nanowire field-effect transistors (NWFETs) using a two-dimensional model and explore the scaling issues in device performance focusing on transconductance characteristics, output characteristics, average velocity, Switching speed, subthreshold swing and with different gate oxide thicknesses (t

ox

) and nanowire diameters. Also, our results show the output conductance, transconductance, voltage gain and average electron velocity at the top of the barrier get improved in NWFETs with thinner t

ox

and larger nanowire diameter.

Rakesh Prasher, Devi Dass, Rakesh Vaid

Inductively Coupled Plasma Etching of GaAs with High Anisotropy for Photonics Applications

Inductively Coupled Plasma Reactive Ion Etching (ICPRIE) of Gallium Arsenide (GaAs) using BCl

3

/Cl

2

/Ar plasma was carried out for Photonic Crystal (PhC) applications. The recipe was optimized by varying various etch parameters. While the addition of N

2

improved sidewall angle, the surface roughness increased for N

2

flow rate beyond 1 sccm. An optimized BCl

3

/Cl

2

/Ar/N

2

recipe with flow rate 6/1/11/1 sccm was used to etch holes in GaAs. For 4 μm diameter circular pattern, etch rate of about 556 nm/min with a sidewall angle of 86° and surface roughness of the order 1 nm were obtained.

I. Seethalakshmi, Rashmi Joshi, Nandita Das Gupta, Bijoy Krishna Das

Growth and Characterization of Nitrogen Incorporated Amorphous Carbon Films Having Embedded Nanocrystallies

This paper reports the growth and characterization of nitrogen incorporated amorphous carbon films having embedded nanocrystallites deposited by filtered anodic jet carbon arc technique. The films are characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman, residual stress and nanoindentation. The properties are found to depend on the substrate bias. The film deposited at −60 V substrate bias shows maximum hardness of 24 GPa and elastic modulus of 215 GPa.

R. K. Tripathi, O. S. Panwar, Ishpal, Sreekumar Chockalingam

Impact of Silicon Body Thickness on the Performance of Gate-all-around Silicon Nanowire Field Effect Transistor

As the size of the MOSFET is reduced, various short channel effects (SCEs) appears that degrade its performance. Multigate nanowire FET is one of the novel nanoelectronic devices that overcome these MOSFET limitations. The silicon nanowire field effect transistors with multiple gates around the silicon channel can significantly improve the gate control and are considered to be promising candidates for the next generation transistors. In this paper, we have considered the performance limits of Si nanowire field effect transistors in a Gate All Around (GAA) structure. Furthermore, we have studied the effects of Silicon body thickness on the characteristics of GAA silicon nanowire FET. It has been observed that Si-NWFET afford high drive-current (I

on

), high transconductance and hence high gain. Thus, GAA configuration has good control of gate, which reduces the short-channel effects to a great extent.

Richa Gupta, Devi Dass, Rakesh Prasher, Rakesh Vaid

Room Temperature Synthesis of Al:ZnO Quantum Dots

Al Doped and undoped ZnO nanoparticles were synthesized at room temperature followed by quenching at relatively low temperature for size control. The XRD patterns of Al doped nanoparticles were similar to those of undoped nanoparticles, indicating the presence of Al ions at substitutional sites and that the AZO retained the crystal structure of ZnO. The presence of Al ions was confirmed by the XPS study. UV Visible spectroscopy reveals blue shift which in turn indicates an increase in the band gap.

Muchhal Laksh, Krishna Richa, O. P. Sinha

Phonon-limited Diffusion Thermopower in Graphene

Phonon-limited diffusion thermopower,

S

d

, of graphene is studied, for 10 < T < 300 K taking into account the influence of substrate. The electrons are assumed to be scattered by the acoustic phonons (APs), optical phonons as well as the surface optical phonons (SOPs). The first order perturbation distribution function

ϕ

(

E

), as a function of carrier energy

E

, is computed by directly solving the linearized Boltzmann equation using the iteration technique. Numerical calculations of energy dependence of

ϕ

(

E

), bring out the characteristics of phonon scattering mechanisms. Determined mainly by APs at low temperatures and then by SOPs,

S

d

for SiO

2

substrate is found to increase with T reaching a room temperature value of ~30 μV/K.

K. Rizwana Begum, N. S. Sankeshwar

Humidity Sensing by Chemically Reduced Graphene Oxide

Reduced Graphene Oxide (RGO) has been synthesized chemically by reducing micron-sized Graphene Oxide (GO) flakes using sodium borohydride solution. Indium Tin Oxide (ITO) coated glass was taken as the basic substrate for sensing layer deposition. Sensitivity tests for relative humidity (RH) measurements were carried out at five different concentrations of humid air at room temperature. The response of the sensor was found to vary between 3.8 for 10 % humid air and 20.4 for 100 % humid air. Characterizations of the sensing layer were carried out using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM).

Ruma Ghosh, Anupam Midya, Sumita Santra, Samit K. Ray, Prasanta K. Guha

Toxicity Study of TiO2, ZnO and CNT Nanomaterials

Nanotechnology based industry is expected to turn into a one trillion dollar industry as their applications are emerged in various fields like consumer products, medicine, and the environment. Rapid development of Nanosciences, therefore, resulted in significant synthesis of various inorganic and organic Nanomaterials followed by their characterization which are highly applicable globally. However, potential negative effects of this burgeoning industry were not well studied, especially toxicity of nanoparticle on aquatic environments. Present study reports the cytotoxicity of Carbon Nanotubes, ZnO nanoparticle and TiO

2

nanoparticle to

Chlorella

sp. algae. Nanoparticles suspensions were prepared in various concentrations from 0.03 to 0.12 g/l using algal test medium and further quantified by UV/Vis spectroscopy. Algal cultures were maintained in 3–4 K Lux cool white fluorescent light on 16 h/8 h alternate light and dark cycles at 28 ± 2 °C temperature. A growth study of algae was done by measuring the transmittances of algal cultures on 680 nm wavelength at different time interval. It has been observed that with the increase of the concentrations nanoparticles, the growth of algae decreases simultaneously. It shows 90 % growth in presence of CNT’s, 86 % growth in presence of TiO2 and 38 % growth in presence of ZnO nanoparticles as compare to control i.e. 100 %. Reduce growth of Chlorella cells in presence of CNT, TiO2 and ZnO nanoparticles indicates clearly cytotoxicity of these nanoparticles. In our study we found ZnO 62 % toxic, TiO2 14 % toxic and CNT 10 % toxic against

Chlorella

sp.

Rupesh Kumar Basniwal, Vasuda Bhatia, Nitin Bhardwaj, V. K. Jain

Synthesis and Characterization of Zinc Oxide Nanoparticles for Ethanol Detection

Pure phase, zinc oxide (ZnO) nanoparticles were synthesized at lower temperature by microwave assisted auto combustion synthesis method. As-synthesized particles had sizes ~50 nm with spherical shape. Gas responses of the nanocrystalline ZnO film were measured by exposing the film to ethanol gas vapors. It was found that the sensors exhibited various sensing responses to ethanol gas at different operating temperature. The lower limit of detection was observed to be at 170 °C for 200 ppm ethanol.

Sachin Tyagi, Sarita Devi, Ashok K. Paul

Structural and Optical Studies of Sol-Gel Deposited Nanostructured ZnO Thin Films: Annealing Effect

Zinc oxide (ZnO) thin films were deposited by sol–gel spin coating method on the glass substrate and then the film was annealed at 350, 450, 550 °C for 1 h. Effect of annealing temperature on the structural and optical properties of the film was investigated. Annealed ZnO thin films are polycrystalline with (002) preferential orientation. The information on Crystalline size is obtained from the full width-at half- maximum (FWHM) of the diffraction peaks. The surface morphology of the films was investigated by atomic force microscopy (AFM). Surface roughness was found minimum (8.4 nm) for ZnO sample annealed at 450 °C. The maximum transmittance of 87 % is observed for the film annealed at 450 °C. The optical band gap value decreased and crystalline size increased with increasing the annealing temperatures.

Sanjeev Kumar, Fouran Singh, A. Kapoor

Gold Catalyzed Plasma Assisted Growth of Germanium Nanoneedles

A systematic study of Gold catalyzed growth of Ge nanoneedles by PECVD at low temperatures (<400

°

C) is presented. Morphology, growth rate and aspect ratio of the needles are studied as a function of power, gas flow rate and chamber pressure. Nanoneedles were grown at pre-defined positions with catalytic particles obtained by e-Beam Lithography and lift off. This opens up the possibility of using Ge Nano needles in photovoltaic, nanoelectronics and nanosensor device applications.

Sangeeth Kallatt, Smitha Nair, M. N. Vijayaraghavan, Navakanta Bhat

Studies on Structural Parameters of ZrO2–SnO2 Binary System

Nanocrystalline powders of ZrO

2

–SnO

2

system with molar ratio 0.75/0.25 were prepared at room temperature by sol–gel wet chemical route. The as-prepared samples were annealed at 500, 700 and 850 °C for 3 h. Structural parameters of annealed powdered samples were determined by X-ray diffraction (XRD). The crystallite size was calculated using Debye–Scherrer formula as well as Williamson-Hall relation and then compared. Other structural parameters such as lattice parameters, micro-strain, dislocation density and activation energy were also estimated. The functional groups present in the samples were confirmed by Fourier transform infrared spectroscopy (FTIR).

Saruchi Surbhi, Sushil Kumar

Nano Lithium Iron Phosphate Cathode Material for Li-ion Based Batteries for Underwater Applications

In batteries for underwater applications, cathode materials in nano size play a key role in achieving high-power capability due to the increased reaction rate and short diffusion lengths required for underwater vehicles and weapons. Lithium Iron Phosphate (LiFePO

4

) is a promising cathode material for Li-ion batteries. Nano sized particles of the above cathode material were successfully synthesized from precursors without impurity phases through Microwave synthesis method. The required microwave power and exposure time were optimized. The material was characterized for its structure and particle size. In this paper, procedure of microwave synthesis, the discharge capacities at different C-rates and the cyclability of this nano cathode material are discussed.

T. V. S. L. Satyavani, A. Srinivas Kumar, P. S. V. Subbarao

Porous Anodic Alumina Template Formation: Deposition Technique Dependence

Porous anodic alumina (PAA) oxide layers have been deposited on TiN/SiO

2

/Si by both the vacuum evaporation (VE) and RF magnetron sputtering (MS) techniques. The deposition technique dependence of the pore size at the surfaces of the anodic aluminum oxide (AAO) membranes has been investigated after two step anodization process. The nanochannel arrays of AAO membranes were characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared attenuated total reflectance (FTIR-ATR) analysis. Chemical composition and film structural properties were investigated by x-ray photoelectron spectroscopy (XPS) and high resolution x-ray diffraction (HR-XRD) analyses. It is shown that uniform pore density in AAO templates is obtained using Al films deposited using RF sputtering technique.

S. Upreti, K. Mukherjee, M. Palit, A. Bag, S. Mallik, S. Chattopadhyay, C. K. Maiti

Synthesis and Characterization of CuO-TiO2 Core Shell Nanocomposites for Hydrogen Generation Via Photoelectrochemical Splitting of Water

Sol–gel derived CuO–TiO

2

core shell nanocomposites were synthesized by modified Stöber method [

1

] and characterized. XRD analysis revealed dominant evolution of CuO (tenorite phase) at the core on to which TiO

2

(anatase) was coated. The average crystallite size, estimated from Scherrer’s computations was 30–33 nm. PEC studies indicated that core shell composites offer significant photocurrent. The effect of variation in concentration of titanium (IV) butoxide (precursor used for generating TiO2 coat over CuO) was also investigated. The increase in concentration of TBOT led to increase in photocurrent.

Shailja Sharma, Babita Kumari, Nirupama Singh, Anuradha Verma, Vibha R. Satsangi, Sahab Dass, Rohit Shrivastav

Highly Efficient Field Emission Characteristics of Ultra-long Vertical Aligned Single Wall Carbon Nanotubes

In this work, ultra long vertically aligned single wall carbon nanotubes are synthesised by Plasma enhanced chemical vapour deposition (PECVD) technique at 600 °C temperature. The presence of built-in electric field in a plasma sheath aligns the growing CNTs along the field lines. Also, PECVD method favours low temperature synthesis of VA-SWCNTs. SEM and Raman are used to characterized as grown sample. Enhanced Field emission properties of as-grown VA-SWCNTs are also studied.

Shama Parveen, Samina Husain, Avshish Kumar, Javid Ali, Harsh, Mushahid Husain

Temperature Dependence Thermal Conductivity of ZnS/PMMA Nanocomposite

ZnS/PMMA nanocomposite with 4 weight percent of ZnS nanoparticles were prepared by solution casting method. The obtained ZnS/PMMA nanocomposites were characterized through XRD and TEM measurements. Transient plane source (TPS) technique was used to determine the thermal conductivity of ZnS/PMMA nanocomposite over the temperature range from 30

o

C to 120 °C. The results indicated that the thermal conductivity shows increasing behavior up to glass transition temperature beyond which, it becomes constant due to the straightening of chains and vacant site scattering of phonons, respectively. It is also observed that thermal conductivity of ZnS/PMMA nanocomposite increases as compared to pure polymer. This behavior of thermal conductivity of nanocomposite is explained on the basis of their structure.

Sonalika Agarwal, N. S. Saxena, Vipin Kumar

Nanoindentation Study of Mechanical Properties of Diamond Like Carbon Coatings

Nanoindentation is a depth sensing indentation technique to probe the mechanical properties of small volume. In this contribution, the results of nanoindentation response of diamond like carbon (DLC) coatings on SiAlON ceramics are presented. Indentation measurements were performed with an applied load of 3 mN in order to examine the pressure induced deformation of the structure. The DLC coated SiAlON ceramics exhibited increased elastic modulus and hardness compared to uncoated samples. The other mechanical parameters estimated from nanoindentation measurements are elastic recovery, stiffness and plastic deformation energy.

S. Chockalingam, R. K. Tripathi, O. S. Panwar

Fabrication of Vertically Aligned Carbon Nanotubes on MgO Support Layer by Thermal Chemical Vapor Deposition for Field Emission Application

Vertically aligned multiwalled carbon nanotubes (MWCNTs) were synthesized by simple thermal chemical vapor deposition on MgO support layer. MgO layer was deposited on Si (001) wafer by magnetron sputtering. With acetylene as carbon source and iron as catalyst vertically aligned multiwalled carbon nanotubes have been grown at 700 °C by our home made thermal chemical vapor deposition setup. As synthesized MWCNTs have been characterized by field emission scanning electron microscopy, transmission electron microscopy and confocal Raman spectroscopy. Field emission characteristic of vertically aligned MWCNTs forest was measured by our home made field emission setup and showed good field emission properties. Turn-on and threshold field have been obtained as 0.56 V/μm (at J = 10 μΑ/cm

2

) and 3.83 V/μm (at J = 1 mA/cm

2

) respectively from vertically aligned MWCNTs. Field emission characteristic was explained on the basis of follows the Fowler-Nordheim (F-N) equation.

Supratim Maity, Subhajit Rakshit, Kalyan Kumar Chattopadhyay

Thermal Evolution of Mixed Oxides of Zirconia-Silica Prepared by Sol-gel Route

The thermal evolution of nanodimensional mixed metal oxides prepared by sol-gel route through structural characterization is reported. ZrO

2

-SiO

2

sol-gel powders were produced using zirconium propoxide and tetraethoxysilane (TEOS) as precursors. The gel was dried at 110 °C for 6 h in air. After drying, thermal treatment of as prepared samples was carried out at 650, 875 and 1,100 °C for 4 h. The crystallization of samples and the crystalline phases evolved are related to annealing temperature. The phases of zirconia and silica are identified, and the lattice parameters are calculated using X-ray diffraction. The results suggest that annealing at higher temperature enhances the crystallinity and hence crystallite size of nanodimensional samples.

Surbhi Saruchi, Sushil Kumar

Chalcogenide Micro/Nanostructures by Evaporation Condensation Method

Chalcogenide (As-S-Se) micro/nanostructures have been successfully synthesized using thermal evaporation-condensation method in evacuated glass ampoule. The nanowires have diameter ranging from 10 to 20 nm and they are few microns in length. The structures are characterized using Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X Ray Diffraction (XRD) for their morphology, composition and structure respectively. These nanowires show promising applications in the field of nanoelectronics and nanophotonics.

Swati Raman, Ravi K. Kumar, M. Husain

Effect of Parasitic Capacitance on DG-HGTFET and Its Influence on Device RF Performance

In this paper, for the first time, the design of double-gate hetero-gate-dielectric tunnel field effect transistor (DG-HGTFET) for asymmetric drain doping for RF (Radio frequency) application is discussed. The impact of drain parasitic capacitance on the device performance is analyzed. The results indicate that parasitic capacitances are dominating factor which will degrade the RF characteristics. For this, the RF figures of merit for DG-HGTFET are analyzed in terms of unit-gain cut-off frequency (

f

T

), maximum frequency of oscillation (

f

max

). Further, asymmetric drain doping is also analyzed for suppressing the ambipolar behavior.

Vikas Vijayvargiya, Santosh Kumar Vishvakarma

Optoelectronics

Frontmatter

Optimizing the Optical Properties of ZnO Nanoparticles with Al Doping

This paper reports on the structural and optical properties of Al with different doping concentrations on ZnO nanoparticles prepared through Sol–Gel method. The XRD results revealed the wurtzite structure of ZnO without any secondary phase related to Al. The absorption spectrum of the sample exhibited an absorption in UV region and the Photoluminescence properties of Al doped ZnO were studied.

A. N. Mallika, A. Ramachandra Reddy, K. SowriBabu, K. Venugopal Reddy

An Accurate Measurement of Carrier Concentration in an Inhomogeneous GaN Epitaxial Layer from Hall Measurements

An appropriate method for an accurate determination of carrier concentration from Hall measurements for samples having large inhomogeneities is presented. Parasitic contributions in such samples generally limit the capabilities of Hall experiments where even the measurement of carrier type in some samples becomes doubtful. Here, we eliminate the major parasitic contributions from the measured Hall voltage through a systematic averaging procedure over the current and magnetic field polarities. Further, the carrier concentration values are unambiguously determined from the magnetic field dependent Hall measurements, where the slope of true Hall voltage versus magnetic field plot provides realistic values of carrier concentrations.

Abhishek Chatterjee, Shailesh. K. Khamari, V. K. Dixit, T. K. Sharma, S. M. Oak

Effect of Substrate Temperature Variation and Tartarization on micro-Structural and Optical Properties of Pulsed DC Sputtered Hydrogenated ZnO: Al Films

In this work, hydrogenated ZnO: Al films have been deposited on glass substrate by pulsed dc magnetron sputtering unit at various substrate temperatures. The effect of substrate temperature on microstructural and optical properties of deposited films in hydrogen and Argon ambient was analyzed. Transmittance of films improved for films deposited at higher substrate temperature and reflectance decrease which is good as transparent conducting oxide for solar cells application. The wet chemical etching of hydrogenated films was performed to improve the light trapping in films. Films deposited at 250 °C showed lower resistivity and higher roughness after wet chemical etching than films deposited at room temperature. Films deposited at 150 °C shows better films quality as well as lower resistivity than films deposited at room temperature and 250 °C. This suggests that film’s microstructural, optical and electrical properties behave differently in hydrogen gas ambient and hydrogen improve films quality and conductivity at lower temperature.

Chandra Bhal Singh, Surajit Sarkar, Vandana Singh

Single Crystalline Films of Zinc Oxide for Nanorod Applications

Zinc oxide (ZnO) thin films were deposited by sol–gel spin coating method on to the glass substrate. Effect of post annealing temperature on structural and optical properties has been investigated. The films were characterized by X-Ray diffraction (XRD) and spectrophotometer. Nanocrystalline films having grain size of 90.89 nm has been deduced from X-ray diffraction studies. The single crystalline nature of the films has been confirmed by single mighty peak obtained for (101) orientation. All the films exhibit good transparency more than 90 % in the visible region and average transmittance was found to be decreased with an increase in annealing temperature. The thickness of the films was found to be varying with different post annealing temperature. The post annealing temperature of 300 °C was found to be optimum with reference to the quality and physical parameters of ZnO. Results obtained show the potential applicability of ZnO for nano-rods.

Chetan Kasar, Ulhas Sonawane, Prasantha Mudimela, Jean-Francois Colomer, D. S. Patil

Calculation of Direct E0 Energy Gaps for III–V–Bi Alloys Using Quantum Dielectric Theory

A mathematical model based on Quantum Dielectric Theory has been used to calculate the direct E

0

energy gaps of bismuth containing ternary alloys. The variation of E

0

with x for In Sb

1–x

Bi

x

and GaSb

1–x

Bi

x

are in good agreement with the experimental results. The composition dependence of E

0

at different temperatures is also found out for some other ternary alloys like InPBi and AlSbBi.

D. P. Samajdar, T. D. Das, S. Dhar

Transport of Nitrogen Atoms During the Liquid Phase Epitaxial Growth of InGaAsN

A mathematical model has been used to study the concentration profile of the nitrogen atoms during the liquid phase epitaxial growth of InGaAsN. This model is based on the one dimensional diffusive transport of the nitrogen atoms at equally spaced layers in the proximity of the grown epitaxial interface. Various growth parameters such as growth temperature, melt supercooling and the continuous cooling ramp applied during growth have been optimized to find out the suitable conditions of growth. We have also estimated the thickness of the epitaxial layers as a function of time.

D. P. Samajdar, S. Dhar

Laser Assisted Surface Photovoltage Spectroscopy: A New Tool for an Accurate Determination of the Bandgap of Semiconductor Epitaxial Layers

A new technique is presented for an accurate determination of the bandgap of semiconductor bulk and quantum structures under the strong influence of localized states. It is based on a pump-probe configuration where an additional sub bandgap cw pump laser beam is used in a conventional chopped light geometry surface photovoltage spectroscopy setup. The main role of pump beam is limited to saturate the sub bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states.

Dipankar Jana, S. Porwal, T. K. Sharma, Shailendra Kumar, S. M. Oak

Influence of Lateral Current Spreading on the Characteristics of High Fill Factor Mesa-Stripe Laser Diode Arrays

We have investigated the effect of mesa depth on the characteristics of high fill factor (typically the inter- element spacing is < ~20 μm and stripe width ~ 150 μm) laser diode arrays (LDAs). Measurements were carried out on different laser diode bars and it was observed that a shallow mesa not only increases the threshold current of these laser bars but it can prevent lasing condition for a combination of geometrical parameters of mesa. Minimum mesa depth required to achieve lasing in these laser diode arrays is calculated as a function of inter-element spacing considering the effect of lateral current spreading. The work reported here shows that in order to achieve lasing in laser diode arrays with small inter-element distance, the mesa should be deep enough to prevent electrical coupling between the neighboring stripes of LDAs.

Deepti Jain, Kamal Lohani, S. K. Mehta, Subodh Chandra, Pramod Kumar, Abhishek Sharma, Deepak Mohanty, Alok Jain, Satish Mohan

Voltage Modulated Electroluminescence and Forward Bias Impedance Characteristics of Light Emitting Semiconductor Devices

Voltage modulated electroluminescence and forward bias impedance characteristics of AlGaInP based multi quantum well light emitting devices are studied in frequency (up to 1 MHz) and temperature domain. We observed inductive like reactance for low frequencies and high biases. A frequency dependent modulated light output has also been observed which also increases when modulation frequency is lowered. We explained the occurrence of inductive response and correlated modulated light output at low frequencies by considering defect participation in fast radiative recombination process. Temperature variation of reactance and modulated light output supports our understanding based on defect contribution model. However, with temperature change, dynamics of charge carriers inside the quantum well starts to affect the optical as well as electrical response. This work can be useful in improving the efficiency of light emitting devices for their applications involving direct modulation. This can also help in understanding the physics of a semiconductor junction under high carrier injection.

Kanika Bansal, Shouvik Datta

Enhanced Hole Transport in Polyfluorene Polymer by Using Hole Injection Layer

Hole transport in poly(9,9-dioctylfluorene) (PFO) are measured by performing current density- voltage (J-V) measurements as a function of temperatures. For the J–V measurements, F

4

TCNQ is used as hole injection layer (HIL). Two different devices of PFO polymer are fabricated F

4

TCNQ having device configuration ITO/PFO/Au (with interface modification) and ITO/PFO/F

4

TCNQ/Au (with interface modification) respectively. Since, F

4

TCNQ is evaporated on the top of PFO film so that the contacts are taken from Au.

Manisha Bajpai, Ritu Srivastava, R. S. Tiwari, R. Dhar

Study of Phase Matching Schemes in PPLN for THz Generation

In this paper we have studied the phase matching geometries of the slant—striped PPLN and the PPLN with grating vector normal to the input wave-vectors. In both of these PPLNs, the grating parameters (grating period and grating angle) are designed such that the THz is emitted from the surface of the PPLN thereby, reducing the loss of THz power due to absorption in lithium niobate. It was found that while keeping one of the input wavelength fixed at 1064 nm and tuning another wavelength from 1,070 to 1,080 nm we could obtain the THz wavelength tunable from 189.7 to 71.8 μm which corresponds to 1.58–4.17 THz frequency. In case of slant stripe PPLN, the grating period and grating angle required for generating this range of THz frequency, varies from 33.27 to 9.15 μm and 22.83°–16. 37. For PPLN with novel QPM, the required periods for the same range of THz frequency, varied from 39.8 to 10 μm. Study of effect of ±1 % systematic error in grating parameters on THz emission angle was also performed. It was found that error in grating parameters led to the deviation in THz emission angle in order to satisfy the phase matching condition. It was also found that in case of simultaneous occurrence of errors in grating parameters, the effect of errors was summed up when it occurred in opposite direction while, when errors were introduced in same direction the total effect (i. e. deviation in emission angle) was the difference of effect due individual error. However, the deviation in THz emission angle was very small and therefore, does not affect the THz extraction technique.

Maria Farooqui, Ajay Mishra, Nimish Dixit, A. K. Gupta

Low Temperature Growth of GaN Epitaxial Layer on Sapphire (0001) Substrate by Laser Molecular Beam Epitaxy Technique

GaN epitaxial layers have been grown on sapphire (0001) substrate by laser molecular beam epitaxy. The Ga and N fluxes have been optimized for a good quality, smooth surface GaN layer growth by suitably adjusting the laser power and frequency. It is found that the moderate laser energy with high frequency up to 45 Hz yields more uniform Ga flux for the growth. Similar to conventional MBE, the N-rich growth condition produced rough surface GaN layers while flat surface GaN was obtained under slightly Ga-rich condition. The effect of growth temperature in the range 300–750 °C on the structural properties of the grown GaN layers has been studied. The (0002) plane x-ray rocking curve full width at half maximum (FWHM) of GaN epilayers has been found to decrease dramatically with increasing growth temperature. A narrow x-ray rocking curve value of about 245 arcsec has been achieved for GaN (0002) plane reflection for the epilayers grown in the range of 500–600 °C, which is about 150 °C lower than the conventional MBE growth.

M. Senthil Kumar, S. S. Kushvaha, K. K. Maurya

Pitch Polishing of Semiconductor Optical Materials Using Continuous Iterative Interferrogram Analysis

Semiconductor optical materials including Germanium, Silicon, ZnS and ZnSe are widely used to fabricate high precision optical components for focusing infrared radiation to the detector of thermal imaging system. For better performance of thermal imager, the quality of optical components in terms of surface accuracy, surface quality and other fabrication parameters must meet tighter tolerances. In the present work, we report a conventional pitch polishing technique using continuous slurry polishing to maintain surface accuracy of the order of sub micron accuracy and surface quality as per MIL-O-13830A. A phase shift laser interferometer with wavelength 632.8 nm is used as in-process measurement of surface accuracy. The hardness and viscosity of pitch, slurry concentration, polishing pressure and pitch lap compliance has been monitored and optimized for optimum polishing time and best results. During polishing, surface wedge was also monitored and controlled within 30 s of an arc.

Neeraj Pandey, K. K. Pant, S. Mishra, L. M. Pant, A. Ghosh

Optical Spectroscopic Studies on Mono-Layer MoS2

Mono-layer Molybdenum Disulphide (MoS

2

) crystalline films were obtained on SiO

2

/Si substrate by mechanical exfoliation. The layer thickness was verified using Raman spectroscopy and Reflectance Contrast spectroscopy. Low temperature (4.5 K) micro-photoluminescence (μ-PL) measurements were performed on the MoS

2

samples using a setup we have built which has a spatial resolution of <2 μm. The PL spectra shows two distinct features, one associated with the direct interband transition as the K point of the Brillouin zone of MoS

2

and the other most likely associated with a defect. These results are compared with other reports of PL measurements on mono-layer MoS

2

crystals.

Nihit Saigal, Amlan Mukherjee, Sandip Ghosh

Fabrication of n-ZnO/p-GaAs Heterojunction and Prediction of Its Luminescence Based on Photoluminescence Study

Self-compensation arising out of non-stoichiometry makes ZnO as-grown n-type. Nonavailability of stable p-type doping with required carrier concentration limits the formation of homojunction of ZnO. Fabrication of semiconductor heterojunction is thus an alternative approach in device fabrication. In the present study n-ZnO has been grown on p-GaAs substrates using MOCVD technique. The colour of the light which is supposed to be emitted from the said heterojunction has been predicted to be purplish red from the room temperature photoluminescence study. The corresponding colour temperature is found to be less than 1,000 K. Efforts have been made to explain the prediction on the basis of band diagram.

Nripendra N. Halder, Sanjay Kumar Jana, Pranab Biswas, D. Biswas, P. Banerji

Varying Photoconductivity of ZnO as a Function of Annealing Temperature

Arsenic has been doped in MOCVD grown ZnO thin films using thermal diffusion technique from semi-insulating GaAs substrate. Hall measurements showed p-type conductivity in ZnO. XPS analyses reveal that As

Zn

–V

Zn

is the shallow acceptor complex which contributes p-type conductivity of the films. As the post-growth annealing temperature increased from 600 to 700

°

C the hole concentration also increased from 1.1 × 10

18

to 2.8 × 10

19

cm

−3

respectively. It shows an increase in UV-to-dark current ratio from 284 to 488 at 10 V respectively.

Pranab Biswas, P. Banerji

Effect of Packing Density on Crosstalk in On-chip Optical Interconnects

Optical interconnects hold the promise of revolutionizing computing speed having higher bandwidth and lower power consumption. For high packing density of optical interconnects, crosstalk is calculated considering the coupling of fields of two parallel identical neighboring waveguides. The study shows that there exists minimum pitch for a particular length and width of the interconnects to avoid significant amount of crosstalk. Again, an optimum ratio of width-to-pitch exists for which crosstalk is minimum.

Prativa Agarwalla, N. R. Das

Observation of Low Mobility Electron in Vacancy Doped LPE Grown HgCdTe

Variable magnetic field Hall and resistivity data at different temperatures for vacancy doped LPE grown Hg

0.71

Cd

0.29

Te samples have been analyzed using multicarrier fitting. Samples grown from Te-rich melts by Horizontal Slider techniques have been investigated. Measurements were carried out at temperatures from 20 to 300 K using magnetic fields in 0–8 Tesla range. In addition to heavy hole and light hole an electron with low mobility (77 K value of ~812 cm

2

V

−1

s

−1

) was observed at temperatures below 150 K. Its presence has been attributed to interface as confirmed by Hall measurements of the interfacial layer (~4 µm above CdZnTe substrate) and is reported here for HgCdTe for the first time.

Tapasya Jain, Rachna Manchanda, B. L. Sharma, O. P. Thakur, R. K. Sharma

Observation of Over-Layer Deposition on HgCdTe Epilayers Grown by Vertical dipping Liquid Phase Epitaxy

The HRXRD and FTIR characterization of HgCdTe epilayers grown by vertical Dipping Liquid Phase Epitaxy was analyzed to indicate the presence of <2 μm low-

x

HgCdTe over layer. A higher angle shoulder in HRXRD rocking curve and a graded cut-on as well as a double fringe pattern in FTIR was observed. Removal of ~2 μm surface layer by chemical etching improved the FTIR and HRXRD curves.

Radheshyam Nokhwal, Akhilesh Pandey, B. L. Sharma, Puneet Sharma, Preeti Garg, S. A. Hashmi, R. K. Sharma

A Multi-Scale Approach to Wavefunction Engineering of Subdimensional Quantum Semiconductor Structures

With on going reduction in dimension of nano-devices it becomes imperative to include interface and structure boundaries accounting for complex, mixed boundary conditions. A Lagrangian approach to the physics provides the natural framework for such calculations, with computational work based on the finite element method. This variational approach has led to the design of mid-IR cascade lasers and the solution of the Schrödinger-Poisson self-consistency in arbitrary layered structures. Applications of this methodology lead to the solution for energy levels in a magnetic field in the Voigt geometry. The effect of surface proximity on binding energy for impurity states in nanowires and the beautiful physics of complex topological surfaces such as a Mobius ring are displayed as further examples of the issues addressable through multi-scale parallel computing within this variational framework.

L. R. Ram-Mohan

Synthesis of Cubic Indium Oxide Thin Film by Microwave Irradiation

The indium metal thin films were deposited at room temperature by dc magnetron sputtering on glass substrate. This indium thin film is post-treated with microwave irradiation at ambient atmosphere to convert it into the In

2

O

3

thin film. Indium oxide (In

2

O

3

) thin film was successfully synthesized on glass substrate by using microwave irradiation. This method has advantages over the conventional heating method because it takes lesser treatment time, and the quality of film is better. The effect of microwave irradiation for different time was studied by XRD and UV–VIS spectroscopy. X-ray diffraction result shows the presence of cubic phases in synthesized In

2

O

3

thin film without any significant impurity. Optical spectroscopy measurements show a large optical transparency, greater than 60 %. This In

2

O

3

thin film is highly suitable for the transparent conducting oxide, solar cell and gas sensor applications.

Ruchi Srivastva, K. Ibrahim, C. S. Yadav

Growth of ZnO nanorod on flexible polyethylene terephthalate substrate by chemical bath deposition and microwave method

We report the synthesis of Zinc Oxide (ZnO) nanorods on the flexible Polyethylene tetraphalate (PET) substrate by chemical bath deposition and microwave irradiation methods. X-Ray diffraction and Field emission scanning microscopic data confirm the growth of nanorod. In the microwave process, the formation of nanoflowers was also observed along with the nanorods. The band gap of the grown ZnO nanorods by chemical bath deposition and microwave methods was found to be 3.0 eV and 3.2 eV, respectively.

Ruchi Srivastava, Izzati Husna, K. Ibrahim, C. S. Yadav

Bi incorporation in GaSbBi films grown by liquid phase epitaxy

We present here the Bi incorporation properties of GaSbBi layers grown by liquid phase epitaxy technique. Secondary ion mass spectroscopy technique indicates that Bi is distributed uniformly along the depth of the layer with slowly decreasing concentration away from the surface. Room temperature optical absorption measurements show a band gap lowering of 25 meV for a layer grown from a melt containing 1 at% Bi.

S. K. Das, T. D. Das, S. Dhar

Study of Optical Parameters of the Thin Films of Se100-x Hgx with Laser Irradiation

In this study the bulk samples of Se

100-x

Hg

x

(x = 0, 5, 15) have been prapered by conventional melt quenching technique. The thin films of the material were prepared by thermal evaporation technique. These thin films were irradiated with pulsed diode laser of wavelength 405 nm and power 100 mW for different durations of time. The transmission spectra was recorded by UV- visible spectrophotometer (200–1100 nm) before and after irradiation. The transmission spectra has been studied to measure the optical constants like extinction coefficient (k), absorption coefficient (α), optical band gap (E

g

) and urbach’s energy (E

e

). It has been found that the value of absorption coefficient and extinction coefficient increases after irradiation. Also the Urbach’s energy increases and the optical band gap decreases after irradiation. This indicates that the irradiation induces variety of defect states in the material system. It has also been found that the change of these optical parameters is more if the concentration of mercury is increased. This may be due to the addition of mercury and the bonding arrangement of the material system changes. These materials are found suitable for optoelectronic devices due to their high absorption coefficient.

Shabir Ahmad, Mohsin Ganaie, Nasir Neetu, Shahid Khan, M. Zulfequar

Photo-Induced Inverse Spin Hall Effect in Au/InP hybrid structure

Photo-induced inverse spin Hall effect (ISHE) measurements on a Au/InP metal–semiconductor junction are performed. Spin polarized electrons, which are generated in InP by the circularly polarized laser light of 2.33 eV (532 nm), provide a net spin current in thin Au-layer after crossing the Schottky barrier. This generates a transverse electric current because of large spin orbit coupling in Au-layer. ISHE origin of the measured signal is confirmed by a linear variation of the spin current with the degree of circular polarization of incident light. Furthermore, angle dependence of spin current matches well with the predicted trends.

Shailesh K. Khamari, S. Porwal, T. K. Sharma, S. M. Oak

MBE Growth of Hg1-xCdxTe on Cadmium Zinc Telluride Substrates

A dual Chamber RIBER 32P Molecular beam epitaxy (MBE) system was used to grow high quality HgCdTe epilayers. For growth, the critical parameters are: 1) accurate determination and control of real substrate temperature 2) precise identification of the Hg/Te ratios 3) CdZnTe substrates with reproducible surface finish and structural characteristics. Because the substrate holder rotates during growth, the junction of spring-loaded thermocouple does not contact the molyblock leading to irreproducible temperature measurements.

We modified the manipulator thermocouple design and its contact with the molyblock and the real molyblock temperature is measured to an accuracy of ± 0.5 °C even if we use different molyblocks. During the complete growth run of 4 - 5 h (growth rate 1.5 - 2 μm/h), the manipulator thermocouple temperature was kept constant as opposed to the temperature ramping reported by other groups. With the above modifications, we do not require to monitor the substrate temperature using a pyrometer, which needs emissivity and refractive index values. We also do not regularly need the melting (calibration) points of 3 standard metals (In, Pb/Sn & Sn): we only use Pb/Sn eutectic alloy (melting point 183 °C) to routinely check the temperature calibration within the growth window.

HgCdTe epilayer growth experiments are carried out in the temperature range of 175 - 185 °C for different Hg/Te ratios (80 - 110) for high quality epilayers. The Hg/Te ratio is found to be higher for a rough CdZnTe substrate than for a smooth one. HgCdTe epilayers grown on 30 mm x 30 mm CdZnTe substrates show FWHM < 30 arc sec with composition and thickness uniformity < 1.5 %.

Arun Kumar Garg, Shiv Kumar, Arun Tanwar, S. S. Rana, S. Tyagi, Vikram Dhar

Effect of Growth Temperature on Properties of CdZnO Thin Films

Ternary CdZnO thin films were grown on sapphire substrate with varied growth temperature from 300 to 600 °C using dual ion-beam sputtering system. The structural, morphological and optical properties of the films were deeply studied. X-ray Diffraction (XRD) measurements indicate phase separation in the deposited CdZnO films. The photoluminescence studies indicate emission centered around 440 nm ~ 2.8 eV. The optical band gap was confirmed by UV–Vis spectrometric measurements. It was also found that band gap narrows down with the increase in growth temperature.

Shruti Verma, Sushil K. Pandey, Mukul Gupta, Shaibal Mukherjee

RETRACTED CHAPTER: An Intense Green Emission From ZnO Nanoparticles Coated with MgO

This paper addresses the effects of annealing temperature on photoluminescence of ZnO nanoparticles coated with MgO. ZnO nanoparticles as well as ZnO coated with MgO showed only a sharp UV emission peak positioned at 396 nm at an annealing temperature of 600 °C. As the annealing temperature increased from 600 to 900 °C, the intensity of green emission enhanced monotonously. The green emission intensity at 900 °C is 18 times higher than its value at 700 °C. But at 1,000 °C, green emission intensity decreased. FT-IR spectra of ZnO@MgO showed that MgO evaporation took place with increase of temperature from 700 to 1,000 °C. These results indicates that intensity of green emission depends on thickness of MgO shell coated over the ZnO nanoparticles.

K. Sowri Babu, A. Ramachandra Reddy, K. Venugopal Reddy

Laser Molecular Beam Epitaxy Growth of GaN Layer on Sapphire (0001) Under Various Process Conditions

We have grown high quality epitaxial GaN films on sapphire (0001) substrates using a ultra-high vacuum laser molecular beam epitaxy (MBE) system at different growth temperatures, deposition rate and nitrogen species. The HVPE grown GaN solid target was ablated at laser energy density ~5 J/cm

2

with laser frequency ~ 5 Hz (low flux) and 10 Hz (high flux) in presence of r.f. nitrogen plasma. Structural properties of the epitaxial GaN films were characterized using high resolution x-ray diffraction, atomic force microscopy (AFM), and photoluminescence spectroscopy (PL). At high flux, the full width at half maximum (FWHM) of x-ray diffraction rocking curve of GaN (0002) peak decreases with increasing growth temperature from 500 to 720 °C. The GaN film grown at 700 °C with low flux shows a large FWHM (368 arc sec) with small grain sizes in comparison to the GaN film grown with high flux (FWHM: 110 arc sec). We have also studied the effect of high pressure nitrogen ambient during ablation of GaN target for growth of GaN films on sapphire with and without pre-nitridation of sapphire at growth temperature 500 °C. The typical PL measurement on the GaN film grown on sapphire using laser MBE system shows the high quality of GaN film with minimum defects. The obtained results suggest that the present growth technique could be an alternative for fabrication of high quality GaN based devices.

Sunil S. Kushvaha, M. Senthil Kumar, Bipin K. Gupta, K. K. Maurya

Hg/Cd Interdiffusion in Thin CdTe Film on HgCdTe Epilayer

Cd/Hg Interdiffusion in CdTe passivation layers on HgCdTe epilayer by heat treatment under different annealing conditions have been studied using Secondary Ion Mass Spectrometry (SIMS). Cdmium and Mercury composition profiles have been generated from SIMS depth profiles. The results are important from the point of view of passivation of HgCdTe surface with CdTe layer of graded composition, in order to achieve flat band conditions at CdTe/HgCdTe interface and simultaneously adjusting metal vacancy concentration in the bulk of the material.

Tapasya Jain, Anuradha Dhaul, Rachna Manchanda, Shiv Kumar, O. P. Thakur, R. K. Sharma

Characterization of InP1-xBix Alloy Grown by Liquid Phase Epitaxy

I have investigated the effect of Bi incorporation on InPBi layers grown by liquid phase epitaxial technique. High resolution x-ray diffraction (HRXRD) patterns show high crystalline quality and secondary ion mass spectroscopy (SIMS) technique is used to get the amount of Bi incorporated into the layer ~1.25 %. 10 K Photoluminescence is clearly resolved that maximum band gap reduction of 20 meV.

T. D. Das

Modeling Current Voltage Characteristics of MWIR HgCdTe Diodes at High Reverse Bias Voltage

In this paper we model the current voltage (I–V) characteristics of Hg

1 − x

Cd

x

Te (x = 0.3) diodes at high reverse bias voltage. The breakdown characteristics are indicative of n

+

/n

/p kind of doping profile. Various current limiting mechanisms affecting the soft breakdown characteristics of Hg

1 − x

Cd

x

Te diodes have been identified. We also found that the existing models do not accurately fit the I–V curves above a certain reverse bias voltage, which led us to investigate possible additional dark current mechanisms responsible for this kind of behavior. Thus, a new current limiting model is also proposed in this paper.

Vanya Srivastav, Navneet Kaur Saini, L. Sareen, R. K. Bhan, R. K. Sharma

Growth and Characterization of Screen-Printed Zinc Sulpho Selenide Composite Thin Layer for Solar Cell Buffer Layer Application

Zinc sulpho selenide has been proposed as a novel buffer layer, alternative to CdS for solar cell applications. In this paper Zn-Se-S composite thin layers have been synthesized on ultra clean glass substrate by screen-printing method followed by sintering process. Zinc sulphide, zinc selenide and zinc chloride have been used as the basic source material. To deposit good quality films, optimum conditions have been determined. X-ray diffraction analysis exhibited polycrystalline nature of layers with strong preferential orientation of grains along (200) direction. These layers have the wurtzite crystal structure. The optical band gap (E

g

) of the films has been studied by using reflection spectra in wavelength range 325–600 nm. The optical band gap of Zn-Se-S composite thin layer has been found to be in between individual band-gaps of ZnS and ZnSe. The DC electrical conductivity of the layers has been measured in vacuum by a two probe technique and was found to be of the order of 10

−6

ohm

−1

cm

−1.

These properties make these layers suitable for application as a buffer layer in solar cells.

Vipin Kumar, D. K. Sharma, Kapil Sharma, D. K. Dwivedi

Organic Electronics

Frontmatter

Mixed Ligand Orange Emitter Zinc Complex for Organic Light Emitting Diodes

We report synthesis, characterization and use of ternary zinc complex as emissive and electron transport material in organic light emitting devices (OLED). 5,7-dimethyl-8-hydroxyquinoline have been used with 2-(2-hydroxyphenyl) benzoxazole to synthesize (2-(2-hydroxyphenyl)benzoxazolato) (5,7-dimethyl-8-hydroxyquinolinato)zinc(II) [Zn(HPB)(Me

2

q)]. The complex possessed high thermal stability and having good film forming property. Optical properties of the synthesized complex have been studied by UV–visible absorption, photo-luminescence and transient photo-luminescence spectroscopy. Synthesized material shows quite good efficiency in multilayered device structure ITO/α-NPD/Zn(HPB)(Me

2

q)/BCP/Alq

3

/LiF/Al with maximum brightness of 4017 cd/m

2

having electroluminescence spectral peak emission centered at 567 nm. Electron mobility of the synthesized complex was found to be 1.5 × 10

−6

− 1.2 × 10

−5

cm

2

/V s. for electric field range 1,000–1,200 (V/cm)

1/2

and hence can be used as electron transport material in OLEDs.

Amit Kumar, Akshaya Kumar Palai, Kanchan Saxena, Vinod K. Jain, Ritu Srivastava, Modeeparampil N. Kamalasanan, Ishwar Singh

Effect of Slow Traps on Capacitance–Voltage Measurement

Charge density inside a two terminal device is probed using two different methods—integration of Capacitance–Voltage characteristic and integration of discharge current following a voltage step. Difference in the two measured values is explained due to presence of slow traps. Simulations are done to validate the proposed explanation.

Ankita Gangwar, Baquer Mazhari

Bluish-Green Light Emitting Zinc Complex for OLED Application

Zinc (II) was complexed with 8-hydroxyquinoline-5-sulphonic acid (L) to give an ZnL

2

complex (1:2 molar ratio). The synthesized complex was characterized by infrared spectra, differential thermal analysis and thermogravimetry. The UV-absorption and photoluminescence (PL) spectra show peaks at 377 nm and 502 nm respectively. The OLED device has been fabricated by depositing the thin films of different materials on ITO, hole transport layer was obtained by depositing a thin film of 4,4-bis[

N

-(1-naphthyl)-

N

-phenyl-amino]biphenyl (α-NPD), Bis(8-hydroxyquinolinato-5-sulphonic acid)zinc(ZnL

2

) as emissive layer, BCP as hole blocking layer, thin film of Alq

3

as electron transport layer and LiF/Al as electron injecting electrode. The EL device was characterized for electroluminescence and the peak was reported at 503 nm. The EL spectrum of complexes ZnL

2

is found that there is a considerable blue shift in the EL spectra from its un-substituted counter complex when electron-withdrawing group is introduced at 5th position in quinoline ring.

Kapoor Singh, Akshaya Kumar Palai, Amit Kumar, Ishwar Singh

Variable Range Hopping Transport in Polypyrrole Composite Films

Organic materials have enough potential to replace the role of conventional semiconductors due to their superior relative properties like light weight, flexibility, corrosion resistance, inexpensive production and ease of processing. Among the conducting organic polymers, polypyrrole (PPy) is of particular interest because of its high electrical conductivity (~ 1S/cm) and environmental stability in the doped state. In this study, we have synthesized free standing PPy composite films. These samples were then characterized by scanning electron microscopy and their charge transport study was carried out in the temperature range of 10-300 K.

Manish Taunk, Subhash Chand

Low Voltage Pentacene Organic Field Effect Transistors with High-K Gate Dielectric

In organic transistors, generally SiO

2

is used as the gate insulator for their high quality and commercial availability despite its relatively low dielectric constant (~ 3.9) which is responsible for high operating voltage of organic transistors. We have fabricated low operating voltage pentacene based organic field effect transistors (OFETs) with high-k STO gate dielectric. The operating voltage of OFETs is reduced by a factor of ten with STO gate dielectric. Pentacene OFETs show operating voltage < 5 V, high charge carrier mobility (1.3 cm

2

/Vs) and high on–off ratio (10

6

).

Sarita Yadav, Subhasis Ghosh

Engineering the Optical Properties of insitu Polymerized poly (o-toluidine/V2O5) Composites

Conducting polymer composites of poly (o-toluidine)/vanadium pentoxide (POT/V

2

O

5

) were synthesized by polymerization of o-toluidine with V

2

O

5

using (NH

4

)

2

S

2

O

8

) as an oxidant. The optical properties as photoluminescence, UV–visible absorption, optical band gap, UV–visible reflection and refractive index are studied. The optical band gap of composites found to decrease with increase in the weight percent of V

2

O

5

and the PL intensity has been found to increase with V

2

O

5

. From UV–visible absorption and reflection studies, the dielectric constant has been estimated and found to increase with V

2

O

5

. The PL emission intensity of all the polymer/V

2

O

5

composites makes them suitable for various optoelectronic devices.

M. Zulfequar, Shama Islam, G. B. V. S. Lakshmi, M. Husain Azher M. Siddiqui

Surface Morphology of Pentacene Thin Film

Growth mechanism of Pentacene thin film has been investigated with a combination of atomic force microscopy measurements and numerical modeling. Initially Pentacene grows as a monolayer fractal islands caused by DLA mechanism and evolves into compact islands as the surface coverage increases. As the branches of the first layer are widened, the monomer density on the top of the first layer increases and eventually becomes large enough to form critical islands for the growth of second layer. This phenomenon is mainly attributed to a growth instability caused by the Schwoebel barrier that prevents the newly landing molecules from hopping down the edge. Simulations based on a simple model of film growth are found to agree with experimental observations.

Varsha Rani, Akanksha Sharma, Harish Chandr Chauhan, Subhasis Ghosh

Influence of Deposition Rate on Morphology and Optical Properties of Alq3, Used as Emitter in OLEDs

Film deposition rates during vacuum evaporation influences the nucleation and growth of thin films affecting the film microstructure and hence the physical and device properties. The microstructure and surface morphologies of thin films affect the device behavior of OLEDs, particularly when films are very thin. We are reporting a systematic study on the role of film deposition rate in determining the microstructure of small molecular organic thin films. The study would be important for the throughput, performance and stability of OLED based displays and white lights. In this work, we deposited a large number of organic thin films of popular small molecular material Alq

3

(Tris (8-hydroxyquinoline) aluminium) at a wide deposition range from ~ 1 to 100 A

0

/s. The influence of deposition rates on the surface roughness and optical constants of Alq

3

films has been studied using atomic force microscopy (AFM), photoluminescence (PL), spectroscopic ellipsometry (SE) and Time Correlated Single Photon Counting (TCSPC) measurements. We find a correlation between deposition rates, film densities and surface roughness.

Vivek Kumar Shukla, Vibha Tripathi, Debjit Datta, Satyendra Kumar

Display and Lightening

Frontmatter

An Energy Efficient and High Color Rendering Index Candle Light-Style Organic Light Emitting Diode for Illumination

We demonstrate in this communication the feasibility of using organic light-emitting diode (OLED) technology to fabricate a environmental-friendly, energy efficient and high quality candle light-style OLED for illumination devices. Resulting device with yellowish orange emission, CIE coordinates (0.52, 0.43), with a color temperature of 2,000 K and color rendering index 93, closely matching to (0.52, 0.42) and 1,914 K of a white candle studied. The emissive spectrum of candle light OLED shows an 81 % similarity with that of the white candle. The candle light-style OLED exhibits a color rendering index of 93 and power efficiency of 19 lm/W, which is nearly 20 times more efficient than the conventional candles.

Sudhir Kumar, Jwo-Huei Jou, Chun-Yu Hsieh, Yung-Cheng Jou, Jing-Ru Tseng

Design and Fabrication of Computer Generated Hologram for Virtual Projection of a Reticle Pattern

In this paper, we present the design and fabrication of an on-axis Fresnel Computer Generated Hologram (CGH) which on illuminating with the laser diode projects the virtual image of a reticle pattern. This can find application in an aiming sight where the reticle pattern is projected onto a distant target. An iterative optimization algorithm has been used to design the CGH. The CGH of about 20 mm size with 5 microns pixel size is fabricated using a maskless lithography system.

Alpana Bhagatji, Amit K. Agarwal, G. Unnikrishnan

An OFDMA PHY System on Chip Design Methodology

This topic presents the design methodology for designing a real-time OFDMA based wireless physical layer (PHY) system. An OFDMA based wireless system consists of complex and computationally intensive processing modules, such as FFT/IFFT, User Allocator, Turbo Encoder/Decoder, Channel Estimator and Compensator, MIMO and Time-Frequency Synchronizer. However, the computation has to be done within a very short time regarding to fix frame duration restriction of OFDMA system. On the other hand, the power consumption and chip size also have to be very small due to battery operated system and mobile application. Therefore, optimization has to be done from all stages of design steps, such as from algorithm and architecture exploration, up to implementation level such as design synthesis, and placement and routing. Algorithm and architecture level plays an important role in determining final system performances. Some architecture design method for performance improvement, such as parallel processing, pipelined, folding, unfolding are also used in this design approach. The real-time performance is measured in FPGA based system prototyping. System validation is done in RTL level, Radio Conformance Test and Field Test.

Trio Adiono

Physical and Electrical Characterisation of 3C-SiC and 4H-SiC for Power Semiconductor Device Applications

This paper brings together a host of physical and electrical characterization aimed at overcoming the main issues that are hampering the widespread uptake of silicon carbide power device technology. We present three major obstacles and subsequently provide analysis and possible solutions. The first is reducing wafer bow via a novel with 3C-SiC epitaxial process above wafer bonded poly silicon carbide/silicon structures. Next thermal gate oxidation of silicon carbide and corresponding interface quality as a function of flow rate is analysed. We show that interface trap density is best for minimized oxygen flow rates. Finally we examine the robustness of silicon carbide ohmic contacts to p-type material, demonstrating specific contact resistivities that are close to the state of the art.

M. R. Jennings, C. A. Fisher, S. M. Thomas, Y. Sharma, D. Walker, A. Sanchez, A. Pérez-Tomás, D. P. Hamilton, P. M. Gammon, S. E. Burrows, F. Li, P. A. Mawby
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