Carbon Nanomaterial Electronics: Devices and Applications

Since the last 30 years, incredible amount of research has been performed toward finding novel, smart, and cost-effective materials for device applications. Carbon among other materials is one of the most versatile elements present in nature that can produce different allotropes due to the existence of its variable hybridizations. Moreover, graphene is being considered as the mother of other carbon allotropes as they are the structurally derived allotropes of different dimensionalities such as fullerene, graphene quantum dots (0-D), carbon nanotubes, nanohorns, nanofibers, graphene nanoribbon (1-D), graphene (2-D), graphite and diamond (3-D) and are being implemented for various device applications. The synthesis methodologies of these allotropes including arc discharge, laser ablation, and chemical vapor deposition (CVD) techniques are discussed in this chapter to produce 0-D, 1-D, and 2-D carbon allotropes. CVD is considered as the most reliable technique for bulk production of highly crystalline graphene and its derivatives, single-crystalline diamonds, CNTs, and aligned CNTs on certain pre-treated substrates which are beneficial for device applications. Further, solid-state synthesis approaches such as ball milling and annealing have been adopted to generate CNTs, while graphene and offshoots have been synthesized by employing wet milling, top-down, and bottom-up processes. Also, it is noteworthy to mention that the bottom-up processes have been proven to be more effective compared to the top-down approaches for device fabrications. Furthermore, allotropes of carbon are known to be functionalized with metal-based nanoparticles, biomolecules, etc. to generate smart materials in order to obtain high-performance devices.

The discovery of fullerenes and other nanosized carbon allotropes has opened a vast new field of possibilities in nanotechnology and has become one of the most promising research areas. Carbon nanomaterials have a wide-scale scientific as well as technological importance because of their distinctly different physical, chemical and electronic properties. ‘Carbon Nanotropes’, the nanoscale carbon allotropes such as Buckminsterfullerenes (C₆₀), Carbon nanotubes (CNTs) and Graphene, show a huge potential toward various devices, sensors and catalytic applications and therefore draw a wide-scale industrial attentions. A better understanding of their formation mechanism along with their direct visualization down to nanometer-scale structural analysis is of high technological demand. Recent advancements in nanoscience and nanotechnology make it possible to study the growth/synthesis along with structure and bonding by analyzing the atomic-scale imaging of these carbon nanotropes. In this aspect, scanning tunneling microscopy (STM) would be a useful tool with extremely high spatial resolution. This chapter is mainly focused on STM imaging of some of the recent carbon nanotropes such as C₆₀, CNTs and graphene to bring together the atomic-scale structure and their related material properties.

Clever combinations of elements store energy in chemical form like a battery and then release energy pulses whenever and wherever it is needed. Every chemical element in the periodic table is special, but some elements are more special than others. An essential element of life has to multitask. Carbon, the sixth element, is unwonted in its impact on our lives. Carbon lies at the heart of progression intriguing the emergence of planets, life, and us. And, more than any other entirety, carbon has greased the rapid emergence of new technologies. If we discover to replenish our rhapsodically beautiful carbon-rich world, then we may hope to leave a peerless, high-end legacy for all the generations to come. Fullerenes, graphene, carbon nanotubes, fluorescent carbon quantum dots, activated carbon, and carbon black belong to the carbon family with tremendous optical, physical, mechanical, and thermal properties. Among them, carbon nanocomposites can be synthesized with the amalgamation of different elements. Carbon nitride with covalent network compound are unlinked into beta carbon nitride and graphitic carbon nitride (g-C₃N₄) that are relatively new type of carbon based material retaining high photoresponsiveness, high intrinsic photoabsorption, semiconductive properties, high stability under physiological conditions and good biocompatibility. Use of sunlight as a sustainable source for energy generation, environmental medicament photocatalysts for heavy metal pollutant control, and water splitting by use of polymeric materials with incorporation of carbon can be achieved. An oxocarbon consists of a single carbon and single oxygen which has the ability to polymerize at the atomic level, thus forming very long carbon chains. The smart material can be obtained by homogenizing with carbon nanocomposites synthesized in an inexpensive process like printing and roll to roll which are ideal for flexible energy generation and storage. To overcome the extremely high volume change by alloying reaction with lithium for commercialization, carbonaceous materials are induced to improve the structural stability of the electrodes. Lithium-ion batteries (LIBs) are considered as efficacious and practical technology for electrochemical energy storage. Due to high theoretical capacities, electrochemically active metal oxides materialize as promising candidate for the anodes in LIBs. Carbon coating can productively improve the surface chemistry of active material and electrode conductivity and protect the electrode from interacting with electrolyte, enhancing the shelf life of batteries, etc. The fascinating properties of these materials are observed in the emerging strategies for tailoring carbon-based nanocomposites in catalytic organic transformation properties, energy storage, absorbents, biomedical, textile, sensor, molecular imaging, bioimaging, drug, and gene delivery.

The last two decades have witnessed a large volume of research revolving around structure–property correlation in carbon-based nanocomposites, synthesized by several methods. The electronic properties of carbon-based nanocomposites vary mainly as a function of the kind of reinforcement, method of synthesis, and structure-dependent parameter. The structure-dependent parameter is highly influenced by the reinforcement and method of synthesis and plays a vital role in determining the ionic and electronic transport phenomenon in these materials. In other words, the interaction between electrons and the equilibrium 0-D (point) defects, along with different types of 2-D interfaces, plays an imperative function in the understanding of electronic properties, apart from the physical and chemical properties of these materials. The present chapter offers a concise overview of the state of the art on research and detailed discussions on some recent developments in understanding the electronic properties of some conventional carbon-based nanocomposites (synthesized by different techniques) based on the structure–property correlation in these materials. Finally, some of the significant challenges in this field have been addressed from industrial and fundamental viewpoints.

Metal-matrix nanocomposite has a multitude of applications. The local structure and optical modifications of these materials are studied  using fullerene as a matrix material, incorporated by noble metal nanoparticles of Cu. These metal-fullerene nanocomposites are useful because of the amalgamation of different properties of the fullerene and metal nanoparticles. Cu being cheap and abundant in nature has an advantage over other metal nanoparticles. Cu nanoparticles being more reactive are stabilized by incorporating them in fullerene matrix and therefore can be used in various applications. The structural and optical properties (mainly SPR) of Cu-fullerene nanocomposites are tuned by different methods and synthesis procedures such as (a) Ion irradiation, (b) ion implantation, (c) thermal annealing and (d) increasing the concentration of the Cu nanoparticles in the matrix material. In this review all the factors influencing the tuning of structural and optical properties of Cu-fullerene nanocomposites are investigated in detail. Each property is studied by different characterization techniques such as, TEM, UV–visible spectroscopy and electron diffraction method.

Carbon is one of the most versatile elements in the periodic table and is known to occur in various allotropic forms. It has been widely explored since the eighteenth century and its investigation in various forms has witnessed continuous growth thereafter. The effect of these advancements has guided numerous discoveries which have not only addressed several aspects of materials physics, but also their applications. The development of theoretical and computational tools accompanied by novel characterization techniques along with the ability to synthesize these reduced dimensionalities of the carbon family like fullerene, carbon nanotubes, graphene, carbon quantum dots, etc. has significantly improved the understanding of these nanostructures. The ability of computational and theoretical techniques to predict and provide insights into the structure and properties of systems plays a crucial part in substantiating experimental findings. Theoretical and computational modeling of various carbon nanostructures such as fullerene, carbon nanotubes, graphene, and carbon quantum dots will be critically reviewed. The chapter begins with the description of the historical timeline of carbon nanostructures. How the models developed over time have led to the development of carbon nanoforms is reviewed. The impact of theoretical and computational approaches in understanding the physics of these carbon nanostructures is also highlighted.

Low-dimensional carbon-based nanomaterials have generated enormous interest in the scientific community due to their quantum confinement induced novel electronic, magnetic, optical, thermal, mechanical, and chemical properties. The synthesis of two-dimensional graphene has provided a fertile experimental platform for studying these exotic properties and harnessing them for promising carbon-based nanoelectronic devices. This chapter reviews the edge-induced spintronic properties of nanographene ribbons (GNR) from a theoretical perspective and discusses their possible applications in nanoscale devices. The presence of edges bears a crucial impact on the low-energy spectrum of the itinerant Dirac electrons in graphene. Nanoribbons with zigzag edges (ZGNR) possess robust localized edge states near the Fermi energy that induces ferrimagnetic spin polarization along the zigzag edge. In contrast, such localized edge states are absent in nanoribbons with armchair edges (AGNR). We discuss how applying a transverse electric field to ZGNRs, or chemical modification of its edges, can break the spin degeneracy and lead to a half-metallic state which shows spin polarization of the current or the spin-filtering behavior that is very crucial for spintronic device applications. The presence of edges also endows GNRs with peculiar transport properties characterized by the absence of Anderson localization, making them ideal for ultra-low power electronics. Our review highlights the edge states’ role as the origin of GNR’s diverse physical and chemical properties. It hence has a significant bearing on the future realization of carbon nanomaterial electronics.

The problems associated with attempting to scale down traditional metal oxide field-effect transistors (MOSFET) have led researchers to look into CNT-based field-effect transistors (CNFETs), as an alternative. Though the scaling of MOSFET has been the driving force toward the technological advancement, but due to continuous scaling, various secondary effects which include short channel effects, high leakage current, excessive process variation, and reliability issues degrade the device performance. On the other hand, CNFETs are not subjected to the scaling problems. The operation principle of the CNFET is similar to traditional MOSFET but the conduction phenomena are different. The traditional MOSFETs are based on the drift and diffusion phenomena in which channel length is very large as compared to mean free path of charge carriers whereas the CNFETs are based on ballistic transport conduction mechanism, in which channel length is very small as compared to mean free path of charge carriers. In CNFET, electrons are injected from source to drain and transported through the nanotubes without scattering. Due to ballistic transport the nanotubes act as a perfect conductor for electrons such that the full quantum information of these electrons (momentum, energy, spin) can be transferred without losses. The channel current in CNFETs depends on gate voltage, number of nanotubes in channel, dielectric material and its thickness, and diameter and chirality of carbon nanotubes. So in this chapter we shall discuss different device structures of CNFET, steps involved in the fabrication of CNFETs, advantages and limitations of various methods involved in the synthesis of CNTs, conduction models, and performance parameters.

Over the last two decades, carbon nanomaterials including two-dimensional graphene, one-dimensional carbon nanotubes (CNTs), and zero-dimensional carbon quantum dots, fullerenes have gained tremendous attention from researchers due to their unique optical, electronic, mechanical, chemical, and thermal properties. Furthermore, to enhance the properties of pristine carbon nanomaterials, their hybrid materials have been synthesized. Even though tremendous advancement in carbon nanomaterials-based electronic devices and sensors has been achieved, a few challenges need to be addressed before the commercialization of carbon nanomaterials-based devices. Apart from the improvements, the device to device variations, and extrinsic factors like dielectric layers, metal contact resistance remain an issue. Strategies such as chemically tuning and enhancing the properties of carbon nanomaterials are important for the further improvement of carbon nanomaterial-based device performance. This chapter focuses on understanding the basic electronic properties of graphene, CNT. and carbon quantum dots/fullerenes and their applications in electronic devices (field-effect transistors, diodes, etc.), optoelectronics, and various chemical and physical sensors.

The carbon nanomaterials have been receiving great interest in department of nanoscience and technology an account of their extraordinary physical, chemical and electronic properties. Carbon nanomaterials have found emerging applications in various fields, viz. drug delivery, energy conversion and storage devices, field emission electronics, biosensors and water treatment. This book chapter is focused on health and environmental applications of fullerenes, carbon nanotubes and graphene. The closed cage structure, various redox states, stability, functionalization ability and light-induced switching behaviour of fullerenes trend in development of supercapacitors, sensors, optical and other electronic devices. The large surface area and fast charge transfer ability of carbon nanotubes enable their sensing ability for the detection of catechol, para-cresol and para-nitrophenol, hydroquinone, etc. that are widely located in aqueous and diverse biological systems. The adsorption and conjugating ability of carbon nanotubes with therapeutic and diagnostic agents signifies their importance in pharmaceutical and medical applications. Carbon nanotubes are also important in regeneration of tissues, diagnosis of biomolecules, extraction or enantiomer separation of chiral drug molecules and analysis of various drug molecules. The high surface-to-volume ratio and hydrophobic nature of carbon nanotubes facilitate strong affinities towards adsorption and removal of wide range of aliphatic and aromatic contaminants which include pathogenic organisms, and cyanobacterial toxins in water samples. The anti-microbial activity of carbon nanotubes helps in killing of pathogen present in water treatment plants. The unique morphological and structural features of graphene make them suitable for emerging energy and environmental applications, ranging from energy conversion and storage to green corona discharges for pollution control.

An enormous demand for advance touchscreen gadgets has drawn significant scientific attention for last few years due to the substantial developments in the field of flexible and portable electronics. Thin coating of tin doped indium oxide (ITO) material offers good electrical conductivity and high optical transparency and thus, is widely adopted as the transparent conductive material for touchscreens and optoelectronic display devices. However, limited availability of indium (In), and brittleness of ITO thin coatings limits their use in next-generation flexible displays. Graphene is an emerging material in this aspect due to good electrical conductivity, high optical transparency and mechanical stretchability makes graphene a better choice for flexible electronics and display devices. Graphene possesses sufficient robustness to be used in the harsh environment. Though, defect free-high quality, volume production and limited fabrication compatibility are the major challenges in commercialization of graphene-based flexible devices. In this chapter we have briefly reviewed the basic understanding of touchscreen technology and the importance of graphene in flexible touchscreens as well as the remaining challenges for commercialization of graphene-based touchscreens.

Recent progress on the synthesis and scalable manufacturing of carbon nanotubes (CNTs) remain critical to exploit various commercial applications. Here we review breakthroughs in the alignment of CNTs, and highlight related major ongoing research domain along with their challenges. Some promising applications capitalizing the synthesis techniques along with the characteristics of CNTs are also explained in context to the recent developments of CNT alignment. The prime objective of this chapter is to provide an up-to-date scientific framework of this niche emerging research area as well as on the growth of CNTs either by in-situ or ex-situ synthesis techniques followed by its alignment during growth or post-growth processing. This chapter deals with various mechanism of CNTs alignment, its process parameters, and the critical challenges associated with the individual technique. Numerous novel applications utilizing the characteristics of aligned CNTs are also discussed.

Infra-Red (IR) radiation is the thermal radiation which is characterized by the temperature of the emitting source. Hence, IR photodetectors could be used for a number of applications such as surveillance in defence, non-contact thermometry, non-contact human access control, bolometers and terahertz, etc. Infra-Red spans over a vast range of wavelengths, i.e. from 1 μm to several tens of μm. While there are several materials used for sensing the IR radiation, broadly the underlying physical principles of IR detections could be classified into three distinct categories i.e. photothermoelectrics, photovoltaics and photogating. The heating effect of IR radiation brings about the thermopower considerations in case of non-uniform illumination or inhomogeneity of the sample leading to photothermoelectric effect. While, in case photovoltaics, the generation of photocurrent as a result of exitonic contribution modulates the conductivity of the device. However, in photogating, the Fermi energy of the sensor material is controlled through optical illuminations. In this chapter, we restrict ourselves to photovoltaic and photothermoelectrics in case of reduced graphene oxide and its composites. Graphene and its derivatives, such as graphene oxide, graphene nanoribbons, graphene quantum dots, etc., have revealed a wide range of novel physical properties and led to a spectrum of functional devices. Because of its small yet tunable bandgap through controlled reduction, graphene oxide is a potential choice for IR detection devices. Here in this chapter, we discuss its physical attributes which could be utilized for IR detection.

Catalytic palladium nanoparticle modified reduced graphene oxide (rGO) prepared in the laboratory showed a characteristic variation in hydrogen response when the operating temperature was raised from 30 °C to 125 °C. When exposed to a particular hydrogen concentration, the response comprising of initial increase in device resistance (response-1) followed by decrease (response-2) was observed up to 75 °C. Beyond 75 °C a transition in hydrogen response was observed, and only the response-1 prevailed from 100 °C. This transition temperature was reduced to 50 °C, when rGO was pretreated with ammonia solution at a temperature of 100 °C. On pretreatment with lower ammonia concentration, the response-2 was completely eliminated. Furthermore, without treatment with palladium nanoparticles, rGO films (both untreated and ammonia treated) showed negligible response toward various concentrations of hydrogen in the studied temperature range (30 °C–125 °C). The material characterization and sensing results were analyzed in detail and a suitable sensing model was proposed to explain the performance of these sensors.

It has long been concluded that solar energy holds the best potential for meeting the planet’s long-term energy needs, however, as of now, more than 70% of the global energy demand is still being fulfilled by non-renewable sources. Recently, perovskite solar cells (PSCs) have attracted enormous interest because they can combine the benefits of low cost and high efficiency with the ease of processing. In the last decade, PSCs have seen a remarkable improvement in terms of efficiency, however, there are still some hurdles in its path before they can be commercialized. The major obstacle being their long-term stability in harsh environmental conditions. In addition, the use of vacuum deposited transparent conductive oxides and noble metals as an electrode is also hindering its prospects. Among potential candidates, carbon-based materials provide a good alternative because of their suitable work function, high- carrier mobility, electrical conductivity, stability, and flexibility. The chapter discusses detailed information about different carbon-based materials and their properties which make them a front-runner in future generation PSCs. We will also discuss different advantages like flexibility, photostability, thermal stability, and scalability which will lead to a pathway toward the commercialization of PSCs using carbon-based electrodes.

Nanostructured carbon allotropes have gained much attention in the scientific community due to their vast applications in various fields. The carbon nanomaterials can be found in form of various different hybridization states and each of them having unique electronic properties. The reduced dimensionalities with sp² bonded graphitic carbon form a highly delocalized electronic state, suggesting their applicability as high mobility electronic materials. Additionally, the tunable optical band gap makes them promising materials for optoelectronic device applications. Recently, carbon nanomaterials such as zero-dimensional fullerenes, one-dimensional carbon nanotubes (CNTs), and two-dimensional graphene and their derivatives have been widely investigated for the latest generation photovoltaic and optoelectronic device applications because of their chemical stability, mechanical stability, and exceptional optoelectronic properties. For example, fullerene derivatives are widely used as acceptor materials for efficient bulk heterojunction solar cells because of their ability to well-diffuse into the semiconducting polymer films and to form an intermixed layer with desired morphology, while these are used as electron transport/injection layer for perovskite solar cells and light-emitting diodes. CNTs and graphene show promise as transparent conducting electrodes for flexible and lightweight organic and perovskite optoelectronic devices. In addition, CNTs are gaining popularity as active layer components of photovoltaic devices owing to their higher aspect ratio and electrical conductivity. Furthermore, graphene oxide has also been used in the active layer of organic solar cells for efficient charge separation and charge transport owing to their large acceptor/donor interface area and continuous pathway. Recently, graphene oxide (GO) is used as a buffer layer in organic and perovskite optoelectronic devices. Specifically, GO and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) composite has been used as hole transport layer for improving the stability and efficiency of inverted perovskite solar cells. This is due to the reduced contact barrier between perovskite active layer and charge transport layer, enhanced crystallinity of perovskite morphology, and suppressed leakage current.