Optical characterization of poly(methyl methacrylate) implanted with low energy ions

doi:10.1016/j.apsusc.2012.09.056

Applied Surface Science

Volume 263, 15 December 2012, Pages 334-338

https://doi.org/10.1016/j.apsusc.2012.09.056 Get rights and content

Abstract

The samples of poly(methyl methacrylate) (PMMA) were subjected to 100 keV N⁺ and Ar⁺ ion implantation up to a maximum fluence of 2 × 10¹⁶ ions/cm². The effect of ion implantation on the optical energy gap and the refractive index has been studied through UV–visible spectroscopy. The results clearly indicate a decrease in the values of optical energy gap and an increase in the values of refractive index as an effect of ion implantation corresponding to both of the ions. It has also been observed that the changes induced by the implanted ions are more pronounced for N⁺ ions in comparison to Ar⁺ ions. This variation has been correlated with the calculated ranges of these ions in PMMA polymer using Stopping and Range of Ions in Matter (SRIM) code. Finally, an attempt has been made to correlate all the observed changes with the induced structural changes as revealed through Raman spectroscopy.

Highlights

► The study provides the optical behavior of ion-implanted poly(methyl methacrylate). ► Optical energy gap reduces from 3.13 to 0.8 and 2.8 eV for N and Ar implanted PMMA. ► Refractive index increases from 1.54 to 2.71 and 2.02 for N and Ar implanted PMMA. ► The changes after N and Ar implantation are justified by Raman spectroscopy. ► The implanted PMMA may find extensive applications in opto-electronic devices.

Introduction

In modern era, polymers have emerged as most promising materials for various scientific and technological applications. This has become possible because of their excellent inherent properties which can further be modified by various treatments including chemical doping, heat treatment, ion implantation, etc. [1], [2], [3]. It is well known that energetic ions, when bombarded on a polymeric surface, can drastically alter its various chemical and physical properties. These changes, in general, are incorporated by various elastic and inelastic collisions between the energetic incident ions and the target polymer. However, the extent of these changes produced depends on the structure of the polymer and the experimental parameters of the ion irradiation like ion energy, fluence, mass, charge, etc. [4], [5], [6], [7]. The improved properties of the polymers through proper tailoring make them promising materials in today's world.

Among the broad variety of available polymers, PMMA (monomer composition: C₅H₈O₂) is one of the outstanding material most widely studied in the last decade [8], [9], [10]. Due to its excellent and promising chemico-physical properties, it finds wide applications in many technological and productive fields. It exhibits good mechanical strength, chemical inertness, thermal stability, weather resistance, moldability, etc. Apart from all these, it finds an extensive application in various optical and opto-electronic devices due to its excellent optical properties from near-UV to near-IR regions [11], [12]. Ion implantation studies in PMMA attract special attention because of its usability in the fabrication of optical waveguides, lithography, biomedical applications, etc. [12], [13], [14], [15], [16], [17]. Some studies on the effect of N⁺ and Ar⁺ ion implantation in PMMA are available in the literature, but from different point of view. Leontyev et al. [13] and Kulish et al. [14] have concentrated mainly on the refractive index behavior of PMMA under N⁺ ion implantation. He et al. [15] studied the biomedical applications of Ar⁺ ion-implanted PMMA. Koval [16] has studied the etching mechanism of Ar⁺ ion-implanted PMMA. Tsvetkova et al. [17] have quoted the enhanced photoluminescence after implantation to Si⁺ ions in PMMA at different energies.

In the present work, we have carried out a systematic study on the effect of 100 keV N⁺ and Ar⁺ ion implantation on the optical energy gap and refractive index of PMMA polymer and simultaneously correlated to the induced structural changes as revealed through Raman spectroscopy. Such studies will not only lead to the better understanding of the fundamental processes involved during the ion–polymer interaction responsible for the tuning of various properties of the polymers but will also enhance the industrial applications of polymers as materials with the reduced cost.

Section snippets

Materials and methods

The samples (1 cm × 1 cm) of PMMA (Goodfellow, UK) were cut from a flat sheet of thickness 500 μm and subjected to implantation of 100 keV N⁺ and Ar⁺ ions using Low Energy Ion Beam Facility (LEIBF) available at Inter University Accelerator Centre (IUAC), New Delhi, India. The irradiation of these samples was performed at room temperature at normal incidence to the surface under high vacuum (∼10⁻⁶ Torr) up to a maximum dose of 2 × 10¹⁶ ions/cm². The beam current density was kept ∼0.6 μA/cm² in order to

UV–visible studies

The optical behavior of the virgin- and ion-implanted samples has been analyzed by recording the UV–visible transmission (T) and reflection (R) spectra in the wavelength range 190–900 nm. Since the measured values of T involve the reflection from top and bottom air–sample interfaces, therefore, these values need to be corrected before incorporating them in the relevant equations. Taking into account these corrections, the transmission coefficient (t) for light for a single pass through the

Conclusion

From the observed behavior of PMMA under ion implantation, it may be concluded that it shows a drastic change in its optical parameters. The values of optical energy gap decreases while those for refractive index increases with the increasing fluence of implanted ion. It may also be inferred that the changes induced also depends upon the implanted ion and the depth of the ion to which it impinges in the host polymer matrix. All the observed changes have been correlated to the induced structural

Acknowledgements

The authors are thankful to Dr. D. Kanjilal, IUAC, New Delhi, for valuable discussions. Thanks are due to Dr. P. Kumar, IUAC for helping during irradiation. Raman spectroscopic measurements were performed at UGC-DAE Consortium for Scientific Research, Indore, India. Authors are grateful to Prof. Vasant Sathe and Mr. Manoj Kumar for their kind cooperation during the Raman experiments. One of the authors (PKG) is thankful to CSIR, New Delhi for financial assistance in form of SRF.

References (26)

E.H. Lee
Nucl. Instrum. Methods B
(1999)
W. Hong et al.
Appl. Surf. Sci.
(2001)
R.M. Radwan et al.
Nucl. Instrum. Methods Phys. Res. B
(2008)
S.R. Tatro et al.
Polymer
(2003)
G.B. Hadjichristov et al.
Appl. Surf. Sci.
(2008)
C.T. Lin et al.
Polymer
(2010)
S.W. Kuo et al.
Polymer
(2003)
T. Tsvetkova et al.
Vacuum
(2009)
F.W. Billmeyer
Textbook of Polymer Science
(2005)
M.F. Zaki
J. Phys. D: Appl. Phys.
(2008)

T. Sharma et al.

J. Appl. Phys.

(2007)

D. Dorranian et al.

J. Non-oxide Glasses

(2009)

Cited by (29)

Investigations of N+-ion implanted polymethylmethacrylate for flexible electronics
2022, Optical Materials
The samples of Polymethylmethacrylate (PMMA) have been implanted with 700 keV N⁺-ions at different fluences ranging from 3 × 10¹³ to 5 × 10¹⁴ ions/cm² using Pelletron accelerator. The modifications in structural, electrical, morphological and optical properties of implanted polymer are examined using Raman spectrometer, Four probe technique, scanning electron microscope and UV–visible spectrometer, respectively. Raman spectroscopic analysis confirms the formation of carbonaceous structures at relatively lower fluence ≥2 × 10¹⁴ N⁺/cm². The formation of carbonaceous network results in enhancement of conductivity of a PMMA sample from 2.14 × 10⁻¹⁰ to semiconducting regime (1.06 × 10⁻⁶ S/cm). The microscopic images show surface modifications in terms of ion-induced cracks, pores and wrinkles with increasing ion fluence. The optical bandgap reduces from 3.18 to 2.97 eV after implantation at 5 × 10¹⁴ ions/cm². Moreover, the Urbach energy, photoconductivity and refractive index are found to increase with increasing ion fluence. The combination of increased electrical conductivity and reduced optical band gap energy makes PMMA a promising candidate for flexible electronics.
Role of energy loss-range profile of heavy ions in tailoring the optical properties of polycarbonate
2021, Optical Materials
Citation Excerpt :
Recently, in our previous investigation on N+, Ar+ and Kr+ implantation in optically important polymers, poly-allyl-diglycol-carbonate (CR-39) and polymethyl methacrylate (PMMA), the changes in optical properties have also been observed to be more pronounced in the case of N+ implantation in comparison to the Ar+ and Kr+ implantation [21,37]. Many reports have studied ion implantation in polymers with different ions having the same energy and the same doses [1,2,14–38], however reports that are related to the modification in optical properties of polymers through ion implantation with different ions having energies in such a way to have the same penetration depth are scarce [38]. Therefore, in this work we have investigated the effect of low-energy (46–200 keV) N+, Ar+ and Kr+ ion implantation on the optical and structural properties of optically important polymer, polycarbonate (PC) [12,18–20,22,23,31].
Polycarbonate (PC) samples have been implanted with 115 keV N⁺, Ar⁺ and Kr⁺ at fluences ranging from 5x10¹⁴ to 1x10¹⁶ ions/cm² to be employed for optical studies. A Decrease in optical energy gap, enhancement in reflectivity and reduction in transmittance, particularly in UV-region, is observed for all implanted samples. The change in optical properties of PC, first, by keeping energy deposited/cm² constant (i.e. keeping energy*fluence constant) and then by keeping same depth of penetration for different ions have been analysed in detail. The changes are found to be more prominent for N⁺ compared to Ar⁺ and Kr⁺ when the fluence/energy deposited/cm² by the ions is same. Further, the energy for N⁺ is reduced to 46 keV, while for Kr⁺ it is increased to 200 keV to ensure the same penetration depth for N⁺, Ar⁺ and Kr⁺ in PC. Finally, the results are explained on the basis of energy loss-range profiles of these ions in polycarbonate and through Raman spectroscopy. This study convincingly demonstrates that not only the types of ion species, their energies and fluences, but the total energy deposited by ions and their depth of penetration also plays an important role in tailoring the optical properties of polymeric materials.
Argon ion implanted CR-39 polymer: Optical and structural characterization
2021, Optical Materials
The samples of Polyallyl diglycol Carbonate (CR-39) were implanted with 100 keV argon ions at fluences 1 × 10¹⁵, 5 × 10¹⁵ and 1 × 10¹⁶ ions/cm² to be employed for optical and structural studies. The changes in transmittance, reflectance, optical energy gap and refractive index have been studied through the UV–Vis–NIR spectroscopic technique. The enhancement in reflectivity and a strong reduction in transmittance, particularly in the UV region, are observed after Ar⁺ implantation in CR-39 samples. The absorbance value remains low ~0.10, 0.15 and 0.20 in the key communication wavelength region i.e. 800–1600 nm for sample implanted at the fluence of 1 × 10¹⁵, 5 × 10¹⁵, 1 × 10¹⁶ Ar⁺/cm², respectively. The Optical energy gap (E_OPT) is determined to be 0.92 eV for the implanted layer of the sample implanted at the fluence of 1 × 10¹⁶ Ar⁺/cm², whereas 3.70 eV for the pristine sample. The surface electrical conductivity is increased from ~1.49 × 10⁻¹⁴ S (pristine sample) to ~8.34 × 10⁻¹⁰ S for sample implanted at the fluence of 1 × 10¹⁶ Ar⁺/cm². The formation of conjugated π-bond (-CC-) structure with Ar⁺ implantation is confirmed via FTIR and Raman measurements. TGA results are analysed in detail and are found to be in strong agreement with the changes observed in different properties of CR-39 after ion implantation.
Surface layer morphology of the high fluence Fe implanted polyethylene - Correlation with the magnetic and optical behavior
2020, Vacuum
Fe/Polyethylene nanocomposite was synthesized by ion beam implantation of ⁵⁶Fe⁺ into bulk high-density polyethylene. Nanoscale surface morphology along with magnetic and optical behavior was investigated. The aim of the research was to investigate changes of polyethylene's surface layer morphology with the change of Fe implantation fluence in the high fluence range and to find correlations with the magnetic and optical behavior. Four implantation fluences were applied: 5 × 10¹⁶, 1 × 10¹⁷, 2 × 10¹⁷ and 5 × 10¹⁷ cm⁻², while the implantation energy was 95 keV. Concentration profiles of implanted Fe were analyzed by Rutherford backscattering spectrometry, showing Fe concentration profile maxima closer to the surface with increasing implantation fluence. Cross-sectional transmission electron microscopy showed the formation of metallic nanoparticles with sizes in a range from below 1 nm up to few tens of nanometers, depending on the fluence, and for the highest implantation fluence, a continuous layer was formed. Magneto-optic Kerr effect magnetometry demonstrates weak ferromagnetic behavior for the 2 higher fluences, and superparamagnetic for the 2 lower fluences. The UV-VIS remission function spectra show the peak in the UV region, which we attribute to iron nanoparticles.
Low energy B<sup>+</sup> implantation induced optical and structural characteristics of aliphatic and aromatic polymers
2019, Vacuum
Citation Excerpt :
The peak observed at 1449 cm−1 is due to CH3 deformation. Presence of C=O carbonyl group in virgin PMMA is confirmed by the appearance of the peak at 1728 cm−1 [16,27,44,45]. With implantation for fluences of 1 × 1015 B+ cm−2 and 1 × 1016 B+ cm−2 (Fig. 2, curve b and c), the intensities of all characteristics bands decrease pointing towards rupture of chemical bonds and structural modification in PMMA after ion implantation.
Influence of 50 keV boron ion implantation on the optical and structural properties of aliphatic PMMA and aromatic PET polymers has been studied. Samples were implanted with various fluences ranging from 1 × 10¹⁵ to 5 × 10¹⁶ B⁺ cm⁻² at normal incidences. The intensity of most of the fundamental bands of these polymers, appearing in Raman and FTIR spectra, decreases significantly pointing towards structural rearrangement as an effect of low energy B⁺ implantation. UV–visible spectroscopy reveals significant increase in the value of disorder content (Urbach energy) and refractive index with increasing implantation dose for both the polymers. The decline in optical energy gap is found to be 22.3% for PMMA and 11.3% for PET due to B⁺ implantation. The degree of structural and optical modifications is more in PMMA in comparison to PET besides having same electronic to nuclear energy loss ratio. Both the chain scissioning and cross-linking mechanisms play significant role in the modification of the structure and properties of PMMA while chain scissioning is dominant in PET for the same. Such ion beam induced alteration in optical and structural properties makes these polymers ideal for making optical sensors, sun glasses, UV blocking devices and intraocular lenses etc.
Effect of silver ion-induced disorder on morphological, chemical and optical properties of poly (methyl methacrylate)
2016, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Ion implantation is a versatile technique to tailor the surface properties of polymers in a controlled manner. In the present study, samples of poly (methyl methacrylate) (PMMA) have been implanted with 400 keV silver (Ag⁺) ion beam to various ion fluences ranging from 5 × 10¹³ to 5 × 10¹⁵ ions/cm². The effect of Ag⁺ ion-induced disorder on morphological, chemical and optical properties of PMMA is analyzed using Atomic Force Microscope (AFM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–Vis) spectroscopy. Furthermore, the electrical conductivity of pristine and implanted PMMA is measured using four probe apparatus. The AFM images revealed the growth of nano-sized grainy structures and hillocks above the surface of implanted PMMA. The FTIR spectra confirmed the modifications in chemical structure of PMMA along with the formation of CC carbon contents. The refractive index, extinction coefficient and photoconductivity of implanted PMMA have been found to increase as a function of ion fluence. Simultaneously, indirect optical band gap is reduced from 3.13 to 0.81 eV at a relatively high fluence (5 × 10¹⁵ ions/cm²). A linear correlation has been established between the band gap and Urbach energies. Moreover, the electrical conductivity of Ag⁺ implanted PMMA has increased from 2.14 × 10⁻¹⁰ (pristine) to 9.6 × 10⁻⁶ S/cm.

View all citing articles on Scopus

View full text

Optical characterization of poly(methyl methacrylate) implanted with low energy ions

Abstract

Highlights

Introduction

Section snippets

Materials and methods

UV–visible studies

Conclusion

Acknowledgements

Nucl. Instrum. Methods B

Appl. Surf. Sci.

Nucl. Instrum. Methods Phys. Res. B

Polymer

Appl. Surf. Sci.

Polymer

Polymer

Vacuum

Textbook of Polymer Science

J. Phys. D: Appl. Phys.

J. Appl. Phys.

J. Non-oxide Glasses