Asian Research Thesis Index

Abstract

In recent years, the demand of polymers is growing progressively in a wide variety of fields extending from everyday life to medical and high technological applications due to their unique inherent properties like lightweight, flexibility, weather and corrosion-resistance and low cost. Considering the bulk properties of polymer an effort has been made to modify the structural, morphological, electrical and optical properties of near-surface layer of polymer by ion implantation. Indeed, it is a useful technique to modify surface properties of polymers without altering their bulk properties. In particular, with an improvement in electrical conductivity the implanted polymer can be utilized as a promising candidate for its future utilization in the field of plastic electronics. In the present study, the effects of 400 keV C+, Cr+ and Ag+ ion implantation on Polymethylmethacrylate (PMMA) have been examined at different ion fluences ranging from 5x1013 to 5x1015 ions/cm2. The ion penetration depths have been estimated with the help of SRIM simulation. The chemical and structural modifications in implanted PMMA are examined by Fourier Transform Infrared and Raman Spectroscopy (FTIR), respectively. The surface topographical examination of the implanted polymer has been performed using Atomic Force Microscope (AFM). The effects of ion implantation on electrical and optical properties of PMMA have been investigated by four probe apparatus and UV–Visible spectroscopic analysis. The FTIR spectra confirmed the formation of C = C bonds in C+ and Cr+ implanted PMMA at a fluence of 5 × 1015 ions/cm2 while for Ag+ implanted PMMA the peak for C=C is developed at relatively lower fluence of 1 × 1015 ions/cm2. Moreover, the Raman spectra justified the growth of sp2 carbon clusterization and transformation of C+, Cr+ and Ag+ implanted layer of PMMA into quasi-continuous amorphous carbon at implantation fluence of about ≥5x1014 ions/cm2. The AFM images showed the topographical modification due to ion implantation on PMMA. However, the extent of modification depends on the type of ions and increase in ion fluence. The roughness analysis revealed the smoothness of the surface of C+ and Cr+ implanted PMMA with increasing ion fluence. On the other hand, the implantation of Ag+ ions showed dominant effects on the surface of PMMA rather than C+ and Cr+ implantation. As a result, the surface of Ag+ implanted PMMA became rougher due to the formation of nano-hillocks and nano sized grainy structures above the surface. Due to ion-induced structural modifications the electrical conductivity of PMMA is increased to semiconducting range with a rise in ion fluence. After C+ ion implantation the electrical conductivity of PMMA is increased from 2.14 × 10-10 S/cm (pristine) to 1.46 × 10-6 S/cm. Similarly, for Cr+ and Ag+ ion implantation the electrical conductivity has improved to 7.21 × 10-6 S/cm and 9.60 × 10-6 S/cm, respectively. The results of UV-Visible analysis also confirmed an increase in sp2 carbon clusters in implanted PMMA in the favor of other results. Due to creation of carbonaceous clusters the optical absorption spectra of PMMA exhibit a shift towards higher wavelength after C+, Cr+ and Ag+ implantation along with a significant reduction in the optical band gap energies. For C+ implanted PMMA the optical band gap is reduced from 3.13 (pristine) to 0.66 eV whereas, after Cr+ and Ag+ ion implantation it shrinks to 0.85 and 0.81 eV, respectively.

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