Preparation and investigation of the optical and DC electrical properties of plasma polymerized thin flims of 1, 1, 3, 3- tetramethoxypropane

Abstract

Plasma polymerized 1,1,3,3-tetramethoxypropane (PPTMP) thin films of different thickness yverc prepared through glow discharge of 1,1,3,3-tetramethoxypropane (TMP) under various deposition conditions using a capacitively coupled glow discharge reactor. The surface morphology of the PPTMP thin films has been studied by scanning electron speetroscopy and is observed to be smooth, uniform and pinholefree. The carbon(C), hydrogen (H) and oxygen (0) contents in PPTMP thin films were determine by Elemental Analysis. The empirical formula of the PPTMP thin films is C6.1gHs.37051OT. he structural analyses of prTMP has been characterized by infrared (IR) spectroscopy and their thermal properties were also studied by differential thermal analysis (OTA) and thermogravimetric analysis (IGA). IR investigation reveals that PPIMP thin film may be formed with certain amount of conjugation. DTAfTGA analyses show that the degradation in the structure and evaluation of gases may occur at temperatures above 660 K, which may probably due to dehydrogenation and oxidative reactions in PPTMP. It is observed that the PPTMP thin films are thermally stable below about 660 K. The optical properties of as-deposited and heat-treated PPTMP thin films were analyzed by ultraviolet-visible (UV"vis) spectroscopy. From the UV-vis absorption spectra, absorption co-efficient, allowed direct transition, Eqd, allowed indirect transition, Eq,energy gaps, and Tauc parameter, B, were determined. The red shift in the maximum absorption wavelength for all the PPTMP thin films was observed as compared with the monomer maximum absorption wavelength. The current density.voltage(J-V) characteristics of PPTMP thin films of diflercnt thicknesses have been investigated at different temperatures. The J-V curves show three slopes at the lower, intermediate and higher voltage regions. It is observed that the lower voltage region, J varies as VI12, intennediate voltage region shows approximately ohmic nature and the higher voltage region is a non-ohmic region. The J-V and J-thickncss characteristics indicate that conduction in PPIMP thin films is due to space-charge-limited conduction. From the Arrhenius plots of J vs. inverse of absolute temperature for the applied voltages 2 and 10 V, the activation energies (~E) arc estimated to be about 0.\9:t 0.02 and 0.81 :t 0.02 eV in the lower and higher temperature regions respectively. In the low temperature region the electron and/or holes from traps and/or sublevels and in the high temperature region ions from the material may be involved in the conduction mechanisms.