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.
