Abstract:
In this work, plasma polymerized cyclohexane (PPCH) thin films were synthesized at
room temperature on to glass substrates by using a capacitively coupled parallel plate
glow discharge system. The surface morphology and elemental analysis of PPCH thin
films were investigated by Field Emission Scanning Electron Microscopy (FESEM) and
Energy Dispersive X-ray (EDX) Analysis. From SEM analysis, a smooth, flawless and
pinhole free surface of PPCH thin films was observed. No significant change was
observed between the surface of the PPCH thin films of different thicknesses. The EDX
analysis indicated the presence of prominent percentage of carbon in PPCH thin films
with a small percentage of oxygen. The structural analyses were performed by
Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR).
Chemical structures of PPCH thin films by ATR-FTIR revealed that the polymerized
films are structurally different to some extent compared with the monomer. The films are
hydrocarbon-rich with presence of oxygen in the form of O-H and C-O functional
groups. Thermal analyses were performed by DTA/TGA. From thermal analysis, it is
observed that below the temperature 510 K and 530 K, the rate of weight loss is very
slow in both air and N2
atmosphere respectively and are thermally stable. Above 510 K
weight loss takes place in different stages in air and that in N2 takes place in one stage
reaction above 530 K. The optical properties of PPCH thin films were investigated by
UV-visible spectroscopic analysis. The absorption coefficients, at various wavelengths
were calculated using UV-vis data. The direct transition energy (Eg(d)) and indirect
transition energy (Eg(i)) were obtained by Tauc formula. Eg(d) of PPCH thin films is found
between 2.97 and 3.61 eV for different thicknesses and Eg(i) is found to be 1.83 to 2.31
eV.
The current density-voltage (J-V) characteristics of PPCH revealed that in the low
voltage region, the conduction current obeys Ohm’s law while in higher voltage region
the conduction current shows non-Ohmic behavior. Schottky conduction mechanism is
dominant in PPCH thin films in the non-Ohmic region. It is found that at low
temperature region, activation energies are about 0.14±0.05 and 0.16±0.05 eV for
applied voltages 10 and 50 V respectively and at the higher temperature region,
activation energies are about 0.57 ±0.05 and 0.83±.05 eV for applied voltages 10 and
50 V respectively.
