Fabrication and structural characterization of plasma polymerized polypyrrole thin film

Abstract

Polypyrrole films deposited on glass or silicon substrates by plasma polymerization under different radio frequency power are investigated in this study. Targeting on electrical conduction, lower RF power for deposition is particularly chosen. The microstructures of deposited films were carefully studied by following instruments; Scanning electron microscope for surface morphology; Fourier transform infrared spectroscopy for the molecular vibrational modes; X-ray photoelectron spectroscopy for chemical binding energy; Energy-dispersive X-ray spectroscopy for elemental composition; current-voltage measure for electrical resistance. Results from these material characterizations indicate that a stronger plasma field breaks down the pyrrole rings while creates more nitrogen groups containing N−H, C−N+ or C=N+. However, a certain amount of undamaged pyrrole rings were deposited into films. These intact pyrrole rings make electrical conduction to be possible in films. From the linear regression for the measured current-voltage data, we found that lower RF power (10W) can improve the electrical conduction; however, a noticeable enhancement in conduction is achieved by the doping of iodine such that the film's electrical resistance is reduced to almost half of other un-doped pyrrole films.