Impedance spectroscopy of sensitive to harmful gases tellurium thin films

Abstract

Impedance spectra of tellurium thin films with interdigital platinum electrodes have been investigated in different gaseous media. For the first time it is pointed out that tellurium films exhibit sensitivity to H2 at room temperature along with sensitivity to NO2 and H2S. Analyses in Cole – Cole interpretation allowed evaluating the characteristic frequency, time constant, resistance and capacity of the film in different target gases. It is shown that impedance spectra being strongly influenced by gaseous environment do not change their general shape. The effect of target gas is mainly due to variation of resistance of the film but capacitance does not vary essentially. The sensitivity for impedance or its imaginary part depends on frequency, being the highest to NO2 (~50 % / ppm) but 8 % / ppm and 10-2 % / ppm to H2S and H2 respectively. It is suggested that effect of H2 is due to removal the amount of adsorbed oxygen on the Te surface, whereas effect of NO2 and H2S results respectively from "strong" and "weak" chemisorptions of these molecules on the surface and intra grain regions.