Impedance Spectroscopy of Tellurium Thin Films Sensitive to NO2

Abstract

Impedance spectra of tellurium thin films with interdigital platinum electrodes have been measured in dry synthetic air and gaseous media with nitrogen dioxide. Analyses of Cole-Cole plots allowed to evaluate the characteristic frequency, time constant, resistance and capacity of the film in dry air and a mixture containing NO2. It is shown that the impedance spectra, being strongly influenced by the gaseous environment, do not change their general shape. The effect of NO2 is mainly a variation of the resistance of the while the capacitance does not vary significantly. The sensitivity of the impedance or its imaginary part depends on the frequency and is on the order of ~50%/ppm. It is suggested that the effect of NO2 results from “strong” chemisorptions of NO2 molecules on the surface and the intragrain regions of the Te film.