Impedance Spectroscopy of Tellurium Thin Films Sensitive to NO2

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 NO(2) It is shown that the impedance spectra, being strongly influenced by the gaseous environment, do not change their general shape. The effect of NO(2) 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 similar to 50%/ppm. It is suggested that the effect of NO(2) results from "strong" chemisorptions of NO(2) molecules on the surface and the intragrain regions of the Te film.