Hydrogen sensing behavior of tellurium thin films studied by A.C. measurements

Abstract

For the first time it is pointed out that tellurium films exhibit sensitivity to H2 at room temperature along with sensitivity to NO2. The hydrogen gas sensing performance of tellurium thin films was investigated by method of impedance spectroscopy. The impedance spectra are strongly influenced by gaseous environment but the effect of target gas is mainly due to variation of resistance of the film. It is assumed that the sensitivity of tellurium films to H2 arises because – of reducing effect of oxygen priory absorbed on the surface of the film from carrier (dry air) gas. The high concentration of oxygen in carrier gas promotes the formation of a catalytic gate, which can be removed by other gases including hydrogen. Removing of the priory-adsorbed oxygen results in decreasing of both, hole concentration and conductivity of the surface and intragrain regions of tellurium film. Due to impedance change in different direction, reducing H2 may be distinguished from oxidizing NO2, hence the effective, operating at room temperature H2 sensors can be manufactured using tellurium-based films.