Room Temperature Operating Nh3 Gas Sensor Based on Tellurium Thin Film

Tellurium thin films were studied for use as ammonia gas sensors operable at room temperature. The films showed a reversible increase in resistance when exposed to ammonia and the response was found to be linear in the range of 0-100 ppm. The interaction of ammonia with tellurium film was investigated using Raman, X-ray photoelectron and impedance spectroscopy techniques. The results of Raman and XPS spectroscopy showed that ammonia reduces tellurium oxide present on the surface and grain boundary region of the film to tellurium. Results of impedance spectroscopy revealed that the change in resistance of the film after exposure to NH3 is mainly contributed by intragrain region. On interaction with NH3 the electrons trapped by adsorbed oxygen in the grain boundary are released which decreases in the majority carriers and thus increasing the resistance of the Te film.