H2S sensors based on SnO2 films: RGTO verses RF sputtering

Abstract Gas sensing characteristics of SnO 2 thin films prepared by RF sputteringhave been investigated and compared to that of RGTO ( RheotaxiallyGrown and Thermally Oxidized) films. Both the sensor films exhibited a highly selective response towards H 2 S with RF sputteredfilm showing better response characteristics. RF sputteredand RGTO films exhibited a maximum response of 54 and 15 towards 10 ppm of H 2 S at an optimum operating temperature of 150 and 250 °C, respectively. Sputteredfilms exhibited a linear response in the wide concentration range from 500 ppb to 500 ppm while RGTO films were found to saturate for concentrations above 100 ppm. XPS investigations revealed that the RGTO films are more sub–stoichiometric or oxygen deficient than the sputteredfilms. Raman studies further indicates that the surface of sputteredand RGTO films are characterized by the presence of oxygen deficiency attributed to the “bridging-type” and deeper “in-plane/sub-bridging” oxygen vacancies, respectively. The improved response kinetics of the RF sputteredfilms is attributed to the presence of bridging type oxygen vacancies that facilitates the charge transfer between the sensor surface and H 2 S molecules.