Contribution of adsorbed oxygen and interfacial space charge for enhanced response of SnO2 sensors having CuO catalyst for H2S gas

The contribution of adsorbed oxygen and interfacial space charge for enhanced H2S gas detection (20 ppm) has been investigated for four different SnO2 thin film based sensor configurations namely (1) pure SnO2: (2) composite SnO2-CuO: (3) continuous CuO over-layer on SnO2 and (4) nano-thin CuO islands on SnO2. Equivalent electrical conductance models have been developed for all sensor configurations based on the sensor conductance in air and in presence of H2S gas to explain the chemical and electronic changes occurring at the interface between sensing SnO2 thin film and catalyst CuO. The oxygen activity was found to be maximized on the surface of SnO2 film loaded with nano-thin CuO catalytic islands, besides spillover mechanism at similar to 150 degrees C, thereby giving maximum sensing response (similar to 8.0 x 10(3)) for 20 ppm H2S gas. The origin of the enhanced sensor response has been identified and will pay a way to realize novel sensor design structure with improved response characteristics. (C) 2009 Elsevier B.V. All rights reserved.