An H 2 S sensor based on randomly distributed nano p–n junction between CuO and WO 3 has been demonstrated. Modification with CuO resulted in enhanced response kinetics towards H 2 S with high selectivity. CuO modified WO 3 thin films corresponding to 2.25at% of Cu exhibited a sensor response of 534 in comparison to that of pure WO 3 thin films that exhibited a sensor response of 21 towards 10ppm of H 2 S at an operating temperature of 300°C. This enhanced response kinetics has been attributed to the formation of random nano p–n junctions distributed over the surface of the sensor film and the unique interaction of CuO with H 2 S. At elevated temperature exposure to H 2 S resulted in the conversion of CuO to CuS, which being metallic in nature causes a drastic change in the resistance of the sensor films. Formation of nano p–n junctions is supported by the increase in the sensor resistance upon CuO modification and is further corroborated by the work function studies.
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