Selective H2S sensing characteristics of CuO modified WO3 thin films

An H2S sensor based on randomly distributed nano p–n junction between CuO and WO3 has been demonstrated. Modification with CuO resulted in enhanced response kinetics towards H2S with high selectivity. CuO modified WO3 thin films corresponding to 2.25 at% of Cu exhibited a sensor response of 534 in comparison to that of pure WO3 thin films that exhibited a sensor response of 21 towards 10 ppm of H2S 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 H2S. At elevated temperature exposure to H2S 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.