Selective H2S sensing characteristics of hydrothermally grown ZnO-nanowires network tailored by ultrathin CuO layers

Random networks of ZnO nanowires (ZnO-NWs) have been fabricated on the Si/SiO2 substrates by hydrothermal process using ZnO-nanoparticles as seed. The ZnO-NWs networks have been modified by depositing ultrathin CuO layers (nominal thickness: 10 nm) using thermal evaporation of Cu followed by oxygen annealing at 600 °C. The results of photoluminescence measurements on ZnO-NWs and CuO:ZnO-NWs networks suggest formation of a p–n junction between p-CuO and n-type ZnO. The gas sensing characteristics of both ZnO-NWs and CuO:ZnO-NWs networks have been investigated. It has been demonstrated that CuO:ZnO-NWs network has selective response toward H2S with a sensitivity of ∼40 (for 10 ppm) at an operating temperature of 200 °C. A sensing mechanism based on the destruction of p–n junctions due to the formation of metallic CuS (product of chemical reaction between CuO and H2S) has been proposed.