H₂S gas sensing properties of ZnO–SnO₂ branch–stem nanowires grown on a copper foil

ZnO–SnO₂ branch–stem nanowires were fabricated on a Cu foil using a chemical vapor deposition system through a two-step process. Firstly, SnO₂ NWs were synthesized directly on a Cu foil substrate by evaporating SnO powder as a source material. Then, the as-synthesized SnO₂ NWs were used as templates for the growth of ZnO–SnO₂ branch–stem NWs. The effect of growth time on the growth of the SnO₂ NWs on the Cu foil was studied. The gas sensing properties of the SnO₂ NW and ZnO–SnO₂ branch–stem NW devices were studied using various toxic gases at different temperatures. Both devices exhibited high sensitivity, high selectivity, fast response and recovery times, and stability toward H₂S gas. Compared to the pristine SnO₂ NW device, the ZnO–SnO₂ branch–stem NW device exhibited higher sensitivity and faster response rate toward H₂S. Finally, the gas sensing mechanism was also discussed.