Enhanced gas sensing properties of branched ZnO nanowires

초록

Branched ZnO nanowires were synthesized using a three-step process: synthesis of ZnO nanowires by thermal evaporation of a mixture of ZnO and graphite powders on Au-coated c-plane sapphire substrates for 1 h, deposition of Au on the as-synthesized ZnO nanowires, and resumption of the thermal evaporation process for 10 min. The multiple net-worked nanowire gas sensors fabricated from the branched ZnO nanowires showed substantially enhanced electrical responses to NO2 gas at 300°C compared to the ordinary ZnO nanowire gas sensors. The NO2 gas sensing properties of the branched ZnO nanowires increased more rapidly with increasing NO2 concentration. The multiple-networked branched ZnO nanowire sensor showed response values of 26 - 106% in the NO2 gas concentration range of 1 – 5 ppm at 300oC, whereas the ordinary ZnO nanowire sensor showed responses of 14 – 43% in the same NO2 gas concentration range. The response and recovery times of the branched ZnO nanowire sensor were much shorter than those of the ordinary ZnO nanowire sensor over the NO2 concentration range of 1-5 ppm. The enhanced NO2 gas sensing properties of the branched ZnO nanowires is might be attributed to the increased surface-to-volume ratio compared to ordinary ZnO nanowires.