Electrochemical deposition of ZnO nanostructures onto porous silicon and their enhanced gas sensing to NO2 at room temperature

The porous silicon (PS) was produced by electrochemical etching of the P-type monocrystalline silicon in a double-tank cell and used as a substrate. The high-density zinc oxide nanosheets and nanorods were grown onto PS substrates by electrochemical deposition. The obtained ZnO nanostructures/PS products were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). The gas-sensing properties of ZnO nanostructures/PS composites to NO2 at different temperatures were studied. The result indicates that the addition of ZnO nanosheets greatly improve the gas-sensing properties of PS, especially at room temperature (RT). The ZnO nanosheets/PS sensor showed higher response values and gas selectivity, as well as much better response-recovery characteristics to NO2 gas compared with PS and ZnO nanorods/PS sensor due to its high specific surface area and special structural and morphological properties. The related mechanisms will be also discussed in this paper. This novel composite structure is of great significance for NO2 detection at room temperature.