Morphology and gas sensing characteristics of density-controlled CuO nanostructures obtained by varying the oxygen partial pressure during growth

摘要

By exerting different O-2 partial pressures (0, 20, 40, and 60 sccm) onto copper substrates, we discovered that the growth parameter, namely, the O-2 flow rate, affects the degree of nucleation, diameter, length, and crystalline quality of CuO nanowires (NWs). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to analyze the evolution of the morphological and the microstructural changes in the CuO nanostructures. The formation of a Cu2O interlayer between the Cu and the CuO layers could be adjusted by controlling more precisely the O-2 flow rate. In addition, the reducing (H2S) and the oxidizing (O-2, NO2, and SO2) gas sensing performances of these O-2-assisted CuO NWs were compared with those of CuO NWs grown in static air. The response to the reducing H2S of the sensors based on CuO NWs grown using O-2 at 40 sccm showed a higher electrical change and faster response and recovery times than the sensors based on CuO NWs grown using lower O-2 flow rates, including the ones grown in static air and/or used for sensing oxidizing gases (O-2, NO2, and SO2) did. On the basis of their growth and their gas-sensing applications, the possible mechanisms characteristic of the density-controlled CuO NWs grown using various O-2 partial pressures are discussed.