Randomly oriented ZnO nanowires grown on amorphous SiO2 by metal-catalyzed vapour deposition

Randomly oriented ZnO nanowire (NW) networks have been grown on thermal SiO2 substrates by the simple carbothermal reaction-assisted thermal evaporation of ZnO. One-dimensional growth was achieved with the aid of Au nanocluster catalysts dispersed on the substrates. The structures were studied by scanning electron microscopy, energy dispersive X-ray analysis, and X-ray absorption spectroscopy. The NW diameters and lengths were found to strongly depend on the substrate temperature (TS) and to be in the 5–10 nm and 40–110 nm ranges for TS = 520 °C, and in the 50–80 nm and 1–3 μm ranges for TS = 700 °C, respectively. The growth regime was characterized by comparing the NW structures obtained on SiO2 with those grown in the same deposition run on (1 0 0) Si substrates also covered with the Au catalyst. The NW structure prepared at 700 °C behaves as a dense NW network with net electrical conductance and persistent photoconductance. These results suggest a method to deposit size-controlled ZnO NW networks on insulating cost-effective substrates with important potential applications as in chemical sensors and solar cells.