Annealing effects on the photoluminescence and morphology of ZnO nanowires

For the fabrication of ZnO NWs, we have used Si wafers as smooth surface substrates. Gold was deposited on to the substrates with an electron beam evaporator, since it is known that gold particles can serve as the catalyst to grow ZnO NWs on substrates in Vapor-Liquid-Solid (VLS) method. In the VLS method, the mixture of ZnO powder and graphite was placed at 1100 degrees C and the substrates were at 800 degrees C in a two-zone furnace. The reduction of ZnO of the source generates Zn vapor that diffuses to gold particles on Si substrates, and the oxidation of Zn-Au alloy grows ZnO crystals. The gold deposited area has ZnO crystal growth and that the gold particles play the role of nucleation sites. ZnO crystals have the dimension of a few hundred run wide and 2-3 mu m long under this particular condition. SEM, XRD, and PL have been used for characterization. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.