Synthesis and characterization of zinc oxide and bismuth oxide nanowires grown by magnetron sputtering

Nanowires of Zinc oxide and bismuth oxide were grown on silicon substrates using vapor-liquid-solid (VLS) and unbalanced magnetron sputtering. Characterization using x-ray diffraction (XRD) and scanning electron microscopy (SEM) was conducted to investigate how growth conditions influence the structural and morphological properties of the materials. Optical properties were investigated using photoluminescence (PL), direct absorption spectra and cyclic voltammetry. The physical properties of sputtered ZnO were found to be dependent on oxygen flow rate, temperature, and the initial foreign metal catalysis seed layer. Nanowires were grown using a two-step process whereby an initial Au layer was deposited followed by Zn with oxygen. Doped ZnO-TiO2 nanostructures were created by sputtering Ti and Zn simultaneously. Homo- and hetero-structured ZnO-ZnO and ZnO-TiO 2 were created using additional sputtering cycles. A systematic approach was taken to produce nanoarrays of Bi2O3 by adjusting initial seed layer thickness and oxygen flow rates. A two step process involving variable oxygen flow rates was found to create the highest density of Bi 2O3 nanowires in the array. Top-view and cross-sectional SEM micrographs suggested that the resulting Bi2O3 nanowires were approximately 300 nm in length with diameters of 100 nm at the base and 30 nm at the top. Investigation into the growth method suggests a self-catalytic VLS-like process. Degradation tests using rhodamine 6G dye were compared to SEM images. Samples of ZnO and Bi2O3 displayed a direct correlation between nanowire density and photocatalytic efficiency.