Low-temperature orientation-selective growth and ultraviolet emission of single-crystal ZnO nanowires

We fabricated single-crystal ZnO nanowires at a low temperature of 500 degreesC without using any metal catalysts via the simple thermal oxidation of metallic Zn precursors. Scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM) studies showed that the ZnO nanowires with orientation-selectivity grew laterally along the sides of the hexagonal-shaped ZnO matrix transformed from the metallic Zn precursors. It was found that the nanowires grew along the <11 (2) over bar0> direction and were single crystals by HRTEM study. Typically, the lengths of the ZnO nanowires ranged from 0.5 to 3 mum and their mean diameter was 20+/-5 nm. Photoluminescence and cathodoluminescence measurements at room temperature showed a strong ultraviolet emission peak with negligibly weak green emissions, confirming that the individual ZnO nanowire was of excellent optical quality. Based on these results, we conclude that the simple thermal oxidation of metal Zn precursors is a useful, feasible approach for fabricating high-quality one-dimensional ZnO nanostructures for integration into nanophotonic integrated circuits. (C) 2004 American Institute of Physics.