Catalyst-free synthesis of ZnO nanowires on Si by oxidation of Zn powders

ZnO nanowires were grown on Si (1 0 0) substrates by oxidation of metallic Zn powder at 600 °C. Sea-urchin-like nanostructures, consisting of straight nanowires of ZnO with blunt faceted ends with a sudden reduction in diameter projecting out, were observed, having diameters of 30-60 nm and lengths of 2-4 μm. TEM analysis and SAED patterns showed that the as-grown nanostructures are highly crystalline in nature and preferably grown along the [0 0 0 1] direction, which is consistent with XRD analysis. Room-temperature photoluminescence (PL) measurements showed a reduced near band-edge emission in the UV region at 380 nm, while a strong deep level emission was observed in the visible region at 500-530 nm. A model for vapor-solid (VS) growth mechanism of ZnO nanowires was presented.