Selective growth of ZnO nanoneedles by thermal oxidation of Zn microstructures

Zinc film containing hexagonal plate stack and tower-like microstructures were grown on Si substrates at high temperature by thermal evaporation. Thermal oxidation studies on these microstructures have shown that ZnO nanoneedles selectively grow from the facets of the zinc microstructure at temperature above 300 °C in atmosphere. TEM analysis showed that single crystalline and bicrystalline nanoneedles were formed in this oxidation process and the growth direction of these nanoneedles was identified along the [1 1 2¯ 0]. Based on the structural studies and morphological observation, we have proposed a possible mechanism for the selective growth of ZnO nanoneedles during thermal oxidation.