Effect of surface morphology of metallic zinc films deposited by ion beam sputter deposition on the formation of ZnO nanowires

Metallic zinc film with various surface roughnesses was deposited on Si (100) substrates by ion beam sputter deposition utilizing beam energies at 8, 12 and 16 keV. The surface roughness of the metallic zinc film increased as ion beam energy increased and was found to act as a crucial factor for the formation of ZnO nanowires by subsequent thermal oxidation. ZnO nanowires with diameters of ∼30 nm and average length of ∼1 μm were obtained from 12 to 16 keV ion beam deposited samples while no ZnO nanowires were found on 8 keV ion beam deposited samples. Photoluminescence study of ZnO nanowires exhibits a strong UV emission at 377.2 nm (3.287 eV) with a full-width at half maximum of 95.0 meV and negligible defect related deep level emission. The ZnO nanowires are grown along the [110] direction and the growth mechanism is likely due to a solid state based-up diffusion process. Field-emission measurement shows a turn-on field of 7.9 MV/m and a field enhancement factor β of 691 is achieved.