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ZnO nanoneedles prepared by ion implantation and thermal oxidation on metallic zinc foils

ZnO nanoneedles are prepared on polycrystalline metallic zinc foils by oxygen/nitrogen ion implantation and thermal oxidation. The ZnO nanoneedles are grown along the [1 1 0] direction and their orientations are dependent on the crystallographic grain orientations of the substrate. ZnO nanoneedles prepared by oxygen implantation and thermal oxidation exhibit a turn-on field of 6.5 V µm−1 and field emission properties are improved as exposure ion fluence increases. ZnO nanoneedles prepared by nitrogen implantation shows similar morphology but inferior field emission properties. Energy dispersive x-ray spectroscopy analysis indicates that ZnO nanoneedles prepared by oxygen implantation contain excess zinc, while those prepared by nitrogen implantation contain excess oxygen. The difference in stoichiometry is probably due to different degrees of porosity of the zinc foil after ion implantation.