Modification of structure and optical property of ZnO nanowires by Ga ion beam
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1201-H07-05
Modification of structure and optical property of ZnO nanowires by Ga ion beam Yao Cheng1, Yao Liang2, Ming Lei1, Sui Kong Hark2 and Ning Wang1 1 Physics Department, the William Mong Institution of Nano Science and Technology, the Hong Kong University of Science and Technology, Hong Kong, China. 2 Physics Department, the Chinese University of Hong Kong, Hong Kong, China. ABSTRACT Based on the focused ion beam (FIB) technology, we have prepared ZnO containing periodic nano-sized structures by an ultra thin Ga ion beam. ZnO nanowires can keep a good crystal quality after Ga ion bombardment. The cathodoluminescence (CL) spectroscopy study of the Gadoped ZnO nanowires at low temperatures shows that the Ga doping effect can largely suppress the green emission that may mainly originate from the defects on the surfaces of ZnO nanowires. INTRODUCTION Zinc oxide has attracted great attentions because of its interesting properties of wide bandgap (3.37eV) and large exciton binding energy (60meV). In recent years, novel morphologies of ZnO structures, such as nanocantilever arrays [1], nanohelixes [2, 3], nanorings [4] and nanosheets [5], have been synthesized. By controlling the sizes, shapes, crystal structures, and surface structures, these ZnO nanostructures are exploiting a wide range of technological application in chemical, optical, electronic and mechanical fields. Because most of these novel nanostructures were directly grown from solution or vapor process, their morphologies largely relied on growth conditions. Therefore, development of nanostructural modification methods for desiring properties is timely and of extremely high importance in current nanomaterials research. In addition to the development of methods for fabricating various ZnO nanostructures, much effort has been devoted to investigating the optical properties of these nanostructures. Besides the UV excitonic emission peak, ZnO nanostructures often exhibit different peaks in the visible spectra region, which have been attributed to defect emissions. For example, the green emission [6-14] has been commonly observed in ZnO nanostructures. Several mechanisms have been proposed in order to explain the origin of the green emission such as the vacancies and oxygen (or zinc) interstitials [6-11], antisite oxygen [12], surface defects [13] and Cu impurities [14]. So far, the origin of the green emission still remains an open and controversial question and requires further studies. In the meantime, however, some methods have been developed to influence the green emission. For example, coating a surfactant layer on ZnO nanostructures may suppress the green emission [13]. In this work, we report a method for creating periodic nanostructures based on nanowires templates by the FIB technique. We observed the damaging effect induced by the high-energy Ga beam and the optical property changes resulted from the selective Ga doping effect in ZnO nanostructures. EXPERIMENT DETAILS
ZnO nanowires were grown by direct oxidation of pure zinc powder placed in a
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