The synthesis of metal oxide nanowires by directly heating metal samples in appropriate oxygen atmospheres

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Abstract
ZnO, MgO, and GeO2 nanowires were successfully synthesized by simply heating the desired metal powder to a temperature above its melting point in a flow of mixed gases (20% O2, 80% Ar, with the total flow rate of 120 sccm). Transmission electron microscopy observations show that as-synthesized products are exclusively nanowires, structurally uniform and single crystalline. The same technique was used to fabricate arrays of ZnO nanowires on silicon substrates, which would be of particular interest for direct integration in the current silicon-technology-based optoelectronic devices. Based on our experimental results, a metal self-catalytic growth mechanism was proposed and described conceptually. Because of the absence of impurities such as transition metal or noble metal throughout the whole growth process, the intrinsic properties of the resulting metal oxide nanowires could be expressed and utilized. And with in-depth understanding of the growth mechanism, our method could be efficient and controllable in extension to many other low-melting-point metals, such as Al, In, and Sn, for the synthesis of corresponding metal oxide nanostructures.