Germanium nanowires (GeNWs) have been synthesized by the thermal evaporation of Ge powder at 950 deg C onto silicon wafer and ceramic (alumina) substrate using Au nanoparticles as a catalyst via a vapour-liquid-solid (VLS) process. The morphology, crystal structure and growth direction of the as-prepared GeNWs have been characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). GeNWs are uniform with a diameter of approx 30 nm and lengths of tens of micrometres. High-resolution TEM shows that an individual GeNW is a single crystal with a diamond structure and a preferred growth along the (111) direction. Au nanoparticles are found at the tip of GeNWs indicating that the growth of GeNWs follows a VLS mechanism. The electronic and local structures of the as-prepared GeNWs have also been investigated by x-ray absorption fine structure spectroscopy (XAFS). The results and the implications will be discussed.
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