XPS and SEM studies of oxide reduction of germanium nanowires

Single-crystal germanium nanowires (GeNWs) were grown by vapour–liquid–solid deposition onto silicon oxide substrates with Au catalyst nanoparticles. The GeNW surface and morphology were studied by means of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. Complete oxidation of the GeNW outer shells was evidenced by an XPS analysis. Most of the surface oxide could be removed by aqueous HF, aqueous HCl, and by pure H2O. A complete reduction of the oxide was evidenced after chemical treatment by XPS measurements. Furthermore, we could observe by a SEM analysis that the chemical etching produced a reduction of the diameter of the GeNWs, in agreement with effective surface oxide removal. In addition, the GeNW oxidation process was controlled after various exposure times in ambient atmosphere.