Carbon-assisted growth of SiOx nanowires

During attempts to fabricate ZnO nanowires, we accidentally observed the growth of SiOx nanowires on Au-coated Si substrate. Detailed characterizations on the resulting nanowires were carried out by field-emission scanning electron microscopy, electron microprobe analysis, transmission electron microscopy, selective area electron diffraction, energy-dispersed X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The resulting nanowires have a Si-to-O ratio of 1:1.63 and a diameter of 50-300 nm. It was found that the presence of graphite powder in the growth furnace was critical. A systematic investigation of how the growth conditions, such as the growth temperature, the oxygen-to-Ar carrier gas ratio, and growth time, affect the formation of SiOx nanowires was performed. Higher growth temperature and appropriate low oxygen gas flow helped to promote long nanowire growth. The diameters of the nanowires increased with growth time. It was demonstrated that the formation of the SiOx nanowires was due to a solid-liquid-solid mechanism, and the locally catalytic oxidation of CO by Au nanoclusters may play a role in accelerating nanowire formation.