Effects of Cu Catalyst and Water Vapor on the Growth of Ge–GeOx Core–Shell Nanowires via the Carbothermal Reduction of GeO2 Powders

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The enhanced growth of Ge–GeOx core–shell nanowires (Ge–GeOx NWs) on Cu-coated Si substrates via the carbothermal reduction of GeO2 powder at 1100 °C in moist Ar was studied. In dry Ar, the amount of Ge–GeOx NWs increased with the thickness of Cu films in the range of 10–30 nm. The water vapor introduced into Ar further enhanced the growth of Ge–GeOx NWs, which simultaneously served as the oxidizer and reducer. The amount of Ge–GeOx NWs increased with the volume of water in the range of 0.5–2 ml. More water degraded the growth of Ge–GeOx NWs because of the exhaustion of much graphite powder. In dry Ar, the growth of Ge–GeOx NWs on Cu-coated Si substrates follows the vapor–liquid–solid (VLS) process, while in moist Ar, it follows both the VLS and vapor–solid (VS) processes.
2008-04-25