>SiO2- and CuO-enhanced growth of Ge–Si1−xGexOy and GeO2–Si1−xGexOy core–shell nanowires on a Si substrate via carbothermal reduction
The effects of a SiO layer grown on a Si substrate and the CuO additive in GeO powders for the enhanced growth of Ge–SiGeO and GeO–SiGeO core–shell nanowires (hereafter referred to as Ge–SiGeO and GeO–SiGeO nanowires, respectively) via carbothermal reduction at 1050–1100 °C in flowing Ar were studied. Using GeO powders as the feedstock alone, nanowires having a composition of Ge–SiGeO were grown on a SiO/Si substrate, whereas the same nanowires could not be grown on a Si substrate. Adding CuO into GeO powders enhanced the growth of GeO–SiGeO and Ge–SiGeO nanowires on the Si substrate as well as that of GeO–SiGeO nanowires on the SiO/Si substrate. The crystal growth mechanism seems to follow the vapour–solid process. The present study reveals that the oxidation of the Si substrate plays an important role in enhancing the growth of Ge–SiGeO and GeO–SiGeO nanowires via carbothermal reduction of GeO powders. The mechanisms for the precipitation of the Ge or GeOcore inside the SiGeO shell on Si and SiO/Si substrates are discussed, respectively.
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