Growth of amorphous silicon oxide nanowires in the absence of a Si precursor through a solid state transformation

Amorphous silicon oxide nanowires (a-SiONWs) were prepared by heating a silicon substrate in the absence of any silicon source. To investigate the mechanism of this growth, we experimented with a variety of growth conditions, including the condition of the substrate and the growth ambient. The distribution of the density of a-SiONWs increased when titanium was present during the operation process. The results as a function of the temperature indicate that the growth mechanism for the high-temperature position (Tsub > ∼1000 ~C) can be explained by a solid-liquid-solid (S-L-S) mechanism. In contrast, the growth at the relatively low-temperature zone (∼900 °C) cannot be explained by the S-L-S mechanism because of the insufficient vapor pressure at the temperature. From various gas flow conditions, the growth region depends significantly on the flow rate of Ar gas. This result indicates that the source of the nanowire (silicon vapor) is the silicon substrate located in a higher temperature region (Tsub > ~1000 °C). Therefore, the mechanism of growth of a-SiONWs is consistent with both the vapor-liquid-solid and the S-L-S mechanism for reactions in different temperature regions.