Growth of SiO₂nanowires without a catalyst via carbothermal reduction of CuO powders

Abstract

The growth of SiO2 nanowires (SiONWs) via carbothermal reduction of CuO powders as functions of the Ar flow rate, the carbon concentration in the CuO/carbon powders, and the oxygen concentration in the Ar/O2 flow was studied. Significant amounts of SiONWs were grown on the Si substrate without a catalyst from CuO/carbon powders at a temperature of 1000–1100 °C in flowing Ar with the flow rate of 100 sccm. Without using CuO/carbon powders SiONWs could not be readily grown. A small amount of SiC associated with SiONWs was grown from CuO/carbon powders with a higher proportion of carbon. The minimum Ar flow rate required for the growth of SiONWs was about 10 sccm and the amount as well as the diameter of the SiONWs increased with increase of the Ar flow rate, revealing that vapour transport assisted by Ar flow is an important mechanism for the nucleation and growth of SiONWs. The growth of SiONWs mainly originated in the cracks which were formed in the Si substrate due to the generation of SiO(g) from the reaction between CO2 and the Si substrate. The introduction of O2 into the Ar flow could generate a significant amount of CO and thereby suppress the growth of SiONWs. The present studies reveal that the growth of SiONWs via carbothermal reduction of CuO powders mainly follows the vapour–solid mechanism.