Enhancement of Oxide VLS Growth by Carbon on Substrate Surface

Abstract

Oxide nanowires formed via the vapor−liquid−solid (VLS) mechanism are potential candidates to incorporate the rich functionalities into the nanowire-based devices. However, the complex nature of oxide VLS mechanism has held back the formation of well-defined oxide nanowires. Here we report the enhancement of oxide VLS growth by carbon and discuss the underlying mechanism. In ZnO nanowire growth, the presence of carbon layers predeposited on the substrate surface strongly enhances the VLS growth. Spectroscopy analysis demonstrates that the carbon predeposited on the surfaces could only exist at the initial stage of the VLS growth, as also evidenced from the optical quality of the ZnO nanowires. Thus, the existence of carbon at the initial stage of the VLS growth plays an important role on enhancing the oxide VLS growth and might act as a seed material in addition to Au catalyst. Furthermore, the presence of carbon enhances various oxide VLS growths, including SnO2 and MgO, indicating the universal effect on oxide VLS growth mechanism.