Fabrication of Coaxial Si 1-xGe x Heterostructure Nanowires by O 2 Flow-Induced Bifurcate Reactions

Abstract

We report on bifurcate reactions on the surface of well-aligned Si 1-xGe x nanowires that enable fabrication of two different coaxial heterostructure nanowires. The Si 1-xGe x nanowires were grown in a chemical vapor transport process using SiCl 4 gas and Ge powder as a source. After the growth of nanowires, SiCl 4 flow was terminated while O 2 gas flow was introduced under vacuum. On the surface of nanowires was deposited Ge by the vapor from the Ge powder or oxidized into SiO 2 by the O 2 gas. The transition from deposition to oxidation occurred abruptly at 2 torr of O 2 pressure without any intermediate region and enables selectively fabricated Ge/Si 1-xGe x or SiO 2/Si 1-xGe x coaxial heterostructure nanowires. The rate of deposition and oxidation was dominated by interfacial reaction and diffusion of oxygen through the oxide layer, respectively. © 2010 The Author(s).