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Open Access Nano Express

Fabrication of Coaxial Si1−xGex Heterostructure Nanowires by O2 Flow-Induced Bifurcate Reactions

Ilsoo Kim, Ki-Young Lee, Ungkil Kim, Yong-Hee Park, Tae-Eon Park and Heon-Jin Choi*

Author Affiliations

Department of Materials Science and Engineering, Yonsei University, Seoul, 120-749, Korea

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Nanoscale Research Letters 2010, 5:1535-1539  doi:10.1007/s11671-010-9673-3

Published: 17 June 2010

Abstract

We report on bifurcate reactions on the surface of well-aligned Si1−xGex nanowires that enable fabrication of two different coaxial heterostructure nanowires. The Si1−xGex nanowires were grown in a chemical vapor transport process using SiCl4 gas and Ge powder as a source. After the growth of nanowires, SiCl4 flow was terminated while O2 gas flow was introduced under vacuum. On the surface of nanowires was deposited Ge by the vapor from the Ge powder or oxidized into SiO2 by the O2 gas. The transition from deposition to oxidation occurred abruptly at 2 torr of O2 pressure without any intermediate region and enables selectively fabricated Ge/Si1−xGex or SiO2/Si1−xGex coaxial heterostructure nanowires. The rate of deposition and oxidation was dominated by interfacial reaction and diffusion of oxygen through the oxide layer, respectively.

Keywords:
Si1−xGex nanowires; Coaxial heterostructure; Bifurcate reactions; Interfacial reaction; Diffusion-controlled reaction; Self-limiting oxidation; Kinetics of gas diffusion