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Journal of Nanomaterials
Volume 2012, Article ID 274618, 9 pages
http://dx.doi.org/10.1155/2012/274618
Research Article

A Novel Method to Grow Vertically Aligned Silicon Nanowires on Si (111) and Their Optical Absorption

1Department of Chemical Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan
2Center for Micro/Nano Science and Technology, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan
3Advanced Optoelectronic Technology Center, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan
4NCKU Research Center for Energy Technology and Strategy, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan

Received 5 April 2012; Revised 21 May 2012; Accepted 22 May 2012

Academic Editor: Vladimir Sivakov

Copyright © 2012 Tzuen-Wei Ho and Franklin Chau-Nan Hong. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In this study we grew silicon nanowires (SiNWs) on Si (111) substrate by gold-catalyzed vapor liquid solid (VLS) process using tetrachlorosilane (SiCl4) in a hot-wall chemical vapor deposition reactor. SiNWs with 150–200 nm diameters were found to grow along the orientations of all 111 family, including the vertical and the inclined, on Si (111). The effects of various process conditions, including SiCl4 concentration, SiCl4 feeding temperature, H2 annealing, and ramp cooling, on the crystal quality and growth orientation of SiNWs, were studied to optimize the growth conditions. Furthermore, a novel method was developed to reliably grow vertically aligned SiNWs on Si (111) utilizing the principle of liquid phase epitaxy (LPE). A ramp-cooling process was employed to slowly precipitate the epitaxial Si seeds on Si (111) after H2 annealing at 650°C. Then, after heating in SiCl4/H2 up to 850°C to grow SiNWs, almost 100% vertically aligned SiNWs could be achieved reproducibly. The high degree of vertical alignment of SiNWs is effective in reducing surface reflection of solar light with the reflectance decreasing with increasing the SiNWs length. The vertically aligned SiNWs have good potentials for solar cells and nano devices.