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 SiCl4concentration, SiCl4feeding temperature, H2annealing, 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 H2annealing at 650°C. Then, after heating in SiCl4/H2up 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.
Highlights
Nanowire devices have attracted a great deal of attention recently because of their potentials for many industrial applications due to their unique properties including single crystal nature, mechanical flexibility, and high-surface areas
A new method was attempted utilizing the principle of liquid phase epitaxy (LPE) for controlling the vertical alignment of epitaxial silicon nanowires (SiNWs)
By starting to feed SiCl4 reactant into the reactor at the growth temperature, we found that the SiNWs grown exhibited poor quality
Summary
Nanowire devices have attracted a great deal of attention recently because of their potentials for many industrial applications due to their unique properties including single crystal nature, mechanical flexibility, and high-surface areas. The catalyst-assisted vapor liquid solid (VLS) growth mechanism is still the most widely used approach for fabricating nanowires due to no requirement of patterning [6, 7]. According to this mechanism, a small eutectic particle acts as a catalyst to decompose and dissolve the gas phase reaction species, and the precursor precipitates out of the catalyst to grow nanowires after supersaturation. A new method was attempted utilizing the principle of liquid phase epitaxy (LPE) for controlling the vertical alignment of epitaxial SiNWs. A ramp-cooling process was employed to slowly precipitate the epitaxial Si seeds on Si (111) after H2 annealing at 650◦C. We have already demonstrated that this is a highly reproducible method to grow vertically-aligned SiNWs on Si (111)
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