Silicon nanowire growth on poly-silicon-on-quartz substrates formed by aluminum-induced crystallization

The vertical growth of Si nanowires on non-monocrystalline substrates is of significant interest for photovoltaics and other energy harvesting applications. In this paper, we present results on using poly-Si layers formed by aluminum-induced crystallization (AIC) on fused quartz wafers as an alternative substrate for the vapor-liquid-solid (VLS) growth of vertical Si nanowires. Oxidation of the Al surface to Al2O3 before the a-Si deposition was shown to be a key requirement in the formation of the poly-Si template since it promotes the crystallization of the a-Si into Si(111) which is required for vertical silicon nanowire growth. The effect of Al deposition technique (DC sputtering versus thermal evaporation) on a-Si crystallization and Si nanowire growth was investigated. The use of Al thermal evaporation yielded AIC poly-Si layers with the highest fraction of 111 grains as measured by orientation imaging microscopy (OIM) which enabled the growth of vertical Si nanowires. Cross-sectional transmission electron microscopy analysis confirmed that the 111 Si nanowires grew epitaxially off of {111}poly-Si grains in the AIC layer. This study demonstrates the potential of using AIC poly-Si as a template layer for the vertical growth of silicon nanowires on amorphous substrates. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim