VLS growth mechanism of Si-nanowires for flexible electronics

Nanowires (NWs) are promising building blocks for flexible electronics and sensors and a number of approaches have been used to develop them. Among these, the vapor-liquid-solid (VLS) mechanism has been most appealing as it provides the electronic quality NWs at low fabrication cost. For these reasons, this method plays an important role in many applications including NWs based flexible electronics. The performance of NWs based electronics and sensors depend on their quality and the underlying growth mechanism, which thus far has not attracted much attention. In this paper, we present the physical chemistry model that explains the atomistic aspects of the growth mechanism of silicon nanowires. The mechanistic equations have been derived for various steps involved in a standard VLS growth process. The supersaturation under the steady state conditions has been calculated and utilized to estimate the growth rate of Si-NWs under different temperature conditions. The estimated values are found to be consistent with the reported measured values. The results from our study indicate that the Si-NW growth rate is directly related to the temperature. High-temperatures (∼900°C) lead to longer Si-NWs (tens of microns length). This knowledge about growth conditions for Si-NW will enable better control of Si-NW dimensions and hence will have significant positive impact on using Si-NW in flexible electronics — especially the contact printing of NWs based electronic layers on flexible substrates.