Kinetics of Surface-Guided Nanowire Growth

Semiconductor nanowires (NWs) are promising building blocks for nanoelectronic and nano-optoelectronic devices, such as field-effect transistors, photodetectors and LEDs. However, it is still challenging to integrate NWs into practical devices that require planar arrays. During the past few years, our group has demonstrated the guided growth of horizontal NWs of different semiconductors materials and their parallel integration into various functional systems with controlled directions and crystallographic orientations. In order to predict and fully control these growth directions and crystallographic orientations, an understanding of the mechanism of the guided NWs growth is needed.

Herein, we study a newly developed theoretical model of the growth kinetics of planar NWs grown on C-plane sapphire. Non-monotonic dependence of the NWs growth rate versus radius showing increasing radius dependence for thin NWs and decreasing dependence for wider NWs as was observed for vertical NWs. Such dependence is been explained by a competition of the Gibbs-Thomson effect suppressing the vapor-liquid-solid (VLS) growth of NWs and the diffusion-induced growth effects that lead to inverse length-radius correlation. The new growth model for planar NWs introduces the dependence (dL/dt)~ (1/R)^m for the diffusion part with dimensionality of surface-diffusion m=1 as was shown previously for vertical NWs or the unique value for planar NWs of m=1.5,2. The model describes well the growth of planar ZnSe and ZnS NWs suggesting that the main diffusion-induced contribution to the growth originates from the NWs sidewalls or the substrate, respectively.