Model of patterned self-assisted nanowire growth.

Vertically oriented and ordered GaAs nanowire arrays have been grown by the self-assisted mechanism using substrates prepared with nano-patterned oxide templates. Patterned Ga-assisted GaAs nanowire growth on (111) silicon by molecular beam epitaxy showed that the axial and radial growth rates increased with increasing interhole spacing. A model is described which accounts for the correlation of the final length and diameter with pattern pitch. The model considers that growth material is supplied by a secondary flux of both gallium and arsenic adatoms desorbing from the oxide surface between the nanowires which subsequently impinge on the liquid droplet and nanowire sidewalls. We show that shading of the incident and scattered flux by neighboring nanowires in the array can strongly affect the axial and radial growth rates, leading to significant differences in final nanowire morphologies.