Model of group IV semiconductor NW growth by MBE. The NW has a length L and a diameter D. Elemental compounds are evaporated with a rate J and impinge on the surface as well as on the Au seed particle, positioned at the top of the NW. Once adsorbed, the adatoms diffuse on the substrate and on the NW sidewalls with diffusion lengths λs and λf, respectively. Au adatoms can also diffuse away from the seed particle.
Xu et al. Nanoscale Research Letters 2011 6:113 doi:10.1186/1556-276X-6-113