Kinetics of Step Propagation at the Sidewalls of 3D Islands and Nanowires

Models of adatom surface diffusion and incorporation at the sidewalls of nanowires and 3D islands are proposed. The models account for the presence of an atomic step on the sidewall facet and for the adatom transport from the substrate to the sidewall. Peculiarities of the potential relief for migrating adatoms as well as the effect of step permeability are taken into account. It is shown that kinetics of the step propagation at the nanowire sidewall is affected by the presence of a strong sink for adatoms at the nanowire top facet and by adatom desorption from the sidewall. As a consequence, survival of the step at the nanowire sidewall depends strongly on the nanowire length. For 3D islands it is shown that the adatom concentration at the island apex can be considerable even in the absence of the deposition flux provided that the step is permeable for adatoms and there exists substantial material transfer from the wetting layer to the island facet. This favors formation of new steps at the island apex and may trigger the morphological transition of the 3D island. [DOI: 10.1380/ejssnt.2014.68]