A theoretical study was made of the step-wandering and step-bunching which were induced by the drift of adatoms; allowing for the permeability of steps. The critical drift velocity which was required in order to induce the instability was calculated, and Monte Carlo simulations were performed in order to test the analysis. It was noted that during sublimation, when the step-distance was small in comparison with the surface-diffusion length, wandering and bunching of steps could occur simultaneously with step-down drift; if the steps were impermeable. The instabilities did not occur simultaneously if the steps were permeable. Bunching then occurred with step-up drift, and wandering with step-down drift. During growth, when the step-distance was small, bunching occurred with step-down drift and step-wandering occurred with step-up drift; regardless of the permeability. A change in permeability with increasing temperature could explain experimentally observed instabilities.

Instabilities of Steps Induced by the Drift of Adatoms and Effect of the Step Permeability. M.Sato, M.Uwaha, Y.Saito: Physical Review B, 2000, 62[12], 8452-72