Instabilities of Permeable Steps Induced by the Drift of Adatoms

Abstract

We study the effect of permeability on the two types of step instabilities, bunching and wandering. When the step is permeable for adatom diffusion, the wandering instability occurs with step-down drift and the bunching instability occurs with step-up drift. In contrast, when the step is impermeable for adatom diffusion, both the wandering and the bunching instabilities occur with step-down drift. We derive the linear amplification rates of step fluctuation and the critical drift velocities to induce the instabilities. The results of the linear analysis are tested by Monte Carlo simulation.