Drift-Induced Step Instabilities on Si(111) Vicinal Face near 1×1↔7×7 Transition Temperature

Abstract

A Si(111) vicinal face near 860 °C consists of the 1×1 structure and the 7×7 structure. The 1×1 structure is on the lower side and the 7×7 structure is on the upper side of steps. The diffusion coefficient on the 1×1 structure is larger than that on the 7×7 structure. We study drift-induced step instabilities with two different diffusion coefficients. Irrespective of the drift direction, step bunching occurs with the drift. The ratio of the width of the two regions changes with the drift: the structure with fast diffusion is dominant with step-down drift and that with slow diffusion is dominant with step-up drift. Bunches with step-up drift are more straight than that with step-down drift. If the repulsive interaction between a step and a structural boundary is strong enough to suppress the step bunching, the inphase step wandering occurs and grooves perpendicular to the steps appear with step-up drift.