Motion of step pairs during drift-induced step bunching on a Si(0 0 1) vicinal face

Abstract

By Monte Carlo simulation of a lattice model with the periodic boundary condition, we study the motion of step pairs during step bunching on a Si(0 0 1) vicinal face heated by direct electric current. When the anisotropy of the surface diffusion is taken into account, step bunching occurs with the drift of adatoms. When the system width along the steps is so large that bunches fluctuate widely, the bunches with step-up drift recombine with neighboring bunches more frequently and grow faster than those with step-down drift. When the system width along the steps is so small that bunches are straight, the recombination is suppressed irrespective of the drift direction. The bunches with step-up drift grow slower than those with step-down drift. With increasing the drift velocity, separation of the step pair from the bunch occurs. The separated step pairs recede with step-down drift and advances with step-up drift.