Step Bunching with Alternation of Structural Parameters

TL;DR

This paper investigates how alternating structural parameters like diffusion coefficients and kinetic coefficients influence step bunching on Si(001) vicinal faces, revealing the effects of drift direction and parameter alternation on bunching behavior.

Contribution

It introduces a detailed analysis of step bunching caused by structural parameter alternation, highlighting the impact of drift direction and parameter type on bunching dynamics.

Findings

Step bunching occurs with diffusion coefficient alternation regardless of drift direction.

Step-down drift accelerates step bunch growth more than step-up drift.

Evaporation reduces the difference in bunching behavior caused by drift direction.

Abstract

By taking account of the alternation of structural parameters, we study bunching of impermeable steps induced by drift of adatoms on a vicinal face of Si(001). With the alternation of diffusion coefficient, the step bunching occurs irrespective of the direction of the drift if the step distance is large. Like the bunching of permeable steps, the type of large terraces is determined by the drift direction. With step-down drift, step bunches grows faster than those with step-up drift. The ratio of the growth rates is larger than the ratio of the diffusion coefficients. Evaporation of adatoms, which does not cause the step bunching, decreases the difference. If only the alternation of kinetic coefficient is taken into account, the step bunching occurs with step-down drift. In an early stage, the initial fluctuation of the step distance determines the type of large terraces, but in a late stage, the type of large terraces is opposite to the case of alternating diffusion coefficient.