Effect of Two-Dimensionality on Step Bunching Induced by the Drift of Adatoms

TL;DR

This paper investigates how two-dimensional effects influence step bunching caused by adatom drift, revealing that anisotropy and step kinetics significantly alter bunching dynamics and speed.

Contribution

It introduces a two-dimensional model showing how anisotropy and kinetic differences affect step bunching behavior under adatom drift.

Findings

Step bunching with step-up drift can be faster when two-dimensional effects are considered.

Anisotropy causes heavy wandering and more frequent recombination of step bunches.

Kinetic coefficient differences can reverse the speed order of bunching with step-up versus step-down drift.

Abstract

We study the effect of two-dimensionality on step bunching induced by drift of adatoms. When anisotropy of the diffusion coefficient changes alternately on consecutive terraces like a Si(001) vicinal face, bunching occurs with the drift of adatoms. If the fluctuation of step bunches is neglected as in the one-dimensional model, the bunching with step-down drift is faster than that with step-up drift in contradiction with the experiment by Latyshev and coworkers. In a two-dimensional model, the step bunches wander heavily with step-up drift and recombination with neighboring bunches occur more frequently than those with step-down drift and the bunching is accelerated. When the difference of kinetic coefficients between two types of steps is taken into account, the bunching with step-up drift can be faster than that with step-down drift.