Effect of the Surface Diffusion and Evaporation of Impurities on Step Bunching Induced by Impurities

TL;DR

This paper investigates how impurity surface diffusion and evaporation influence step bunching on vicinal surfaces, revealing that impurity lifetime and diffusion rates significantly affect bunch size and step separation behaviors.

Contribution

It introduces a model analyzing the effects of impurity surface diffusion and evaporation on step bunching, highlighting the roles of impurity lifetime and diffusion in surface morphology.

Findings

Long impurity lifetime leads to tight step bunches.

Shorter impurity lifetime reduces bunch size without step separation.

Fast impurity diffusion causes repeated step separation and collision.

Abstract

We consider a vicinal face, where atoms and impurities impinge and evaporate to a vapor phase, to study how the surface diffusion and evaporation of impurities affect step bunching induced by impurities. When the lifetime of impurities on the vicinal face $\tau_\mathrm{imp}$ is long and the surface diffusion of impurities is neglected, the step bunches induced by impurities are tight. When $\tau_\mathrm{imp}$ decreases, the size of the step bunches, which means the number of steps in the bunches, decreases but the separation of single steps from bunches does not occur. When we take into account fast surface diffusion of impurities, the separation and collision between single steps and step bunches occur repeatedly.