Schwoebel barriers on Si(111) steps and kinks

TL;DR

This study calculates Schwoebel barriers at Si(111) step edges and kinks, revealing how rebonding influences barrier heights and suggesting multi-atom processes may have lower barriers, with implications for surface diffusion.

Contribution

It provides detailed calculations of Schwoebel barriers at different kink types on Si(111) steps, highlighting the impact of rebonding and atom movement on barrier values.

Findings

Rebonding reduces Schwoebel barriers at kinks.

Barrier estimates vary with binding energy calculations.

Multi-atom processes may have smaller barriers.

Abstract

Motivated by our previous work using the Stillinger-Weber potential, which shows that the [$\overline{2}11$] step on 1$\times$1 reconstructed Si(111) has a Schwoebel barrier of 0.61$\pm$0.07 eV, we calculate here the same barrier corresponding to two types of kinks on this step - one with rebonding between upper and lower terrace atoms (type B) and the other without (type A). From the binding energy of an adatom, without additional relaxation of other atoms, we find that the Schwoebel barrier must be less than 0.39 eV (0.62 eV) for the kink of type A (type B). From the true adatom binding energy we determine the Schwoebel barrier to be 0.15$\pm$0.07eV (0.50$\pm$0.07 eV). The reduction of the Schwoebel barrier due to the presence of rebonding along the step edge or kink site is argued to be a robust feature. However, as the true binding energy plots show discontinuities due to significant movement of atoms at the kink site, we speculate on the possibility of multi-atom processes having smaller Schwoebel barriers.