Lattice Effects in Crystal Evaporation

TL;DR

This paper investigates the limitations of the continuum approximation in modeling crystal surface evaporation, highlighting issues caused by angular points and the Schwoebel effect through numerical and qualitative analysis.

Contribution

It provides a detailed assessment of the continuum model's validity and identifies specific limitations related to surface geometry and adatom detachment asymmetries.

Findings

Continuum approximation has limitations near angular points.

The Schwoebel effect influences surface dynamics significantly.

Numerical calculations reveal discrepancies with the continuum model.

Abstract

We study the dynamics of a stepped crystal surface during evaporation, using the classical model of Burton, Cabrera and Frank, in which the dynamics of the surface is represented as a motion of parallel, monoatomic steps. The validity of the continuum approximation treated by Frank is checked against numerical calculations and simple, qualitative arguments. The continuum approximation is found to suffer from limitations related, in particular, to the existence of angular points. These limitations are often related to an adatom detachment rate of adatoms which is higher on the lower side of each step than on the upper side ("Schwoebel effect").