Dynamic phase transitions in electromigration-induced step bunching

TL;DR

This paper theoretically investigates how electromigration-induced step bunching undergoes a phase transition depending on kinetic asymmetry and step drift, revealing different behaviors in step emission and absorption.

Contribution

It introduces a theoretical model predicting a phase transition in step bunching behavior based on the relative strength of asymmetry and drift.

Findings

Logarithmic growth of steps between bunches at weak asymmetry

Single step crossing at strong asymmetry

Collective step emission and absorption above critical parameters

Abstract

Electromigration-induced step bunching in the presence of sublimation or deposition is studied theoretically in the attachment-limited regime. We predict a phase transition as a function of the relative strength of kinetic asymmetry and step drift. For weak asymmetry the number of steps between bunches grows logarithmically with bunch size, whereas for strong asymmetry at most a single step crosses between two bunches. In the latter phase the emission and absorption of steps is a collective process which sets in only above a critical bunch size and/or step interaction strength.