Ratchet Effect in Surface Electromigration: Smoothing Surfaces by an ac Field

TL;DR

This paper shows that applying an ac electric field to surfaces with a Schwoebel barrier induces a net downhill electromigration current, which can smooth surfaces and prevent mound formation during growth.

Contribution

It provides an analytical calculation and simulation evidence that ac fields can induce a net downhill current, aiding surface smoothing and growth control.

Findings

Ac fields induce a net downhill electromigration current.

The current magnitude is analytically calculated and validated by simulations.

Application of ac fields can suppress mound formation during growth.

Abstract

We demonstrate that for surfaces that have a nonzero Schwoebel barrier the application of an ac field parallel to the surface induces a net electro- migration current that points in the descending step direction. The magnitude of the current is calculated analytically and compared with Monte Carlo simulations. Since a downhill current smoothes the surface, our results imply that the application of ac fields can aid the smoothing process during annealing and can slow or eliminate the Schwoebel-barrier-induced mound formation during growth.