Directed long-range transport of a nearly pure component atom clusters by the electromigration of a binary surface alloy

TL;DR

This paper presents a continuum model showing how electromigration can transport nearly pure atom clusters across a surface alloy, with the electron wind influencing their movement, growth, and purity.

Contribution

The study introduces a model for electromigration-driven transport of atom clusters on surface alloys, highlighting effects of current, anisotropy, and charge ratios on cluster behavior.

Findings

Clusters can be transported over hundreds of lattice spacings by electron wind.

Cluster purity increases during electromigration.

Transport characteristics depend on current density, anisotropy, and charge ratios.

Abstract

Assuming a vacancy-mediated diffusion, a continuum model for electromigration-driven transport of an embedded atom cluster across a surface terrace of a phase-separating A$_x$B$_{1-x}$ surface alloy, such as fcc AgPt(111), is presented. Computations show that the electron wind carries the cluster over hundreds of lattice spacings and in the set direction, while the cluster grows and its purity improves during the drift. Impacts of the current density, the diffusion anisotropy, the magnitude and sign of the ratio of the effective charges $q_A/q_B$, and the jump frequencies ratio $\Gamma_A/\Gamma_B$ on the cluster's drift speed, drift direction, purity and shape are demonstrated.