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

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.