Island Shape Controls Magic-Size Effect for Heteroepitaxial Diffusion

TL;DR

This paper reveals that the shape of islands influences the diffusion mechanism and magic-size effects in heteroepitaxial systems, highlighting the importance of shape in diffusion behavior.

Contribution

It introduces the role of island shape in controlling the reptation-based diffusion mechanism and magic-size effects, a factor not considered in prior studies.

Findings

Shape determines the dominant diffusion mechanism.

Multiple magic-size trends depend on island shape.

Reptation mechanism is shape-dependent.

Abstract

Lattice mismatch of Cu on Ag(111) produces fast diffusion for special "magic sizes" of islands. A size- and shape-dependent reptation mechanism is responsible for low diffusion barriers. Initiating the reptation mechanism requires a suitable island shape, a property not considered in previous studies of 1D island chains and 2D closed-shell islands. Shape determines the dominant diffusion mechanism and leads to multiple clearly identifiable magic-size trends for diffusion depending on the number of atoms whose bonds are shortened during diffusion.