Size-selective, rapid dynamics of large, hetero-epitaxial islands on fcc (001) surfaces

OU Uche and HG Le and LB Brunner, COMPUTATIONAL MATERIALS SCIENCE, 188, 110225 (2021).

DOI: 10.1016/j.commatsci.2020.110225

In this work, we use molecular dynamics simulations to investigate the diffusion of two-dimensional, hexagonal silver islands on copper and nickel substrates below room temperature. Our results indicate that certain sized islands diffuse orders of magnitude faster than other islands and even single atoms under similar conditions. An analysis of several low-energy pathways reveals two governing processes: a rapid, glide-centric process and a slower, vacancy-assisted one. The relative magnitude of the energies required to nucleate a vacancy plays a role in determining the size-selective diffusion of these islands. In addition, we propose a model which can be used to predict magic-sized islands in related systems. These findings should provide insight to future experimental research on the size distribution and shapes observed during the growth of metal-on-metal thin films.

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