Diffusion Of Small Cu Islands On The Ni(111) Surface: A Self-Learning Kinetic Monte Carlo Study

Keywords

Activation energy barrier; Diffusion coefficient; Island diffusion; Lateral interaction; Self-Learning Kinetic Monte Carlo; Single-atom, multi-atom, concerted process

Abstract

We elucidate the diffusion kinetics of a heteroepitaxial system consisting of two-dimensional small (1–8 atoms) Cu islands on the Ni(111) surface at (100–600) K using the Self-Learning Kinetic Monte Carlo (SLKMC-II) method. Study of the statics of the system shows that compact CuN (3≤N≤8) clusters made up of triangular units on fcc occupancy sites are the energetically most stable structures of those clusters. Interestingly, we find a correlation between the height of the activation energy barrier (Ea) and the location of the transition state (TS). The Ea of processes for Cu islands on the Ni(111) surface are in general smaller than those of their counterpart Ni islands on the same surface. We find this difference to correlate with the relative strength of the lateral interaction of the island atoms in the two systems. While our database consists of hundreds of possible processes, we identify and discuss the energetics of those that are the most dominant, or are rate-limiting, or most contributory to the diffusion of the islands. Since the Ea of single- and multi-atom processes that convert compact island shapes into non-compact ones are larger (with a significantly smaller Ea for their reverse processes) than that for the collective (concerted) motion of the island, the later dominate in the system kinetics – except for the cases of the dimer, pentamer and octamer. Short-jump involving one atom, long jump dimer-shearing, and long-jump corner shearing (via a single-atom) are, respectively, the dominating processes in the diffusion of the dimer, pentamer and octamer. Furthermore single-atom corner-rounding are the rate-limiting processes for the pentamer and octamer islands. Comparison of the energetics of selected processes and lateral interactions obtained from semi-empirical interatomic potentials with those from density functional theory show minor quantitative differences and overall qualitative agreement.

Publication Date

8-1-2017

Publication Title

Surface Science

Volume

662

Number of Pages

42-58

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.susc.2017.03.012

Socpus ID

85016821492 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85016821492

This document is currently not available here.

Share

COinS