The crossover from collective motion to periphery diffusion for two-dimensional adatom-islands on Cu(111)

Area of Science:

• Surface Science
• Materials Science
• Computational Physics

Background:

• Understanding adatom-island diffusion on metal surfaces is crucial for thin-film growth and nanotechnology.
• Previous studies have explored island dynamics, but a comprehensive analysis of size-dependent diffusion mechanisms is needed.

Purpose of the Study:

• To investigate the diffusion mechanisms of two-dimensional adatom-islands on Cu(111) using advanced simulation techniques.
• To determine the size dependence of diffusion coefficients and effective diffusion barriers for islands up to 100 atoms.
• To identify the crossover point between different diffusion regimes.

Main Methods:

• Utilized the self-learning kinetic Monte Carlo (SLKMC) method for atomistic simulations.
• Simulated the diffusion of two-dimensional adatom-islands on a Cu(111) surface.
• Analyzed multiple- and single-atom processes, calculating diffusion coefficients and barriers.

Main Results:

• Revealed a crossover in diffusion mechanisms for island sizes between 13 and 19 atoms.
• Identified a transition from collective island motion to periphery-dominated mass transport.
• Observed a scaling exponent of 1.5 for islands of 19-100 atoms, consistent with prior research.
• Found that smaller islands (2-13 atoms) exhibit diffusion primarily governed by collective motion with size-dependent barriers.

Conclusions:

• The diffusion behavior of adatom-islands on Cu(111) is strongly dependent on island size.
• A distinct crossover in diffusion mechanisms occurs around 13-19 atoms, marking a shift in dominant transport processes.
• The findings provide valuable insights into surface kinetics and island dynamics relevant to materials fabrication.