Coalescence dynamics of 3D islands on weakly-interacting substrates

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Nanoscale island formation is crucial for thin film growth.
• Understanding island coalescence dynamics is key to controlling film morphology.
• Weakly-interacting substrates present unique challenges for film growth.

Purpose of the Study:

• To investigate the coalescence mechanisms of 3D silver island pairs on fcc(111) substrates.
• To determine the influence of vapor flux and adatom supply on coalescence.
• To elucidate the role of substrate-island interactions and facet dynamics.

Main Methods:

• Kinetic Monte Carlo (KMC) simulations.
• Analytical modeling.
• Mean-field thermodynamic description.

Main Results:

• At vapor flux F < 1 ML/s, coalescence occurs via sidewall facet migration, mediated by 2D layer nucleation and growth.
• Mobile adatom supply enhances nucleation probability and reduces coalescence time.
• At F > 1 ML/s, coalescence is dominated by vapor phase deposition, leading to agglomeration and compact shapes.
• Facet energetics and kinetics significantly influence coalescence dynamics.

Conclusions:

• The study explains experimental observations of 2D film growth promotion when island coalescence is suppressed.
• Deviations in film morphology evolution from standard theories can be attributed to deposition flux effects on facet-layer nucleation during coalescence.
• Facet-mediated processes are critical for understanding nanoscale island behavior on weakly-interacting surfaces.