Abstract
We use kinetic Monte Carlo simulations and analytical modelling to study coalescence of three-dimensional (3D) nanoscale faceted silver island pairs on weakly-interacting fcc(111) substrates, with and without concurrent supply of mobile adatoms from the vapor phase. Our simulations show that for vapor flux arrival rates F < 1 monolayer/second (ML/s) coalescence manifests itself by one of the islands absorbing the other via sidewall facet migration. This process is mediated by nucleation and growth of two-dimensional (2D) layers on the island facets, while the supply of mobile atoms increases the nucleation probability and shortens the time required for coalescence completion. When F is increased above 1 ML/s, coalescence is predominantly governed by deposition from the vapor phase and the island pair reaches a compact shape via agglomeration. The crucial role of facets for the coalescence dynamics is further supported by a mean-field thermodynamic description of the nucleation energetics and kinetics. Our findings explain experimental results which show that two-dimensional film growth morphology on weakly-interacting substrates is promoted when the rate of island coalescence is suppressed. The present study also highlights that deviations of experimentally reported film morphological evolutions in weakly-interacting film/substrate systems from predictions based on the sintering and particle growth theories may be understood in light of the effect of deposition flux atoms on the energetics and kinetics of facet-layer nucleation during coalescence.
Highlights
Our results point out that disagreement between theoretical works predicting different scaling behavior for the percolation transition thickness than that observed experimentally might be due to the effect of deposition rate in the coalescence of island pairs
Process rates for the KMC algorithm are calculated via Arrhenius equations νi activation barrier of the
The chosen island sizes represent a low end of possible sizes that can be encountered in experiments[34]. We argue that this choice does not impair our ability to draw reliable conclusions for coalescence of islands with sizes beyond the simulated ones because: (i) islands exhibit a self-similar shape evolution[25], which means that the atomic scale processes that govern coalescence are size-independent; and (ii) formation and coalescence of faceted islands has been reported to occur over a wide range of sizes, spanning from nanometers to micrometers[34]
Summary
Our results point out that disagreement between theoretical works predicting different scaling behavior for the percolation transition thickness than that observed experimentally might be due to the effect of deposition rate in the coalescence of island pairs. The results from this study may become relevant for knowledge-based synthesis of thin films and nanostructures with controlled morphology on weakly-interacting substrates[8], in particular on 2D-materials for nanoelectronic, sensing, and catalytic devices[5,20,21].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
