Dual-Mode Nucleation and Dynamic Alloying of Silicon on Ag(111)

Silicon growth on Ag(111) is a prototypical system for exploring silicene-like monolayers and complex Si-metal interfaces, yet its atomistic nucleation and alloying mechanisms remain unclear. Using first-principles calculations and machine-learning force-field molecular dynamics, we clarify its structural evolution and growth dynamics. Energetic analysis shows that the honeycomb Si monolayer is favored only up to 1.0 atomic layer, whereas higher coverages favor an Ag-terminated surface alloy with sp³-hybridized Si. Large-scale simulations reveal dual-mode nucleation: conventional surface incorporation and a Ag-displacement-assisted pathway in which expelled Ag atoms aggregate into islands that promote Si-layer expansion. Elevated temperatures improve crystalline quality by reducing Ag-island density and promoting larger Si domains. At high coverages, the simulations capture dynamic Ag-Si surface-alloy formation. These findings identify dual-mode nucleation and dynamic alloying as key processes, providing a unified microscopic picture of Si/Ag(111) growth.