Surface alloying at the nanoscale: Mo on Au nanocrystalline films.

Aiming at the physical and chemical mechanisms of surface alloying at the nanometer scale in immiscible binary metallic systems, we have studied the Mo growth mode upon depositing Mo on the surface of Au nanocrystalline films via molecular beam epitaxy. Mo-Au surface alloying was observed when Mo was deposited on Au nanocrystalline films at a high temperature. A relevant thermodynamic and kinetic model was established to address the surface alloying at the nanoscale. The size-dependent interface energy between the Mo particles and the Au nanocrystalline films, as the thermodynamic driving force, is attributed to be the reason behind the physical and chemical mechanisms of the Mo-Au surface alloying on Au nanocrystalline films.