Evolution of a liquid-like fluid phase on Ge/Au(111) at room temperature: A direct observation by STM

The evolution of a Au(111) surface after deposition of a submonolayer amount of Ge atoms has been investigated by STM. Diffusion and incorporation of Ge atoms into Au are active at room temperature where only negligible solubility is expected at equilibrium. It turned out that this surface phase is fluid, where the migration of step edges and successive appearance and disappearance of monolayer islands on the surface are confirmed. These phenomena seem to imply the weakening of the bonding strength between Au atoms by Ge incorporation and could be playing an important role in the low temperature crystallization process of Ge nanowires and thin films using Au as a catalyst.