Quantitative analysis of Si mass transport during formation of Cu/Si(111)-(5x5) from scanning tunneling microscopy

The Si mass transport taking place during the formation of the Cu/Si(111)-(5x5) surface phase has been studied using scanning tunneling microscopy. From the measurement of the areas occupied by various structural domains and the quantitative consideration of the Si mass balance, the top Si atom density in the Cu/Si(111)-(5x5) phase is found to be 0.96 monolayer. The Cu/Si(111)-(5x5) structure is suggested to consist of a planar CuSi overlayer with an atomic ratio of Cu:Si close to 1:1. Further Cu deposition beyond the formation of Cu/Si(111)-(5x5) phase results in the formation of Cu nanocrystals on the intermediate (5x5) layer.