Morphology and dynamics of 2D Sn-Cu alloys on (100) and (111) Cu surfaces

We have performed calculations of Sn deposition on Cu(111) and Cu(100) surfaces. The atomic interactions are described by modified embedded atom method (MEAM) potentials. This is a modification of the embedded atom method (EAM) to include higher moments in the electron density. We find that at low coverages Sn deposited on Cu(111)leads to the formation of a two-dimensional (2D) alloy phase with a p(root 3 x root 3)-R 30 degrees structure which is stable up to temperatures of 1200K. For deposition of Sn on Cu(100), a coverage of one-quarter of a monolayer results in the formation of a stable 2D alloy phase with a p(2 x 2) structure. These results are in agreement with ion-scattering experiments. It is found that on both Cu(100) and Cu(111) surfaces, the resulting alloy phases are rippled with the Sn atoms displaced outward from the surfaces.