Diffusion of Six-Atom Cu Islands on Cu(111) and Ag(111)

Diffusion of Cu hexamer islands on Cu(111) and Ag(111) is studied using a molecular dynamics simulation technique with many-body potentials obtained from the embedded atom method. Simulations are carried out at temperatures 300, 500 and 700 K, showing that shape-changing multiple-atom processes are more helpful for the diffusion rather than concerted motion of islands. Arrhenius plots of the diffusion coefficients provide effective energy barrier values of 161.29±5 meV for Cu(111) and 179.34±5 meV for Ag(111) surfaces. At 700 K, one pop-up atom among island atoms is observed with correlative changes in the position and shape of the lower-layer adatoms.