Atomic structures and behaviors of a fcc Cu(111) surface with submonolayer Pb coverage

Atomic structure, bond formation, and surface diffusion in a fcc Pb/Cu(111) surface system were quantitatively investigated using molecular dynamics (MD) simulation and density functional theory (DFT) based ab initio calculations. Pb adatoms deposited on the fcc Cu(111) surface in the MD simulation were observed to diffuse actively in lateral directions to form clean 2D Pb islands without any 3D growth or surface intermixing across the interface. Through the ab initio calculations, the extraordinarily low energy barriers for the surface diffusion of Pb adatoms on both Pb islands and Cu(111) surface were found to contribute to the active surface diffusion of Pb adatom and the clean 2D island formation on the Cu(111) surface. The calculated adsorption energy of the Pb adatom to Pb islands on Cu(111) was proportional to the number of new Pb-Pb bondings, which explained the tendency of the Pb island to have maximum Pb-Pb bonding.