Asymmetric Surface Intermixing during Thin-Film Growth in the Co-Al System: Role of Local Acceleration of the Deposited Atoms

Sang-Pil Kim, Seung-Cheol Lee, Kwang-Ryeol Lee, Yong-Chae Chung
 

Surface intermixing behavior during thin-film deposition in the Co–Al system was investigated on atomic scale by three-dimensional classical molecular dynamics simulation. Asymmetry of the surface intermixing was observed: Al deposition on a Co substrate resulted in an Al thin film with an atomically sharp interface, while a Co thin film deposited on an Al substrate had an interfacial intermixing layer of B2 structure. This phenomenon is discussed in the view point of kinetics of the atomic intermixing on the surface. A kinetic criterion for the atomic intermixing is whether the increased kinetic energy of the deposited atom near the surface is larger than the energy barrier for the atomic intermixing on the surface. Local acceleration of the deposited atoms near the surface provides an explanation of the puzzling phenomenon of the significant intermixing under low energy deposition conditions such as thermal evaporation or molecular beam epitaxy.