Asymmetric intermixing in a Co–Al thin film system: An investigation using coaxial impact collision ion scattering spectroscopy

Abstract

Surface structure evolution during atomic deposition in a Co–Al system was investigated using coaxial impact collision ion scattering spectroscopy (CAICISS). Half monolayer of Al and Co atoms were deposited on Co(0001) and Al(001) single crystal surfaces, respectively, in an ultrahigh-vacuum environment. CAICISS analysis of the deposited surface revealed an asymmetric interfacial reaction, as predicted by previous molecular dynamics simulations. Al atoms deposited on a Co substrate are placed on the surface with no interatomic intermixing. In contrast, significant surface intermixing with the deposited Co atoms occurs on the Al(001) substrate, resulting in the formation of a CoAl intermetallic surface layer of B2 structure. These asymmetric features would be important to the understanding of the structural evolution of thin film multilayers.