Kinetic-anisotropy-induced ordering-orientation transition in epitaxial growth: a method to synthesize...

The epitaxial growth has a distinct kinetic feature that the lateral surface diffusion is faster than the longitudinal bulk diffusion. We show there is an ordering-orientation transition of alloy films with the change of growth rate due to this kinetic anisotropy. As an example, we have calculated the epitaxial growth of CoPt alloy films on the Pt buffer layer. We show the ordered structure of CoPt films changes from the L1(0) [001] (a compositional modulation along the [001] direction) variant to the L1(0) [100] variant with the increase of growth rate. This ordering-orientation transition also occurs with the decrease of temperature at adequate growth rate. Based on this mechanism, we propose a simple method to synthesize the ordering-orientation superlattices.