A misfit structure in the Co/Pt(1 1 1) system studied by scanning tunnelling microscopy and embedded atom method calculations

We have performed scanning tunnelling microscopy (STM) measurements of thin films of Co and CoPt alloys on Pt(1 1 1). In contrast to the interpretation of an earlier low energy electron diffraction investigation by Tsay and Shern [Surf. Sci. 396 (1998) 313] we find that the structure observed upon annealing a Pt(1 1 1) sample with a 2 ML (monolayer, ML) thick film of Co does not consist of a rotated Co film but rather of a CoPt alloy film with hexagonal areas of fcc stacking, single and double stacking faults, delimited by misfit dislocations (Shockley partial dislocations). Comparison of STM images with embedded atom method calculations confirms our model. The structure at the Pt–PtCo interface in our model is similar to that proposed by Henzler [Surf. Sci. 419 (1999) 321].