Epitaxial growth and structural properties of CoxMnySiz thin films on Ge 111 substrates, including
the Heusler alloy Co2 MnSi 111, have been studied using combinatorial molecular beam epitaxy
MBE techniques. In situ reflection high energy electron diffraction and ex situ x-ray diffraction
experiments show that high quality coherent MBE growth with fcc 111 stacking can be achieved
over a relatively large composition space that includes Co2 MnSi. The highest structural and
chemical ordering is observed near the composition of Co0.63Mn0.14Si0.23 rather than that at the
Heusler stoichiometry of Co2 MnSi. The in-plane crystallographic axis of the fcc film exhibits a 60°
rotation with respect to that of the Ge substrate. The rotation appears to be originated at the
film-substrate interface, as a result of the symmetry and stacking of the Ge 111 surface
reconstruction.