Low temperature epitaxial growth of Ge on CaF2 buffered cube-textured Ni

Quasi-single crystal Ge films were grown on cube textured Ni substrate at a temperature of 350 °C using an insulating buffer layer of CaF2. A direct deposition of Ge on Ni at 350 °C was shown to alloy with Ni. From x-ray pole figure analysis, it was shown that Ge grew epitaxially with the same orientation as CaF2 and the dispersions in the out-of-plane and in-plane directions were found to be 1.7±0.1° and 6±1°, respectively. In the out-of-plane direction, Ge[111]‖CaF2[111]‖Ni[001]. In addition, the Ge consisted of four equivalent in-plane oriented domains such that two mutually orthogonal directions: Ge〈2̄11〉 and Ge〈01̄1〉 are parallel to mutually orthogonal directions: Ni〈1̄10〉 and Ni〈1̄1̄0〉, respectively, of the Ni(001) surface. This was shown to originate from the four equivalent in-plane oriented domains of CaF2 created to minimize the mismatch strain between CaF2 and Ni in those directions.

► Epitaxial Ge layer was grown on Ni using CaF2 buffer layer.
► The epitaxial CaF2 layer inhibited alloy formation between Ge and Ni.
► Both Ge(111) and CaF2(111) consisted of four equivalent in-plane orientations.
► Misfit strain minimization was shown to lead to CaF2[111]‖Ni[001].