Heteroepitaxy of large grain Ge film on cube-textured Ni(001) foils through CaF2 buffer layer

Cube-textured Ni(001) foils have been considered as a viable alternative substrate to grow high quality functional films for large area optoelectronic devices. In this work, we report the heteroepitaxial growth of CaF2(001) films on cube-textured Ni(001) foils at 350-600 °C with in-plane orientation of CaF2[110]//Ni[100] and CaF2[1-10]//Ni[010] with 45° rotation respect to the Ni(001) substrate. Unlike CaF2(111)/Ni(001) films where there exist four independent rotational domains with rotational domain boundaries, CaF2(001)/Ni(001) contains no rotational domains or rotational domain boundaries. This makes CaF2(001)/Ni(001) films better candidates as templates for the growth of high quality functional semiconductors. We also demonstrate that Ge(001) film with no rotational domains and with a grain size of ~ 50 μm similar to that of the Ni substrate can be grown on the CaF2(001) buffered Ni substrate.