  We demonstrate high-quality epitaxial germanium (Ge) films on a metallic
silicide, Fe3Si, grown directly on a Ge(111) substrate. Using molecular beam
epitaxy techniques, we can obtain an artificially controlled arrangement of
silicon (Si) or iron (Fe) atoms at the surface on Fe3Si(111). The Si-terminated
Fe3Si(111) surface enables us to grow two-dimensional epitaxial Ge films,
whereas the Fe-terminated one causes the three-dimensional epitaxial growth of
Ge films. The high-quality Ge grown on the Si-terminated surface has almost no
strain, meaning that the Ge films are not grown on the low-temperature-grown Si
buffer layer but on the lattice matched metallic Fe3Si. This study will open a
new way for vertical-type Ge-channel transistors with metallic source/drain
contacts.
