Surface Structures of Epitaxial B20 FeGe(-1-1-1) Thin Films via Scanning Tunneling Microscopy.

We grew 20-100 nm thick films of B20 FeGe by molecular beam epitaxy and investigated the surface structures via scanning tunneling microscopy. We observed the atomic resolution of each of the four possible chemical layers in FeGe(-1-1-1). An average hexagonal surface unit cell is observed via scanning tunneling microscopy, low energy electron diffraction, and reflection high energy electron diffraction resulting in a size of ~6.84 {\AA} in agreement with the bulk expectation. Furthermore, the atomic resolution and registry across triple-layer step edges definitively determine the grain orientation as (111) or (-1-1-1). Further verification of the grain orientation is made by Ar+ sputtering FeGe(-1-1-1) surface allowing direct imaging of the subsurface layer.