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

TL;DR

This study used scanning tunneling microscopy to analyze the atomic surface structures of epitaxial B20 FeGe thin films grown by molecular beam epitaxy, revealing detailed surface and subsurface layer information.

Contribution

It provides the first atomic resolution imaging of all four chemical layers of FeGe(-1-1-1) surfaces and confirms grain orientations using multiple microscopy techniques.

Findings

Atomic resolution of four chemical layers achieved

Surface unit cell size matches bulk expectations (~6.84 Å)

Grain orientations confirmed as (111) or (-1-1-1)

Abstract

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.