Determining Surface Terminations and Chirality of Noncentrosymmetric FeGe Thin Films via Scanning Tunneling Microscopy

Abstract

Scanning tunneling microscopy was used to study the surfaces of 20−100 nm thick FeGe films grown by molecular beam epitaxy. An average surface lattice constant of ∼6.8 Å, in agreement with the bulk value, was observed via scanning tunneling microscopy, low energy electron diffraction, and reflection high energy electron diffraction. Each of the four possible chemical terminations in the FeGe films were identified by comparing atomic-resolution images, showing distinct contrast with simulations from density functional theory calculations. A detailed study of the atomic layering order and registry across step edges allows us to uniquely determine the grain orientation and chirality in these noncentrosymmetric films.

Atomic-scale visualization of topological spin textures in the chiral magnet MnGe

“…layers determines the structural and magnetic chiralities (19,20). The surface lattice constant from these images is 0.67 ± 0.01 nm, within experimental uncertainty of the expected bulk value for a (111) surface (0.678 nm).…”

“…4 of the main text. Following the procedure for comparing experimental STM images and simulated images from density functional theory (DFT) we developed for B20 FeGe (19) , we assign the bright spots in Fig. 12c to a Mn-sparse layer (Fig.…”

“…The structure comprises a quadruple layer of alternating planes of Mn and Ge atoms with sparse or dense packing; the atomic arrangements exactly repeat after a sequence of three such layers. The relative stacking order and orientation of these layers determine the structural and magnetic chiralities ( 19 – 22 ). The surface lattice constant from these images is 0.67 ± 0.01 nm, within experimental uncertainty of the expected bulk value for the (111) surface (0.678 nm).…”

An Atomically Tailored Chiral Magnet with Small Skyrmions at Room Temperature

“…As shown in Fig. 1b (top view), the dense layers have a three atom basis on a hexagonal lattice and the sparse layers have a one atom basis on a hexagonal lattice 25 . The growth of stoichiometric FeGe by ALMBE proceeded successfully over an expanded growth temperature window down to room temperature (RT), where the RHEED pattern is streaky (upper right image of Fig.…”