Understanding the Atomic Structure of a Topological Insulator–2D Material Heterostructure*

Topological insulators have emerged as promising materials for efficient spin–charge conversion. One avenue to harness the promise of this new class of materials is to integrate them into heterostructures with two-dimensional materials. However, the ability to grow films with the desired properties relies on understanding the film structure and defects on the atomic scale. Here, detailed structural characterization is presented, in which aberration-corrected transmission electron microscopy of (Bi,Sb)₂Te₃ grown on h-BN elucidates details of the heterostructure. The presence of several types of grain boundaries is highlighted, in addition to the identification of an impurity phase and small asymmetries within the film thickness. Finally, a comparison is drawn between the features observed and knowledge gained from the study of topological insulator films grown on more traditional, single-crystal, bulk substrates.