# X-ray tools for van der Waals epitaxy of bismuth telluride topological insulator films

## TL;DR

This paper introduces an X-ray diffraction method to analyze the atomic structure and lattice coherence in van der Waals epitaxial films of bismuth telluride, aiding the understanding of their electrical properties.

## Contribution

The paper presents a novel X-ray diffraction technique specifically designed to study in-plane atomic displacements and lattice coherence in vdW epitaxy of bismuth telluride films.

## Key findings

- Strong correlation between lateral lattice features and charge carrier types.
- Lattice mismatch effects are influenced by growth conditions such as temperature and tellurium pressure.
- The method provides insights into the structural quality of vdW epitaxial films.

## Abstract

Potential applications in spintronics and quantum computing have motivated much recent research in epitaxial films of bismuth telluride. This system is also an example of van der Waals (vdW) epitaxy where the interface coherence between film and substrate is based on vdW bonds instead of strong ionic or covalent bonds. Effects of lattice mismatch on electrical properties and film structure are more difficult to control due to the weakness of the vdW forces. Here we present a general x-ray diffraction method to investigate in-plane atomic displacements and lateral lattice coherence length in vdW epitaxy. The method is demonstrated in a series of films grown at different temperatures and pressures of additional tellurium sources, revealing strong intercorrelations between the lateral features as well as with the n/p-types of free charge carries.