Morphology Control in van der Waals Epitaxy of Bismuth Telluride Topological Insulators

TL;DR

This paper explores how lattice misfit influences the size and shape of crystalline domains in van der Waals epitaxial films of bismuth telluride, a topological insulator, using advanced synchrotron X-ray and microscopy techniques.

Contribution

It provides new insights into the relationship between lattice misfit and domain morphology in van der Waals epitaxy of bismuth telluride.

Findings

Lattice misfit affects the size and morphology of crystalline domains.

Reciprocal-space maps reveal the spatial conformation of domains through film thickness.

Atomic force microscopy shows surface domain morphology.

Abstract

Bismuth telluride have regained significant attention as a prototype of topological insulator. Thin films of high quality have been investigated as a basic platform for novel spintronic devices. Low mobility of bismuth and high desorption coefficient of telluride compose a scenario where growth parameters have drastic effects on structural and electronic properties of the films. Recently [J. Phys. Chem. C 2019, 123, 24818-24825], a detailed investigation has been performed on the dynamics of defects in epitaxial films of this material, revealing the impact of film/substrate lattice misfit on the films' lateral coherence. Very small lattice misfit (<0.05%) are expected to have no influence on quality of epitaxial system with atomic layers weakly bonded to each other by van der Waals forces, contrarily to what was observed. In this work, we investigate the correlation between lattice misfit and size and morphology of the film crystalline domains. Three-dimensional reciprocal-space maps of film Bragg reflections obtained with synchrotron X-rays are used to visualize the spatial conformation of the crystallographic domains through film thickness, while atomic force microscopy images provide direct information of the domains morphology at the film surface.