High-resolution x-ray diffraction of epitaxial bismuth chalcogenide topological insulator layers*

V Holý, D Kriegner, H Steiner, J Stangl, G Bauer and G Springholz

Abstract

Stoichiometry and lattice structure of epitaxial layers of topological insulators Bi₂Te₃ and Bi₂Se₃ grown by molecular-beam epitaxy is studied by high-resolution x-ray diffraction. We show that the stoichiometry of Bi₂X_{3 – δ} (X  =  Te, Se) epitaxial layers depends on the additional flux of the chalcogens Te or Se during growth. If no excess flux is employed, the resulting structure is very close to Bi₁X₁ (δ  =  1), whereas with a high excess flux the stoichiometric Bi₂X₃ phase is obtained. From the x-ray data we determined the lattice parameters of the layers and their dependence on composition δ, as well as the degree of crystal quality of the layers