High-resolution x-ray diffraction of epitaxial bismuth chalcogenide topological insulator layers3

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 Bi2X3 – 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.