Epitaxial Growth of the BiySb2–yTe3–xSex 3D Topological Insulator: Physical Vapor Deposition and Molecular Beam Epitaxy

BiySb2–yTe3–xSex (BSTS) topological insulator (TI) thin films were grown by physical vapor deposition (PVD) and molecular-beam epitaxy (MBE) and compared by growth parameters, substrate selection, preparation, and resulting film properties. For the MBE-grown BSTS on Si(111)-(7 × 7), preliminary deposition of the Bi2Te3 buffer layer at the Te-rich growth condition was found to improve the film structural properties. Using a BSTS crystal as the main source for deposition allows us to significantly decrease the molecular Te flux. For the PVD growth, optimal conditions (gas flux, source, and substrate temperatures) were found for a morphologically smooth BSTS film on mica. In order to grow the epitaxial BSTS film on a Si/SiO2 substrate, graphene was successfully used as the pre-epitaxial layer. A newly developed chemical preparation method of atomically clean and structurally ordered epi-layer surfaces allowed us to study the electronic structure of the grown TI films without using capping layers. The surface states with Dirac-like dispersion at the Γ-point in the surface Brillouin zone were detected by angle-resolved photoelectron spectroscopy. Photoemission measurements showed a change in the surface Fermi level position depending on the composition of BSTS films. The magnetoconductivity data demonstrated a strong dependence of the parameters describing a weak antilocalization on the substrate used.