Epitaxial Growth of the Bi_ySb_2–yTe_3–xSe_x 3D Topological Insulator: Physical Vapor Deposition and Molecular Beam Epitaxy

Abstract

Bi y Sb2–y Te3–x Se x (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.

Raman scattering spectroscopy of MBE grown thin film topological insulator Bi2−xSbxTe3−ySey

“…A detailed description of the film growth is reported elsewhere. 15 In the present study, SiC/graphene composites used for the growth of BSTS thin films were deposited on semi-insulating 6H-SiC substrates by thermal decomposition. 20,21 Atomic force microscopy in scanning mode was employed for the investigation of topography and roughness of the samples.…”

“…12 Stepina et al observed a higher degree of bulk insulation in BSTS compounds. 15 In this work, 15 the choice of substrate for the growth of BSTS films also played an important role in their bulk insulating properties, electronic properties, and transport. Weak antilocalization was observed for the BSTS films grown on the Si/SiO 2 /graphene substrate.…”

“…Weak antilocalization was observed for the BSTS films grown on the Si/SiO 2 /graphene substrate. 15 Bulk insulating properties may largely depend on the localized crystal structure and formation of defects in BSTS films, the characteristic which have not been well understood so far. These aspects may lead to local inversion symmetry breaking, 16 and have greater impact on topological phases and transport.…”