Abstract
Molecular-beam epitaxy (MBE) of three-dimensional (3D) topological insulator (TI) Bi2Se3 thin films on different substrates is presented. Multiple characterization techniques are employed to investigate epifilm’s structural, morphological and electrical properties. Films grown along [111] and [221] directions are demonstrated, which showed critical roles played by the substrates.
Twin defects in epitaxial Bi2Se3 (111) films grown on hexagonal substrate surfaces have been found inevitable in the past. However, such defects are found to be effectively suppressed when using InP(111)A and GaAs(111)A substrates, which is evidenced in electron diffraction and STM measurements. An explanation is given based on DFT calculations. For growing high-index (221) film, facetted InP(001) substrate is used. Angle-resolved photoemission spectroscopy (ARPES) measurements unambiguously showed the Dirac surface states on this surface. Moreover, the anisotropic Fermi surface is revealed, which agrees with theoretical results. Transport studies of the Bi2Se3(221) films also show a conductivity difference along the two perpendicular directions.