Topological insulators Bi2Se3 thin films have been grown by Pulsed Laser Deposition on (111)-SrTiO3 and (0001)-Al2O3 substrates. X-ray diffraction (XRD) was used to investigate the effects of the substrate temperature (ranging from 270°C up to 400°C) and the background pressure (ranging from 10-5 mbar to 10-1 mbar) on the structural properties of the Bi2Se3 films. XRD investigation demonstrates that epitaxial Bi2Se3 with single (0001)-orientation can be obtained on several substrates in a narrow (i.e. 20°C) range of deposition temperatures at 10-1 mbar of background pressure. In-situ Low-Energy Electron Diffraction (LEED) showed that films grown on (001)-Al2O3 substrates have almost-unique in-plane orientation and good surface quality to perform Spin and Angle-Resolved Photo-Emission Spectroscopy (SARPES) experiments.
In-situ Spin-resolved and conventional ARPES experiments on the topological surface state of Bi2Se3 thin films were performed by using synchrotron radiation. ARPES band dispersion of the Bi2Se3 thin films show a single Dirac cone centered at the Γ point of the Brillouine zone. The spin-resolved spectra confirmed the spin-momentum locking fingerprint of the topological surface state, where opposite spin polarization occurs for opposite momenta.
Orgiani P. et al Appl. Phys. Lett. 110, 171601 (2017)