Two-step growth of high quality Bi2Te3 thin films on Al2O3 (0001) by molecular beam epitaxy

Large-area topological insulator Bi2Te3 thin films were grown on Al2O3 (0001) using a two-temperature step molecular beam epitaxy growth process. By depositing a low temperature nucleation layer to serve as a template for high temperature epitaxial film growth, a high quality terrace-step surface morphology with a significant reduction in three-dimensional defect structures was achieved. X-ray diffraction measurements indicate that high crystalline quality Bi2Te3 layers were grown incoherently by van der Waals epitaxy using this technique. Angle resolved photoemission spectroscopy measurements verified the integrity of this growth method by confirming the presence of metallic surface states on cleaved two-step Bi2Te3 samples.