Topological insulator Sb$_{2}$Te$_{3}$ thin films grown by MBE*

Atomically flat Sb$_{2}$Te$_{3}$ thin films were grown by molecular beam epitaxy (MBE) on Si(111) substrate. Layer-by-layer growth was characterized by real time reflection high-energy electron diffraction (RHEED) intensity oscillations. \textit{In situ }angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM) measurements reveal that the as-grown films are stoichiometric Sb$_{2}$Te$_{3}$. When the thickness is larger than two quintuple layers, the films show the predicted topological property with a single Dirac-cone on the surface. The measured band structure for the films with a thickness from one to five quintuple layers agrees well with our first principle calculations.