Atomic and island scale diffusion events on Bi2Te3 (0001) surfaces & ultra-thin Bi2Te3 films on SiO2 substrates

Topological insulators (TI) are new phase of materials. They were reported as they have conducting surface states at their edges whereas they have insulating band in bulk. While Bismuth Telluride (Bi2Te3) is well-known thermoelectric material for several decades, it attracted attention again in recent years after declared as a TI. TI are promising materials in novel fields such as spintronics, quantum computation and topological superconductivity. Before any application in these fields, further investigations on their incompleted both morphological and electronic structure require. Bi2Te3 has rhomboherdral primitive cell which contains five atoms. It consists of five atomic planes of (Te1-Bi-Te2-Bi-Te1) along c-axis named as quintuple layer (QL). QLs are bind each other with weak van der Waals bonds, yields most cleavable interface. After cleaving, resulting Te1 terminated (0001) surface has trigonal lattice, and its both morphological and electronic structure can be determined at atomic scale by means of scanning tunneling microscopy (STM). In addition, Bi2Te3 has four type of defects. Depending on the doping type, types of the observable defects may change. In this thesis, we studied general morphology of (0001) surfaces of Bi2Te3 under ambient conditions with STM, including the defects and their electronic structure. In addition to investigations on morphological structure, we focused on diffusion events of the Te1 vacancies. To the best our knowledge, we report for the first time diffusion of individual atomic scale defects as well as Ostwald ripening of vacancy islands on a TI surface. Also, we investigated the nature of mass flow on Bi2Te3 surface according to previous studies that express the thermodynamic and kinetics behind growing islands. On the other hand, the knowledge on the electronic structure of this material at ultra-thin limit is still incomplete. We modified chemical vapor deposition (CVD) technique to grow ultra-thin Bi2Te3 films on SiO2/Si wafers. In this process, we obtained ultra-thin films and micro-particles of Bi2Te3. The heights of obtained Bi2Te3 films are measured to be a few QLs. The radius of Bi2Te3 micro-particles are few micrometers. Structural and spectroscopic characteristics of these ultra-thin films are also discussed.