Characterization of Bismuth Telluride Thin Films Grown by MBE

Abstract

Bismuth telluride, Bi2Te3, has been predicted to be a topological insulator; it has however been difficult to manufacture good quality thin films of it. This project focuses on the characterization and analysis of bismuth telluride thin films that have been manufactured using molecular beam epitaxy in the Chalmers cleanroom. Substrate material and several growth condition parameters have been varied and are here analyzed using X-ray diffraction and atomic force microscopy to draw conclusions about the optimal growth conditions. It turns out that the growth mode of the bismuth telluride thin films changes when grown on vicinal vs. flat substrates. Other effects include a phase change from Bi2Te3 to Bi4Te3 when the tellurium flux is decreased below 20 times the bismuth flux. This phase change leads to the destruction of the topological insulator properties.