Dynamic of Defects in Van Der Waals Epitaxy of Bismuth Telluride Topological Insulators

Potential applications in spintronics and quantum information processing have motivated much recent research in epitaxial films of bismuth telluride. This system is also an example of van der Waals (vdW) epitaxy, where the interface coherence between the film and substrate is based on vdW bonds instead of strong ionic or covalent bonds. Because of the weakness of the vdW bonds, the overall quality of the epitaxial films is difficult to control and structural defects are easily introduced with a significant impact on the electronic phase diagram of the epitaxial films. To elucidate the evolution of defects as a function of the growth parameters, we combine nondestructive methods for electrical and structural analysis, as well as to establish intercorrelations between structural features and density of free charge carriers. It clearly shows that point defects and twinned domains favor p-type of charge carriers. Passivation of points defects by formation of metallic bismuth bilayers (BLs) drastically changes...