No abstract

The structural perfection of the topological insulator (TI) Bi 2 Te 3 is a key issue for its employment in future device applications. State of the art TIs, featuring exotic electronic properties, predominantly suffer from structural defects such as twin domains. A suppression of such domains in molecular beam epitaxy-grown Bi 2 Te 3 thin films on Si(111) substratesmeasured by X-ray diffraction pole figure scansis presented in this paper. A numerical analysis of van der Waals potentials was performed, revealing the nucleation collinear with the Si(311) reflections of the Si(111) substrate to be energetically preferred.

Layered materials such as graphene, bi-, and multilayer graphene as well as various compounds of topological insulators are currently in the focus of interest due to their extraordinary physical properties related to Dirac surface states. The ability to grow thin films of these complex layered materials is the key to explore their fundamental phenomena giving insights into modern solid-state physics. However, complex materials composed of layers only weakly bonded via van der Waals forces offer unmatched challenges for the deposition of thin epitaxial films. Here, we report on the growth of Bi 2 Te 3 ultrathin films on Si (111) substrates using molecular beam epitaxy. Special emphasis is put on the nucleation phenomena and growth dynamics studied in detail by in situ scanning tunnelling microscopy and high-resolution scanning transmission electron microscopy. The morphology of the Bi 2 Te 3 surface and the structure of the Si(111)/Bi 2 Te 3 interface as well as the formation of threading dislocations and crystal domains are studied at the atomic level. Our data indicate that the film is formed via the nucleation of islands, which float on the substrate; thus, the islands are only weakly bonded to the substrate and rather mobile. Apparently, these floating islands are able to arrange themselves by moving in the x−y direction to perfectly coalesce and form a continuous film. The results present a crucial step toward understanding growth and defect formation in this class of materials and thus pave the avenue to a higher control over both their structural and electronic properties, in order to study the electronic properties of the Dirac surface states.