Domain formation due to surface steps in topological insulator Bi_2Te_3 thin films grown on Si (111) by molecular beam epitaxy

摘要

The atomic structure of topological insulators Bi_2Te_3 thin films on Si (111) substrates grown in van der Waals mode by molecular beam epitaxy has been investigated by in situ scanning tunneling microscopy and scanning transmission electron microscopy. Besides single and multiple quintuple layer (QL) steps, which are typical for the step-flow mode of growth, a number of 0.4 QL steps is observed. We determine that these steps originate from single steps at the substrate surface causing domain boundaries in the Bi_2Te_3 film. Due to the peculiar structure of these domain boundaries the domains are stable and oenetrate throughout the entire film.