22Molecular Beam Epitaxial Growth of Topological Insulators
Xiao Feng Ke He Xucun Ma and Qi‐Kun Xue
State Key Laboratory of Low‐Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, 100084, China
22.1 Introduction
Molecular beam epitaxy (MBE) has sparked a veritable explosion of materials research since its invention in the late 1960s. Owing to its ability to accurately control film thickness and chemical composition, this technique has been widely used in growing high‐quality semiconductor films and heterostructures. In the past several years, MBE has also been proved to be an ideal method of preparing topological insulator (TI) films and engineering their electronic and magnetic properties.
A TI has a bulk bandgap and gapless surface states protected by time‐reversal symmetry (TRS) [1–11]. In momentum space, topological surface states usually have Dirac‐cone‐shaped band dispersion and are spin‐polarized except at some high‐symmetric points of the surface Brillouin zone. An ideal TI material has the Fermi level (EF) residing in the bulk gap and only intersecting the topological surface states. Such a material can show the unique properties and quantum phenomena of the topological surface states. However, most TI materials are narrow‐gap chalcogenide semiconductors [ 1–3], which are usually vulnerable to the formation of vacancies and anti‐site defects. The defects can heavily charge‐dope TI materials, making them degenerate semiconductors with EF lying ...