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| Hauptseite > Publikationsdatenbank > Structural and Electronic Characterization of MBE-grown Topological Insulator Thin Films |
| Hauptseite > Publikationsdatenbank > Structural and Electronic Characterization of MBE-grown Topological Insulator Thin Films |
| Book/Dissertation / PhD Thesis | FZJ-2026-02468 |
2026
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-95806-919-0
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Please use a persistent id in citations: doi:10.34734/FZJ-2026-02468
Abstract: As a new class of quantum matter, topological insulators (TIs) have attracted significant attention in the field of condensed matter physics due to their exotic intrinsic physical properties. TIs, which exhibits either two-dimensional (2D) or three-dimensional (3D) topology, are materials that are insulating in the bulk and conducting at the edge or surface. This behavior arises from the presence of the gapless edge or surface states at the boundary, which are protected by time-reversal symmetry and exhibit spin momentum locking. Such unique properties provide an excellent platform for developing novel electronic and spintronic devices, as well as potential applications including topological quantum computing. This work focuses on the systematic study of epitaxial growth of 2D and 3D TIs via molecular beam epitaxy (MBE) and atomic-scale structural characterization via scanning transmission electron microscope (STEM). In addition, the surface electronic structures of TI thin films and bulk crystals are investigated using angle-resolved photoemission spectroscopy (ARPES). Bi is classified as a higher-order topological insulator (HOTI); however, Bi in thin-film form is proposed to exhibit 2D topology. This study is extended in-depth to achieve controlled growth of various Bi phases, including the trigonal phase (demonstrated as HOTI) and the orthorhombic phase (theoretically predicted to be a 2D TI). It has also been observed that the thickness plays a significant role in controlling the lattice strain of the orthorhombic phase, which directly influences its topology. Later, Sb is incorporated into the Bi thin film to form the BiSb alloy, which can also serve as a promising platform for realizing a 2D TI. Apart from 2D TIs, 3D TIs, especially BixSbyTez, suffer from the high density of point defects, resulting in the formation of electronic puddles. However, by replacing Sb with Sn, which is also a p-type dopant, the SnxBiyTez alloy presents a new material platform, which has been adopted in this study. Various stoichiometries such as SnBi4Te7, SnBi2Te4 and Sn2Bi2Te5 are grown and structurally characterized, providing another opportunity to engineer the topological band structure. Finally, the focus is shifted to MnxBiyTez, a magnetic topological insulator (MTI), where the Mn acts as magnetic dopant incorporated into Bi2Te3. Particularly, MnBi6Te10 has been intensively investigated by circular dichroism ARPES, revealing the orbital angular momentum features of the electronic band structure of one of the two Bi2Te3 terraces on the cleaved crystal. The results are further supported by theoretical calculations. In short, this study not only provides an alternative platform to yield 2D topology, but also offers a promising approach to tune the Fermi level of 3D TIs through topological band engineering via Sn doping. This work can be further extended to fabricate novel and sophisticated quantum device architectures on a scalable platform.
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