Chemical Migration and Dipole Formation at van der Waals Interfaces between Magnetic Transition Metal Chalcogenides and Topological Insulators
| Autor: | Noesges, Brenton A., Zhu, Tiancong, Repicky, Jacob J., Yu, Sisheng, Yang, Fenguan, Gupta, Jay A., Kawakami, Roland K., Brillson, Leonard J. |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | Phys. Rev. Materials 4, 054001 (2020) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevMaterials.4.054001 |
| Popis: | Metal and magnetic overlayers alter the surface of the topological insulator (TI) bismuth selenide (Bi$_2$Se$_3$) through proximity effects but also by changing the composition and chemical structure of the Bi$_2$Se$_3$ sub-surface. The interface between Bi$_2$Se$_3$ and Mn metal or manganese selenide was explored using x-ray photoelectron spectroscopy (XPS) revealing chemical and electronic changes at the interface. Depositing Mn metal on Bi$_2$Se$_3$ without an external source of Se shows unexpected bonding within the Mn layer due to Mn-Se bonding as Se diffuses out of the Bi$_2$Se$_3$ layer into the growing Mn film. The Se out-diffusion is further evidenced by changes in Bi core levels within the Bi$_2$Se$_3$ layers indicating primarily Bi-Bi bonding over Bi-Se bonding. No out-diffusion of Se occurred when excess Se is supplied with Mn, indicating the importance of supplying enough chalcogen atoms with deposited metals. However, Bi$_2$Se$_3$ core level photoelectrons exhibited a rigid chemical shift toward higher binding energy after depositing a monolayer of MnSe$_{2-x}$, indicating a dipole within the overlayer. Stoichiometry calculations indicated that the monolayer forms MnSe preferentially over the transition metal dichalcogenide (TMD) phase MnSe$_2$, providing a consistent picture of the dipole formation in which a plane of Se anions sits above Mn cations. This study shows that chemical diffusion and dipole formation are important for Mn-Bi$_2$Se$_3$ and MnSe$_{2-x}$-Bi$_2$Se$_3$ and should be considered carefully for TMD/TI interfaces more generally. Comment: 12 pages, 6 figures + 1 supplemental figure |
| Databáze: | arXiv |
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