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Zhussupbekov K, Walshe K, Walls B, Ionov A, Bozhko SI, Ksenz A, Mozhchil RN, Zhussupbekova A, Fleischer K, Berman S, Zhilyaev I, O’Regan DD, Shvets IV. Surface Modification and Subsequent Fermi Density Enhancement of Bi(111). THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:5549-5558. [PMID: 34276852 PMCID: PMC8279637 DOI: 10.1021/acs.jpcc.0c07345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 02/24/2021] [Indexed: 06/13/2023]
Abstract
Defects introduced to the surface of Bi(111) break the translational symmetry and modify the surface states locally. We present a theoretical and experimental study of the 2D defects on the surface of Bi(111) and the states that they induce. Bi crystals cleaved in ultrahigh vacuum (UHV) at low temperature (110 K) and the resulting ion-etched surface are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) as well as spectroscopy (STS) techniques in combination with density functional theory (DFT) calculations. STS measurements of cleaved Bi(111) reveal that a commonly observed bilayer step edge has a lower density of states (DOS) around the Fermi level as compared to the atomic-flat terrace. Following ion bombardment, the Bi(111) surface reveals anomalous behavior at both 110 and 300 K: Surface periodicity is observed by LEED, and a significant increase in the number of bilayer step edges and energetically unfavorable monolayer steps is observed by STM. It is suggested that the newly exposed monolayer steps and the type A bilayer step edges result in an increase to the surface Fermi density as evidenced by UPS measurements and the Kohn-Sham DOS. These states appear to be thermodynamically stable under UHV conditions.
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Affiliation(s)
- Kuanysh Zhussupbekov
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
| | - Killian Walshe
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
| | - Brian Walls
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
| | - Andrei Ionov
- Institute
of Solid State Physics, Russian Academy
of Sciences, Chernogolovka, Russia
| | - Sergei I. Bozhko
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
- Institute
of Solid State Physics, Russian Academy
of Sciences, Chernogolovka, Russia
| | - Andrei Ksenz
- Institute
of Solid State Physics, Russian Academy
of Sciences, Chernogolovka, Russia
| | - Rais N. Mozhchil
- Institute
of Solid State Physics, Russian Academy
of Sciences, Chernogolovka, Russia
| | - Ainur Zhussupbekova
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
| | - Karsten Fleischer
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
- School
of Physical Sciences, Dublin City University, Dublin 9, Ireland
| | - Samuel Berman
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
| | - Ivan Zhilyaev
- Institute
of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences, Chernogolovka, Russia
| | - David D. O’Regan
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
- AMBER,
the SFI Research Centre for Advanced Materials and BioEngineering
Research, Dublin 2, Ireland
| | - Igor V. Shvets
- School
of Physics and Centre for Research on Adaptive Nanostructures and
Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
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Khatun S, Bhunia H, Pal AJ. Bi 2Se 3 topological insulator at the 2D-limit: role of halide-doping on Dirac point. Phys Chem Chem Phys 2018; 20:17934-17941. [PMID: 29926058 DOI: 10.1039/c8cp02604a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2D topological insulators exhibit insulating bulk and conducting edge states with a Dirac point, which at times is within the energy gap and could be on either side of the Fermi energy. In this study, we demonstrate a method to tune the energy of the Dirac edge state by introducing halides as dopants in Bi2Se3. We chose halides to substitute the anion, so that due to higher atomic number (of iodine, for example) with respect to selenium, the spin-orbit coupling parameter could be enhanced, leading to the significant separation of the Dirac point from the Fermi energy. With different halogens having different atomic numbers on either side of selenium, the Dirac point could hence be tuned towards both directions. The dopants, due to their heterovalent nature with respect to selenide, introduce carriers in the lattice and consequently, also shift the Fermi energy. We show that the Dirac point with respect to Fermi energy could be correlated to the dopant's atomic number and thus the atomic-number-induced spin-orbit coupling parameter. Strains developed in the lattice due to a mismatch in the effective ionic radii of the dopants and the host anion affected distribution of band energies, leaving the (distribution of) Dirac point unaffected due to its topologically protected nature.
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Affiliation(s)
- Salma Khatun
- Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
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