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Xu T, Zheng Y, Wang X, Sun Z, Han B. Study of dielectric polarization and electrical transport in Bi 1·2Sb 0·8Te 0·4Se 2.6 nanofilms. Heliyon 2024; 10:e27444. [PMID: 38509921 PMCID: PMC10950573 DOI: 10.1016/j.heliyon.2024.e27444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 02/28/2024] [Indexed: 03/22/2024] Open
Abstract
Studying the dielectric response of topological insulators (TIs) can unveil their unique physical mechanisms such as charge transport and spin-orbit coupling effects. However, due to the manifestation of material's topological nature and band structure primarily in nanofilm, such thickness poses challenges for dielectric testing. To date, research on TI dielectric aspects remains relatively unexplored. Therefore, this paper successfully synthesizes nanofilm of quaternary topological insulator Bi1·2Sb0·8Te0·4Se2.6 (BSTS) using laser molecular beam epitaxy (LMBE) technique. Utilizing a wide-frequency dielectric spectrometer and a comprehensive physical properties measurement system (PPMS), we measured and thoroughly analyzed the dielectric polarization and charge transport characteristics of BSTS. We observed various polarization responses in the frequency range of 101-103 Hz, with the dipole orientation gradually failing to keep pace with the frequency increase in the range of 103-105 Hz, and the relaxation polarization unable to establish itself in the range of 105-107 Hz, with polarization primarily contributed by displacement polarization. Subsequently, we further analyzed the dependence of BSTS dielectric polarization response on temperature and film thickness, which will help reveal the influence of external factors on TI dielectric response, providing crucial insights for controlling TI materials' dielectric response. This not only deepens our understanding of the fundamental physical properties of this novel material but also offers important scientific basis and technological support for its applications in quantum computing, photonics, spintronics, and other fields.
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Affiliation(s)
- Tao Xu
- Department of Electric Engineering, Harbin University of Science and Technology, 52 Xuefu Rd, Nangang, Harbin, Heilongjiang, 150080, China
| | - Yueqian Zheng
- Department of Electric Engineering, Harbin University of Science and Technology, 52 Xuefu Rd, Nangang, Harbin, Heilongjiang, 150080, China
| | - Xuan Wang
- Department of Electric Engineering, Harbin University of Science and Technology, 52 Xuefu Rd, Nangang, Harbin, Heilongjiang, 150080, China
| | - Zhi Sun
- Department of Electric Engineering, Harbin University of Science and Technology, 52 Xuefu Rd, Nangang, Harbin, Heilongjiang, 150080, China
| | - Bai Han
- Department of Electric Engineering, Harbin University of Science and Technology, 52 Xuefu Rd, Nangang, Harbin, Heilongjiang, 150080, China
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2
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Hong S, Kim D, Kim J, Park J, Rho S, Huh J, Lee Y, Jeong K, Cho M. Enhanced Photocharacteristics by Fermi Level Modulating in Sb 2 Te 3 /Bi 2 Se 3 Topological Insulator p-n Junction. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2307509. [PMID: 38161227 PMCID: PMC10953576 DOI: 10.1002/advs.202307509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 12/13/2023] [Indexed: 01/03/2024]
Abstract
Topological insulators have recently received attention in optoelectronic devices because of their high mobility and broadband absorption resulting from their topological surface states. In particular, theoretical and experimental studies have emerged that can improve the spin generation efficiency in a topological insulator-based p-n junction structure called a TPNJ, drawing attention in optospintronics. Recently, research on implementing the TPNJ structure is conducted; however, studies on the device characteristics of the TPNJ structure are still insufficient. In this study, the TPNJ structure is effectively implemented without intermixing by controlling the annealing temperature, and the photocharacteristics appearing in the TPNJ structure are investigated using a cross-pattern that can compare the characteristics in a single device. Enhanced photo characteristics are observed for the TPNJ structure. An optical pump Terahertz probe and a physical property measurement system are used to confirm the cause of improved photoresponsivity. Consequently, the photocharacteristics are improved owing to the change in the absorption mechanism and surface transport channel caused by the Fermi level shift in the TPNJ structure.
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Affiliation(s)
- Seok‐Bo Hong
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
| | - Dajung Kim
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
| | - Jonghoon Kim
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
| | - Jaehan Park
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
| | - Seungwon Rho
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
| | - Jaeseok Huh
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
| | - Youngmin Lee
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
| | - Kwangsik Jeong
- Division of Physics and Semiconductor ScienceDongguk UniversitySeoul04620Republic of Korea
| | - Mann‐Ho Cho
- Department of PhysicsYonsei University50 Yonsei‐roSeoul03722Republic of Korea
- Department of System Semiconductor EngineeringYonsei University50 Yonsei‐roSeoul03722Republic of Korea
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3
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Zheng Y, Xu T, Wang X, Sun Z, Han B. Study on Bulk-Surface Transport Separation and Dielectric Polarization of Topological Insulator Bi 1.2Sb 0.8Te 0.4Se 2.6. Molecules 2024; 29:859. [PMID: 38398611 PMCID: PMC10893539 DOI: 10.3390/molecules29040859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 02/02/2024] [Accepted: 02/08/2024] [Indexed: 02/25/2024] Open
Abstract
This study successfully fabricated the quaternary topological insulator thin films of Bi1.2Sb0.8Te0.4Se2.6 (BSTS) with a thickness of 25 nm, improving the intrinsic defects in binary topological materials through doping methods and achieving the separation of transport characteristics between the bulk and surface of topological insulator materials by utilizing a comprehensive Physical Properties Measurement System (PPMS) and Terahertz Time-Domain Spectroscopy (THz-TDS) to extract electronic transport information for both bulk and surface states. Additionally, the dielectric polarization behavior of BSTS in the low-frequency (10-107 Hz) and high-frequency (0.5-2.0 THz) ranges was investigated. These research findings provide crucial experimental groundwork and theoretical guidance for the development of novel low-energy electronic devices, spintronic devices, and quantum computing technology based on topological insulators.
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Affiliation(s)
| | | | - Xuan Wang
- Department of Electric Engineering, Harbin University of Science and Technology, 52 Xuefu Rd., Nangang, Harbin 150080, China; (Y.Z.); (T.X.); (Z.S.); (B.H.)
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4
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Jin KH, Jiang W, Sethi G, Liu F. Topological quantum devices: a review. NANOSCALE 2023; 15:12787-12817. [PMID: 37490310 DOI: 10.1039/d3nr01288c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
The introduction of the concept of topology into condensed matter physics has greatly deepened our fundamental understanding of transport properties of electrons as well as all other forms of quasi particles in solid materials. It has also fostered a paradigm shift from conventional electronic/optoelectronic devices to novel quantum devices based on topology-enabled quantum device functionalities that transfer energy and information with unprecedented precision, robustness, and efficiency. In this article, the recent research progress in topological quantum devices is reviewed. We first outline the topological spintronic devices underlined by the spin-momentum locking property of topology. We then highlight the topological electronic devices based on quantized electron and dissipationless spin conductivity protected by topology. Finally, we discuss quantum optoelectronic devices with topology-redefined photoexcitation and emission. The field of topological quantum devices is only in its infancy, we envision many significant advances in the near future.
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Affiliation(s)
- Kyung-Hwan Jin
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Republic of Korea
| | - Wei Jiang
- School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Gurjyot Sethi
- Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA.
| | - Feng Liu
- Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, USA.
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5
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Rijal K, Amos S, Valencia-Acuna P, Rudayni F, Fuller N, Zhao H, Peelaers H, Chan WL. Nanoscale Periodic Trapping Sites for Interlayer Excitons Built by Deformable Molecular Crystal on 2D Crystal. ACS NANO 2023; 17:7775-7786. [PMID: 37042658 DOI: 10.1021/acsnano.3c00541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The nanoscale moiré pattern formed at 2D transition-metal dichalcogenide crystal (TMDC) heterostructures provides periodic trapping sites for excitons, which is essential for realizing various exotic phases such as artificial exciton lattices, Bose-Einstein condensates, and exciton insulators. At organic molecule/TMDC heterostructures, similar periodic potentials can be formed via other degrees of freedom. Here, we utilize the structure deformability of a 2D molecular crystal as a degree of freedom to create a periodic nanoscale potential that can trap interlayer excitons (IXs). Specifically, two semiconducting molecules, PTCDI and PTCDA, which possess similar band gaps and ionization potentials but form different lattice structures on MoS2, are investigated. The PTCDI lattice on MoS2 is distorted geometrically, which lifts the degeneracy of the two molecules within the crystal's unit cell. The degeneracy lifting results in a spatial variation of the molecular orbital energy, with an amplitude and periodicity of ∼0.2 eV and ∼2 nm, respectively. On the other hand, no such energy variation is observed in PTCDA/MoS2, where the PTCDA lattice is much less distorted. The periodic variation in molecular orbital energies provides effective trapping sites for IXs. For IXs formed at PTCDI/MoS2, rapid spatial localization of the electron in the organic layer toward the interface is observed, which demonstrates the effectiveness of these interfacial IX traps.
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Affiliation(s)
- Kushal Rijal
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Stephanie Amos
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Pavel Valencia-Acuna
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
- Department of Physics, Jazan University, Jazan 45142, Saudi Arabia
| | - Neno Fuller
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Hui Zhao
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Hartwin Peelaers
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
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6
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Zhang SB, Li CA, Peña-Benitez F, Surówka P, Moessner R, Molenkamp LW, Trauzettel B. Super-Resonant Transport of Topological Surface States Subjected to In-Plane Magnetic Fields. PHYSICAL REVIEW LETTERS 2021; 127:076601. [PMID: 34459623 DOI: 10.1103/physrevlett.127.076601] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/19/2021] [Accepted: 07/13/2021] [Indexed: 06/13/2023]
Abstract
Magnetic oscillations of Dirac surface states of topological insulators are typically expected to be associated with the formation of Landau levels or the Aharonov-Bohm effect. We instead study the conductance of Dirac surface states subjected to an in-plane magnetic field in the presence of a barrier potential. Strikingly, we find that, in the case of large barrier potentials, the surface states exhibit pronounced oscillations in the conductance when varying the magnetic field, in the absence of Landau levels or the Aharonov-Bohm effect. These novel magnetic oscillations are attributed to the emergence of super-resonant transport by tuning the magnetic field, in which many propagating modes cross the barrier with perfect transmission. In the case of small and moderate barrier potentials, we identify a positive magnetoconductance due to the increase of the Fermi surface by tilting the surface Dirac cone. Moreover, we show that for weak magnetic fields, the conductance displays a shifted sinusoidal dependence on the field direction with period π and phase shift determined by the tilting direction with respect to the field direction. Our predictions can be applied to various topological insulators, such as HgTe and Bi_{2}Se_{3}, and provide important insights into exploring and understanding exotic magnetotransport properties of topological surface states.
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Affiliation(s)
- Song-Bo Zhang
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
| | - Chang-An Li
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
| | - Francisco Peña-Benitez
- Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Germany
| | - Piotr Surówka
- Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Germany
- Department of Theoretical Physics, Wrocław University of Science and Technology, 50-370 Wrocław, Poland
| | - Roderich Moessner
- Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Germany
| | - Laurens W Molenkamp
- Würzburg-Dresden Cluster of Excellence ct.qmat, Germany
- Physikalisches Institut (EP3), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Institute for Topological Insulators, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - Björn Trauzettel
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
- Würzburg-Dresden Cluster of Excellence ct.qmat, Germany
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7
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Sakamoto K, Ishikawa H, Wake T, Ishimoto C, Fujii J, Bentmann H, Ohtaka M, Kuroda K, Inoue N, Hattori T, Miyamachi T, Komori F, Yamamoto I, Fan C, Krüger P, Ota H, Matsui F, Reinert F, Avila J, Asensio MC. Spatial Control of Charge Doping in n-Type Topological Insulators. NANO LETTERS 2021; 21:4415-4422. [PMID: 33978424 DOI: 10.1021/acs.nanolett.1c01100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Spatially controlling the Fermi level of topological insulators and keeping their electronic states stable are indispensable processes to put this material into practical use for semiconductor spintronics devices. So far, however, such a method has not been established yet. Here we show a novel method for doping a hole into n-type topological insulators Bi2X3 (X= Se, Te) that overcomes the shortcomings of the previous reported methods. The key of this doping is to adsorb H2O on Bi2X3 decorated with a small amount of carbon, and its trigger is the irradiation of a photon with sufficient energy to excite the core electrons of the outermost layer atoms. This method allows controlling the doping amount by the irradiation time and acts as photolithography. Such a tunable doping makes it possible to design the electronic states at the nanometer scale and, thus, paves a promising avenue toward the realization of novel spintronics devices based on topological insulators.
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Affiliation(s)
- Kazuyuki Sakamoto
- Department of Applied Physics, Osaka University, Osaka 565-0871, Japan
- Center for Spintronics Research Network, Graduate School of Engineering Science, Osaka University, Osaka 560-8531, Japan
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
- Department of Materials Science and Molecular Chirality Research Center, Chiba University, Chiba 263-8522, Japan
| | - Hirotaka Ishikawa
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Takashi Wake
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Chie Ishimoto
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Jun Fujii
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Trieste I-34149, Italy
| | - Hendrik Bentmann
- Experimentelle Physik VII and Röntgen Research Center for Complex Materials, Universität Würzburg, Am Hubland, Würzburg D-97074, Germany
| | - Minoru Ohtaka
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Kenta Kuroda
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Natsu Inoue
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Takuma Hattori
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Toshio Miyamachi
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Fumio Komori
- Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581, Japan
| | - Isamu Yamamoto
- Synchrotron Light Application Center, Saga University, Saga 840-8502, Japan
| | - Cheng Fan
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
| | - Peter Krüger
- Department of Nanomaterials Science, Chiba University, Chiba 263-8522, Japan
- Department of Materials Science and Molecular Chirality Research Center, Chiba University, Chiba 263-8522, Japan
| | - Hiroshi Ota
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - Fumihiko Matsui
- UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
| | - Friedrich Reinert
- Experimentelle Physik VII and Röntgen Research Center for Complex Materials, Universität Würzburg, Am Hubland, Würzburg D-97074, Germany
| | - José Avila
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint Aubin-BP 48, Gif sur Yvette Cedex 91192, France
| | - Maria C Asensio
- Materials Science Institute of Madrid (ICMM), Spanish Scientific Research Council (CSIC), and the CSIC Associated Unit "MATINÉE", between the Institute of Materials Science of the Valencia University (ICMUV) and the ICMM, Cantoblanco, Madrid E-28049, Spain
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8
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Leng P, Chen F, Cao X, Wang Y, Huang C, Sun X, Yang Y, Zhou J, Xie X, Li Z, Zhang E, Ai L, Yang Y, Xiu F. Gate-Tunable Surface States in Topological Insulator β-Ag 2Te with High Mobility. NANO LETTERS 2020; 20:7004-7010. [PMID: 32897723 DOI: 10.1021/acs.nanolett.0c01676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Stimulated by novel properties in topological insulators, experimentally realizing quantum phases of matter and employing control over their properties have become a central goal in condensed matter physics. β-silver telluride (Ag2Te) is predicted to be a new type narrow-gap topological insulator. While enormous efforts have been plunged into the topological nature in silver chalcogenides, sophisticated research on low-dimensional nanostructures remains unexplored. Here, we report the record-high bulk carrier mobility of 298 600 cm2/(V s) in high-quality Ag2Te nanoplates and the coexistence of the surface and bulk state from systematic Shubnikov-de Haas oscillations measurements. By tuning the correlation between the top and bottom surfaces, we can effectively enhance the contribution of the surface to the total conductance up to 87% at 130 V. These results are instrumental to the high-mobility physics study and even suitable to explore exotic topological phenomena in this material system.
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Affiliation(s)
- Pengliang Leng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Fangting Chen
- Department of Nuclear Science and Technology, Fudan University, Shanghai 200433, China
| | - Xiangyu Cao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Yuxiang Wang
- School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Ce Huang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Xuandong Sun
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Yaozhi Yang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Junchen Zhou
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Xiaoyi Xie
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Zihan Li
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Enze Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Linfeng Ai
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Yunkun Yang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
| | - Faxian Xiu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
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9
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Kafle TR, Kattel B, Yao P, Zereshki P, Zhao H, Chan WL. Effect of the Interfacial Energy Landscape on Photoinduced Charge Generation at the ZnPc/MoS 2 Interface. J Am Chem Soc 2019; 141:11328-11336. [PMID: 31259543 DOI: 10.1021/jacs.9b05893] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Monolayer transition-metal dichalcogenide crystals (TMDC) can be combined with other functional materials, such as organic molecules, to form a wide range of heterostructures with tailorable properties. Although a number of works have shown that ultrafast charge transfer (CT) can occur at organic/TMDC interfaces, conditions that would facilitate the separation of interfacial CT excitons into free carriers remain unclear. Here, time-resolved and steady-state photoemission spectroscopy are used to study the potential energy landscape, charge transfer, and exciton dynamics at the zinc phthalocyanine (ZnPc)/monolayer (ML) MoS2 and ZnPc/bulk MoS2 interfaces. Surprisingly, although both interfaces have a type-II band alignment and exhibit sub-100 fs CT, the CT excitons formed at the two interfaces show drastically different evolution dynamics. The ZnPc/ML-MoS2 behaves like typical donor-acceptor interfaces in which CT excitons dissociate into electron-hole pairs. On the contrary, back electron transfer occur at ZnPc/bulk-MoS2, which results in the formation of triplet excitons in ZnPc. The difference can be explained by the different amount of band bending found in the ZnPc film deposited on ML-MoS2 and bulk-MoS2. Our work illustrates that the potential energy landscape near the interface plays an important role in the charge separation behavior. Therefore, considering the energy level alignment at the interface alone is not enough for predicting whether free charges can be generated effectively from an interface.
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Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Bhupal Kattel
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Peng Yao
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States.,Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology , Beijing Jiaotong University , Beijing 100044 , China
| | - Peymon Zereshki
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Hui Zhao
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy , University of Kansas , Lawrence , Kansas 66045 , United States
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10
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Zaitsev NL, Tonner R, Nechaev IA. Spin-orbit split two-dimensional states of BiTeI/Au(1 1 1) interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:204001. [PMID: 30776790 DOI: 10.1088/1361-648x/ab07fa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present an ab initio study of interfaces formed by placing a single trilayer of BiTeI on the Au(1 1 1) surface. We consider two possible interfaces with the parallel and antiparallel orientation of the trilayer dipole moment with respect to the surface normal, i.e. Te-Bi-I/Au(1 1 1) and I-Bi-Te/Au(1 1 1). We show that the resulting interface state that originates from the modified spin-orbit split surface state of the clean Au(1 1 1) surface resides at high energy above the Fermi level and acquires a large spin-splitting and reversal helicity as compared with the original surface state. The former lowest conduction state of the trilayer, which is one of the hitherto known giant Rashba spin-split states of few-atomic-layer structures, becomes partly occupied. In the I-Bi-Te/Au(1 1 1) interface, this state represents a Rashba system with strong spin-orbit interaction, where the outer branch of the spin-split state is mostly populated.
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Affiliation(s)
- N L Zaitsev
- Laboratory of Theoretical Physics, Institute of Molecule and Crystal Physics Ufa Research Center of Russian Academy of Sciences, 450075, Ufa, Russia
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11
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Banerjee A, Sundaresh A, Biswas S, Ganesan R, Sen D, Anil Kumar PS. Topological insulator n-p-n junctions in a magnetic field. NANOSCALE 2019; 11:5317-5324. [PMID: 30843549 DOI: 10.1039/c8nr10306b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Electrical transport in three dimensional topological insulators (TIs) occurs through spin-momentum locked topological surface states that enclose an insulating bulk. In the presence of a magnetic field, surface states get quantized into Landau levels giving rise to chiral edge states that are naturally spin-polarized due to spin momentum locking. It has been proposed that p-n junctions of TIs exposed to external magnetic fields can manifest unique spin dependent effects, apart from forming basic building blocks for highly functional spintronic devices. Here, for the first time we study electrostatically defined n-p-n junctions of dual-gated devices of the three dimensional topological insulator BiSbTe1.25Se1.75 in the presence of a strong magnetic field, revealing striking signatures of suppressed or enhanced electrical transport depending upon the chirality of quantum Hall edge states created at the n-p and p-n junction interfaces. Theoretical modeling combining the electrostatics of the dual gated TI n-p-n junction with the Landauer Buttiker formalism for transport through a network of chiral edge states explains our experimental data. Our work not only opens up a route towards exotic spintronic devices but also provides a test bed for investigating the unique signatures of quantum Hall effects in topological insulators.
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Affiliation(s)
- Abhishek Banerjee
- Department of Physics, Indian Institute of Science, Bengaluru 560012, India.
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Ravi SK, Sun W, Nandakumar DK, Zhang Y, Tan SC. Optical manipulation of work function contrasts on metal thin films. SCIENCE ADVANCES 2018; 4:eaao6050. [PMID: 29511737 PMCID: PMC5837426 DOI: 10.1126/sciadv.aao6050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 01/29/2018] [Indexed: 05/27/2023]
Abstract
Work function is a crucial metric in every optoelectronic device to ensure a specific charge transport scheme. However, the number of stable conductive materials available in a given work function range is scant, necessitating work function modulation. As opposed to all the previous chemical methods of work function modulation, we introduce here an alternative approach involving optical modulation. The work function is the minimum energy needed to eject an electron from a solid into vacuum and is known to be light-intensity-independent. A "light intensity dependent" change in work function was observed in metallic thin films coated on a semiconductor. This new phenomenon, contrasting the existing notions on work function, was tested and affirmed with three different systems, namely, Au/n-Si, Pt/n-Si, and W/n-Si. A work function shift of 0.22 eV is achieved in the Pt/n-Si system merely by tuning the illumination intensity from 0 to 18 mW/cm2. Continuous tuning of work functions to a specified range is now possible just by tuning the light intensity with a few discrete metals in hand. Moreover, selective illumination creates a work function contrast on the metal film, enabling in-plane charge transport. This throws new light on the design and understanding of the optoelectronic devices. In light of this, we also present a simple photodetector design that is sensitive to illumination direction.
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Affiliation(s)
- Sai Kishore Ravi
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117574, Singapore
| | - Wanxin Sun
- Bruker Nano Surface Division, 11 Biopolis Way #10-10, The Helios, Singapore 138667, Singapore
| | - Dilip Krishna Nandakumar
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117574, Singapore
| | - Yaoxin Zhang
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117574, Singapore
| | - Swee Ching Tan
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117574, Singapore
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Kim SH, Jin KH, Kho BW, Park BG, Liu F, Kim JS, Yeom HW. Atomically Abrupt Topological p-n Junction. ACS NANO 2017; 11:9671-9677. [PMID: 28825806 DOI: 10.1021/acsnano.7b03880] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Topological insulators (TI's) are a new class of quantum matter with extraordinary surface electronic states, which bear great potential for spintronics and error-tolerant quantum computing. In order to put a TI into any practical use, these materials need to be fabricated into devices whose basic units are often p-n junctions. Interesting electronic properties of a 'topological' p-n junction were proposed theoretically such as the junction electronic state and the spin rectification. However, the fabrication of a lateral topological p-n junction has been challenging because of materials, process, and fundamental reasons. Here, we demonstrate an innovative approach to realize a p-n junction of topological surface states (TSS's) of a three-dimensional (3D) topological insulator (TI) with an atomically abrupt interface. When a ultrathin Sb film is grown on a 3D TI of Bi2Se3 with a typical n-type TSS, the surface develops a strongly p-type TSS through the substantial hybridization between the 2D Sb film and the Bi2Se3 surface. Thus, the Bi2Se3 surface covered partially with Sb films bifurcates into areas of n- and p-type TSS's as separated by atomic step edges with a lateral electronic junction of as short as 2 nm. This approach opens a different avenue toward various electronic and spintronic devices based on well-defined topological p-n junctions with the scalability down to atomic dimensions.
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Affiliation(s)
- Sung Hwan Kim
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS) , Pohang 37673, Republic of Korea
| | - Kyung-Hwan Jin
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
| | | | | | - Feng Liu
- Department of Materials Science and Engineering, University of Utah , Salt Lake City, Utah 84112, United States
- Collaborative Innovation Center of Quantum Matter , Beijing 100084, China
| | | | - Han Woong Yeom
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS) , Pohang 37673, Republic of Korea
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Trivedi T, Roy A, Movva HCP, Walker ES, Bank SR, Neikirk DP, Banerjee SK. Versatile Large-Area Custom-Feature van der Waals Epitaxy of Topological Insulators. ACS NANO 2017; 11:7457-7467. [PMID: 28692797 DOI: 10.1021/acsnano.7b03894] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
As the focus of applied research in topological insulators (TI) evolves, the need to synthesize large-area TI films for practical device applications takes center stage. However, constructing scalable and adaptable processes for high-quality TI compounds remains a challenge. To this end, a versatile van der Waals epitaxy (vdWE) process for custom-feature bismuth telluro-sulfide TI growth and fabrication is presented, achieved through selective-area fluorination and modification of surface free-energy on mica. The TI features grow epitaxially in large single-crystal trigonal domains, exhibiting armchair or zigzag crystalline edges highly oriented with the underlying mica lattice and only two preferred domain orientations mirrored at 180°. As-grown feature thickness dependence on lateral dimensions and denuded zones at boundaries are observed, as explained by a semiempirical two-species surface migration model with robust estimates of growth parameters and elucidating the role of selective-area surface modification. Topological surface states contribute up to 60% of device conductance at room temperature, indicating excellent electronic quality. High-yield microfabrication and the adaptable vdWE growth mechanism with readily alterable precursor and substrate combinations lend the process versatility to realize crystalline TI synthesis in arbitrary shapes and arrays suitable for facile integration with processes ranging from rapid prototyping to scalable manufacturing.
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Affiliation(s)
- Tanuj Trivedi
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
| | - Anupam Roy
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
| | - Hema C P Movva
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
| | - Emily S Walker
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
| | - Seth R Bank
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
| | - Dean P Neikirk
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
| | - Sanjay K Banerjee
- Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin , Austin, Texas 78758, United States
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Tu NH, Tanabe Y, Satake Y, Huynh KK, Le PH, Matsushita SY, Tanigaki K. Large-Area and Transferred High-Quality Three-Dimensional Topological Insulator Bi 2-xSb xTe 3-ySe y Ultrathin Film by Catalyst-Free Physical Vapor Deposition. NANO LETTERS 2017; 17:2354-2360. [PMID: 28337910 DOI: 10.1021/acs.nanolett.6b05260] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Uniform and large-area synthesis of bulk insulating ultrathin films is an important subject toward applications of a surface of three-dimensional topological insulators (3D-TIs) in various electronic devices. Here we report epitaxial growth of bulk insulating three-dimensional topological insulator (3D-TI) Bi2-xSbxTe3-ySey (BSTS) ultrathin films, ranging from a few quintuple to several hundreds of layers, on mica in a large-area (1 cm2) via catalyst-free physical vapor deposition. These films can nondestructively be exfoliated using deionized water and transferred to various kinds of substrates as desired. The transferred BSTS thin films show good ambipolar characteristics as well as well-defined quantum oscillations arising from the topological surface states. The carrier mobility of 2500-5100 cm2/(V s) is comparable to the high-quality bulk BSTS single crystal. Moreover, tunable electronic states from the massless to the massive Dirac fermion were observed with a decrease in the film thickness. Both the feasible large-area synthesis and the reliable film transfer process can promise that BSTS ultrathin films will pave a route to many applications of 3D-TIs.
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Affiliation(s)
- Ngoc Han Tu
- Department of Physics, Graduate School of Science, Tohoku University , Sendai, 980-8578, Japan
| | - Yoichi Tanabe
- Department of Physics, Graduate School of Science, Tohoku University , Sendai, 980-8578, Japan
| | - Yosuke Satake
- Department of Physics, Graduate School of Science, Tohoku University , Sendai, 980-8578, Japan
| | - Khuong Kim Huynh
- WPI Advanced Institute for Materials Research, Tohoku University , Sendai 980-8577, Japan
| | - Phuoc Huu Le
- Department of Physics, Graduate School of Science, Tohoku University , Sendai, 980-8578, Japan
| | - Stephane Yu Matsushita
- Department of Physics, Graduate School of Science, Tohoku University , Sendai, 980-8578, Japan
| | - Katsumi Tanigaki
- Department of Physics, Graduate School of Science, Tohoku University , Sendai, 980-8578, Japan
- WPI Advanced Institute for Materials Research, Tohoku University , Sendai 980-8577, Japan
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