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Luo Z, Yu Z, Lu X, Niu W, Yu Y, Yao Y, Tian F, Tan CL, Sun H, Gao L, Qin W, Xu Y, Zhao Q, Song XX. Van der Waals Magnetic Electrode Transfer for Two-Dimensional Spintronic Devices. NANO LETTERS 2024; 24:6183-6191. [PMID: 38728596 DOI: 10.1021/acs.nanolett.4c01885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
Two-dimensional (2D) materials are promising candidates for spintronic applications. Maintaining their atomically smooth interfaces during integration of ferromagnetic (FM) electrodes is crucial since conventional metal deposition tends to induce defects at the interfaces. Meanwhile, the difficulties in picking up FM metals with strong adhesion and in achieving conductance match between FM electrodes and spin transport channels make it challenging to fabricate high-quality 2D spintronic devices using metal transfer techniques. Here, we report a solvent-free magnetic electrode transfer technique that employs a graphene layer to assist in the transfer of FM metals. It also serves as part of the FM electrode after transfer for optimizing spin injection, which enables the realization of spin valves with excellent performance based on various 2D materials. In addition to two-terminal devices, we demonstrate that the technique is applicable for four-terminal spin valves with nonlocal geometry. Our results provide a promising future of realizing 2D spintronic applications using the developed magnetic electrode transfer technique.
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Affiliation(s)
- Zhongzhong Luo
- College of Electronic and Optical Engineering & College of Flexible Electronics (Future Technology), State Key Laboratory of Organic Electronics and Information Displays, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
- Guangdong Greater Bay Area Institute of Integrated Circuit and System, Guangzhou 510535, China
| | - Zhihao Yu
- Guangdong Greater Bay Area Institute of Integrated Circuit and System, Guangzhou 510535, China
- College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Xiangqian Lu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Wei Niu
- School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Yao Yu
- College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Yu Yao
- Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Fuguo Tian
- Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Chee Leong Tan
- College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Huabin Sun
- Guangdong Greater Bay Area Institute of Integrated Circuit and System, Guangzhou 510535, China
- College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Li Gao
- School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
- Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Wei Qin
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Yong Xu
- Guangdong Greater Bay Area Institute of Integrated Circuit and System, Guangzhou 510535, China
- College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Qiang Zhao
- College of Electronic and Optical Engineering & College of Flexible Electronics (Future Technology), State Key Laboratory of Organic Electronics and Information Displays, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
- Institute of Advanced Materials, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
| | - Xiang-Xiang Song
- CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China
- Suzhou Institute for Advanced Research, University of Science and Technology of China Suzhou 215123, China
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Fan Z, Liu Y, Wei X, Zhu W, Huang H, Shao Q, Liao F, Shao M, Li W, Mu G, Liu Y, Kang Z. Emergent Intrinsic Ferromagnetism in Two-Dimensional Trigonal Rhodium Oxide. NANO LETTERS 2023; 23:9515-9521. [PMID: 37830516 DOI: 10.1021/acs.nanolett.3c03087] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
Two-dimensional (2D) van der Waals single crystals with long-range magnetic order are the precondition and urgent task for developing a 2D spintronics device. In contrast to graphene and transition metal dichalcogenides, the study of 2D single-crystal metal oxides with intrinsic ferromagnetic properties remains a huge challenge. Here, we report a large-size trigonal single-crystal rhodium oxide (SC-Tri-RhO2), with crystal parameters of a = b = 3.074 Å, c = 6.116 Å, and a space group of P3̅m1 (164), exhibiting strong ferromagnetism (FM) at a rather high temperature. Furthermore, theoretical calculations suggest that the ferromagnetism in SC-Tri-RhO2 originates from spin splitting near the Fermi level, and the total magnetic moment is contributed mainly by the Rh atom.
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Affiliation(s)
- Zhenglong Fan
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, China
| | - Yixin Liu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
| | - Xinyuan Wei
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Wenxiang Zhu
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, China
| | - Hui Huang
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, China
| | - Qi Shao
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, China
| | - Fan Liao
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, China
| | - Mingwang Shao
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, China
| | - Wei Li
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Gang Mu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
| | - Yang Liu
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, China
| | - Zhenhui Kang
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, Jiangsu, China
- Macao Institute of Materials Science and Engineering (MIMSE), MUST-SUDA Joint Research Center for Advanced Functional Materials, Macau University of Science and Technology, Taipa 999078, Macao, China
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Manzo S, Strohbeen PJ, Lim ZH, Saraswat V, Du D, Xu S, Pokharel N, Mawst LJ, Arnold MS, Kawasaki JK. Pinhole-seeded lateral epitaxy and exfoliation of GaSb films on graphene-terminated surfaces. Nat Commun 2022; 13:4014. [PMID: 35851271 PMCID: PMC9293962 DOI: 10.1038/s41467-022-31610-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Accepted: 06/17/2022] [Indexed: 11/25/2022] Open
Abstract
Remote epitaxy is a promising approach for synthesizing exfoliatable crystalline membranes and enabling epitaxy of materials with large lattice mismatch. However, the atomic scale mechanisms for remote epitaxy remain unclear. Here we experimentally demonstrate that GaSb films grow on graphene-terminated GaSb (001) via a seeded lateral epitaxy mechanism, in which pinhole defects in the graphene serve as selective nucleation sites, followed by lateral epitaxy and coalescence into a continuous film. Remote interactions are not necessary in order to explain the growth. Importantly, the small size of the pinholes permits exfoliation of continuous, free-standing GaSb membranes. Due to the chemical similarity between GaSb and other III-V materials, we anticipate this mechanism to apply more generally to other materials. By combining molecular beam epitaxy with in-situ electron diffraction and photoemission, plus ex-situ atomic force microscopy and Raman spectroscopy, we track the graphene defect generation and GaSb growth evolution a few monolayers at a time. Our results show that the controlled introduction of nanoscale openings in graphene provides an alternative route towards tuning the growth and properties of 3D epitaxial films and membranes on 2D material masks. Remote epitaxy represents a promising method for the synthesis of thin films on lattice-mismatched substrates, but its atomic-scale mechanisms are still unclear. Here, the authors demonstrate the growth of exfoliatable GaSb films on graphene-terminated GaSb (001) via seeded lateral epitaxy, showing that pinhole defects in graphene serve as selective nucleation sites.
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Affiliation(s)
- Sebastian Manzo
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Patrick J Strohbeen
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Zheng Hui Lim
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Vivek Saraswat
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Dongxue Du
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Shining Xu
- Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Nikhil Pokharel
- Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Luke J Mawst
- Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Michael S Arnold
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jason K Kawasaki
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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4
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Park JH, Yang SJ, Choi CW, Choi SY, Kim CJ. Pristine Graphene Insertion at the Metal/Semiconductor Interface to Minimize Metal-Induced Gap States. ACS APPLIED MATERIALS & INTERFACES 2021; 13:22828-22835. [PMID: 33950688 DOI: 10.1021/acsami.1c03299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Metal (M) contact with a semiconductor (S) introduces metal-induced gap states (MIGS), which makes it difficult to study the intrinsic electrical properties of S. A bilayer of metal with graphene (Gr), i.e., a M/Gr bilayer, may form a contact with S to minimize MIGS. However, it has been challenging to realize the pristine M/Gr/S junctions without interfacial contaminants, which result in additional interfacial states. Here, we successfully demonstrate the atomically clean M/Gr/n-type silicon (Si) junctions via all-dry transfer of M/Gr bilayers onto Si. The fabricated M/Gr/Si junctions significantly increase the current density J at reverse bias, compared to those of M/Si junctions without a Gr interlayer (e.g., by 105 times for M = Au in Si(111)). The increase of the reverse J by a Gr interlayer is more prominent in Si(111) than in Si(100), whereas in M/Si junctions, J is independent of the type of Si surface. The different transport data between M/Gr/Si(111) and M/Gr/Si(100) are consistent with Fermi-level pinning by different surface states of Si(111) and Si(100). Our findings suggest the effective way to suppress MIGS by an introduction of the clean Gr interlayer, which paves the way to study intrinsic electrical properties of various materials.
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Affiliation(s)
- Jun-Ho Park
- Department of Chemical Engineering Pohang University of Science and Technology 77 Cheongam-Ro, Nam-Gu, Pohang 37673, Republic of Korea
| | - Seong-Jun Yang
- Department of Chemical Engineering Pohang University of Science and Technology 77 Cheongam-Ro, Nam-Gu, Pohang 37673, Republic of Korea
| | - Chang-Won Choi
- Department of Material Science & Engineering Pohang University of Science and Technology 77 Cheongam-Ro, Nam-Gu, Pohang 37673, Republic of Korea
| | - Si-Young Choi
- Department of Material Science & Engineering Pohang University of Science and Technology 77 Cheongam-Ro, Nam-Gu, Pohang 37673, Republic of Korea
| | - Cheol-Joo Kim
- Department of Chemical Engineering Pohang University of Science and Technology 77 Cheongam-Ro, Nam-Gu, Pohang 37673, Republic of Korea
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5
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Zhang Z, Yin F, Wang C, Li Z, Liu H. Magnetic field-controlled spin-dependent thermoelectric current in a single-molecule magnet transistor. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:235302. [PMID: 33784643 DOI: 10.1088/1361-648x/abf385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 03/30/2021] [Indexed: 06/12/2023]
Abstract
Control of the charge, spin, and heat currents in thermoelectric devices is an interesting research field that is currently experiencing a burst of activity. In this work, a new type of spin-current generator is proposed that consists of a single-molecule magnet sandwiched between a pair of nonmagnetic electrodes. By applying an external magnetic field, this tunneling junction can generate a 100% spin-polarized current via thermoelectric effects, and the flow direction and spin polarization can be changed by adjusting the gate voltage or magnetic field. Moreover, regardless of whether the external magnetic field exists, the thermoelectric current is always highly spin polarized and can be switched by using different gate voltage windows. This molecular electrical device can be realized with current technologies and may have practical use in spin caloritronics and quantum information processing.
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Affiliation(s)
- Zhengzhong Zhang
- Faculty of Mathematics and Physics, Huaiyin Institute of Technology, Huaian 223003, People's Republic of China
| | - Fan Yin
- Faculty of Mathematics and Physics, Huaiyin Institute of Technology, Huaian 223003, People's Republic of China
| | - Chao Wang
- Faculty of Mathematics and Physics, Huaiyin Institute of Technology, Huaian 223003, People's Republic of China
| | - Zhongwen Li
- Faculty of Mathematics and Physics, Huaiyin Institute of Technology, Huaian 223003, People's Republic of China
| | - Hao Liu
- Faculty of Mathematics and Physics, Huaiyin Institute of Technology, Huaian 223003, People's Republic of China
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6
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Stephen GM, Hanbicki AT, Schumann T, Robinson JT, Goyal M, Stemmer S, Friedman AL. Room-Temperature Spin Transport in Cd 3As 2. ACS NANO 2021; 15:5459-5466. [PMID: 33705102 DOI: 10.1021/acsnano.1c00154] [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
As the need for ever greater transistor density increases, the commensurate decrease in device size approaches the atomic limit, leading to increased energy loss and leakage currents, reducing energy efficiencies. Alternative state variables, such as electronic spin rather than electronic charge, have the potential to enable more energy-efficient and higher performance devices. These spintronic devices require materials capable of efficiently harnessing the electron spin. Here we show robust spin transport in Cd3As2 films up to room temperature. We demonstrate a nonlocal spin valve switch from this material, as well as inverse spin Hall effect measurements yielding spin Hall angles as high as θSH = 1.5 and spin diffusion lengths of 10-40 μm. Long spin-coherence lengths with efficient charge-to-spin conversion rates and coherent spin transport up to room temperature, as we show here in Cd3As2, are enabling steps toward realizing actual spintronic devices.
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Affiliation(s)
- Gregory M Stephen
- Laboratory for Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740, United States
| | - Aubrey T Hanbicki
- Laboratory for Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740, United States
| | - Timo Schumann
- Materials Department, University of California, Santa Barbara, California 93106-5050, United States
| | - Jeremy T Robinson
- Electronics Science and Technology Division, Naval Research Laboratory, 4555 Overlook Avenue, S.W., Washington, D.C. 20375, United States
| | - Manik Goyal
- Materials Department, University of California, Santa Barbara, California 93106-5050, United States
| | - Susanne Stemmer
- Materials Department, University of California, Santa Barbara, California 93106-5050, United States
| | - Adam L Friedman
- Laboratory for Physical Sciences, 8050 Greenmead Drive, College Park, Maryland 20740, United States
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7
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Tsai SH, Lei S, Zhu X, Tsai SP, Yin G, Che X, Deng P, Ng J, Zhang X, Lin WH, Jin Z, Qasem H, Zhou Z, Vajtai R, Yeh NC, Ajayan P, Xie YH, Wang KL. Interfacial States and Fano-Feshbach Resonance in Graphene-Silicon Vertical Junction. NANO LETTERS 2019; 19:6765-6771. [PMID: 31545901 DOI: 10.1021/acs.nanolett.9b01658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Interfacial quantum states are drawing tremendous attention recently because of their importance in design of low-dimensional quantum heterostructures with desired charge, spin, or topological properties. Although most studies of the interfacial exchange interactions were mainly performed across the interface vertically, the lateral transport nowadays is still a major experimental method to probe these interactions indirectly. In this Letter, we fabricated a graphene and hydrogen passivated silicon interface to study the interfacial exchange processes. For the first time we found and confirmed a novel interfacial quantum state, which is specific to the 2D-3D interface. The vertically propagating electrons from silicon to graphene result in electron oscillation states at the 2D-3D interface. A harmonic oscillator model is used to explain this interfacial state. In addition, the interaction between this interfacial state (discrete energy spectrum) and the lateral band structure of graphene (continuous energy spectrum) results in Fano-Feshbach resonance. Our results show that the conventional description of the interfacial interaction in low-dimensional systems is valid only in considering the lateral band structure and its density-of-states and is incomplete for the ease of vertical transport. Our experimental observation and theoretical explanation provide more insightful understanding of various interfacial effects in low-dimensional materials, such as proximity effect, quantum tunneling, etc. More important, the Fano-Feshbach resonance may be used to realize all solid-state and scalable quantum interferometers.
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Affiliation(s)
- Shin-Hung Tsai
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
- Department of Materials Science and Engineering , University of California , Los Angeles, 410 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Sidong Lei
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
- Department of Physics and Astronomy , Georgia State University , 25 Park PI NE , Atlanta , Gerogia 30303 , United States
| | - Xiaodan Zhu
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
- Department of Materials Science and Engineering , University of California , Los Angeles, 410 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Shiao-Po Tsai
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Gen Yin
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Xiaoyu Che
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Peng Deng
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Jimmy Ng
- Department of Materials Science and Engineering , University of California , Los Angeles, 410 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Xiang Zhang
- Department of Materials Science and Nano Engineering , Rice University , 6100 Main Street , Houston , Texas 77005 , United States
| | - Wei-Hsiang Lin
- Department of Applied Physics and Materials Science , California Institute of Technology , 1200 East California Boulevard , Pasadena , California 91125 , United States
| | - Zehua Jin
- Department of Materials Science and Nano Engineering , Rice University , 6100 Main Street , Houston , Texas 77005 , United States
| | - Hussam Qasem
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
- National Center for Solar Energy Technology , Energy and Water Research Institute , King City for Science and Technology , Riyadh 114442 , Saudi Arabia
| | - Zhongpo Zhou
- College of Physics and Material Science , Henan Normal University , Xinxiang 453007 , China
| | - Robert Vajtai
- Department of Materials Science and Nano Engineering , Rice University , 6100 Main Street , Houston , Texas 77005 , United States
| | - Nai-Chang Yeh
- Department of Applied Physics and Materials Science , California Institute of Technology , 1200 East California Boulevard , Pasadena , California 91125 , United States
| | - Pulickel Ajayan
- Department of Materials Science and Nano Engineering , Rice University , 6100 Main Street , Houston , Texas 77005 , United States
| | - Ya-Hong Xie
- Department of Materials Science and Engineering , University of California , Los Angeles, 410 Westwood Plaza , Los Angeles , California 90095 , United States
| | - Kang L Wang
- Device Research Laboratory, Department of Electrical Engineering , University of California , Los Angeles, 420 Westwood Plaza , Los Angeles , California 90095 , United States
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Courtin J, Le Gall S, Chrétien P, Moréac A, Delhaye G, Lépine B, Tricot S, Turban P, Schieffer P, Le Breton JC. A low Schottky barrier height and transport mechanism in gold-graphene-silicon (001) heterojunctions. NANOSCALE ADVANCES 2019; 1:3372-3378. [PMID: 36133562 PMCID: PMC9418477 DOI: 10.1039/c9na00393b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 07/25/2019] [Indexed: 06/13/2023]
Abstract
The interface resistance at metal/semiconductor junctions has been a key issue for decades. The control of this resistance is dependent on the possibility to tune the Schottky barrier height. However, Fermi level pinning in these systems forbids a total control over interface resistance. The introduction of 2D crystals between semiconductor surfaces and metals may be an interesting route towards this goal. In this work, we study the influence of the introduction of a graphene monolayer between a metal and silicon on the Schottky barrier height. We used X-ray photoemission spectroscopy to rule out the presence of oxides at the interface, the absence of pinning of the Fermi level and the strong reduction of the Schottky barrier height. We then performed a multiscale transport analysis to determine the transport mechanism. The consistency in the measured barrier height at different scales confirms the good quality of our junctions and the role of graphene in the drastic reduction of the barrier height.
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Affiliation(s)
- Jules Courtin
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
| | - Sylvain Le Gall
- Group of Electrical Engineering Paris (GeePs), CNRS, CentraleSupélec, Univ. Paris-Sud, Sorbonne Université, CEDEX 11 rue Joliot-Curie 91192 Gif-sur-Yvette France
| | - Pascal Chrétien
- Group of Electrical Engineering Paris (GeePs), CNRS, CentraleSupélec, Univ. Paris-Sud, Sorbonne Université, CEDEX 11 rue Joliot-Curie 91192 Gif-sur-Yvette France
| | - Alain Moréac
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
| | - Gabriel Delhaye
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
| | - Bruno Lépine
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
| | - Sylvain Tricot
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
| | - Pascal Turban
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
| | - Philippe Schieffer
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
| | - Jean-Christophe Le Breton
- Univ. Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251 F-35000 Rennes France
- Département Matériaux et Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS, Université de Rennes 1 Campus de Beaulieu, Bât 11E 35042 Rennes cedex France
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9
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Zhang S, Gao L, Song A, Zheng X, Yao Q, Ma T, Di Z, Feng XQ, Li Q. Tuning Local Electrical Conductivity via Fine Atomic Scale Structures of Two-Dimensional Interfaces. NANO LETTERS 2018; 18:6030-6036. [PMID: 30165022 DOI: 10.1021/acs.nanolett.8b02921] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Two-dimensional (2D) materials have seen a broad range of applications in electronic and optoelectronic applications; however, full realization of this potential hitherto largely hinges on the quality and performance of the electrical contacts formed between 2D materials and their surrounding metals/semiconductors. Despite the progress in revealing the charge injecting mechanisms and enhancing electrical conductance using various interfacial treatments, how the microstructure of contact interfaces affects local electrical conductivity is still very limited. Here, using conductive atomic force microscopy (c-AFM), for the first time, we directly confirm the conjecture that the electrical conductivity of physisorbed 2D material-metal/semiconductor interfaces is determined by the local electronic charge transfer. Using lattice-resolved conductivity mapping and first-principles calculations, we demonstrate that the electronic charge transfer, thereby electrical conductivity, can be fine-tuned by the topological defects of 2D materials and the atomic stacking with respect to the substrate. Our finding provides a novel route to engineer the electrical contact properties by exploiting fine atomic interactions; in the meantime, it also suggests a convenient and nondestructive means of probing subtle interactions along 2D heterogeneous interfaces.
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Affiliation(s)
- Shuai Zhang
- AML, Center for Nano and Micro Mechanics, Department of Engineering Mechanics , Tsinghua University , Beijing 100084 , China
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Lei Gao
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
- Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE) , University of Science and Technology Beijing , Beijing 100083 , China
| | - Aisheng Song
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Xiaohu Zheng
- State Key Laboratory of Functional Materials for Informatics , Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences , Shanghai 200050 , China
| | - Quanzhou Yao
- AML, Center for Nano and Micro Mechanics, Department of Engineering Mechanics , Tsinghua University , Beijing 100084 , China
| | - Tianbao Ma
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Zengfeng Di
- State Key Laboratory of Functional Materials for Informatics , Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences , Shanghai 200050 , China
| | - Xi-Qiao Feng
- AML, Center for Nano and Micro Mechanics, Department of Engineering Mechanics , Tsinghua University , Beijing 100084 , China
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
| | - Qunyang Li
- AML, Center for Nano and Micro Mechanics, Department of Engineering Mechanics , Tsinghua University , Beijing 100084 , China
- State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China
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10
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Lee MH, Cho Y, Byun KE, Shin KW, Nam SG, Kim C, Kim H, Han SA, Kim SW, Shin HJ, Park S. Two-Dimensional Materials Inserted at the Metal/Semiconductor Interface: Attractive Candidates for Semiconductor Device Contacts. NANO LETTERS 2018; 18:4878-4884. [PMID: 30036065 DOI: 10.1021/acs.nanolett.8b01509] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Metal-semiconductor junctions are indispensable in semiconductor devices, but they have recently become a major limiting factor precluding device performance improvement. Here, we report the modification of a metal/n-type Si Schottky contact barrier by the introduction of two-dimensional (2D) materials of either graphene or hexagonal boron nitride (h-BN) at the interface. We realized the lowest specific contact resistivities (ρc) of 3.30 nΩ cm2 (lightly doped n-type Si, ∼ 1015/cm3) and 1.47 nΩ cm2 (heavily doped n-type Si, ∼ 1021/cm3) via 2D material insertion are approaching the theoretical limit of 1.3 nΩ cm2. We demonstrated the role of the 2D materials at the interface in achieving a low ρc value by the following mechanisms: (a) 2D materials effectively form dipoles at the metal-2D material (M/2D) interface, thereby reducing the metal work function and changing the pinning point, and (b) the fully metalized M/2D system shifts the pinning point toward the Si conduction band, thus decreasing the Schottky barrier. As a result, the fully metalized M/2D system using atomically thin and well-defined 2D materials shows a significantly reduced ρc. The proposed 2D material insertion technique can be used to obtain extremely low contact resistivities in metal/n-type Si systems and will help to achieve major performance improvements in semiconductor technologies.
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Affiliation(s)
- Min-Hyun Lee
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Yeonchoo Cho
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Kyung-Eun Byun
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Keun Wook Shin
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Seong-Geol Nam
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Changhyun Kim
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Haeryong Kim
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Sang-A Han
- School of Advanced Materials Science and Engineering , Sungkyunkwan University (SKKU) , 2066 Seobu-ro , Jangan-gu, Suwon , Gyeonggi-do 440-746 , Republic of Korea
| | - Sang-Woo Kim
- School of Advanced Materials Science and Engineering , Sungkyunkwan University (SKKU) , 2066 Seobu-ro , Jangan-gu, Suwon , Gyeonggi-do 440-746 , Republic of Korea
| | - Hyeon-Jin Shin
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
| | - Seongjun Park
- Samsung Advanced Institute of Technology , Suwon 443-803 , Republic of Korea
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11
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Li X, Li B, Fan X, Wei L, Li L, Tao R, Zhang X, Zhang H, Zhang Q, Zhu H, Zhang S, Zhang Z, Zeng C. Atomically flat and thermally stable graphene on Si(111) with preserved intrinsic electronic properties. NANOSCALE 2018; 10:8377-8384. [PMID: 29701214 DOI: 10.1039/c8nr02005a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Silicon and graphene are two wonder materials, and their hybrid heterostructures are expected to be very interesting fundamentally and practically. In the present study, by adopting fast dry transfer and ultra-high vacuum annealing, atomically flat monolayer graphene is successfully prepared on the chemically active Si(111) substrate. More importantly, the graphene overlayer largely maintains its intrinsic electronic properties, as validated by the results of the energy-dependent electronic transparency, Dirac point observation and quantum coherence characteristics, and further confirmed by first-principles calculations. The intrinsic properties of graphene are retained up to 1030 K. The system of atomically flat and thermally stable graphene on a chemically active silicon surface with preserved inherent characteristics renders the graphene/silicon hybrid a promising system in the design of high-performance devices and the exploitation of interfacial topological quantum effects.
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Affiliation(s)
- Xiaoxia Li
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
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12
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Sakamoto R, Takada K, Pal T, Maeda H, Kambe T, Nishihara H. Coordination nanosheets (CONASHs): strategies, structures and functions. Chem Commun (Camb) 2018; 53:5781-5801. [PMID: 28492690 DOI: 10.1039/c7cc00810d] [Citation(s) in RCA: 129] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Nanosheets, which are two-dimensional polymeric materials, remain among the most actively researched areas of chemistry and physics this decade. Generally, nanosheets are inorganic materials created from bulk crystalline layered materials and have fascinating properties and functionalities. An emerging alternative is molecule-based nanosheets containing organic molecular components. Molecule-based nanosheets offer great diversity because their molecular, ionic, and atomic constituents can be selected and combined to produce a wide variety of nanosheets. The present article focuses on coordination nanosheets (CONASHs), a class of molecule-based nanosheets comprising organic ligand molecules and metal ions/atoms in a framework linked with coordination bonds. Following the Introduction, Section 2 describes CONASHs, including their definition, design, synthetic procedures, and characterisation techniques. Section 3 introduces various examples of CONASHs, and Section 4 explores their functionality and possible applications. Section 5 describes an outlook for the research field of CONASHs.
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Affiliation(s)
- Ryota Sakamoto
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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13
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Yatsukhnenko S, Druzhinin A, Ostrovskii I, Khoverko Y, Chernetskiy M. Nanoscale Conductive Channels in Silicon Whiskers with Nickel Impurity. NANOSCALE RESEARCH LETTERS 2017; 12:78. [PMID: 28127712 PMCID: PMC5267756 DOI: 10.1186/s11671-017-1855-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 01/16/2017] [Indexed: 06/06/2023]
Abstract
The magnetization and magnetoresistance of Si whiskers doped with <Ni, B> to boron concentrations corresponding to the metal-insulator transition (2 × 1018 cm-3 ÷ 5 × 1018 cm-3) were measured at high magnetic fields up to 14 T in a wide temperature range 4.2-300 K. Hysteresis of the magnetic moment was observed for Si p-type whiskers with nickel impurity in a wide temperature range 4.2-300 K indicating a strong interaction between the Ni impurities and the possibility of a magnetic cluster creation. The introduction of Ni impurity in Si whiskers leads to appearance and increase of the magnitude of negative magnetoresistance up to 10% as well as to the decrease of the whisker resistivity in the range of hopping conductance at low temperatures. The abovementioned effects were explained in the framework of appearance of magnetic polarons leading to modification of the conductive channels in the subsurface layers of the whiskers.
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Affiliation(s)
- Serhii Yatsukhnenko
- Lviv Polytechnic National University, 12 S. Bandera Str, 79013 Lviv, Ukraine
| | - Anatoly Druzhinin
- Lviv Polytechnic National University, 12 S. Bandera Str, 79013 Lviv, Ukraine
- International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw, Poland
| | - Igor Ostrovskii
- Lviv Polytechnic National University, 12 S. Bandera Str, 79013 Lviv, Ukraine
- International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw, Poland
| | - Yuriy Khoverko
- Lviv Polytechnic National University, 12 S. Bandera Str, 79013 Lviv, Ukraine
- International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw, Poland
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14
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Jariwala D, Marks TJ, Hersam MC. Mixed-dimensional van der Waals heterostructures. NATURE MATERIALS 2017; 16:170-181. [PMID: 27479211 DOI: 10.1038/nmat4703] [Citation(s) in RCA: 541] [Impact Index Per Article: 77.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 06/21/2016] [Indexed: 05/18/2023]
Abstract
The isolation of a growing number of two-dimensional (2D) materials has inspired worldwide efforts to integrate distinct 2D materials into van der Waals (vdW) heterostructures. Given that any passivated, dangling-bond-free surface will interact with another through vdW forces, the vdW heterostructure concept can be extended to include the integration of 2D materials with non-2D materials that adhere primarily through non-covalent interactions. We present a succinct and critical survey of emerging mixed-dimensional (2D + nD, where n is 0, 1 or 3) heterostructure devices. By comparing and contrasting with all-2D vdW heterostructures as well as with competing conventional technologies, we highlight the challenges and opportunities for mixed-dimensional vdW heterostructures.
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Affiliation(s)
- Deep Jariwala
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Tobin J Marks
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Mark C Hersam
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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15
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Cobas ED, van 't Erve OMJ, Cheng SF, Culbertson JC, Jernigan GG, Bussman K, Jonker BT. Room-Temperature Spin Filtering in Metallic Ferromagnet-Multilayer Graphene-Ferromagnet Junctions. ACS NANO 2016; 10:10357-10365. [PMID: 27806204 DOI: 10.1021/acsnano.6b06092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report room-temperature negative magnetoresistance in ferromagnet-graphene-ferromagnet (FM|Gr|FM) junctions with minority spin polarization exceeding 80%, consistent with predictions of strong minority spin filtering. We fabricated arrays of such junctions via chemical vapor deposition of multilayer graphene on lattice-matched single-crystal NiFe(111) films and standard photolithographic patterning and etching techniques. The junctions exhibit metallic transport behavior, low resistance, and the negative magnetoresistance characteristic of a minority spin filter interface throughout the temperature range 10 to 300 K. We develop a device model to incorporate the predicted spin filtering by explicitly treating a metallic minority spin channel with spin current conversion and a tunnel barrier majority spin channel and extract spin polarization of at least 80% in the graphene layer in our structures. The junctions also show antiferromagnetic coupling, consistent with several recent predictions. The methods and findings are relevant to fast-readout low-power magnetic random access memory technology, spin logic devices, and low-power magnetic field sensors.
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Affiliation(s)
- Enrique D Cobas
- Naval Research Laboratory , 4555 Overlook Avenue SW, Washington D.C. 20375, United States
| | - Olaf M J van 't Erve
- Naval Research Laboratory , 4555 Overlook Avenue SW, Washington D.C. 20375, United States
| | - Shu-Fan Cheng
- Naval Research Laboratory , 4555 Overlook Avenue SW, Washington D.C. 20375, United States
| | - James C Culbertson
- Naval Research Laboratory , 4555 Overlook Avenue SW, Washington D.C. 20375, United States
| | - Glenn G Jernigan
- Naval Research Laboratory , 4555 Overlook Avenue SW, Washington D.C. 20375, United States
| | - Konrad Bussman
- Naval Research Laboratory , 4555 Overlook Avenue SW, Washington D.C. 20375, United States
| | - Berend T Jonker
- Naval Research Laboratory , 4555 Overlook Avenue SW, Washington D.C. 20375, United States
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16
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Chang LT, Fischer IA, Tang J, Wang CY, Yu G, Fan Y, Murata K, Nie T, Oehme M, Schulze J, Wang KL. Electrical detection of spin transport in Si two-dimensional electron gas systems. NANOTECHNOLOGY 2016; 27:365701. [PMID: 27479155 DOI: 10.1088/0957-4484/27/36/365701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Spin transport in a semiconductor-based two-dimensional electron gas (2DEG) system has been attractive in spintronics for more than ten years. The inherent advantages of high-mobility channel and enhanced spin-orbital interaction promise a long spin diffusion length and efficient spin manipulation, which are essential for the application of spintronics devices. However, the difficulty of making high-quality ferromagnetic (FM) contacts to the buried 2DEG channel in the heterostructure systems limits the potential developments in functional devices. In this paper, we experimentally demonstrate electrical detection of spin transport in a high-mobility 2DEG system using FM Mn-germanosilicide (Mn(Si0.7Ge0.3)x) end contacts, which is the first report of spin injection and detection in a 2DEG confined in a Si/SiGe modulation doped quantum well structure (MODQW). The extracted spin diffusion length and lifetime are l sf = 4.5 μm and [Formula: see text] at 1.9 K respectively. Our results provide a promising approach for spin injection into 2DEG system in the Si-based MODQW, which may lead to innovative spintronic applications such as spin-based transistor, logic, and memory devices.
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Affiliation(s)
- Li-Te Chang
- Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA. Institut für Halbleitertechnik (IHT), Universität Stuttgart, Pfaffenwaldring 47, Stuttgart, 70569, Germany
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17
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Sverdlov V, Osintsev D, Selberherr S. Silicon-on-insulator for spintronic applications: spin lifetime and electric spin manipulation. PHYSICAL SCIENCES REVIEWS 2016. [DOI: 10.1515/psr-2016-0009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
With complementary metal-oxide semiconductor feature size rapidly approaching ultimate scaling limits, the electron spin attracts much attention as an alternative to the electron charge degree of freedom for low-power reprogrammable logic and nonvolatile memory applications. Silicon, the main element of microelectronics, appears to be the perfect material for spin-driven applications. Despite an impressive progress in understanding spin properties in metal-oxide-semiconductor field-effect transistors (MOSFETs), spin manipulation in a silicon channel by means of the electric field–dependent Rashba-like spin–orbit interaction requires channels much longer than 20 nm channel length of modern MOSFETs. Although a successful realization of the spin field-effect transistor seems to be unlikely without a new concept for an efficient way of spin manipulation in silicon by purely electrical means, it is demonstrated that shear strain dramatically reduces the spin relaxation, thus boosting the spin lifetime by an order of magnitude. Spin lifetime enhancement is achieved by lifting the degeneracy between the otherwise equivalent unprimedsubbands by [110] uniaxial stress. The spin lifetime in stressed ultra-thin body silicon-on-insulator structures can reach values close to those in bulk silicon. Therefore, stressed silicon-on-insulator structures have a potential for spin interconnects.
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18
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Averyanov DV, Tokmachev AM, Karateeva CG, Karateev IA, Lobanovich EF, Prutskov GV, Parfenov OE, Taldenkov AN, Vasiliev AL, Storchak VG. Europium Silicide - a Prospective Material for Contacts with Silicon. Sci Rep 2016; 6:25980. [PMID: 27211700 PMCID: PMC4876492 DOI: 10.1038/srep25980] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 04/26/2016] [Indexed: 11/25/2022] Open
Abstract
Metal-silicon junctions are crucial to the operation of semiconductor devices: aggressive scaling demands low-resistive metallic terminals to replace high-doped silicon in transistors. It suggests an efficient charge injection through a low Schottky barrier between a metal and Si. Tremendous efforts invested into engineering metal-silicon junctions reveal the major role of chemical bonding at the interface: premier contacts entail epitaxial integration of metal silicides with Si. Here we present epitaxially grown EuSi2/Si junction characterized by RHEED, XRD, transmission electron microscopy, magnetization and transport measurements. Structural perfection leads to superb conductivity and a record-low Schottky barrier with n-Si while an antiferromagnetic phase invites spin-related applications. This development opens brand-new opportunities in electronics.
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Affiliation(s)
- Dmitry V Averyanov
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Andrey M Tokmachev
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Christina G Karateeva
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Igor A Karateev
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Eduard F Lobanovich
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Grigory V Prutskov
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Oleg E Parfenov
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Alexander N Taldenkov
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Alexander L Vasiliev
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
| | - Vyacheslav G Storchak
- National Research Center "Kurchatov Institute", Kurchatov Square 1, Moscow 123182, Russia
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19
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Averyanov DV, Karateeva CG, Karateev IA, Tokmachev AM, Vasiliev AL, Zolotarev SI, Likhachev IA, Storchak VG. Atomic-Scale Engineering of Abrupt Interface for Direct Spin Contact of Ferromagnetic Semiconductor with Silicon. Sci Rep 2016; 6:22841. [PMID: 26957146 PMCID: PMC4783778 DOI: 10.1038/srep22841] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 02/24/2016] [Indexed: 11/15/2022] Open
Abstract
Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics.
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Affiliation(s)
- Dmitry V. Averyanov
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
| | - Christina G. Karateeva
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
| | - Igor A. Karateev
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
| | - Andrey M. Tokmachev
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
| | - Alexander L. Vasiliev
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
| | - Sergey I. Zolotarev
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
| | - Igor A. Likhachev
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
| | - Vyacheslav G. Storchak
- National Research Center “Kurchatov Institute”, Kurchatov Square 1, Moscow 123182, Russia
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20
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Garlow JA, Barrett LK, Wu L, Kisslinger K, Zhu Y, Pulecio JF. Large-Area Growth of Turbostratic Graphene on Ni(111) via Physical Vapor Deposition. Sci Rep 2016; 6:19804. [PMID: 26821604 PMCID: PMC4731759 DOI: 10.1038/srep19804] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 12/07/2015] [Indexed: 11/22/2022] Open
Abstract
Single-layer graphene has demonstrated remarkable electronic properties that are strongly influenced by interfacial bonding and break down for the lowest energy configuration of stacked graphene layers (AB Bernal). Multilayer graphene with relative rotations between carbon layers, known as turbostratic graphene, can effectively decouple the electronic states of adjacent layers, preserving properties similar to that of SLG. While the growth of AB Bernal graphene through chemical vapor deposition has been widely reported, we investigate the growth of turbostratic graphene on heteroepitaxial Ni(111) thin films utilizing physical vapor deposition. By varying the carbon deposition temperature between 800 –1100 °C, we report an increase in the graphene quality concomitant with a transition in the size of uniform thickness graphene, ranging from nanocrystallites to thousands of square microns. Combination Raman modes of as-grown graphene within the frequency range of 1650 cm−1 to 2300 cm−1, along with features of the Raman 2D mode, were employed as signatures of turbostratic graphene. Bilayer and multilayer graphene were directly identified from areas that exhibited Raman characteristics of turbostratic graphene using high-resolution TEM imaging. Raman maps of the pertinent modes reveal large regions of turbostratic graphene on Ni(111) thin films at a deposition temperature of 1100 °C.
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Affiliation(s)
- Joseph A Garlow
- Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, NY 11973.,Material Science and Engineering Department, Stony Brook University, Stony Brook, NY 11794
| | - Lawrence K Barrett
- Division of Materials Science and Engineering, Boston University, Boston, MA 02215
| | - Lijun Wu
- Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, NY 11973
| | - Kim Kisslinger
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973
| | - Yimei Zhu
- Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, NY 11973.,Material Science and Engineering Department, Stony Brook University, Stony Brook, NY 11794
| | - Javier F Pulecio
- Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, NY 11973
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21
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Averyanov DV, Tokmachev AM, Likhachev IA, Lobanovich EF, Parfenov OE, Pashaev EM, Sadofyev YG, Subbotin IA, Yakunin SN, Storchak VG. Structural coupling across the direct EuO/Si interface. NANOTECHNOLOGY 2016; 27:045703. [PMID: 26655284 DOI: 10.1088/0957-4484/27/4/045703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The ferromagnetic semiconductor EuO is believed to be an effective spin injector when directly integrated with silicon (Si). Injection through spin-selective ohmic contact requires superb structural quality of the interface EuO/Si. A recent breakthrough in manufacturing free-of-buffer-layer EuO/Si junctions calls for structural studies of the interface between the semiconductors. The synthesis of EuO employs an advanced protection of the Si substrate surface and a two-step growth protocol. It prevents unwanted chemical reactions at the interface. Ex situ high-resolution x-ray diffraction (XRD) and reflectivity (XRR) accompanied by in situ reflection high-energy electron diffraction reveal direct coupling at the interface. A combined analysis of XRD and XRR data provides a common structural model. The structural quality of the EuO/Si spin contact far exceeds that of previous reports and thus makes a step forward to the ultimate goals of spintronics.
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Affiliation(s)
- Dmitry V Averyanov
- National Research Center 'Kurchatov Institute', Kurchatov Sq. 1, Moscow 123182, Russia
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22
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Wang Z, Pan D, Wang L, Wang T, Zhao B, Wu Y, Yang M, Xu X, Miao J, Zhao J, Jiang Y. Room-temperature spin transport in InAs nanowire lateral spin valve. RSC Adv 2016. [DOI: 10.1039/c6ra13516a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report room temperature spin transport in an InAs nanowire device. A large spin signal of 35 kΩ and long spin diffusion length of 1.9 μm are achieved. We believe that these results open a practical way to design InAs NW based spintronic devices.
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23
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Sutton B, Datta S. Manipulating quantum information with spin torque. Sci Rep 2015; 5:17912. [PMID: 26648524 PMCID: PMC4673422 DOI: 10.1038/srep17912] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 11/09/2015] [Indexed: 11/09/2022] Open
Abstract
The use of spin torque as a substitute for magnetic fields is now well established for classical operations like the switching of a nanomagnet. What we are describing here could be viewed as an application of spin torque like effects to quantum processes involving single qubit rotations as well as two qubit entanglement. A key ingredient of this scheme is the use of a large number of itinerant electrons whose cumulative effect is to produce the desired qubit operations on static spins. Each interaction involves entanglement and collapse of wavefunctions so that the operation is only approximately unitary. However, we show that the non-unitary component of the operations can be kept below tolerable limits with proper design. As a capstone example, we present the implementation of a complete CNOT gate using the proposed spin potential based architecture, and show that the fidelity under ideal conditions can be made acceptably close to one.
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Affiliation(s)
- Brian Sutton
- School of Electrical and Computer Engineering and Purdue Quantum Center, Purdue University, West Lafayette, IN, 47907
| | - Supriyo Datta
- School of Electrical and Computer Engineering and Purdue Quantum Center, Purdue University, West Lafayette, IN, 47907
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24
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Friedman AL, van 't Erve OMJ, Robinson JT, Whitener KE, Jonker BT. Hydrogenated Graphene as a Homoepitaxial Tunnel Barrier for Spin and Charge Transport in Graphene. ACS NANO 2015; 9:6747-6755. [PMID: 26047069 DOI: 10.1021/acsnano.5b02795] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate that hydrogenated graphene performs as a homoepitaxial tunnel barrier on a graphene charge/spin channel. We examine the tunneling behavior through measuring the IV curves and zero bias resistance. We also fabricate hydrogenated graphene/graphene nonlocal spin valves and measure the spin lifetimes using the Hanle effect, with spintronic nonlocal spin valve operation demonstrated up to room temperature. We show that while hydrogenated graphene indeed allows for spin transport in graphene and has many advantages over oxide tunnel barriers, it does not perform as well as similar fluorinated graphene/graphene devices, possibly due to the presence of magnetic moments in the hydrogenated graphene that act as spin scatterers.
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Affiliation(s)
- Adam L Friedman
- †Materials Science and Technology Division, ‡Electronics Science and Technology Division, and §Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Olaf M J van 't Erve
- †Materials Science and Technology Division, ‡Electronics Science and Technology Division, and §Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Jeremy T Robinson
- †Materials Science and Technology Division, ‡Electronics Science and Technology Division, and §Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Keith E Whitener
- †Materials Science and Technology Division, ‡Electronics Science and Technology Division, and §Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Berend T Jonker
- †Materials Science and Technology Division, ‡Electronics Science and Technology Division, and §Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375, United States
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25
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Liu WQ, Wang WY, Wang JJ, Wang FQ, Lu C, Jin F, Zhang A, Zhang QM, Laan GVD, Xu YB, Li QX, Zhang R. Atomic-Scale Interfacial Magnetism in Fe/Graphene Heterojunction. Sci Rep 2015; 5:11911. [PMID: 26145155 PMCID: PMC4491707 DOI: 10.1038/srep11911] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/15/2015] [Indexed: 11/16/2022] Open
Abstract
Successful spin injection into graphene makes it a competitive contender in the race to become a key material for quantum computation, or the spin-operation-based data processing and sensing. Engineering ferromagnetic metal (FM)/graphene heterojunctions is one of the most promising avenues to realise it, however, their interface magnetism remains an open question up to this day. In any proposed FM/graphene spintronic devices, the best opportunity for spin transport could only be achieved where no magnetic dead layer exists at the FM/graphene interface. Here we present a comprehensive study of the epitaxial Fe/graphene interface by means of X-ray magnetic circular dichroism (XMCD) and density functional theory (DFT) calculations. The experiment has been performed using a specially designed FM1/FM2/graphene structure that to a large extent restores the realistic case of the proposed graphene-based transistors. We have quantitatively observed a reduced but still sizable magnetic moments of the epitaxial Fe ML on graphene, which is well resembled by simulations and can be attributed to the strong hybridization between the Fe 3dz2 and the C 2pz orbitals and the sp-orbital-like behavior of the Fe 3d electrons due to the presence of graphene.
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Affiliation(s)
- W Q Liu
- York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, School of Electronics Science and Engineering, Nanjing University, Nanjing 210093, China.,Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD, UK
| | - W Y Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.,Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - J J Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.,Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - F Q Wang
- York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, School of Electronics Science and Engineering, Nanjing University, Nanjing 210093, China
| | - C Lu
- Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD, UK
| | - F Jin
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - A Zhang
- Department of Physics, Renmin University of China, Beijing 100872, China
| | - Q M Zhang
- Department of Physics, Renmin University of China, Beijing 100872, China
| | | | - Y B Xu
- York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, School of Electronics Science and Engineering, Nanjing University, Nanjing 210093, China.,Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD, UK
| | - Q X Li
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.,Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - R Zhang
- York-Nanjing Joint Centre (YNJC) for Spintronics and Nanoengineering, School of Electronics Science and Engineering, Nanjing University, Nanjing 210093, China
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26
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van ’t Erve OMJ, Friedman AL, Li CH, Robinson JT, Connell J, Lauhon LJ, Jonker BT. Spin transport and Hanle effect in silicon nanowires using graphene tunnel barriers. Nat Commun 2015; 6:7541. [DOI: 10.1038/ncomms8541] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 05/16/2015] [Indexed: 11/09/2022] Open
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27
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Wang B, Li J, Xu F, Wei Y, Wang J, Guo H. Transient dynamics of magnetic Co-graphene systems. NANOSCALE 2015; 7:10030-10038. [PMID: 25955767 DOI: 10.1039/c5nr01525a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report the investigation of response time of spin resolved electron traversing through a magnetic Co-graphene nano-device. For this purpose, we calculate the transient current under a step-like upward pulse for this system from first principles using non-equilibrium Green's function (NEGF) formalism within the framework of density functional theory (DFT). In the absence of dephasing mechanisms, transient current shows a damped oscillatory behavior. The turn-on time of the magnetic Co-graphene nano-device was found to be around 5-20 femtoseconds, while the relaxation time can reach several picoseconds due to the damped oscillation of transient current for both majority spin and minority spin. The response time was determined by the resonant states below the Fermi level, but does not depend on the chirality of graphene and the amplitude of pulse bias. Each resonant state contributes to the damped oscillation of transient current with the same frequency and different decay rates. The frequency of the oscillation is half the pulse bias and the decay rate equals the lifetime of the corresponding resonant state. When inelastic phase-relaxing scattering is considered, the long duration oscillatory behavior of the transient current is suppressed and the relaxation time is reduced to hundreds of femtoseconds.
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Affiliation(s)
- Bin Wang
- College of Physics Science and Technology, Shenzhen University, Shenzhen, 518060, China.
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28
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Homoepitaxial tunnel barriers with functionalized graphene-on-graphene for charge and spin transport. Nat Commun 2015; 5:3161. [PMID: 24445349 DOI: 10.1038/ncomms4161] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 12/19/2013] [Indexed: 11/08/2022] Open
Abstract
The coupled imperatives for reduced heat dissipation and power consumption in high-density electronics have rekindled interest in devices based on tunnelling. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, layer uniformity, interface stability and electronic states that severely complicate fabrication and compromise performance. Two-dimensional materials such as graphene obviate these issues and offer a new paradigm for tunnel barriers. Here we demonstrate a homoepitaxial tunnel barrier structure in which graphene serves as both the tunnel barrier and the high-mobility transport channel. We fluorinate the top layer of a graphene bilayer to decouple it from the bottom layer, so that it serves as a single-monolayer tunnel barrier for both charge and spin injection into the lower graphene channel. We demonstrate high spin injection efficiency with a tunnelling spin polarization >60%, lateral transport of spin currents in non-local spin-valve structures and determine spin lifetimes with the Hanle effect.
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29
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Tang J, Wang KL. Electrical spin injection and transport in semiconductor nanowires: challenges, progress and perspectives. NANOSCALE 2015; 7:4325-4337. [PMID: 25686092 DOI: 10.1039/c4nr07611g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Spintronic devices are of fundamental interest for their nonvolatility and great potential for low-power electronics applications. The implementation of those devices usually favors materials with long spin lifetime and spin diffusion length. Recent spin transport studies on semiconductor nanowires have shown much longer spin lifetimes and spin diffusion lengths than those reported in bulk/thin films. In this paper, we have reviewed recent progress in the electrical spin injection and transport in semiconductor nanowires and drawn a comparison with that in bulk/thin films. In particular, the challenges and methods of making high-quality ferromagnetic tunneling and Schottky contacts on semiconductor nanowires as well as thin films are discussed. Besides, commonly used methods for characterizing spin transport have been introduced, and their applicability in nanowire devices are discussed. Moreover, the effect of spin-orbit interaction strength and dimensionality on the spin relaxation and hence the spin lifetime are investigated. Finally, for further device applications, we have examined several proposals of spinFETs and provided a perspective of future studies on semiconductor spintronics.
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Affiliation(s)
- Jianshi Tang
- Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA.
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30
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Wong CPY, Koek TJH, Liu Y, Loh KP, Goh KEJ, Troadec C, Nijhuis CA. Electronically transparent graphene barriers against unwanted doping of silicon. ACS APPLIED MATERIALS & INTERFACES 2014; 6:20464-72. [PMID: 25329365 DOI: 10.1021/am506055h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Diffusion barriers prevent materials from intermixing (e.g., undesired doping) in electronic devices. Most diffusion barrier materials are often very specific for a certain combination of materials and/or change the energetics of the interface because they are insulating or add to the contact resistances. This paper presents graphene (Gr) as an electronically transparent, without adding significant resistance to the interface, diffusion barrier in metal/semiconductor devices, where Gr prevents Au and Cu from diffusion into the Si, and unintentionally dope the Si. We studied the electronic properties of the n-Si(111)/Gr/M Schottky barriers (with and without Gr and M=Au or Cu) by I(V) measurements and at the nanoscale by ballistic electron emission spectroscopy (BEEM). The layer of Gr does not change the Schottky barrier of these junctions. The Gr barrier was stable at 300 °C for 1 h and prevented the diffusion of Cu into n-Si(111) and the formation of Cu3Si. Thus, we conclude that the Gr is mechanically and chemically stable enough to withstand the harsh fabrication methods typically encountered in clean room processes (e.g., deposition of metals in high vacuum conditions at high temperatures), it is electronically transparent (it does not change the energetics of the Si/Au or Si/Cu Schottky barriers), and effectively prevented diffusion of the Cu or Au into the Si at elevated temperatures and vice versa.
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Affiliation(s)
- Calvin Pei Yu Wong
- NUS Graduate School for Integrative Sciences and Engineering, Centre for Life Sciences (CeLS), 28 Medical Drive, Singapore 117597, Singapore
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31
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Txoperena O, Song Y, Qing L, Gobbi M, Hueso LE, Dery H, Casanova F. Impurity-assisted tunneling magnetoresistance under a weak magnetic field. PHYSICAL REVIEW LETTERS 2014; 113:146601. [PMID: 25325651 DOI: 10.1103/physrevlett.113.146601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Indexed: 06/04/2023]
Abstract
Injection of spins into semiconductors is essential for the integration of the spin functionality into conventional electronics. Insulating layers are often inserted between ferromagnetic metals and semiconductors for obtaining an efficient spin injection, and it is therefore crucial to distinguish between signatures of electrical spin injection and impurity-driven effects in the tunnel barrier. Here we demonstrate an impurity-assisted tunneling magnetoresistance effect in nonmagnetic-insulator-nonmagnetic and ferromagnetic-insulator-nonmagnetic tunnel barriers. In both cases, the effect reflects on-off switching of the tunneling current through impurity channels by the external magnetic field. The reported effect is universal for any impurity-assisted tunneling process and provides an alternative interpretation to a widely used technique that employs the same ferromagnetic electrode to inject and detect spin accumulation.
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Affiliation(s)
- Oihana Txoperena
- CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Yang Song
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA
| | - Lan Qing
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Marco Gobbi
- CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain and Université de Strasbourg, Institut de Science et d'Ingénierie Supramoléculaires (I.S.I.S.), 67083 Strasbourg, France
| | - Luis E Hueso
- CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain and IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain
| | - Hanan Dery
- Department of Electrical and Computer Engineering, University of Rochester, Rochester, New York 14627, USA and Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Fèlix Casanova
- CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain and IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain
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32
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Decker R, Bazarnik M, Atodiresei N, Caciuc V, Blügel S, Wiesendanger R. Local tunnel magnetoresistance of an iron intercalated graphene-based heterostructure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:394004. [PMID: 25212093 DOI: 10.1088/0953-8984/26/39/394004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The lateral variation of the tunnel magnetoresistance (TMR) of a graphene-based vertical heterostructure is studied by spin-polarized scanning tunneling microscopy (SP-STM) using an Fe-coated probe tip. The well-defined heterostructure is obtained by the intercalation of a magnetic Fe monolayer at the graphene/Ir(1 1 1) interface. Its structure is characterized by a moiré pattern with a high corrugation. In contrast to the Fe / Ir(1 1 1) surface, graphene/Fe / Ir(1 1 1) exhibits ferromagnetic order with an out-of-plane easy magnetization axis. At the nanometer scale, our experiments reveal that the moiré pattern induces a lateral variation of the TMR, which reaches 80%. The measured TMR at valleys of the moiré pattern is higher than at hills. We interpret this modulation in terms of a different hybridization between graphene and Fe at valleys and hills due to a different graphene-Fe distance at these sites, which leads to a different transmission of spin-polarized states.
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Affiliation(s)
- R Decker
- Institute of Applied Physics, University of Hamburg, Jungiusstrasse 11, D-20355 Hamburg, Germany
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33
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Zhong X, Amorim RG, Rocha AR, Pandey R. Hybridization effects on the out-of-plane electron tunneling properties of monolayers: is h-BN more conductive than graphene? NANOTECHNOLOGY 2014; 25:345703. [PMID: 25101928 DOI: 10.1088/0957-4484/25/34/345703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Electron transport properties through multilayers of hexagonal boron nitride (h-BN) sandwiched between gold electrodes is investigated by density functional theory together with the non-equilibrium Green's function method. The calculated results find that despite graphene being a gapless semimetal and h-BN two-dimensional layer being an insulator, the transmission function perpendicular to the atomic layer plane in both systems is nearly identical. The out-of-plane tunnel current is found to be strongly dependent on the interaction at the interface of the device. As a consequence, single layer h-BN coupled with atomically flat weakly interacting metals such as gold may not work as a good dielectric material, but the absence of sharp resonances would probably lead to more stable out-of-plane electronic transport properties compared to graphene.
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Affiliation(s)
- Xiaoliang Zhong
- Department of Physics, Michigan Technological University, Houghton, Michigan 49931, USA
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34
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Kamalakar MV, Dankert A, Bergsten J, Ive T, Dash SP. Enhanced tunnel spin injection into graphene using chemical vapor deposited hexagonal boron nitride. Sci Rep 2014; 4:6146. [PMID: 25156685 PMCID: PMC4143790 DOI: 10.1038/srep06146] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 07/31/2014] [Indexed: 12/22/2022] Open
Abstract
The van der Waals heterostructures of two-dimensional (2D) atomic crystals constitute a new paradigm in nanoscience. Hybrid devices of graphene with insulating 2D hexagonal boron nitride (h-BN) have emerged as promising nanoelectronic architectures through demonstrations of ultrahigh electron mobilities and charge-based tunnel transistors. Here, we expand the functional horizon of such 2D materials demonstrating the quantum tunneling of spin polarized electrons through atomic planes of CVD grown h-BN. We report excellent tunneling behavior of h-BN layers together with tunnel spin injection and transport in graphene using ferromagnet/h-BN contacts. Employing h-BN tunnel contacts, we observe enhancements in both spin signal amplitude and lifetime by an order of magnitude. We demonstrate spin transport and precession over micrometer-scale distances with spin lifetime up to 0.46 nanosecond. Our results and complementary magnetoresistance calculations illustrate that CVD h-BN tunnel barrier provides a reliable, reproducible and alternative approach to address the conductivity mismatch problem for spin injection into graphene.
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Affiliation(s)
- M Venkata Kamalakar
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - André Dankert
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - Johan Bergsten
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - Tommy Ive
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
| | - Saroj P Dash
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
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35
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Song Y, Dery H. Magnetic-field-modulated resonant tunneling in ferromagnetic-insulator-nonmagnetic junctions. PHYSICAL REVIEW LETTERS 2014; 113:047205. [PMID: 25105652 DOI: 10.1103/physrevlett.113.047205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Indexed: 06/03/2023]
Abstract
We present a theory for resonance-tunneling magnetoresistance (MR) in ferromagnetic-insulator-nonmagnetic junctions. The theory sheds light on many of the recent electrical spin injection experiments, suggesting that this MR effect rather than spin accumulation in the nonmagnetic channel corresponds to the electrically detected signal. We quantify the dependence of the tunnel current on the magnetic field by quantum rate equations derived from the Anderson impurity model, with the important addition of impurity spin interactions. Considering the on-site Coulomb correlation, the MR effect is caused by competition between the field, spin interactions, and coupling to the magnetic lead. By extending the theory, we present a basis for operation of novel nanometer-size memories.
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Affiliation(s)
- Yang Song
- Department of Electrical and Computer Engineering, University of Rochester, Rochester 14627, New York, USA
| | - Hanan Dery
- Department of Electrical and Computer Engineering, University of Rochester, Rochester 14627, New York, USA and Department of Physics and Astronomy, University of Rochester, Rochester 14627, New York, USA
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36
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Forrester DM, Kusmartsev FV, Kovács E. Designing magnetic superlattices that are composed of single domain nanomagnets. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2014; 5:956-963. [PMID: 25161831 PMCID: PMC4142982 DOI: 10.3762/bjnano.5.109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Accepted: 06/16/2014] [Indexed: 06/03/2023]
Abstract
BACKGROUND The complex nature of the magnetic interactions between any number of nanosized elements of a magnetic superlattice can be described by the generic behavior that is presented here. The hysteresis characteristics of interacting elliptical nanomagnets are described by a quasi-static method that identifies the critical boundaries between magnetic phases. A full dynamical analysis is conducted in complement to this and the deviations from the quasi-static analysis are highlighted. Each phase is defined by the configuration of the magnetic moments of the chain of single domain nanomagnets and correspondingly the existence of parallel, anti-parallel and canting average magnetization states. RESULTS We give examples of the phase diagrams in terms of anisotropy and coupling strength for two, three and four magnetic layers. Each phase diagrams character is defined by the shape of the magnetic hysteresis profile for a system in an applied magnetic field. We present the analytical solutions that enable one to define the "phase" boundaries between the emergence of spin-flop, anti-parallel and parallel configurations. The shape of the hysteresis profile is a function of the coupling strength between the nanomagnets and examples are given of how it dictates a systems magnetic response. Many different paths between metastable states can exist and this can lead to instabilities and fluctuations in the magnetization. CONCLUSION With these phase diagrams one can find the most stable magnetic configurations against perturbations so as to create magnetic devices. On the other hand, one may require a magnetic system that can easily be switched between phases, and so one can use the information herein to design superlattices of the required shape and character by choosing parameters close to the phase boundaries. This work will be useful when designing future spintronic devices, especially those manipulating the properties of CoFeB compounds.
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Affiliation(s)
- Derek M Forrester
- Department of Physics, School of Science, Loughborough University, Leicestershire, LE11 3TU United Kingdom
| | - Feodor V Kusmartsev
- Department of Physics, School of Science, Loughborough University, Leicestershire, LE11 3TU United Kingdom
| | - Endre Kovács
- Department of Physics, University of Miskolc, H-3515 Miskolc, Hungary
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37
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Sipahi GM, Žutić I, Atodiresei N, Kawakami RK, Lazić P. Spin polarization of Co(0001)/graphene junctions from first principles. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:104204. [PMID: 24553047 DOI: 10.1088/0953-8984/26/10/104204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Junctions comprised of ferromagnets and nonmagnetic materials are one of the key building blocks in spintronics. With the recent breakthroughs of spin injection in ferromagnet/graphene junctions it is possible to consider spin-based applications that are not limited to magnetoresistive effects. However, for critical studies of such structures it is crucial to establish accurate predictive methods that would yield atomically resolved information on interfacial properties. By focusing on Co(0001)/graphene junctions and their electronic structure, we illustrate the inequivalence of different spin polarizations. We show atomically resolved spin polarization maps as a useful approach to assess the relevance of Co(0001)/graphene for different spintronics applications.
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Affiliation(s)
- G M Sipahi
- Department of Physics, University at Buffalo, State University of New York, Buffalo, NY 14260, USA
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38
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Li CH, van 't Erve OMJ, Robinson JT, Liu Y, Li L, Jonker BT. Electrical detection of charge-current-induced spin polarization due to spin-momentum locking in Bi2Se3. NATURE NANOTECHNOLOGY 2014; 9:218-224. [PMID: 24561354 DOI: 10.1038/nnano.2014.16] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 01/17/2014] [Indexed: 06/03/2023]
Abstract
Topological insulators exhibit metallic surface states populated by massless Dirac fermions with spin-momentum locking, where the carrier spin lies in-plane, locked at right angles to the carrier momentum. Here, we show that a charge current produces a net spin polarization via spin-momentum locking in Bi2Se3 films, and this polarization is directly manifested as a voltage on a ferromagnetic contact. This voltage is proportional to the projection of the spin polarization onto the contact magnetization, is determined by the direction and magnitude of the charge current, scales inversely with Bi2Se3 film thickness, and its sign is that expected from spin-momentum locking rather than Rashba effects. Similar data are obtained for two different ferromagnetic contacts, demonstrating that these behaviours are independent of the details of the ferromagnetic contact. These results demonstrate direct electrical access to the topological insulators' surface-state spin system and enable utilization of its remarkable properties for future technological applications.
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Affiliation(s)
- C H Li
- Materials Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
| | - O M J van 't Erve
- Materials Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
| | - J T Robinson
- Electronics Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
| | - Y Liu
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211, USA
| | - L Li
- Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211, USA
| | - B T Jonker
- Materials Science and Technology Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
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39
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Garcia-Lekue A, Balashov T, Olle M, Ceballos G, Arnau A, Gambardella P, Sanchez-Portal D, Mugarza A. Spin-dependent electron scattering at graphene edges on Ni(111). PHYSICAL REVIEW LETTERS 2014; 112:066802. [PMID: 24580701 DOI: 10.1103/physrevlett.112.066802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Indexed: 06/03/2023]
Abstract
We investigate the scattering of surface electrons by the edges of graphene islands grown on Ni(111). By combining local tunneling spectroscopy and ab initio electronic structure calculations we find that the hybridization between graphene and Ni states results in strongly reflecting graphene edges. Quantum interference patterns formed around the islands reveal a spin-dependent scattering of the Shockley bands of Ni, which we attribute to their distinct coupling to bulk states. Moreover, we find a strong dependence of the scattering amplitude on the atomic structure of the edges, depending on the orbital character and energy of the surface states.
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Affiliation(s)
- A Garcia-Lekue
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain and IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain
| | - T Balashov
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
| | - M Olle
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
| | - G Ceballos
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
| | - A Arnau
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain and Centro de Física de Materiales CFM - MPC, Centro Mixto CSIC-UPV, Paseo Manuel de Lardizabal 5, E-20018, San Sebastián, Spain and Dpto. de Física de Materiales UPV/EHU, Facultad de Quimica, Paseo Manuel de Lardizabal 3, E-20018, San Sebastián, Spain
| | - P Gambardella
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain and Instituciò Catalana de Recerca i Estudis Avancats (ICREA), E-08193 Barcelona, Spain and Department of Materials, ETH Zurich, Hönggerbergring 64, CH-8093 Zurich, Switzerland
| | - D Sanchez-Portal
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain and Centro de Física de Materiales CFM - MPC, Centro Mixto CSIC-UPV, Paseo Manuel de Lardizabal 5, E-20018, San Sebastián, Spain
| | - A Mugarza
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
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Godel F, Pichonat E, Vignaud D, Majjad H, Metten D, Henry Y, Berciaud S, Dayen JF, Halley D. Epitaxy of MgO magnetic tunnel barriers on epitaxial graphene. NANOTECHNOLOGY 2013; 24:475708. [PMID: 24192567 DOI: 10.1088/0957-4484/24/47/475708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Epitaxial growth of electrodes and tunnel barriers on graphene is one of the main technological bottlenecks for graphene spintronics. In this paper, we demonstrate that MgO(111) epitaxial tunnel barriers, one of the prime candidates for spintronic application, can be grown by molecular beam epitaxy on epitaxial graphene on SiC(0001). Ferromagnetic metals (Fe, Co, Fe20Ni80) were epitaxially grown on top of the MgO barrier, thus leading to monocrystalline electrodes on graphene. Structural and magnetic characterizations were performed on these ferromagnetic metals after annealing and dewetting: they form clusters with a 100 nm typical lateral width, which are mostly magnetic monodomains in the case of Fe. This epitaxial stack opens the way to graphene spintronic devices taking benefits from a coherent tunnelling current through the epitaxial MgO/graphene stack.
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Dankert A, Dulal RS, Dash SP. Efficient spin injection into silicon and the role of the Schottky barrier. Sci Rep 2013; 3:3196. [PMID: 24217343 PMCID: PMC3824168 DOI: 10.1038/srep03196] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 10/28/2013] [Indexed: 11/09/2022] Open
Abstract
Implementing spin functionalities in Si, and understanding the fundamental processes of spin injection and detection, are the main challenges in spintronics. Here we demonstrate large spin polarizations at room temperature, 34% in n-type and 10% in p-type degenerate Si bands, using a narrow Schottky and a SiO2 tunnel barrier in a direct tunneling regime. Furthermore, by increasing the width of the Schottky barrier in non-degenerate p-type Si, we observed a systematic sign reversal of the Hanle signal in the low bias regime. This dramatic change in the spin injection and detection processes with increased Schottky barrier resistance may be due to a decoupling of the spins in the interface states from the bulk band of Si, yielding a transition from a direct to a localized state assisted tunneling. Our study provides a deeper insight into the spin transport phenomenon, which should be considered for electrical spin injection into any semiconductor.
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Affiliation(s)
- André Dankert
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296, Göteborg, Sweden
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Meng J, Chen JJ, Yan Y, Yu DP, Liao ZM. Vertical graphene spin valve with Ohmic contacts. NANOSCALE 2013; 5:8894-8898. [PMID: 23907712 DOI: 10.1039/c3nr03168c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Evident spin valve signals are observed in Co/graphene/Co sandwich structures with both monolayer and two-layer graphene stacks at temperatures from 1.5 K to 300 K. All the devices demonstrate linear current-voltage curves, indicating that an Ohmic property is dominating rather than a tunneling effect. The vertical graphene spin valves have potential applications in high-density non-volatile memories.
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Affiliation(s)
- Jie Meng
- State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871, P.R. China.
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Current-Perpendicular-to-Plane Magnetoresistance in Chemical Vapor Deposition-Grown Multilayer Graphene. ELECTRONICS 2013. [DOI: 10.3390/electronics2030315] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Rybkina AA, Rybkin AG, Adamchuk VK, Marchenko D, Varykhalov A, Sánchez-Barriga J, Shikin AM. The graphene/Au/Ni interface and its application in the construction of a graphene spin filter. NANOTECHNOLOGY 2013; 24:295201. [PMID: 23799659 DOI: 10.1088/0957-4484/24/29/295201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A modification of the contact of graphene with ferromagnetic electrodes in a model of the graphene spin filter allowing restoration of the graphene electronic structure is proposed. It is suggested for this aim to intercalate into the interface between the graphene and the ferromagnetic (Ni or Co) electrode a Au monolayer to block the strong interaction between the graphene and Ni (Co) and, thus, prevent destruction of the graphene electronic structure which evolves in direct contact of graphene with Ni (Co). It is also suggested to insert an additional buffer graphene monolayer with the size limited by that of the electrode between the main graphene sheet providing spin current transport and the Au/Ni electrode injecting the spin current. This will prevent the spin transport properties of graphene from influencing contact phenomena and eliminate pinning of the graphene electronic structure relative to the Fermi level of the metal, thus ensuring efficient outflow of injected electrons into the graphene. The role of the spin structure of the graphene/Au/Ni interface with enhanced spin-orbit splitting of graphene π states is also discussed, and its use is proposed for additional spin selection in the process of the electron excitation.
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Affiliation(s)
- A A Rybkina
- St.-Petersburg State University, Ulyanovskaya 1, Petrodvoretz, St.-Petersburg 198504, Russia
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Dery H. Spin injection: Graphene wins the match. NATURE NANOTECHNOLOGY 2012; 7:692-693. [PMID: 23042492 DOI: 10.1038/nnano.2012.180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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