1
|
Iqbal T, Irfan M, Ramay SM, Alhamidi A, Shaikh H, Saleem M, Siddiqi SA. Mg and Ni incorporated ZnO diluted magnetic semiconductor for magnetic and photo-catalytic applications. CHINESE J CHEM PHYS 2020. [DOI: 10.1063/1674-0068/cjcp1908157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Tahir Iqbal
- Department of Physics, Mirpur University of Science and Technology, Mirpur 10250 AJK, Pakistan
| | - M. Irfan
- Department of Physics, Mirpur University of Science and Technology, Mirpur 10250 AJK, Pakistan
| | - Shahid M. Ramay
- Physics and Astronomy Department, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Abdullah Alhamidi
- SABIC Polymer Research Center, Chemical Engineering Department, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia
| | - Hamid Shaikh
- SABIC Polymer Research Center, Chemical Engineering Department, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia
| | - Murtaza Saleem
- School of Science and Engineering, Lahore University of Management Sciences, Lahore 54792, Pakistan
| | - Saadat A. Siddiqi
- IRCBM, COMSATS University Islamabad, Lahore Campus, Lahore-54600, Pakistan
| |
Collapse
|
2
|
Lin CY, Chen CF, Chang YM, Yang SH, Lee KC, Wu WW, Jian WB, Lin YF. A Triode Device with a Gate Controllable Schottky Barrier: Germanium Nanowire Transistors and Their Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1900865. [PMID: 31264786 DOI: 10.1002/smll.201900865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 06/12/2019] [Indexed: 06/09/2023]
Abstract
Electrical contacts often dominate charge transport properties at the nanoscale because of considerable differences in nanoelectronic device interfaces arising from unique geometric and electrostatic features. Transistors with a tunable Schottky barrier between the metal and semiconductor interface might simplify circuit design. Here, germanium nanowire (Ge NW) transistors with Cu3 Ge as source/drain contacts formed by both buffered oxide etching treatments and rapid thermal annealing are reported. The transistors based on this Cu3 Ge/Ge/Cu3 Ge heterostructure show ambipolar transistor behavior with a large on/off current ratio of more than 105 and 103 for the hole and electron regimes at room temperature, respectively. Investigations of temperature-dependent transport properties and low-frequency current fluctuations reveal that the tunable effective Schottky barriers of the Ge NW transistors accounted for the ambipolar behaviors. It is further shown that this ambipolarity can be used to realize binary-signal and data-storage functions, which greatly simplify circuit design compared with conventional technologies.
Collapse
Affiliation(s)
- Che-Yi Lin
- Department of Electrophysics, National Chiao Tung University, Hsinchu, 300, Taiwan
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Chao-Fu Chen
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Yuan-Ming Chang
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Shih-Hsien Yang
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
- Department of Electrical Engineering and Institute of Electronic Engineering, National Tsing Hua University, Hsinchu, 300, Taiwan
| | - Ko-Chun Lee
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
- Department of Electrical Engineering and Institute of Electronic Engineering, National Tsing Hua University, Hsinchu, 300, Taiwan
| | - Wen-Wei Wu
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 300, Taiwan
- Center for the Intelligent Semiconductor Nano-system Technology Research, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Wen-Bin Jian
- Department of Electrophysics, National Chiao Tung University, Hsinchu, 300, Taiwan
| | - Yen-Fu Lin
- Department of Physics, National Chung Hsing University, Taichung, 40227, Taiwan
- Institute of Nanoscience, National Chung Hsing University, Taichung, 40227, Taiwan
| |
Collapse
|
3
|
Facile Microemulsion Synthesis of Vanadium-Doped ZnO Nanoparticles to Analyze the Compositional, Optical, and Electronic Properties. MATERIALS 2019; 12:ma12050821. [PMID: 30862056 PMCID: PMC6427287 DOI: 10.3390/ma12050821] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/05/2019] [Accepted: 03/06/2019] [Indexed: 11/17/2022]
Abstract
In this work, microemulsion method has been followed to synthesize vanadium-doped Zn1-xVxO (with x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.10) nanoparticles. The prepared samples are characterized by several techniques to investigate the structural, morphology, electronic, functional bonding, and optical properties. X-ray diffractometer (XRD) analysis confirms the wurtzite phase of the undoped and V-doped ZnO nanoparticles. Variation in the lattice parameters ensures the incorporation of vanadium in the lattice of ZnO. Scanning electron microscopy (SEM) shows that by increasing contents of V ions, the average particle size increases gradually. X-ray Absorption Near Edge Spectroscopy (XANES) at the V L3,2 edge, oxygen K-edge, and Zn L3,2 edge reveals the presence and effect of vanadium contents in the Zn host lattice. Furthermore, the existence of chemical bonding and functional groups are also asserted by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). UV⁻Visible analysis shows that by increasing V⁺ contents, a reduction up to 2.92 eV in the energy band gap is observed, which is probably due to an increase in the free electron concentration and change in the lattice parameters.
Collapse
|
4
|
Kountouriotis K, Barreda JL, Keiper TD, Zhang M, Xiong P. Electrical Spin Injection and Detection in Silicon Nanowires with Axial Doping Gradient. NANO LETTERS 2018; 18:4386-4395. [PMID: 29898367 DOI: 10.1021/acs.nanolett.8b01423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The interest in spin transport in nanoscopic semiconductor channels is driven by both the inevitable miniaturization of spintronics devices toward nanoscale and the rich spin-dependent physics the quantum confinement engenders. For such studies, the all-important issue of the ferromagnet/semiconductor (FM/SC) interface becomes even more critical at nanoscale. Here we elucidate the effects of the FM/SC interface on electrical spin injection and detection at nanoscale dimensions, utilizing a unique type of Si nanowires (NWs) with an inherent axial doping gradient. Two-terminal and nonlocal four-terminal lateral spin-valve measurements were performed using different combinations from a series of FM contacts positioned along the same NW. The data are analyzed with a general model of spin accumulation in a normal channel under electrical spin injection from a FM, which reveals a distinct correlation of decreasing spin-valve signal with increasing injector junction resistance. The observation is attributed to the diminishing contribution of the d-electrons in the FM to the injected current spin polarization with increasing Schottky barrier width. The results demonstrate that there is a window of interface parameters for optimal spin injection efficiency and current spin polarization, which provides important design guidelines for nanospintronic devices with quasi-one-dimensional semiconductor channels.
Collapse
Affiliation(s)
| | - Jorge L Barreda
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
| | - Timothy D Keiper
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
| | - Mei Zhang
- Department of Industrial and Manufacturing Engineering, College of Engineering , Florida A&M University-Florida State University (FAMU-FSU) , Tallahassee , Florida 32310 , United States
| | - Peng Xiong
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
| |
Collapse
|
5
|
Chen JY, Chin LC, Li GA, Tuan HY. Zinc diphosphide nanowires: bismuth nanocrystal-seeded growth and their use as high-capacity lithium ion battery anodes. CrystEngComm 2017. [DOI: 10.1039/c6ce02206e] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
6
|
Enhancing electric-field control of ferromagnetism through nanoscale engineering of high-T c Mn xGe 1-x nanomesh. Nat Commun 2016; 7:12866. [PMID: 27762320 PMCID: PMC5080415 DOI: 10.1038/ncomms12866] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 08/10/2016] [Indexed: 11/28/2022] Open
Abstract
Voltage control of magnetism in ferromagnetic semiconductor has emerged as an appealing solution to significantly reduce the power dissipation and variability beyond current CMOS technology. However, it has been proven to be very challenging to achieve a candidate with high Curie temperature (Tc), controllable ferromagnetism and easy integration with current Si technology. Here we report the effective electric-field control of both ferromagnetism and magnetoresistance in unique MnxGe1−x nanomeshes fabricated by nanosphere lithography, in which a Tc above 400 K is demonstrated as a result of size/quantum confinement. Furthermore, by adjusting Mn doping concentration, extremely giant magnetoresistance is realized from ∼8,000% at 30 K to 75% at 300 K at 4 T, which arises from a geometrically enhanced magnetoresistance effect of the unique mesh structure. Our results may provide a paradigm for fundamentally understanding the high Tc in ferromagnetic semiconductor nanostructure and realizing electric-field control of magnetoresistance for future spintronic applications. Voltage control of magnetism in ferromagnetic semiconductor is appealing for spintronic applications, which is yet hindered by compound formation and low Curie temperature. Here, Nie et al. report electric-field control of ferromagnetism in MnxGe1−x nanomeshes with a Curie temperature above 400 K and controllable giant magnetoresistance.
Collapse
|
7
|
Wang L, Liu T, Wang S, Zhong Z, Jia Q, Jiang Z. Fabrication and ferromagnetism of Si-SiGe/MnGe core-shell nanopillars. NANOTECHNOLOGY 2016; 27:405705. [PMID: 27581545 DOI: 10.1088/0957-4484/27/40/405705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Si-Si0.5Ge0.5/Mn0.08Ge0.92 core-shell nanopillar samples were fabricated on ordered Si nanopillar patterned substrates by molecular beam epitaxy at low temperatures. The magnetic properties of the samples are found to depend heavily on the growth temperature of the MnGe layer. The sample grown at a moderate temperature of 300 °C has the highest Curie temperature of 240 K as well as the strongest ferromagnetic signals. On the basis of the microstructural results, the ferromagnetic properties of the samples are believed to come from the intrinsic Mn-doped amorphous or crystalline Ge ferromagnetic phase rather than any intermetallic ferromagnetic compounds of Mn and Ge. After being annealed at a temperature of 500 °C, all the samples exhibit the same Curie temperature of 220 K, which is in sharp contrast to the different Curie temperature for the as-grown samples, and the ferromagnetism for the annealed samples comes from Mn5GeSi2 compounds which are formed during the annealing.
Collapse
Affiliation(s)
- Liming Wang
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, People's Republic of China. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | | | | | | | | | | |
Collapse
|
8
|
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.
Collapse
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
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Tang J, Yu G, Wang CY, Chang LT, Jiang W, He C, Wang KL. Versatile Fabrication of Self-Aligned Nanoscale Hall Devices Using Nanowire Masks. NANO LETTERS 2016; 16:3109-3115. [PMID: 27046777 DOI: 10.1021/acs.nanolett.6b00398] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this work, we present an ingenious method to fabricate self-aligned nanoscale Hall devices using chemically synthesized nanowires as both etching and deposition masks. This versatile method can be extensively used to make nanoribbons out of arbitrary thin films without the need for extremely high alignment accuracy to define the metal contacts. The fabricated nanoribbon width scales with the mask nanowire width (diameter), and it can be easily reduced down to tens of nanometers. The self-aligned metal contacts from the sidewall extend to the top surface of the nanoribbon, and the overlap can be controlled by tuning the deposition recipe. To demonstrate the feasibility, we have fabricated Ta/CoFeB/MgO nanoribbons sputtered on a SiO2/Si substrate with different metal contacts, using synthesized SnO2 nanowires as masks. Anomalous Hall effect measurements have been carried out on the fabricated nanoscale Hall device in order to study the current-induced magnetization switching in the nanoscale heavy metal/ferromagnet heterostructure, which has shown distinct switching behaviors from micron-scale devices. The developed method provides a useful fabrication platform to probe the charge and spin transport in the nanoscale regime.
Collapse
Affiliation(s)
- Jianshi Tang
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| | - Guoqiang Yu
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| | - Chiu-Yen Wang
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology , Taipei City, Taiwan 10607, Republic of China
| | - Li-Te Chang
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| | - Wanjun Jiang
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| | - Congli He
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| | - Kang L Wang
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| |
Collapse
|
10
|
Hubmann J, Bauer B, Körner HS, Furthmeier S, Buchner M, Bayreuther G, Dirnberger F, Schuh D, Back CH, Zweck J, Reiger E, Bougeard D. Epitaxial Growth of Room-Temperature Ferromagnetic MnAs Segments on GaAs Nanowires via Sequential Crystallization. NANO LETTERS 2016; 16:900-905. [PMID: 26756067 DOI: 10.1021/acs.nanolett.5b03658] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We investigate the incorporation of manganese into self-catalyzed GaAs nanowires grown in molecular beam epitaxy. Our study reveals that Mn accumulates in the liquid Ga droplet and that no significant incorporation into the nanowire is observed. Using a sequential crystallization of the droplet, we then demonstrate a deterministic and epitaxial growth of MnAs segments at the nanowire tip. This technique may allow the seamless integration of multiple room-temperature ferromagnetic segments into GaAs nanowires with high-crystalline quality.
Collapse
Affiliation(s)
- Joachim Hubmann
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Benedikt Bauer
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Helmut S Körner
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Stephan Furthmeier
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Martin Buchner
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Günther Bayreuther
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Florian Dirnberger
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Dieter Schuh
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Christian H Back
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Josef Zweck
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Elisabeth Reiger
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| | - Dominique Bougeard
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg , D-93040 Regensburg, Germany
| |
Collapse
|
11
|
Michez LA, Spiesser A, Petit M, Bertaina S, Jacquot JF, Dufeu D, Coudreau C, Jamet M, Le Thanh V. Magnetic reversal in Mn5Ge3 thin films: an extensive study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:266001. [PMID: 26075337 DOI: 10.1088/0953-8984/27/26/266001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a comprehensive study of magnetization reversal process in thin films of Mn5Ge3. For this investigation, we have studied the magnetic anisotropy of Mn5Ge3 layers as a function of the film thickness using VSM and SQUID magnetometers. The samples grown by molecular beam epitaxy exhibit a reorientational transition of the easy axis of magnetization from in-plane to out-of-plane as the film thickness increases. We provide evidence that above a critical thickness estimated as 20 nm, the magnetic structure is most probably constituted of stripes with out-of-plane magnetization pointing alternately up and down. We have analyzed our results using different phenomenological models and all the calculations converge towards values for magnetocrystalline anisotropy constant and saturation magnetization that are in excellent agreement with the reported values for bulk Mn5Ge3. This study has also led to the first estimation in Mn5Ge3 of the exchange constant, the surface energy of domain walls as well as their width. These parameters are essential for determining whether this material can be used in the next generation of spintronic devices.
Collapse
Affiliation(s)
- L-A Michez
- Aix Marseille Université, CNRS, CINaM-UMR 7325, 13288, Marseille, France
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
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.
Collapse
Affiliation(s)
- Jianshi Tang
- Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA.
| | | |
Collapse
|
13
|
Nie T, Kou X, Tang J, Fan Y, Lang M, Chang LT, Chu CP, He L, Lee SW, Xiu F, Zou J, Wang KL. Superlattice of Fe(x)Ge(1-x) nanodots and nanolayers for spintronics application. NANOTECHNOLOGY 2014; 25:505702. [PMID: 25420510 DOI: 10.1088/0957-4484/25/50/505702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Fe(x)Ge(1-x) superlattices with two types of nanostructures, i.e. nanodots and nanolayers, were successfully fabricated using low-temperature molecular beam epitaxy. Transmission electron microscopy (TEM) characterization clearly shows that both the Fe(x)Ge(1-x) nanodots and nanolayers exhibit a lattice-coherent structure with the surrounding Ge matrix without any metallic precipitations or secondary phases. The magnetic measurement reveals the nature of superparamagnetism in Fe(x)Ge(1-x) nanodots, while showing the absence of superparamagnetism in Fe(x)Ge(1-x) nanolayers. Magnetotransport measurements show distinct magnetoresistance (MR) behavior, i.e. a negative to positive MR transition in Fe(x)Ge(1-x) nanodots and only positive MR in nanolayers, which could be due to a competition between the orbital MR and spin-dependent scatterings. Our results open a new growth strategy for engineering Fe(x)Ge(1-x) nanostructures to facilitate the development of Ge-based spintronics and magnetoelectronics devices.
Collapse
Affiliation(s)
- Tianxiao Nie
- Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, California, USA, 90095
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Xue N, Xie H, Wang Z, Liang JQ. Realization of extreme tunnel magnetoresistance with a molecule-magnet-dimer junction. RSC Adv 2014. [DOI: 10.1039/c4ra12154f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
15
|
Tang J, Chang LT, Kou X, Murata K, Choi ES, Lang M, Fan Y, Jiang Y, Montazeri M, Jiang W, Wang Y, He L, Wang KL. Electrical detection of spin-polarized surface states conduction in (Bi(0.53)Sb(0.47))2Te3 topological insulator. NANO LETTERS 2014; 14:5423-5429. [PMID: 25158276 DOI: 10.1021/nl5026198] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Strong spin-orbit interaction and time-reversal symmetry in topological insulators enable the spin-momentum locking for the helical surface states. To date, however, there has been little report of direct electrical spin injection/detection in topological insulator. In this Letter, we report the electrical detection of spin-polarized surface states conduction using a Co/Al2O3 ferromagnetic tunneling contact in which the compound topological insulator (Bi0.53Sb0.47)2Te3 was used to achieve low bulk carrier density. Resistance (voltage) hysteresis with the amplitude up to about 10 Ω was observed when sweeping the magnetic field to change the relative orientation between the Co electrode magnetization and the spin polarization of surface states. The two resistance states were reversible by changing the electric current direction, affirming the spin-momentum locking in the topological surface states. Angle-dependent measurement was also performed to further confirm that the abrupt change in the voltage (resistance) was associated with the magnetization switching of the Co electrode. The spin voltage amplitude was quantitatively analyzed to yield an effective spin polarization of 1.02% for the surface states conduction in (Bi0.53Sb0.47)2Te3. Our results show a direct evidence of spin polarization in the topological surface states conduction. It might open up great opportunities to explore energy-efficient spintronic devices based on topological insulators.
Collapse
Affiliation(s)
- Jianshi Tang
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Chang LT, Wang CY, Tang J, Nie T, Jiang W, Chu CP, Arafin S, He L, Afsal M, Chen LJ, Wang KL. Electric-field control of ferromagnetism in Mn-doped ZnO nanowires. NANO LETTERS 2014; 14:1823-1829. [PMID: 24564741 DOI: 10.1021/nl404464q] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this Letter, the electric-field control of ferromagnetism was demonstrated in a back-gated Mn-doped ZnO (Mn-ZnO) nanowire (NW) field-effect transistor (FET). The ZnO NWs were synthesized by a thermal evaporation method, and the Mn doping of 1 atom % was subsequently carried out in a MBE system using a gas-phase surface diffusion process. Detailed structural analysis confirmed the single crystallinity of Mn-ZnO NWs and excluded the presence of any precipitates or secondary phases. For the transistor, the field-effect mobility and n-type carrier concentration were estimated to be 0.65 cm(2)/V·s and 6.82 × 10(18) cm(-3), respectively. The magnetic hysteresis curves measured under different temperatures (T = 10-350 K) clearly demonstrate the presence of ferromagnetism above room temperature. It suggests that the effect of quantum confinements in NWs improves Tc, and meanwhile minimizes crystalline defects. The magnetoresistace (MR) of a single Mn-ZnO NW was observed up to 50 K. Most importantly, the gate modulation of the MR ratio was up to 2.5 % at 1.9 K, which implies the electric-field control of ferromagnetism in a single Mn-ZnO NW.
Collapse
Affiliation(s)
- Li-Te Chang
- Device Research Laboratory, Department of Electrical Engineering, University of California , Los Angeles, California 90095, United States
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|