1
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Chan HL, Fields SS, Chen Y, O’Neill TP, Lenox MK, Hubbard WA, Ihlefeld JF, Regan BC. Mapping Ferroelectric Fields Reveals the Origins of the Coercivity Distribution. ACS NANO 2024; 18:20380-20388. [PMID: 39017620 PMCID: PMC11308779 DOI: 10.1021/acsnano.4c04526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 06/28/2024] [Accepted: 07/01/2024] [Indexed: 07/18/2024]
Abstract
Better techniques for imaging ferroelectric polarization would aid the development of new ferroelectrics and the refinement of old ones. Here we show how scanning transmission electron microscope (STEM) electron beam-induced current (EBIC) imaging reveals ferroelectric polarization with obvious, simply interpretable contrast. Planar imaging of an entire ferroelectric hafnium zirconium oxide (Hf0.5Zr0.5O2, HZO) capacitor shows an EBIC response that is linearly related to the polarization determined in situ with the positive-up, negative-down (PUND) method. The contrast is easily calibrated in MV/cm. The underlying mechanism is magnification-independent, operating equally well on micrometer-sized devices and individual nanoscale domains. Coercive-field mapping reveals that individual domains are biased "positive" and "negative", as opposed to being "easy" and "hard" to switch. The remanent background E-fields generating this bias can be isolated and mapped. Coupled with STEM's native capabilities for structural identification, STEM EBIC imaging provides a revolutionary tool for characterizing ferroelectric materials and devices.
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Affiliation(s)
- Ho Leung Chan
- Department
of Physics and Astronomy, University of
California, Los Angeles, California 90095, United States
- California
NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Shelby S. Fields
- Department
of Materials Science and Engineering, University
of Virginia, Charlottesville, Virginia 22904, United States
| | - Yueyun Chen
- Department
of Physics and Astronomy, University of
California, Los Angeles, California 90095, United States
- California
NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Tristan P. O’Neill
- Department
of Physics and Astronomy, University of
California, Los Angeles, California 90095, United States
- California
NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Megan K. Lenox
- Department
of Materials Science and Engineering, University
of Virginia, Charlottesville, Virginia 22904, United States
| | - William A. Hubbard
- NanoElectronic
Imaging, Inc., Los Angeles, California 90095, United States
| | - Jon F. Ihlefeld
- Department
of Materials Science and Engineering, University
of Virginia, Charlottesville, Virginia 22904, United States
- Charles
L. Brown Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Brian C. Regan
- Department
of Physics and Astronomy, University of
California, Los Angeles, California 90095, United States
- California
NanoSystems Institute, University of California, Los Angeles, California 90095, United States
- NanoElectronic
Imaging, Inc., Los Angeles, California 90095, United States
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2
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Husain S, Harris I, Gao G, Li X, Meisenheimer P, Shi C, Kavle P, Choi CH, Kim TY, Kang D, Behera P, Perrodin D, Guo H, M Tour J, Han Y, Martin LW, Yao Z, Ramesh R. Low-temperature grapho-epitaxial La-substituted BiFeO 3 on metallic perovskite. Nat Commun 2024; 15:479. [PMID: 38212317 PMCID: PMC10784590 DOI: 10.1038/s41467-024-44728-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 01/03/2024] [Indexed: 01/13/2024] Open
Abstract
Bismuth ferrite has garnered considerable attention as a promising candidate for magnetoelectric spin-orbit coupled logic-in-memory. As model systems, epitaxial BiFeO3 thin films have typically been deposited at relatively high temperatures (650-800 °C), higher than allowed for direct integration with silicon-CMOS platforms. Here, we circumvent this problem by growing lanthanum-substituted BiFeO3 at 450 °C (which is reasonably compatible with silicon-CMOS integration) on epitaxial BaPb0.75Bi0.25O3 electrodes. Notwithstanding the large lattice mismatch between the La-BiFeO3, BaPb0.75Bi0.25O3, and SrTiO3 (001) substrates, all the layers in the heterostructures are well ordered with a [001] texture. Polarization mapping using atomic resolution STEM imaging and vector mapping established the short-range polarization ordering in the low temperature grown La-BiFeO3. Current-voltage, pulsed-switching, fatigue, and retention measurements follow the characteristic behavior of high-temperature grown La-BiFeO3, where SrRuO3 typically serves as the metallic electrode. These results provide a possible route for realizing epitaxial multiferroics on complex-oxide buffer layers at low temperatures and opens the door for potential silicon-CMOS integration.
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Affiliation(s)
- Sajid Husain
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Isaac Harris
- Department of Physics, University of California, Berkeley, CA, 94720, USA
| | - Guanhui Gao
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Xinyan Li
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Peter Meisenheimer
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Chuqiao Shi
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Pravin Kavle
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Chi Hun Choi
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Tae Yeon Kim
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Deokyoung Kang
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Piush Behera
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Didier Perrodin
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Hua Guo
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - James M Tour
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
- Department of Chemistry, Rice University, Houston, TX, 77005, USA
| | - Yimo Han
- Department of Materials Science and NanoEngineering, Rice University, Houston, TX, 77005, USA
| | - Lane W Martin
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
- Department of Physics and Astronomy, Rice University, Houston, TX, 77005, USA
| | - Zhi Yao
- Applied Mathematics and Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Ramamoorthy Ramesh
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
- Department of Physics, University of California, Berkeley, CA, 94720, USA.
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA.
- Department of Physics and Astronomy, Rice University, Houston, TX, 77005, USA.
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3
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Wu Q, Wang K, Simpson A, Hao Y, Wang J, Li D, Hong X. Electrode Effect on Ferroelectricity in Free-Standing Membranes of PbZr 0.2Ti 0.8O 3. ACS NANOSCIENCE AU 2023; 3:482-490. [PMID: 38144704 PMCID: PMC10740143 DOI: 10.1021/acsnanoscienceau.3c00032] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 09/30/2023] [Accepted: 10/02/2023] [Indexed: 12/26/2023]
Abstract
We report the effects of screening capacity, surface roughness, and interfacial epitaxy of the bottom electrodes on the polarization switching, domain wall (DW) roughness, and ferroelectric Curie temperature (TC) of PbZr0.2Ti0.8O3 (PZT)-based free-standing membranes. Singe crystalline 10-50 nm (001) PZT and PZT/La0.67Sr0.33MnO3 (LSMO) membranes are prepared on Au, correlated oxide LSMO, and two-dimensional (2D) semiconductor MoS2 base layers. Switching the polarization of PZT yields nonvolatile current modulation in the MoS2 channel at room temperature, with an on/off ratio of up to 2 × 105 and no apparent decay for more than 3 days. Piezoresponse force microscopy studies show that the coercive field Ec for the PZT membranes varies from 0.75 to 3.0 MV cm-1 on different base layers and exhibits strong polarization asymmetry. The PZT/LSMO membranes exhibit significantly smaller Ec, with the samples transferred on LSMO showing symmetric Ec of about -0.26/+0.28 MV cm-1, smaller than that of epitaxial PZT films. The DW roughness exponent ζ points to 2D random bond disorder dominated DW roughening (ζ = 0.31) at room temperature. Upon thermal quench at progressively higher temperatures, ζ values for PZT membranes on Au and LSMO approach the theoretical value for 1D random bond disorder (ζ = 2/3), while samples on MoS2 exhibits thermal roughening (ζ = 1/2). The PZT membranes on Au, LSMO, and MoS2 show TC of about 763 ± 12, 725 ± 25, and 588 ± 12 °C, respectively, well exceeding the bulk value. Our study reveals the complex interplay between the electrostatic and mechanical boundary conditions in determining ferroelectricity in free-standing PZT membranes, providing important material parameters for the functional design of PZT-based flexible nanoelectronics.
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Affiliation(s)
- Qiuchen Wu
- Department
of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588-0299, United
States
| | - Kun Wang
- Department
of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588-0299, United
States
| | - Alyssa Simpson
- Department
of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588-0299, United
States
| | - Yifei Hao
- Department
of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588-0299, United
States
| | - Jia Wang
- Department
of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588-0299, United
States
| | - Dawei Li
- Department
of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588-0299, United
States
| | - Xia Hong
- Department
of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588-0299, United
States
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4
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Recalde-Benitez O, Jiang T, Winkler R, Ruan Y, Zintler A, Adabifiroozjaei E, Arzumanov A, Hubbard WA, van Omme T, Pivak Y, Perez-Garza HH, Regan BC, Alff L, Komissinskiy P, Molina-Luna L. Operando two-terminal devices inside a transmission electron microscope. COMMUNICATIONS ENGINEERING 2023; 2:83. [PMCID: PMC10956025 DOI: 10.1038/s44172-023-00133-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 11/09/2023] [Indexed: 06/23/2024]
Abstract
Advanced nanomaterials are at the core of innovation for the microelectronics industry. Designing, characterizing, and testing two-terminal devices, such as metal-insulator-metal structures, is key to improving material stack design and integration. Electrical biasing within in situ transmission electron microscopy using MEMS-based platforms is a promising technique for nano-characterization under operando conditions. However, conventional focused ion beam sample preparation can introduce parasitic current paths, limiting device performance and leading to overestimated electrical responses. Here we demonstrate connectivity of TEM lamella devices obtained from a novel electrical contacting method based solely on van der Waals forces. This method reduces parasitic leakage currents by at least five orders of magnitude relative to reported preparation approaches. Our methodology enables operation of stack devices inside a microscope with device currents as low as 10 pA. We apply this approach to observe in situ biasing-induced defect formation, providing valuable insights into the behavior of an SrTiO3-based memristor. Oscar Recalde-Benitez and colleagues report a FIB-based sample preparation process to limit current leakage during operando TEM experiments, thus improving the accuracy of device nanocharacterization under operating conditions. The methodology results in leakage currents that are small compared to device currents, which enables the analysis of operating stack devices inside the microscope.
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Affiliation(s)
- Oscar Recalde-Benitez
- Advanced Electron Microscopy Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Tianshu Jiang
- Advanced Electron Microscopy Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Robert Winkler
- Advanced Electron Microscopy Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Yating Ruan
- Advanced Thin Film Technology Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Alexander Zintler
- Advanced Electron Microscopy Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Esmaeil Adabifiroozjaei
- Advanced Electron Microscopy Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Alexey Arzumanov
- Advanced Thin Film Technology Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | | | | | | | | | - B. C. Regan
- NanoElectronic Imaging, Inc., Los Angeles, CA USA
- University of California, Los Angeles and the California NanoSystem Institute, Los Angeles, CA USA
| | - Lambert Alff
- Advanced Thin Film Technology Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Philipp Komissinskiy
- Advanced Thin Film Technology Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
| | - Leopoldo Molina-Luna
- Advanced Electron Microscopy Division, Institute of Materials Science, Department of Materials-and Geosciences, Technische Universität Darmstadt, Darmstadt, Germany
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5
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Holtz ME, Padgett E, Johnston-Peck AC, Levin I, Muller DA, Herzing AA. Mapping Polar Distortions using Nanobeam Electron Diffraction and a Cepstral Approach. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:1422-1435. [PMID: 37488825 DOI: 10.1093/micmic/ozad070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 05/26/2023] [Accepted: 06/18/2023] [Indexed: 07/26/2023]
Abstract
Measuring local polar ordering is key to understanding ferroelectricity in thin films, especially for systems with small domains or significant disorder. Scanning nanobeam electron diffraction (NBED) provides an effective local probe of lattice parameters, local fields, polarization directions, and charge densities, which can be analyzed using a relatively low beam dose over large fields of view. However, quantitatively extracting the magnitudes and directions of polarization vectors from NBED remains challenging. Here, we use a cepstral approach, similar to a pair distribution function, to determine local polar displacements that drive ferroelectricity from NBED patterns. Because polar distortions generate asymmetry in the diffraction pattern intensity, we can efficiently recover the underlying displacements from the imaginary part of the cepstrum transform. We investigate the limits of this technique using analytical and simulated data and give experimental examples, achieving the order of 1.1 pm precision and mapping of polar displacements with nanometer resolution.
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Affiliation(s)
- Megan E Holtz
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
- School of Applied and Engineering Physics, Cornell University, 142 Sciences Drive, Ithaca, NY 14853, USA
- Department of Metallurgical and Materials Engineering, Colorado School of Mines, 1301 19th Street, Golden, CO 80401, USA
| | - Elliot Padgett
- School of Applied and Engineering Physics, Cornell University, 142 Sciences Drive, Ithaca, NY 14853, USA
| | - Aaron C Johnston-Peck
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
| | - Igor Levin
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, 142 Sciences Drive, Ithaca, NY 14853, USA
| | - Andrew A Herzing
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA
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6
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Electric-field control of the nucleation and motion of isolated three-fold polar vertices. Nat Commun 2022; 13:6340. [PMID: 36284138 PMCID: PMC9596422 DOI: 10.1038/s41467-022-33973-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 10/10/2022] [Indexed: 11/21/2022] Open
Abstract
Recently various topological polar structures have been discovered in oxide thin films. Despite the increasing evidence of their switchability under electrical and/or mechanical fields, the dynamic property of isolated ones, which is usually required for applications such as data storage, is still absent. Here, we show the controlled nucleation and motion of isolated three-fold vertices under an applied electric field. At the PbTiO3/SrRuO3 interface, a two-unit-cell thick SrTiO3 layer provides electrical boundary conditions for the formation of three-fold vertices. Utilizing the SrTiO3 layer and in situ electrical testing system, we find that isolated three-fold vertices can move in a controllable and reversible manner with a velocity up to ~629 nm s−1. Microstructural evolution of the nucleation and propagation of isolated three-fold vertices is further revealed by phase-field simulations. This work demonstrates the ability to electrically manipulate isolated three-fold vertices, shedding light on the dynamic property of isolated topological polar structures. Despite various known topological polar structures, the dynamic property of isolated ones is still poorly understood. Here, the authors show the controlled nucleation and ability to move of isolated three-fold vertices under an applied electric field.
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7
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Rani K, Matzen S, Gable S, Maroutian T, Agnus G, Lecoeur P. Quantitative investigation of polarization-dependent photocurrent in ferroelectric thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:104003. [PMID: 34874288 DOI: 10.1088/1361-648x/ac3f67] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 12/02/2021] [Indexed: 06/13/2023]
Abstract
Ferroelectric thin films are investigated for their potential in photovoltaic (PV) applications, owing to their high open-circuit voltage and switchable photovoltaic effect. The direction of the ferroelectric polarization can control the sign of the photocurrent through the ferroelectric layer, theoretically allowing for 100% switchability of the photocurrent with the polarization, which is particularly interesting for photo-ferroelectric memories. However, the quantitative relationship between photocurrent and polarization remains little studied. In this work, a careful investigation of the polarization-dependent photocurrent of epitaxial Pb(Zr, Ti)O3thin films has been carried out, and has provided a quantitative determination of the unswitchable part of ferroelectric polarization. These results represent a systematic approach to study and optimize the switchability of photocurrent, and more broadly to get important insights on the ferroelectric behavior in all types of ferroelectric layers in which pinned polarization is difficult to investigate.
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Affiliation(s)
- Komalika Rani
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), 10 Boulevard Thomas Gobert, 91120 Palaiseau, France
| | - Sylvia Matzen
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), 10 Boulevard Thomas Gobert, 91120 Palaiseau, France
| | - Stéphane Gable
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), 10 Boulevard Thomas Gobert, 91120 Palaiseau, France
| | - Thomas Maroutian
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), 10 Boulevard Thomas Gobert, 91120 Palaiseau, France
| | - Guillaume Agnus
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), 10 Boulevard Thomas Gobert, 91120 Palaiseau, France
| | - Philippe Lecoeur
- Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), 10 Boulevard Thomas Gobert, 91120 Palaiseau, France
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8
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Yang Y, Wu M, Zheng X, Zheng C, Xu J, Xu Z, Li X, Lou X, Wu D, Liu X, Pennycook SJ, Wen Z. Atomic-scale fatigue mechanism of ferroelectric tunnel junctions. SCIENCE ADVANCES 2021; 7:eabh2716. [PMID: 34818041 PMCID: PMC8612688 DOI: 10.1126/sciadv.abh2716] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 10/05/2021] [Indexed: 06/13/2023]
Abstract
Ferroelectric tunnel junctions (FTJs) are promising candidates for next-generation memories due to fast read/write speeds and low-power consumptions. Here, we investigate resistance fatigue of FTJs, which is performed on Pt/BaTiO3/Nb:SrTiO3 devices. By direct observations of the 5–unit cell–thick BaTiO3 barrier with high-angle annular dark-field imaging and electron energy loss spectroscopy, oxygen vacancies are found to aggregate at the Pt/BaTiO3 interface during repetitive switching, leading to a ferroelectric dead layer preventing domain nucleation and growth. Severe oxygen deficiency also makes BaTiO3 lattices energetically unfavorable and lastly induces a destruction of local perovskite structure of the barrier. Ferroelectric properties are thus degraded, which reduces barrier contrast between ON and OFF states and smears electroresistance characteristics of Pt/BaTiO3/Nb:SrTiO3 FTJs. These results reveal an atomic-scale fatigue mechanism of ultrathin ferroelectric barriers associated with the aggregation of charged defects, facilitating the design of reliable FTJs and ferroelectric nanoelectronic devices for practical applications.
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Affiliation(s)
- Yihao Yang
- College of Physics and Center for Marine Observation and Communications, Qingdao University, Qingdao 266071, China
| | - Ming Wu
- State Key Laboratory of Electrical Insulation and Power Equipment and Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Xingwen Zheng
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Ji’nan 250100, China
| | - Chunyan Zheng
- College of Physics and Center for Marine Observation and Communications, Qingdao University, Qingdao 266071, China
| | - Jibo Xu
- College of Physics and Center for Marine Observation and Communications, Qingdao University, Qingdao 266071, China
| | - Zhiyu Xu
- College of Physics and Center for Marine Observation and Communications, Qingdao University, Qingdao 266071, China
| | - Xiaofei Li
- College of Physics and Center for Marine Observation and Communications, Qingdao University, Qingdao 266071, China
| | - Xiaojie Lou
- State Key Laboratory of Electrical Insulation and Power Equipment and Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China
| | - Di Wu
- National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, Jiangsu Key Laboratory of Artificial Functional Materials and Collaborative Innovation Center for Advanced Materials, Nanjing University, Nanjing 210093, China
| | - Xiaohui Liu
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Ji’nan 250100, China
| | - Stephen J. Pennycook
- Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Zheng Wen
- College of Physics and Center for Marine Observation and Communications, Qingdao University, Qingdao 266071, China
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9
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Lindemann S, Irwin J, Kim GY, Wang B, Eom K, Wang J, Hu J, Chen LQ, Choi SY, Eom CB, Rzchowski MS. Low-voltage magnetoelectric coupling in membrane heterostructures. SCIENCE ADVANCES 2021; 7:eabh2294. [PMID: 34767439 PMCID: PMC8589311 DOI: 10.1126/sciadv.abh2294] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 09/27/2021] [Indexed: 06/13/2023]
Abstract
Strain-mediated magnetoelectric (ME) coupling in ferroelectric (FE)/ferromagnetic (FM) heterostructures offers a unique opportunity for both fundamental scientific research and low-power multifunctional devices. Relaxor-FEs, such as (1 − x)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PMN-xPT), are ideal FE layer candidates because of their giant piezoelectricity. However, thin films of PMN-PT suffer from substrate clamping, which substantially reduces piezoelectric in-plane strains. Here, we demonstrate low-voltage ME coupling in an all-thin-film heterostructure that uses the anisotropic strains induced by the (011) orientation of PMN-PT. We completely remove PMN-PT films from their substrate and couple with FM Ni overlayers to create membrane PMN-PT/Ni heterostructures showing 90° Ni magnetization rotation with 3 V PMN-PT bias, much less than the bulk PMN-PT ~100-V requirement. Scanning transmission electron microscopy and phase-field simulations clarify the membrane response. These results provide a crucial step toward understanding the microstructural behavior of PMN-PT thin films for use in piezo-driven ME heterostructures.
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Affiliation(s)
- Shane Lindemann
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Julian Irwin
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Gi-Yeop Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Korea
| | - Bo Wang
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Kitae Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Jianjun Wang
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Jiamian Hu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Long-Qing Chen
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Si-Young Choi
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Korea
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Mark S. Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
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10
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Conlan AP, Luong MA, Gentile P, Moldovan G, Den Hertog MI, Monroy E, Cooper D. Thermally propagated Al contacts on SiGe nanowires characterized by electron beam induced current in a scanning transmission electron microscope. NANOTECHNOLOGY 2021; 33:035712. [PMID: 34633307 DOI: 10.1088/1361-6528/ac2e73] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Abstract
Here, we use electron beam induced current (EBIC) in a scanning transmission electron microscope to characterize the structure and electronic properties of Al/SiGe and Al/Si-rich/SiGe axial nanowire heterostructures fabricated by thermal propagation of Al in a SiGe nanowire. The two heterostructures behave as Schottky contacts with different barrier heights. From the sign of the beam induced current collected at the contacts, the intrinsic semiconductor doping is determined to be n-type. Furthermore, we find that the silicon-rich double interface presents a lower barrier height than the atomically sharp SiGe/Al interface. With an applied bias, the Si-rich region delays the propagation of the depletion region and presents a reduced free carrier diffusion length with respect to the SiGe nanowire. This behaviour could be explained by a higher residual doping in the Si-rich area. These results demonstrate that scanning transmission electron microscopy EBIC is a powerful method for mapping and quantifying electric fields in micrometer- and nanometer-scale devices.
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Affiliation(s)
- Aidan P Conlan
- Univ. Grenoble Alpes, CEA-LETI, F-38000 Grenoble, France
| | - Minh Anh Luong
- Univ. Grenoble Alpes, CNRS-Institut Néel, 25 Avenue des Martyrs, F-38000 Grenoble, France
| | - Pascal Gentile
- Univ. Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, 17 av. des Martyrs, F-38000 Grenoble, France
| | - Grigore Moldovan
- Point Electronic GmbH, Erich-Neuss-Weg 15, D-06120 Halle (Saale), Germany
| | - Martien I Den Hertog
- Univ. Grenoble Alpes, CNRS-Institut Néel, 25 Avenue des Martyrs, F-38000 Grenoble, France
| | - Eva Monroy
- Univ. Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, 17 av. des Martyrs, F-38000 Grenoble, France
| | - David Cooper
- Univ. Grenoble Alpes, CEA-LETI, F-38000 Grenoble, France
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11
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Vogel A, Sarott MF, Campanini M, Trassin M, Rossell MD. Monitoring Electrical Biasing of Pb(Zr 0.2Ti 0.8)O 3 Ferroelectric Thin Films In Situ by DPC-STEM Imaging. MATERIALS (BASEL, SWITZERLAND) 2021; 14:4749. [PMID: 34443272 PMCID: PMC8400982 DOI: 10.3390/ma14164749] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 08/18/2021] [Accepted: 08/19/2021] [Indexed: 11/17/2022]
Abstract
Increased data storage densities are required for the next generation of nonvolatile random access memories and data storage devices based on ferroelectric materials. Yet, with intensified miniaturization, these devices face a loss of their ferroelectric properties. Therefore, a full microscopic understanding of the impact of the nanoscale defects on the ferroelectric switching dynamics is crucial. However, collecting real-time data at the atomic and nanoscale remains very challenging. In this work, we explore the ferroelectric response of a Pb(Zr0.2Ti0.8)O3 thin film ferroelectric capacitor to electrical biasing in situ in the transmission electron microscope. Using a combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and differential phase contrast (DPC)-STEM imaging we unveil the structural and polarization state of the ferroelectric thin film, integrated into a capacitor architecture, before and during biasing. Thus, we can correlate real-time changes in the DPC signal with the presence of misfit dislocations and ferroelastic domains. A reduction in the domain wall velocity of 24% is measured in defective regions of the film when compared to predominantly defect-free regions.
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Affiliation(s)
- Alexander Vogel
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Material Science and Technology, 8600 Dübendorf, Switzerland;
| | - Martin F. Sarott
- Department of Materials, Eidgenössische Technische Hochschule Zürich, 8093 Zürich, Switzerland; (M.F.S.); (M.T.)
| | - Marco Campanini
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Material Science and Technology, 8600 Dübendorf, Switzerland;
| | - Morgan Trassin
- Department of Materials, Eidgenössische Technische Hochschule Zürich, 8093 Zürich, Switzerland; (M.F.S.); (M.T.)
| | - Marta D. Rossell
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Material Science and Technology, 8600 Dübendorf, Switzerland;
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12
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Zhai Y, Feng Z, Zhou Y, Han ST. Energy-efficient transistors: suppressing the subthreshold swing below the physical limit. MATERIALS HORIZONS 2021; 8:1601-1617. [PMID: 34846494 DOI: 10.1039/d0mh02029j] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
With the miniaturization of silicon-based electronic components, power consumption is becoming a fundamental issue for micro-nano electronic circuits. The main reason for this is that the scaling of the supply voltage in the ultra-large-scale integrated circuit cannot keep up with the shrinking of the characteristic size of conventional transistors due to the physical limit termed "Boltzmann Tyranny", in which a gate voltage of at least 60 mV is required to modulate the drain current by one order of magnitude. Accordingly, to solve this problem, several new transistor architectures have been designed to reduce the subthreshold swing (SS) to lower than the fundamental limitation, thus lowering the supply voltage and reducing the power consumption. In this review, we first analytically formulate the SS, summarize the methods for reducing the SS, and propose four new transistor concepts, including tunnelling field-effect transistor, negative capacitance field-effect transistor, impact ionization field-effect transistor, and cold source field-effect transistor. Then, we review their physical mechanisms and optimization methods and consider the potential and drawbacks of these four new transistors. Finally, we discuss the challenges encountered in the investigation of these steep-slope transistors and present the future outlook.
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Affiliation(s)
- Yongbiao Zhai
- Institute of Microscale Optoelectronics, Shenzhen University, 518060, P. R. China.
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13
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Accuracy and precision of position determination in ISTEM imaging of BaTiO 3. Ultramicroscopy 2021; 227:113325. [PMID: 34045084 DOI: 10.1016/j.ultramic.2021.113325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 05/07/2021] [Accepted: 05/18/2021] [Indexed: 11/21/2022]
Abstract
In this paper we study the effect of lens aberrations (spherical aberration and astigmatism), beam tilt, contamination and shot noise on the accuracy and precision of position determination in imaging scanning transmission electron microscopy (ISTEM) on the example of BaTiO3. ISTEM images are simulated as a function of sample thickness and defocus starting from a nearly perfect microscope setting. A defocus range was identified, in which atom column positions were reliably visible and could be decently measured. By averaging over this defocus and thickness range a figure of merit was defined and used to study the influence of above mentioned disturbing effects as a function of their strength. It turned out that column positions might become inaccurate, but distances are measured accurately. These were used to obtain recommendations for the experimental setup to measure the atomic arrangement that induces ferroelectric switching of BaTiO3.
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14
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Li M, Yang S, Shi R, Li L, Zhu R, Li X, Cheng Y, Ma X, Zhang J, Liu K, Yu P, Gao P. Engineering of multiferroic BiFeO 3 grain boundaries with head-to-head polarization configurations. Sci Bull (Beijing) 2021; 66:771-776. [PMID: 36654134 DOI: 10.1016/j.scib.2020.12.032] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/30/2020] [Accepted: 12/14/2020] [Indexed: 01/20/2023]
Abstract
Confined low dimensional charges with high density such as two-dimensional electron gas (2DEG) at interfaces and charged domain walls in ferroelectrics show great potential to serve as functional elements in future nanoelectronics. However, stabilization and control of low dimensional charges is challenging, as they are usually subject to enormous depolarization fields. Here, we demonstrate a method to fabricate tunable charged interfaces with ~77°, 86° and 94° head-to-head polarization configurations in multiferroic BiFeO3 thin films by grain boundary engineering. The adjacent grains are cohesively bonded and the boundary is about 1 nm in width and devoid of any amorphous region. Remarkably, the polarization remains almost unchanged near the grain boundaries, indicating the polarization charges are well compensated, i.e., there should be two-dimensional charge gas confined at grain boundaries. Adjusting the tilt angle of the grain boundaries enables tuning the angle of polarization configurations from 71° to 109°, which in turn allows the control of charge density at the grain boundaries. This general and feasible method opens new doors for the application of charged interfaces in next generation nanoelectronics.
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Affiliation(s)
- Mingqiang Li
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China; International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Shuzhen Yang
- Peking University Shenzhen Graduate School, Peking University, Shenzhen 518055, China; TCL China Star Optoelectronics Technology Co., Ltd., Shenzhen 518132, China; State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Ruochen Shi
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China; International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Linglong Li
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Ruixue Zhu
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China; International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Xiaomei Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yang Cheng
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China; State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Xiumei Ma
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Jingmin Zhang
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Kaihui Liu
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China; State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
| | - Pu Yu
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China; State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China.
| | - Peng Gao
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China; International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China; Collaborative Innovation Centre of Quantum Matter, Beijing 100871, China.
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15
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Li H, Chen W, Zheng Y. Tailoring nanoscale polarization patterns and transport properties in ferroelectric tunnel junctions by octahedral tilts in electrodes. RSC Adv 2020; 10:35367-35373. [PMID: 35515640 PMCID: PMC9056928 DOI: 10.1039/d0ra04740f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 09/08/2020] [Indexed: 11/21/2022] Open
Abstract
Oxygen octahedral tilts are known for the ability to tailor polarization patterns in perovskites. We propose a way to manipulate nanoscale polarization patterns in ferroelectric tunnel junctions (FTJs) by oxygen octahedral tilts in electrodes combined with interface engineering. Here the electrode is epitaxial SrRuO3 on SrTiO3, and the ferroelectric barrier is a BaTiO3/CaTiO3 superlattice. The octahedral tilt mismatch between electrodes and the barrier is found to be eliminated at one of the two most stable interfaces by the imprinting of in-phase oxygen octahedral tilt from electrodes into the barrier, which further results in anti-polar order in the barrier, while uniform polar order is retained for another stable interface. Further analysis of electronic transport properties shows an increased transmission in FTJ with anti-polar order, which is mainly caused by octahedral tilt induced out-of-plane ferroelectric domain walls. Our results indicate that the oxygen octahedral tilts in electrodes can be used to manipulate polarization patterns and create charged domain walls in FTJs, which further expand the application prospects of FTJ-based devices.
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Affiliation(s)
- Hongfang Li
- School of Materials Science and Engineering, Chongqing Jiaotong University Chongqing 400074 China
| | - Weijin Chen
- School of Materials, Sun Yat-sen University Guangzhou 519082 China
| | - Yue Zheng
- State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University Guangzhou 510275 China +86 20 8411 3231
- Micro & Nano Physics and Mechanics Research Laboratory, School of Physics, Sun Yat-sen University Guangzhou 510275 China
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16
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Campanini M, Erni R, Rossell MD. Probing local order in multiferroics by transmission electron microscopy. PHYSICAL SCIENCES REVIEWS 2020. [DOI: 10.1515/psr-2019-0068] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The ongoing trend toward miniaturization has led to an increased interest in the magnetoelectric effect, which could yield entirely new device concepts, such as electric field-controlled magnetic data storage. As a result, much work is being devoted to developing new robust room temperature (RT) multiferroic materials that combine ferromagnetism and ferroelectricity. However, the development of new multiferroic devices has proved unexpectedly challenging. Thus, a better understanding of the properties of multiferroic thin films and the relation with their microstructure is required to help drive multiferroic devices toward technological application. This review covers in a concise manner advanced analytical imaging methods based on (scanning) transmission electron microscopy which can potentially be used to characterize complex multiferroic materials. It consists of a first broad introduction to the topic followed by a section describing the so-called phase-contrast methods, which can be used to map the polar and magnetic order in magnetoelectric multiferroics at different spatial length scales down to atomic resolution. Section 3 is devoted to electron nanodiffraction methods. These methods allow measuring local strains, identifying crystal defects and determining crystal structures, and thus offer important possibilities for the detailed structural characterization of multiferroics in the ultrathin regime or inserted in multilayers or superlattice architectures. Thereafter, in Section 4, methods are discussed which allow for analyzing local strain, whereas in Section 5 methods are addressed which allow for measuring local polarization effects on a length scale of individual unit cells. Here, it is shown that the ferroelectric polarization can be indirectly determined from the atomic displacements measured in atomic resolution images. Finally, a brief outlook is given on newly established methods to probe the behavior of ferroelectric and magnetic domains and nanostructures during in situ heating/electrical biasing experiments. These in situ methods are just about at the launch of becoming increasingly popular, particularly in the field of magnetoelectric multiferroics, and shall contribute significantly to understanding the relationship between the domain dynamics of multiferroics and the specific microstructure of the films providing important guidance to design new devices and to predict and mitigate failures.
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17
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Li L, Xie L, Pan X. Real-time studies of ferroelectric domain switching: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:126502. [PMID: 31185460 DOI: 10.1088/1361-6633/ab28de] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Ferroelectric materials have been utilized in a broad range of electronic, optical, and electromechanical applications and hold the promise for the design of future high-density nonvolatile memories and multifunctional nano-devices. The applications of ferroelectric materials stem from the ability to switch polarized domains by applying an electric field, and therefore a fundamental understanding of the switching dynamics is critical for design of practical devices. In this review, we summarize the progress in the study of the microscopic process of ferroelectric domain switching using recently developed in situ transmission electron microscopy (TEM). We first briefly introduce the instrumentation, experimental procedures, imaging mechanisms, and analytical methods of the state-of-the-art in situ TEM techniques. The application of these techniques to studying a wide range of complex switching phenomena, including domain nucleation, domain wall motion, domain relaxation, domain-defect interaction, and the interplay between different types of domains, is demonstrated. The underlying physics of these dynamic processes are discussed.
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Affiliation(s)
- Linze Li
- Department of Materials Science and Engineering, University of California, Irvine, CA 92697, United States of America
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18
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Wu M, Song D, Guo M, Bian J, Li J, Yang Y, Huang H, Pennycook SJ, Lou X. Remarkably Enhanced Negative Electrocaloric Effect in PbZrO 3 Thin Film by Interface Engineering. ACS APPLIED MATERIALS & INTERFACES 2019; 11:36863-36870. [PMID: 31525289 DOI: 10.1021/acsami.9b13143] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The electrocaloric effect in ferroelectric materials has drawn much attention due to its potential applications in integrated circuit cooling and novel cooling devices. In contrast to the widely researched positive electrocaloric effect, the negative electrocaloric effect has received much less attention due to the lack of any effective methods for significant enhancement. In this work, we fabricated PbZrO3 thin film on a Pt/Si substrate by the sol-gel method. By controlling the interface conditions between the thin film and substrate, we induced defects into the interface and stabilized a transient ferroelectric phase in the PbZrO3 thin film. The emergence of the transient ferroelectric phase postpones the antiferroelectric-ferroelectric phase transition. As a result, a negative electrocaloric effect up to -18.5 K is estimated near room temperature, the highest one ever reported in this temperature range. This result suggests a new strategy to enhance the negative electrocaloric effect and may benefit the application of PbZrO3 thin films in cooling devices.
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Affiliation(s)
- Ming Wu
- Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P.R. China
- Department of Materials Science and Engineering , National University of Singapore , 9 Engineering Drive 1 , Singapore 117575 , Singapore
| | - Dongsheng Song
- NUSNNI-NanoCore , National University of Singapore , Singapore 117411 , Singapore
| | - Mengyao Guo
- Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P.R. China
| | - Jihong Bian
- Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P.R. China
| | - Junning Li
- School of Physics and Astronomy , Queen Mary University of London , London E1 4NS , U.K
| | - Yaodong Yang
- Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P.R. China
| | - Haitao Huang
- Department of Applied Physics , The Hong Kong Polytechnic University , Kowloon , Hong Kong SAR
| | - Stephen J Pennycook
- Department of Materials Science and Engineering , National University of Singapore , 9 Engineering Drive 1 , Singapore 117575 , Singapore
| | - Xiaojie Lou
- Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , P.R. China
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19
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Yang Q, Tao L, Zhang Y, Li M, Jiang Z, Tsymbal EY, Alexandrov V. Ferroelectric Tunnel Junctions Enhanced by a Polar Oxide Barrier Layer. NANO LETTERS 2019; 19:7385-7393. [PMID: 31514498 DOI: 10.1021/acs.nanolett.9b03056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ferroelectric tunnel junctions (FTJs) have recently aroused significant interest due to the interesting physics controlling their properties and potential application in nonvolatile memory devices. In this work, we propose a new concept to design high-performance FTJs based on ferroelectric/polar-oxide composite barriers. Using density functional theory calculations, we model electronic and transport properties of LaNiO3/PbTiO3/LaAlO3/LaNiO3 tunnel junctions and demonstrate that an ultrathin polar LaAlO3(001) layer strongly enhances their performance. We predict a tunneling electroresistance (TER) effect in these FTJs with an OFF/ON resistance ratio exceeding a factor of 104 and ON state resistance as low as about 1 kΩμm2. Such an enhanced performance is driven by the ionic charge at the PbTiO3/LaAlO3 interface, which significantly increases transmission across the FTJ when the ferroelectric polarization of PbTiO3 is pointing against the intrinsic electric field produced by this ionic charge. This is due to the formation of a two-dimensional (2D) electron or hole gas, depending on the LaAlO3 termination being (LaO)+ or (AlO2)-, respectively, which is formed to screen the polarization charge of the nonuniform polarization state. This 2D electron (hole) gas can be switched ON and OFF by the reversal of ferroelectric polarization, resulting in the giant TER effect. The proposed design suggests a new direction for creating FTJs with a stable and reversible ferroelectric polarization, a sizable TER effect, and a low-resistance-area product, as required for memory applications.
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Affiliation(s)
- Qiong Yang
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
- School of Materials Science and Engineering , Xiangtan University , Xiangtan , Hunan 411105 , China
| | - Lingling Tao
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Yuke Zhang
- School of Materials Science and Engineering , Xiangtan University , Xiangtan , Hunan 411105 , China
| | - Ming Li
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Zhen Jiang
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Vitaly Alexandrov
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
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20
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Zhang Y, Han MG, Garlow JA, Tan Y, Xue F, Chen LQ, Munroe P, Valanoor N, Zhu Y. Deterministic Ferroelastic Domain Switching Using Ferroelectric Bilayers. NANO LETTERS 2019; 19:5319-5326. [PMID: 31268341 DOI: 10.1021/acs.nanolett.9b01782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Composition gradients, or dissimilar ferroelectric bilayers, demonstrate colossal electromechanical figures of merit attributed to the motion of ferroelastic domain walls. Yet, mechanistic understanding of polarization switching pathways that drive ferroelastic switching in these systems remains elusive. Here, the crucial roles of strain and electrostatic boundary conditions in ferroelectric bilayer systems are revealed, which underpin their ferroelastic switching dynamics. Using in situ electrical biasing in the transmission electron microscope (TEM), the motion of ferroelastic domain walls is investigated in a tetragonal (T) Pb(Zr,Ti)O3 (PZT)/rhombohedral (R) PZT epitaxial bilayer system. Atomic resolution electron microscopy, in tandem with phase field simulations, indicates that ferroelastic switching is triggered by predominant nucleation at the triple domain junctions located at the interface between the T/R layers. Furthermore, this interfacial nucleation leads to systematic reversable reorientation of ferroelastic domain walls. Deterministic ferroelastic domain switching, driven by the interfacial strain and electrostatic boundary conditions in the ferroelectric bilayer, provides a viable pathway toward novel design of miniaturized energy-efficient electromechanical devices.
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Affiliation(s)
- Yangyang Zhang
- Condensed Matter Physics and Materials Sciences Department , Brookhaven National Laboratory , Upton , New York 11973 , United States
- School of Materials Science and Engineering , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Myung-Geun Han
- Condensed Matter Physics and Materials Sciences Department , Brookhaven National Laboratory , Upton , New York 11973 , United States
| | - Joseph A Garlow
- Condensed Matter Physics and Materials Sciences Department , Brookhaven National Laboratory , Upton , New York 11973 , United States
| | - Yueze Tan
- Department of Materials Science and Engineering , Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Fei Xue
- Department of Materials Science and Engineering , Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Long-Qing Chen
- Department of Materials Science and Engineering , Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Paul Munroe
- School of Materials Science and Engineering , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Nagarajan Valanoor
- School of Materials Science and Engineering , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Yimei Zhu
- Condensed Matter Physics and Materials Sciences Department , Brookhaven National Laboratory , Upton , New York 11973 , United States
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21
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Abstract
The Boltzmann distribution of electrons sets a fundamental barrier to lowering energy consumption in metal-oxide-semiconductor field-effect transistors (MOSFETs). Negative capacitance FET (NC-FET), as an emerging FET architecture, is promising to overcome this thermionic limit and build ultra-low-power consuming electronics. Here, we demonstrate steep-slope NC-FETs based on two-dimensional molybdenum disulfide and CuInP2S6 (CIPS) van der Waals (vdW) heterostructure. The vdW NC-FET provides an average subthreshold swing (SS) less than the Boltzmann’s limit for over seven decades of drain current, with a minimum SS of 28 mV dec−1. Negligible hysteresis is achieved in NC-FETs with the thickness of CIPS less than 20 nm. A voltage gain of 24 is measured for vdW NC-FET logic inverter. Flexible vdW NC-FET is further demonstrated with sub-60 mV dec−1 switching characteristics under the bending radius down to 3.8 mm. These results demonstrate the great potential of vdW NC-FET for ultra-low-power and flexible applications. The adaptation to atomically thin 2D semiconductors and van der Waals layered ferroelectrics can enable negative capacitance transistors with superior performance and bendability. Here, the authors report flexible negative capacitance transistors based on MoS2 and a ferroelectric dielectric CIPS with a minimum sub-threshold slope of 28 mV/dec and high gain logic invertors.
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22
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Meng Q, Xu G, Xin H, Stach EA, Zhu Y, Su D. Quantification of Charge Transfer at the Interfaces of Oxide Thin Films. J Phys Chem A 2019; 123:4632-4637. [PMID: 31050895 DOI: 10.1021/acs.jpca.9b02802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interfacial electronic distribution in transition-metal oxide thin films is crucial to their interfacial physical or chemical behaviors. Core-loss electron energy-loss spectroscopy (EELS) may potentially give valuable information of local electronic density of state at high spatial resolution. Here, we studied the electronic properties at the interface of Pb(Zr0.2Ti0.8)O3 (PZT)/4.8 nm La0.8Sr0.2MnO3 (LSMO)/SrTiO3 (STO) using valance-EELS with a scanning transmission electron microscope. Modeled with dielectric function theory, the charge transfer in the vicinity of the interfaces of PZT/LSMO and LSMO/STO was determined from the shifts of plasma peaks of valence EELS (VEELS), agreeing with theoretical prediction. Our work demonstrates that the VEELS method enables a high-efficient quantification of the charge transfer at interfaces, shedding light on the charge-transfer issues at heterogenous interfaces in physical and chemical devices.
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23
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Ferroelectrics with a controlled oxygen-vacancy distribution by design. Sci Rep 2019; 9:4225. [PMID: 30862877 PMCID: PMC6414602 DOI: 10.1038/s41598-019-40717-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 02/22/2019] [Indexed: 11/21/2022] Open
Abstract
Controlling and manipulating defects in materials provides an extra degree of freedom not only for enhancing physical properties but also for introducing additional functionalities. In ferroelectric oxides, an accumulation of point defects at specific boundaries often deteriorates a polarization-switching capability, but on the one hand, delivers interface-driven phenomena. At present, it remains challenging to control oxygen vacancies at will to achieve a desirable defect structure. Here, we report a practical route to designing oxygen-vacancy distributions by exploiting the interaction with transition-metal dopants. Our thin-film experiments combined with ab-initio theoretical calculations for BiFeO3 demonstrate that isovalent dopants such as Mn3+ with a partly or fully electron-occupied eg state can trap oxygen vacancies, leading to a robust polarization switching. Our approach to controlling oxygen vacancy distributions by harnessing the vacancy-trapping capability of isovalent transition-metal cations will realize the full potential of switchable polarization in ferroelectric perovskite oxides.
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Liang S, Yu Z, Devaux X, Ferri A, Huang W, Yang H, Desfeux R, Li X, Migot S, Chaudhuri D, Yang H, Chshiev M, Yang C, Zhou B, Fang J, Mangin S, Lu Y. Quenching of Spin Polarization Switching in Organic Multiferroic Tunnel Junctions by Ferroelectric "Ailing-Channel" in Organic Barrier. ACS APPLIED MATERIALS & INTERFACES 2018; 10:30614-30622. [PMID: 30125490 DOI: 10.1021/acsami.8b11437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The ferroelectric control of spin-polarization at ferromagnet (FM)/ferroelectric organic (FE-Org) interface by electrically switching the ferroelectric polarization of the FE-Org has been recently realized in the organic multiferroic tunnel junctions (OMFTJs) and gained intensive interests for future multifunctional organic spintronic applications. Here, we report the evidence of ferroelectric "ailing-channel" in the organic barrier, which can effectively pin the ferroelectric domain, resulting in nonswitchable spin polarization at the FM/FE-Org interface. In particular, OMFTJs based on La0.6Sr0.4MnO3/P(VDF-TrFE) ( t)/Co/Au structures with different P(VDF-TrFE) thickness ( t) were fabricated. The combined advanced electron microscopy and spectroscopy studies clearly reveal that very limited Co diffusion exists in the P(VDF-TrFE) organic barrier when the Au/Co electrode is deposited around 80K. Pot-hole structures at the boundary between the P(VDF-TrFE) needle-like grains are evidenced to induce "ailing-channels" that hinder efficient ferroelectric polarization of the organic barrier and result in the quenching of the spin polarization switching at Co/P(VDF-TrFE) interface. Furthermore, the spin diffusion length in the negatively polarized P(VDF-TrFE) is measured to be about 7.2 nm at 20K. The evidence of the mechanism of ferroelectric "ailing-channels" is of essential importance to improve the performance of OMFTJ and master the key condition for an efficient ferroelectric control of the spin polarization of "spinterface".
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Affiliation(s)
- Shiheng Liang
- Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France
- Department of Physics , Hubei University , Wuhan 430062 , P. R. China
| | - Zhongwei Yu
- Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France
- School of Science , Nantong University , 9 Seyuan Road , Nantong 226019 , P. R. China
| | - Xavier Devaux
- Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France
| | - Anthony Ferri
- Univ. Artois, CNRS, Centrale Lille, ENSCL, Univ. Lille, UMR 8181, Unité de Catalyse et Chimie du Solide (UCCS) , F-62300 Lens , France
| | - Weichuan Huang
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics , University of Science and Technology of China , Hefei 230026 , P. R. China
| | - Huaiwen Yang
- Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France
| | - Rachel Desfeux
- Univ. Artois, CNRS, Centrale Lille, ENSCL, Univ. Lille, UMR 8181, Unité de Catalyse et Chimie du Solide (UCCS) , F-62300 Lens , France
| | - Xiaoguang Li
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics , University of Science and Technology of China , Hefei 230026 , P. R. China
| | - Sylvie Migot
- Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France
| | - Debapriya Chaudhuri
- Univ. Grenoble Alpes, CEA, CNRS , Grenoble INP, INAC-Spintec, 38000 Grenoble , France
| | - Hongxin Yang
- Key Laboratory of Magnetic Materials and Devices , Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences , Ningbo 315201 , China
| | - Mairbek Chshiev
- Univ. Grenoble Alpes, CEA, CNRS , Grenoble INP, INAC-Spintec, 38000 Grenoble , France
| | - Changping Yang
- Department of Physics , Hubei University , Wuhan 430062 , P. R. China
| | - Bin Zhou
- Department of Physics , Hubei University , Wuhan 430062 , P. R. China
| | - Jinghuai Fang
- School of Science , Nantong University , 9 Seyuan Road , Nantong 226019 , P. R. China
| | - Stéphane Mangin
- Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France
| | - Yuan Lu
- Institut Jean Lamour, UMR 7198 , CNRS-Université de Lorraine, Campus ARTEM , 2 Allée André Guinier, BP 50840 , 54011 Nancy , France
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25
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Bai Y, Wang ZJ, He B, Cui JZ, Zhang ZD. Enhancement of Polarization in Ferroelectric Films via the Incorporation of Gold Nanoparticles. ACS OMEGA 2017; 2:9067-9073. [PMID: 31457428 PMCID: PMC6645548 DOI: 10.1021/acsomega.7b01626] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 11/29/2017] [Indexed: 06/09/2023]
Abstract
Ferroelectric thin films have been extremely studied for many applications such as nonvolatile memories, super capacitors, and solar cells. For these devices, improving the polarization properties of ferroelectric thin films is of great significance to their performance. Here, Au-lead zirconate titanate (PZT) nanocomposite thin films were prepared by a simple one-step chemical solution deposition (CSD) method on silicon substrates, and the effects of Au concentration on the ferroelectric properties were investigated. The experimental results show that the remanent polarization of the Au-PZT films with 1.2 mol % Au is about 80 μC/cm2, which is 50% higher than that of the pure PZT thin films. On the basis of the analysis of chemical valences, the enhanced polarization properties can be ascribed to the interaction between Au nanoparticles (Au NPs) and PZT at the Au-PZT interfaces. Our results demonstrate that the incorporation of an appropriate amount of Au NPs is an effective way to enhance the polarization properties of ferroelectric films. The Au-PZT nanocomposite thin films with excellent polarization properties on silicon substrates are expected to be widely used in integrated ferroelectric devices.
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Affiliation(s)
- Yu Bai
- School of Materials
Science and Engineering, Northeastern University, No. 3-11 Wenhua Road, Heping District, Shenyang 110819, China
- Shenyang National Laboratory for Materials
Science, Institute of Metal Research, Chinese
Academy of Sciences, 72 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Zhan Jie Wang
- School of Materials
Science and Engineering, Northeastern University, No. 3-11 Wenhua Road, Heping District, Shenyang 110819, China
- Shenyang National Laboratory for Materials
Science, Institute of Metal Research, Chinese
Academy of Sciences, 72 Wenhua Road, Shenhe District, Shenyang 110016, China
- School of
Material Science and Engineering, Shenyang
University of Technology, 111 Shenliao West Road, Shenyang Economy and Technology
Development Zone, Shenyang 110870, China
| | - Bin He
- Shenyang National Laboratory for Materials
Science, Institute of Metal Research, Chinese
Academy of Sciences, 72 Wenhua Road, Shenhe District, Shenyang 110016, China
| | - Jian Zhong Cui
- School of Materials
Science and Engineering, Northeastern University, No. 3-11 Wenhua Road, Heping District, Shenyang 110819, China
| | - Zhi Dong Zhang
- Shenyang National Laboratory for Materials
Science, Institute of Metal Research, Chinese
Academy of Sciences, 72 Wenhua Road, Shenhe District, Shenyang 110016, China
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26
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Sanchez-Santolino G, Tornos J, Hernandez-Martin D, Beltran JI, Munuera C, Cabero M, Perez-Muñoz A, Ricote J, Mompean F, Garcia-Hernandez M, Sefrioui Z, Leon C, Pennycook SJ, Muñoz MC, Varela M, Santamaria J. Resonant electron tunnelling assisted by charged domain walls in multiferroic tunnel junctions. NATURE NANOTECHNOLOGY 2017; 12:655-662. [PMID: 28396607 DOI: 10.1038/nnano.2017.51] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 03/02/2017] [Indexed: 05/28/2023]
Abstract
The peculiar features of domain walls observed in ferroelectrics make them promising active elements for next-generation non-volatile memories, logic gates and energy-harvesting devices. Although extensive research activity has been devoted recently to making full use of this technological potential, concrete realizations of working nanodevices exploiting these functional properties are yet to be demonstrated. Here, we fabricate a multiferroic tunnel junction based on ferromagnetic La0.7Sr0.3MnO3 electrodes separated by an ultrathin ferroelectric BaTiO3 tunnel barrier, where a head-to-head domain wall is constrained. An electron gas stabilized by oxygen vacancies is confined within the domain wall, displaying discrete quantum-well energy levels. These states assist resonant electron tunnelling processes across the barrier, leading to strong quantum oscillations of the electrical conductance.
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Affiliation(s)
- Gabriel Sanchez-Santolino
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Javier Tornos
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
| | - David Hernandez-Martin
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
| | - Juan I Beltran
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto de Ciencia de Materiales de Madrid ICMM-CSIC, Calle Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Carmen Munuera
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto de Ciencia de Materiales de Madrid ICMM-CSIC, Calle Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Mariona Cabero
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Ana Perez-Muñoz
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
| | - Jesus Ricote
- Instituto de Ciencia de Materiales de Madrid ICMM-CSIC, Calle Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Federico Mompean
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto de Ciencia de Materiales de Madrid ICMM-CSIC, Calle Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Mar Garcia-Hernandez
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto de Ciencia de Materiales de Madrid ICMM-CSIC, Calle Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Zouhair Sefrioui
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto de Magnetismo Aplicado, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Carlos Leon
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto de Magnetismo Aplicado, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Steve J Pennycook
- Department of Materials Science &Engineering, National University of Singapore, Singapore 117575, Singapore
| | - Maria Carmen Muñoz
- Instituto de Ciencia de Materiales de Madrid ICMM-CSIC, Calle Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Maria Varela
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Instituto de Magnetismo Aplicado, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Materials Science and Technology Div., Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Jacobo Santamaria
- GFMC, Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Unidad Asociada ICMM-CSIC 'Laboratorio de heteroestructuras con aplicación en Espintrónica', UCM, CSIC, E-28049 Madrid, Spain
- Instituto de Magnetismo Aplicado, Universidad Complutense de Madrid, 28040 Madrid, Spain
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27
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Shindo D, Tanigaki T, Park HS. Advanced Electron Holography Applied to Electromagnetic Field Study in Materials Science. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1602216. [PMID: 27859812 DOI: 10.1002/adma.201602216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 09/02/2016] [Indexed: 06/06/2023]
Abstract
Advances and applications of electron holography to the study of electromagnetic fields in various functional materials are presented. In particular, the development of split-illumination electron holography, which introduces a biprism in the illumination system of a holography electron microscope, enables highly accurate observations of electromagnetic fields and the expansion of the observable area. First, the charge distributions on insulating materials were studied by using split-illumination electron holography and including a mask in the illumination system. Second, the three-dimensional spin configurations of skyrmion lattices in a helimagnet were visualized by using a high-voltage holography electron microscope. Third, the pinning of the magnetic flux lines in a high-temperature superconductor YBa2 Cu3 O7-y was analyzed by combining electron holography and scanning ion microscopy. Finally, the dynamic accumulation and collective motions of electrons around insulating biomaterial surfaces were observed by utilizing the amplitude reconstruction processes of electron holography.
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Affiliation(s)
- Daisuke Shindo
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577, Japan
| | - Toshiaki Tanigaki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Hyun Soon Park
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
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28
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Perspectives on in situ electron microscopy. Ultramicroscopy 2017; 180:188-196. [PMID: 28434784 DOI: 10.1016/j.ultramic.2017.03.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 03/12/2017] [Accepted: 03/18/2017] [Indexed: 12/22/2022]
Abstract
In situ transmission electron microscopy (TEM) with the ability to reveal materials dynamic processes with high spatial and temporal resolution has attracted significant interest. The recent advances in in situ methods, including liquid and gas sample environment, pump-probe ultrafast microscopy, nanomechanics and ferroelectric domain switching the aberration corrected electron optics as well as fast electron detector has opened new opportunities to extend the impact of in situ TEM in broad areas of research ranging from materials science to chemistry, physics and biology. In this article, we highlight the development of liquid environment electron microscopy and its applications in the study of colloidal nanoparticle growth, electrochemical processes and others; in situ study of topological vortices in ferroelectric and ferromagnetic materials. At the end, perspectives of future in situ TEM are provided.
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29
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Depth resolved lattice-charge coupling in epitaxial BiFeO 3 thin film. Sci Rep 2016; 6:38724. [PMID: 27929103 PMCID: PMC5144002 DOI: 10.1038/srep38724] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 11/07/2016] [Indexed: 11/14/2022] Open
Abstract
For epitaxial films, a critical thickness (tc) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the tc in BiFeO3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO3/SrRuO3/SrTiO3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO3 film was resolved into a strained layer with an extremely low piezoelectric coefficient of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical coupling.
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30
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Bai Y, Wang ZJ, Chen YN, Cui JZ. Resistive Switching and Modulation of Pb(Zr 0.4Ti 0.6)O 3/Nb:SrTiO 3 Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2016; 8:32948-32955. [PMID: 27934147 DOI: 10.1021/acsami.6b10992] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this work, epitaxial Pb(Zr0.4Ti0.6)O3 (PZT) thin films with different thicknesses were deposited on Nb-doped SrTiO3 (NSTO) single-crystal substrates by chemical solution deposition (CSD), and their ferroelectric resistive switching behaviors were investigated. The results showed that the maximum ON/OFF ratio up to 850 could be obtained in the PZT/NSTO heterostructure with the 150 nm thick PZT film. On the basis of the Schottky-Simmons model and the modified semiconductor theory, we also evaluated the interfacial built-in field and the depletion layer at the PZT/NSTO interface, which can be modulated strongly by the ferroelectric polarization, but are independent of the thickness of the PZT thin films. It is clear that the ferroelectric resistive switching is related to the ferroelectric polarization and modulated by the thickness of ferroelectric films. Therefore, there is an optimal thickness of the PZT film for the maximum ON/OFF ratio due to the ferroelectricity and conductivity mutually restricting. It can be expected that by adjusting the ferroelectricity and conductivity of the ferroelectric thin film and its thickness, the maximum switching ratio can be further improved.
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Affiliation(s)
- Yu Bai
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Zhan Jie Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
| | - Yan Na Chen
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, China
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31
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Room-temperature ferroelectricity in CuInP2S6 ultrathin flakes. Nat Commun 2016; 7:12357. [PMID: 27510418 PMCID: PMC4987531 DOI: 10.1038/ncomms12357] [Citation(s) in RCA: 313] [Impact Index Per Article: 39.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Accepted: 06/24/2016] [Indexed: 12/22/2022] Open
Abstract
Two-dimensional (2D) materials have emerged as promising candidates for various optoelectronic applications based on their diverse electronic properties, ranging from insulating to superconducting. However, cooperative phenomena such as ferroelectricity in the 2D limit have not been well explored. Here, we report room-temperature ferroelectricity in 2D CuInP2S6 (CIPS) with a transition temperature of ∼320 K. Switchable polarization is observed in thin CIPS of ∼4 nm. To demonstrate the potential of this 2D ferroelectric material, we prepare a van der Waals (vdW) ferroelectric diode formed by CIPS/Si heterostructure, which shows good memory behaviour with on/off ratio of ∼100. The addition of ferroelectricity to the 2D family opens up possibilities for numerous novel applications, including sensors, actuators, non-volatile memory devices, and various vdW heterostructures based on 2D ferroelectricity. Two dimensional materials are promising for electronic applications, which await the exploration of cooperative phenomena. Here, Liu et al. report switchable ferroelectric polarization in thin CuInP2S6 film at room temperature, demonstrating good memory behaviour with on/off ratio of ∼100 based on two-dimensional ferroelectricity.
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32
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Polking MJ. Deciphering the physics and chemistry of perovskites with transmission electron microscopy. NANOSCALE 2016; 8:6237-6248. [PMID: 26762871 DOI: 10.1039/c5nr06186e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Perovskite oxides exhibit rich structural complexity and a broad range of functional properties, including ferroelectricity, ferromagnetism, and superconductivity. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, electron holography, and other techniques has fueled rapid progress in the understanding of the physics and chemistry of these materials. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, chemistry, electrostatics, and dynamics of perovskite oxides are then explored in detail, with a particular focus on ferroelectric materials.
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Affiliation(s)
- Mark J Polking
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
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33
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Lopatin S, Ivanov YP, Kosel J, Chuvilin A. Multiscale differential phase contrast analysis with a unitary detector. Ultramicroscopy 2016; 162:74-81. [DOI: 10.1016/j.ultramic.2015.12.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Revised: 12/16/2015] [Accepted: 12/29/2015] [Indexed: 11/17/2022]
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34
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Ferroelectricity and Self-Polarization in Ultrathin Relaxor Ferroelectric Films. Sci Rep 2016; 6:19965. [PMID: 26817516 PMCID: PMC4730210 DOI: 10.1038/srep19965] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 12/08/2015] [Indexed: 12/02/2022] Open
Abstract
We report ferroelectricity and self-polarization in the (001) oriented ultrathin relaxor ferroelectric PMN-PT films grown on Nb-SrTiO3, SrRuO3 and La0.7Sr0.3MnO3, respectively. Resistance-voltage measurements and AC impedance analysis suggest that at high temperatures Schottky depletion width in a 4 nm thick PMN-PT film deposited on Nb-SrTiO3 is smaller than the film thickness. We propose that Schottky interfacial dipoles make the dipoles of the nanometer-sized polar nanoregions (PNRs) in PMN-PT films grown on Nb-SrTiO3 point downward at high temperatures and lead to the self-polarization at room temperature with the assistance of in-plane compressive strain. This work sheds light on the understanding of epitaxial strain effects on relaxor ferroelectric films and self-polarization mechanism.
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35
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Pennington RS, Koch CT. A three-dimensional polarization domain retrieval method from electron diffraction data. Ultramicroscopy 2015; 155:42-48. [DOI: 10.1016/j.ultramic.2015.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 10/23/2022]
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36
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Leguy AMA, Frost JM, McMahon AP, Sakai VG, Kochelmann W, Law C, Li X, Foglia F, Walsh A, O'Regan BC, Nelson J, Cabral JT, Barnes PRF. The dynamics of methylammonium ions in hybrid organic-inorganic perovskite solar cells. Nat Commun 2015; 6:7124. [PMID: 26023041 PMCID: PMC4458867 DOI: 10.1038/ncomms8124] [Citation(s) in RCA: 229] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 04/07/2015] [Indexed: 12/23/2022] Open
Abstract
Methylammonium lead iodide perovskite can make high-efficiency solar cells, which also show an unexplained photocurrent hysteresis dependent on the device-poling history. Here we report quasielastic neutron scattering measurements showing that dipolar CH3NH3+ ions reorientate between the faces, corners or edges of the pseudo-cubic lattice cages in CH3NH3PbI3 crystals with a room temperature residence time of ∼14 ps. Free rotation, π-flips and ionic diffusion are ruled out within a 1–200-ps time window. Monte Carlo simulations of interacting CH3NH3+ dipoles realigning within a 3D lattice suggest that the scattering measurements may be explained by the stabilization of CH3NH3+ in either antiferroelectric or ferroelectric domains. Collective realignment of CH3NH3+ to screen a device's built-in potential could reduce photovoltaic performance. However, we estimate the timescale for a domain wall to traverse a typical device to be ∼0.1–1 ms, faster than most observed hysteresis. Hysteresis often exists in the characterization of methylammonium lead halide-based solar cells, but is not well understood. Here, the authors use quasielastic neutron scattering to study the dynamics of dipolar organic cations and shed light on the hysteresis behaviour.
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Affiliation(s)
| | - Jarvist Moore Frost
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Andrew P McMahon
- Department of Physics, Imperial College London, London SW7 2AZ, UK
| | | | - W Kochelmann
- Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, UK
| | - ChunHung Law
- Department of Chemistry, Imperial College London, London SW7 2AZ, UK
| | - Xiaoe Li
- Department of Chemistry, Imperial College London, London SW7 2AZ, UK
| | - Fabrizia Foglia
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
| | - Aron Walsh
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Brian C O'Regan
- Department of Chemistry, Imperial College London, London SW7 2AZ, UK
| | - Jenny Nelson
- Department of Physics, Imperial College London, London SW7 2AZ, UK
| | - João T Cabral
- Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
| | - Piers R F Barnes
- Department of Physics, Imperial College London, London SW7 2AZ, UK
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