1
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Gradauskaite E, Meier QN, Gray N, Sarott MF, Scharsach T, Campanini M, Moran T, Vogel A, Del Cid-Ledezma K, Huey BD, Rossell MD, Fiebig M, Trassin M. Defeating depolarizing fields with artificial flux closure in ultrathin ferroelectrics. NATURE MATERIALS 2023; 22:1492-1498. [PMID: 37783942 PMCID: PMC10713449 DOI: 10.1038/s41563-023-01674-2] [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: 03/14/2022] [Accepted: 08/25/2023] [Indexed: 10/04/2023]
Abstract
Material surfaces encompass structural and chemical discontinuities that often lead to the loss of the property of interest in so-called dead layers. It is particularly problematic in nanoscale oxide electronics, where the integration of strongly correlated materials into devices is obstructed by the thickness threshold required for the emergence of their functionality. Here we report the stabilization of ultrathin out-of-plane ferroelectricity in oxide heterostructures through the design of an artificial flux-closure architecture. Inserting an in-plane-polarized ferroelectric epitaxial buffer provides the continuity of polarization at the interface; despite its insulating nature, we observe the emergence of polarization in our out-of-plane-polarized model of ferroelectric BaTiO3 from the very first unit cell. In BiFeO3, the flux-closure approach stabilizes a 251° domain wall. Its unusual chirality is probably associated with the ferroelectric analogue to the Dzyaloshinskii-Moriya interaction. We, thus, see that in an adaptively engineered geometry, the depolarizing-field-screening properties of an insulator can even surpass those of a metal and be a source of functionality. This could be a useful insight on the road towards the next generation of oxide electronics.
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Affiliation(s)
| | | | - Natascha Gray
- Department of Materials, ETH Zurich, Zurich, Switzerland
| | | | | | | | - Thomas Moran
- Department of Materials Science and Engineering, University of Connecticut, Storrs, CT, USA
| | | | - Karla Del Cid-Ledezma
- Department of Materials Science and Engineering, University of Connecticut, Storrs, CT, USA
| | - Bryan D Huey
- Department of Materials Science and Engineering, University of Connecticut, Storrs, CT, USA
| | | | - Manfred Fiebig
- Department of Materials, ETH Zurich, Zurich, Switzerland
| | - Morgan Trassin
- Department of Materials, ETH Zurich, Zurich, Switzerland.
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2
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Ricca C, Skoropata E, Rossell MD, Erni R, Staub U, Aschauer U. Combined Theoretical and Experimental Study of the Moiré Dislocation Network at the SrTiO 3-(La,Sr)(Al,Ta)O 3 Interface. ACS APPLIED MATERIALS & INTERFACES 2023; 15:53678-53687. [PMID: 37945309 PMCID: PMC10685357 DOI: 10.1021/acsami.3c10958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 10/13/2023] [Accepted: 10/23/2023] [Indexed: 11/12/2023]
Abstract
Recently, a highly ordered Moiré dislocation lattice was identified at the interface between a SrTiO3 (STO) thin film and the (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) substrate. A fundamental understanding of the local ionic and electronic structures around the dislocation cores is crucial to further engineer the properties of these complex multifunctional heterostructures. Here, we combine experimental characterization via analytical scanning transmission electron microscopy with results of molecular dynamics and density functional theory calculations to gain insights into the structure and defect chemistry of these dislocation arrays. Our results show that these dislocations lead to undercoordinated Ta/Al cations at the dislocation core, where oxygen vacancies can easily be formed, further facilitated by the presence of cation vacancies. The reduced Ti3+ observed experimentally at the dislocations by electron energy-loss spectroscopy is a consequence of both the structure of the dislocation itself and of the electron doping due to oxygen vacancy formation. Finally, the experimentally observed Ti diffusion into the LSAT around the dislocation core occurs only together with cation vacancy formation in the LSAT or Ta diffusion into STO.
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Affiliation(s)
- Chiara Ricca
- Department
of Chemistry and Biochemistry, University
of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Elizabeth Skoropata
- Swiss
Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Marta D. Rossell
- Electron
Microscopy Center, Empa, Swiss Federal Laboratories
for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Rolf Erni
- Electron
Microscopy Center, Empa, Swiss Federal Laboratories
for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Urs Staub
- Swiss
Light Source, Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Ulrich Aschauer
- Department
of Chemistry and Biochemistry, University
of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
- Department
of Chemistry and Physics of Materials, University
of Salzburg, Jakob-Haringer-Street 2A, A-5020 Salzburg, Austria
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3
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Vogel A, Ruiz Caridad A, Nordlander J, Sarott MF, Meier QN, Erni R, Spaldin NA, Trassin M, Rossell MD. Origin of the Critical Thickness in Improper Ferroelectric Thin Films. ACS APPLIED MATERIALS & INTERFACES 2023; 15:18482-18492. [PMID: 36996320 DOI: 10.1021/acsami.3c00412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Improper ferroelectrics are expected to be more robust than conventional ferroelectrics against depolarizing field effects and to exhibit a much-desired absence of critical thickness. Recent studies, however, revealed the loss of ferroelectric response in epitaxial improper ferroelectric thin films. Here, we investigate improper ferroelectric hexagonal YMnO3 thin films and find that the polarization suppression, and hence functionality, in the thinner films is due to oxygen off-stoichiometry. We demonstrate that oxygen vacancies form on the film surfaces to provide the necessary charge to screen the large internal electric field resulting from the positively charged YMnO3 surface layers. Additionally, we show that by modifying the oxygen concentration of the films, the phase transition temperatures can be substantially tuned. We anticipate that our findings are also valid for other ferroelectric oxide films and emphasize the importance of controlling the oxygen content and cation oxidation states in ferroelectrics for their successful integration in nanoscale applications.
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Affiliation(s)
- Alexander Vogel
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Department of Materials, Eidgenössische Technische Hochschule Zürich, 8092 Zürich, Switzerland
| | - Alicia Ruiz Caridad
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Johanna Nordlander
- Department of Materials, Eidgenössische Technische Hochschule Zürich, 8092 Zürich, Switzerland
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Martin F Sarott
- Department of Materials, Eidgenössische Technische Hochschule Zürich, 8092 Zürich, Switzerland
| | - Quintin N Meier
- Université Grenoble Alpes, CNRS, Institut Néel, 38042 Grenoble, France
| | - Rolf Erni
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Nicola A Spaldin
- Department of Materials, Eidgenössische Technische Hochschule Zürich, 8092 Zürich, Switzerland
| | - Morgan Trassin
- Department of Materials, Eidgenössische Technische Hochschule Zürich, 8092 Zürich, Switzerland
| | - Marta D Rossell
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
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4
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Ran K, Barthel J, Jin L, Park D, Buchheit A, Neuhaus K, Baumann S, Meulenberg WA, Mayer J. Direct Visualization of Distorted Twin Boundaries in Ce-Doped GdFeO 3. NANO LETTERS 2023; 23:2945-2951. [PMID: 36972518 DOI: 10.1021/acs.nanolett.3c00318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Utilizing advanced transmission electron microscopy (TEM), the structure at the (110)-type twin boundary (TB) of Ce-doped GdFeO3 (C-GFO) has been investigated with picometer precision. Such a TB is promising to generate local ferroelectricity within a paraelectric system, while precise knowledge about its structure is still largely missing. In this work, a direct measurement of the cation off-centering with respect to the neighboring oxygen is enabled by integrated differential phase contrast (iDPC) imaging, and up to 30 pm Gd off-centering is highly localized at the TB. Further electron energy loss spectroscopy (EELS) analysis demonstrates a slight accumulation of oxygen vacancies at the TB, a self-balanced behavior of Ce at the Gd sites, and a mixed occupation of Fe2+ and Fe3+ at the Fe sites. Our results provide an informative picture with atomic details at the TB of C-GFO, which is indispensable to further push the potential of grain boundary engineering.
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Affiliation(s)
- Ke Ran
- Central Facility for Electron Microscopy GFE, RWTH Aachen University, 52074 Aachen, Germany
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons ER-C, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Juri Barthel
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons ER-C, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Lei Jin
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons ER-C, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Daesung Park
- Physikalisch-Technische Bundesanstalt PTB, 38116 Braunschweig, Germany
| | - Annika Buchheit
- Institute of Energy and Climate Research IEK-12, Forschungszentrum Jülich GmbH, 48149 Münster, Germany
| | - Kerstin Neuhaus
- Institute of Energy and Climate Research IEK-12, Forschungszentrum Jülich GmbH, 48149 Münster, Germany
| | - Stefan Baumann
- Institute of Energy and Climate Research IEK-1, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Wilhelm A Meulenberg
- Institute of Energy and Climate Research IEK-1, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- Faculty of Science and Technology, Inorganic Membranes, University of Twente, 7500 AE Enschede, The Netherlands
| | - Joachim Mayer
- Central Facility for Electron Microscopy GFE, RWTH Aachen University, 52074 Aachen, Germany
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons ER-C, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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5
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Critical ionic transport across an oxygen-vacancy ordering transition. Nat Commun 2022; 13:5130. [PMID: 36050294 PMCID: PMC9437025 DOI: 10.1038/s41467-022-32826-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 08/17/2022] [Indexed: 11/19/2022] Open
Abstract
Phase transition points can be used to critically reduce the ionic migration activation energy, which is important for realizing high-performance electrolytes at low temperatures. Here, we demonstrate a route toward low-temperature thermionic conduction in solids, by exploiting the critically lowered activation energy associated with oxygen transport in Ca-substituted bismuth ferrite (Bi1-xCaxFeO3-δ) films. Our demonstration relies on the finding that a compositional phase transition occurs by varying Ca doping ratio across xCa ≃ 0.45 between two structural phases with oxygen-vacancy channel ordering along <100> or <110> crystal axis, respectively. Regardless of the atomic-scale irregularity in defect distribution at the doping ratio, the activation energy is largely suppressed to 0.43 eV, compared with ~0.9 eV measured in otherwise rigid phases. From first-principles calculations, we propose that the effective short-range attraction between two positively charged oxygen vacancies sharing lattice deformation not only forms the defect orders but also suppresses the activation energy through concerted hopping. Phase transition points can be used to reduce the ionic migration activation energy. Here, the authors find a lowered activation energy associated with oxygen transport at a compositional phase transition point in Ca-doped bismuth ferrite films.
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6
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Multilevel polarization switching in ferroelectric thin films. Nat Commun 2022; 13:3159. [PMID: 35672404 PMCID: PMC9174202 DOI: 10.1038/s41467-022-30823-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/19/2022] [Indexed: 11/11/2022] Open
Abstract
Ferroic order is characterized by hystereses with two remanent states and therefore inherently binary. The increasing interest in materials showing non-discrete responses, however, calls for a paradigm shift towards continuously tunable remanent ferroic states. Device integration for oxide nanoelectronics furthermore requires this tunability at the nanoscale. Here we demonstrate that we can arbitrarily set the remanent ferroelectric polarization at nanometric dimensions. We accomplish this in ultrathin epitaxial PbZr0.52Ti0.48O3 films featuring a dense pattern of decoupled nanometric 180° domains with a broad coercive-field distribution. This multilevel switching is achieved by driving the system towards the instability at the morphotropic phase boundary. The phase competition near this boundary in combination with epitaxial strain increases the responsiveness to external stimuli and unlocks new degrees of freedom to nano-control the polarization. We highlight the technological benefits of non-binary switching by demonstrating a quasi-continuous tunability of the non-linear optical response and of tunnel electroresistance. Setting any polarization value in ferroelectric thin films is a key step for their implementation in neuromorphic devices. Here, the authors demonstrate continuous modulation of the remanent polarization at the nanoscale in PbZr0.52Ti0.48O3 films.
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7
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Haselmann U, Radlinger T, Pei W, Popov MN, Spitaler T, Romaner L, Ivanov YP, Chen J, He Y, Kothleitner G, Zhang Z. Ca Solubility in a BiFeO 3-Based System with a Secondary Bi 2O 3 Phase on a Nanoscale. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:7696-7703. [PMID: 35558823 PMCID: PMC9082603 DOI: 10.1021/acs.jpcc.2c00674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 04/02/2022] [Indexed: 06/15/2023]
Abstract
In BiFeO3 (BFO), Bi2O3 (BO) is a known secondary phase, which can appear under certain growth conditions. However, BO is not just an unwanted parasitic phase but can be used to create the super-tetragonal BFO phase in films on substrates, which would otherwise grow in the regular rhombohedral phase (R-phase). The super-tetragonal BFO phase has the advantage of a much larger ferroelectric polarization of 130-150 μC/cm2, which is around 1.5 times the value of the rhombohedral phase with 80-100 μC/cm2. Here, we report that the solubility of Ca, which is a common dopant of bismuth ferrite materials to tune their properties, is significantly lower in the secondary BO phase than in the observed R-phase BFO. Starting from the film growth, this leads to completely different Ca concentrations in the two phases. We show this with advanced analytical transmission electron microscopy techniques and confirm the experimental results with density functional theory (DFT) calculations. At the film's fabrication temperature, caused by different solubilities, about 50 times higher Ca concentration is expected in the BFO phase than in the secondary one. Depending on the cooling rate after fabrication, this can further increase since a larger Ca concentration difference is expected at lower temperatures. When fabricating functional devices using Ca doping and the secondary BO phase, the difference in solubility must be considered because, depending on the ratio of the BO phase, the Ca concentration in the BFO phase can become much higher than intended. This can be critical for the intended device functionality because the Ca concentration strongly influences and modifies the BFO properties.
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Affiliation(s)
- Ulrich Haselmann
- Erich
Schmid Institute of Materials Science, Austrian Academy of Sciences, 8700 Leoben, Austria
| | - Thomas Radlinger
- Institute
for Electron Microscopy and Nanoanalysis, Graz University of Technology, 8010 Graz, Austria
| | - Weijie Pei
- School
of Materials Science & Engineering, Hubei University, 430062 Wuhan, Hubei, China
| | - Maxim N. Popov
- Materials
Center Leoben Forschung GmbH, 8700 Leoben, Austria
| | - Tobias Spitaler
- Department
of Materials Science, Montanuniversität
Leoben, 8700 Leoben, Austria
| | - Lorenz Romaner
- Materials
Center Leoben Forschung GmbH, 8700 Leoben, Austria
- Department
of Materials Science, Montanuniversität
Leoben, 8700 Leoben, Austria
| | - Yurii P. Ivanov
- Department
of Materials Science & Metallurgy, University
of Cambridge, Cambridge CB3 0FS, U.K.
- School
of Natural Sciences, Far Eastern Federal University, 690950 Vladivostok, Russia
| | - Jian Chen
- School
of Materials Science & Engineering, Hubei University, 430062 Wuhan, Hubei, China
| | - Yunbin He
- School
of Materials Science & Engineering, Hubei University, 430062 Wuhan, Hubei, China
| | - Gerald Kothleitner
- Institute
for Electron Microscopy and Nanoanalysis, Graz University of Technology, 8010 Graz, Austria
- Graz
Centre for Electron Microscopy, Austrian Cooperative Research, 8010 Graz, Austria
| | - Zaoli Zhang
- Erich
Schmid Institute of Materials Science, Austrian Academy of Sciences, 8700 Leoben, Austria
- Institute
of Material Physics, Montanuniversität Leoben, 8700 Leoben, Austria
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8
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de la Mata M, Molina SI. STEM Tools for Semiconductor Characterization: Beyond High-Resolution Imaging. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:337. [PMID: 35159686 PMCID: PMC8840450 DOI: 10.3390/nano12030337] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/13/2022] [Accepted: 01/18/2022] [Indexed: 12/10/2022]
Abstract
The smart engineering of novel semiconductor devices relies on the development of optimized functional materials suitable for the design of improved systems with advanced capabilities aside from better efficiencies. Thereby, the characterization of these materials at the highest level attainable is crucial for leading a proper understanding of their working principle. Due to the striking effect of atomic features on the behavior of semiconductor quantum- and nanostructures, scanning transmission electron microscopy (STEM) tools have been broadly employed for their characterization. Indeed, STEM provides a manifold characterization tool achieving insights on, not only the atomic structure and chemical composition of the analyzed materials, but also probing internal electric fields, plasmonic oscillations, light emission, band gap determination, electric field measurements, and many other properties. The emergence of new detectors and novel instrumental designs allowing the simultaneous collection of several signals render the perfect playground for the development of highly customized experiments specifically designed for the required analyses. This paper presents some of the most useful STEM techniques and several strategies and methodologies applied to address the specific analysis on semiconductors. STEM imaging, spectroscopies, 4D-STEM (in particular DPC), and in situ STEM are summarized, showing their potential use for the characterization of semiconductor nanostructured materials through recent reported studies.
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Affiliation(s)
- María de la Mata
- Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorganica, IMEYMAT, Universidad de Cádiz, 11510 Puerto Real, Spain;
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9
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Haselmann U, Suyolcu YE, Wu PC, Ivanov YP, Knez D, van Aken PA, Chu YH, Zhang Z. Negatively Charged In-Plane and Out-Of-Plane Domain Walls with Oxygen-Vacancy Agglomerations in a Ca-Doped Bismuth-Ferrite Thin Film. ACS APPLIED ELECTRONIC MATERIALS 2021; 3:4498-4508. [PMID: 34723187 PMCID: PMC8552442 DOI: 10.1021/acsaelm.1c00638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/12/2021] [Indexed: 06/13/2023]
Abstract
The interaction of oxygen vacancies and ferroelectric domain walls is of great scientific interest because it leads to different domain-structure behaviors. Here, we use high-resolution scanning transmission electron microscopy to study the ferroelectric domain structure and oxygen-vacancy ordering in a compressively strained Bi0.9Ca0.1FeO3-δ thin film. It was found that atomic plates, in which agglomerated oxygen vacancies are ordered, appear without any periodicity between the plates in out-of-plane and in-plane orientation. The oxygen non-stoichiometry with δ ≈ 1 in FeO2-δ planes is identical in both orientations and shows no preference. Within the plates, the oxygen vacancies form 1D channels in a pseudocubic [010] direction with a high number of vacancies that alternate with oxygen columns with few vacancies. These plates of oxygen vacancies always coincide with charged domain walls in a tail-to-tail configuration. Defects such as ordered oxygen vacancies are thereby known to lead to a pinning effect of the ferroelectric domain walls (causing application-critical aspects, such as fatigue mechanisms and countering of retention failure) and to have a critical influence on the domain-wall conductivity. Thus, intentional oxygen vacancy defect engineering could be useful for the design of multiferroic devices with advanced functionality.
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Affiliation(s)
- Ulrich Haselmann
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
| | - Y. Eren Suyolcu
- Department
of Materials Science and Engineering, Cornell
University, Ithaca, New York 14850, United States
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ping-Chun Wu
- Department
of Materials Science and Engineering, National
Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yurii P. Ivanov
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
- Department
of Materials Science & Metallurgy, University
of Cambridge, Cambridge CB3 0FS, U.K.
- School of
Natural Sciences, Far Eastern Federal University, Vladivostok 690950, Russia
| | - Daniel Knez
- Graz
Centre for Electron Microscopy, Austrian
Cooperative Research, Graz 8010, Austria
| | - Peter A. van Aken
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Ying-Hao Chu
- Department
of Materials Science and Engineering, National
Chiao Tung University, Hsinchu 30010, Taiwan
| | - Zaoli Zhang
- Erich
Schmid Institute of Materials Science, Austrian
Academy of Sciences, Leoben 8700, Austria
- Institute
of Material Physics, Montanuniversität
Leoben, Leoben 8700, Austria
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10
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Chouprik A, Negrov D, Tsymbal EY, Zenkevich A. Defects in ferroelectric HfO 2. NANOSCALE 2021; 13:11635-11678. [PMID: 34190282 DOI: 10.1039/d1nr01260f] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The discovery of ferroelectricity in polycrystalline thin films of doped HfO2 has reignited the expectations of developing competitive ferroelectric non-volatile memory devices. To date, it is widely accepted that the performance of HfO2-based ferroelectric devices during their life cycle is critically dependent on the presence of point defects as well as structural phase polymorphism, which mainly originates from defects either. The purpose of this review article is to overview the impact of defects in ferroelectric HfO2 on its functional properties and the resulting performance of memory devices. Starting from the brief summary of defects in classical perovskite ferroelectrics, we then introduce the known types of point defects in dielectric HfO2 thin films. Further, we discuss main analytical techniques used to characterize the concentration and distribution of defects in doped ferroelectric HfO2 thin films as well as at their interfaces with electrodes. The main part of the review is devoted to the recent experimental studies reporting the impact of defects in ferroelectric HfO2 structures on the performance of different memory devices. We end up with the summary and perspectives of HfO2-based ferroelectric competitive non-volatile memory devices.
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Affiliation(s)
- Anastasia Chouprik
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, Russia.
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11
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Spaldin NA, Efe I, Rossell MD, Gattinoni C. Layer and spontaneous polarizations in perovskite oxides and their interplay in multiferroic bismuth ferrite. J Chem Phys 2021; 154:154702. [PMID: 33887947 DOI: 10.1063/5.0046061] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We review the concept of surface charge, first, in the context of the polarization in ferroelectric materials and, second, in the context of layers of charged ions in ionic insulators. While the former is traditionally discussed in the ferroelectrics community and the latter in the surface science community, we remind the reader that the two descriptions are conveniently unified within the modern theory of polarization. In both cases, the surface charge leads to electrostatic instability-the so-called "polar catastrophe"-if it is not compensated, and we review the range of phenomena that arise as a result of different compensation mechanisms. We illustrate these concepts using the example of the prototypical multiferroic bismuth ferrite, BiFeO3, which is unusual in that its spontaneous ferroelectric polarization and the polarization arising from its layer charges can be of the same magnitude. As a result, for certain combinations of polarization orientation and surface termination, its surface charge is self-compensating. We use density functional calculations of BiFeO3 slabs and superlattices, analysis of high-resolution transmission electron micrographs, and examples from the literature to explore the consequences of this peculiarity.
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Affiliation(s)
- Nicola A Spaldin
- Department of Materials, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Ipek Efe
- Department of Materials, ETH Zurich, CH-8093 Zürich, Switzerland
| | - Marta D Rossell
- Electron Microscopy Center, Swiss Federal Laboratories for Materials Science and Technology, Empa, 8600 Dübendorf, Switzerland
| | - Chiara Gattinoni
- Department of Materials, ETH Zurich, CH-8093 Zürich, Switzerland
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12
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Seki T, Ikuhara Y, Shibata N. Toward quantitative electromagnetic field imaging by differential-phase-contrast scanning transmission electron microscopy. Microscopy (Oxf) 2021; 70:148-160. [PMID: 33150939 DOI: 10.1093/jmicro/dfaa065] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/26/2020] [Accepted: 10/30/2020] [Indexed: 11/14/2022] Open
Abstract
Differential-phase-contrast scanning transmission electron microscopy (DPC STEM) is a technique to directly visualize local electromagnetic field distribution inside materials and devices at very high spatial resolution. Owing to the recent progress in the development of high-speed segmented and pixelated detectors, DPC STEM now constitutes one of the major imaging modes in modern aberration-corrected STEM. While qualitative imaging of electromagnetic fields by DPC STEM is readily possible, quantitative imaging by DPC STEM is still under development because of the several fundamental issues inherent in the technique. In this report, we review the current status and future prospects of DPC STEM for quantitative electromagnetic field imaging from atomic scale to mesoscopic scale.
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Affiliation(s)
- Takehito Seki
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Yuichi Ikuhara
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, Tokyo 113-8656, Japan.,Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan
| | - Naoya Shibata
- Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, Tokyo 113-8656, Japan.,Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan.,Quantum-Phase Electronics Center (QPEC), The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
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13
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Benyettou F, Das G, Nair AR, Prakasam T, Shinde DB, Sharma SK, Whelan J, Lalatonne Y, Traboulsi H, Pasricha R, Abdullah O, Jagannathan R, Lai Z, Motte L, Gándara F, Sadler KC, Trabolsi A. Covalent Organic Framework Embedded with Magnetic Nanoparticles for MRI and Chemo-Thermotherapy. J Am Chem Soc 2020; 142:18782-18794. [PMID: 33090806 DOI: 10.1021/jacs.0c05381] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Nanoscale imine-linked covalent organic frameworks (nCOFs) were first loaded with the anticancer drug Doxorubicin (Dox), coated with magnetic iron oxide nanoparticles (γ-Fe2O3 NPs), and stabilized with a shell of poly(l-lysine) cationic polymer (PLL) for simultaneous synergistic thermo-chemotherapy treatment and MRI imaging. The pH responsivity of the resulting nanoagents (γ-SD/PLL) allowed the release of the drug selectively within the acidic microenvironment of late endosomes and lysosomes of cancer cells (pH 5.4) and not in physiological conditions (pH 7.4). γ-SD/PLL could efficiently generate high heat (48 °C) upon exposure to an alternating magnetic field due to the nCOF porous structure that facilitates the heat conduction, making γ-SD/PLL excellent heat mediators in an aqueous solution. The drug-loaded magnetic nCOF composites were cytotoxic due to the synergistic toxicity of Dox and the effects of hyperthermia in vitro on glioblastoma U251-MG cells and in vivo on zebrafish embryos, but they were not significantly toxic to noncancerous cells (HEK293). To the best of our knowledge, this is the first report of multimodal MRI probe and chemo-thermotherapeutic magnetic nCOF composites.
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Affiliation(s)
- Farah Benyettou
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Gobinda Das
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Anjana Ramdas Nair
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | | | - Digambar B Shinde
- Advanced Membranes and Porous Materials Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Kingdom of Saudi Arabia
| | - Sudhir Kumar Sharma
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Jamie Whelan
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Yoann Lalatonne
- Inserm, U1148, Laboratory for Vascular Translational Science, Université Sorbonne Paris Nord, Sorbonne Paris Cité, F-93017 Bobigny, France.,Services de Biochimie et Médecine Nucléaire, Hôpital Avicenne Assistance Publique-Hôpitaux de Paris, F-93009 Bobigny, France
| | - Hassan Traboulsi
- Department of Chemistry, College of Science, King Faisal University, P.O. Box 400, Al-Ahsa 31982, Kingdom of Saudi Arabia
| | - Renu Pasricha
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Osama Abdullah
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Ramesh Jagannathan
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Zhiping Lai
- Advanced Membranes and Porous Materials Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955, Kingdom of Saudi Arabia
| | - Laurence Motte
- Université Sorbonne Paris Nord, Laboratory for Vascular Translational Science, LVTS, INSERM, UMR 1148, F-93000 Bobigny, France
| | - Felipe Gándara
- Materials Science Institute of Madrid-CSIC, 28049 Madrid, Spain
| | - Kirsten C Sadler
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Ali Trabolsi
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
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Lim JS, Lee J, Lee BJ, Kim YJ, Park HS, Suh J, Nahm HH, Kim SW, Cho BG, Koo TY, Choi E, Kim YH, Yang CH. Harnessing the topotactic transition in oxide heterostructures for fast and high-efficiency electrochromic applications. SCIENCE ADVANCES 2020; 6:6/41/eabb8553. [PMID: 33036971 PMCID: PMC7546704 DOI: 10.1126/sciadv.abb8553] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 08/19/2020] [Indexed: 06/11/2023]
Abstract
Mobile oxygen vacancies offer a substantial potential to broaden the range of optical functionalities of complex transition metal oxides due to their high mobility and the interplay with correlated electrons. Here, we report a large electro-absorptive optical variation induced by a topotactic transition via oxygen vacancy fluidic motion in calcium ferrite with large-scale uniformity. The coloration efficiency reaches ~80 cm2 C-1, which means that a 300-nm-thick layer blocks 99% of transmitted visible light by the electrical switching. By tracking the color propagation, oxygen vacancy mobility can be estimated to be 10-8 cm2 s-1 V-1 near 300°C, which is a giant value attained due to the mosaic pseudomonoclinic film stabilized on LaAlO3 substrate. First-principles calculations reveal that the defect density modulation associated with hole charge injection causes a prominent change in electron correlation, resulting in the light absorption modulation. Our findings will pave the pathway for practical topotactic electrochromic applications.
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Affiliation(s)
- Ji Soo Lim
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea
- Center for Lattice Defectronics, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Jounghee Lee
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Byeoung Ju Lee
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - Yong-Jin Kim
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea
- Center for Lattice Defectronics, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Heung-Sik Park
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea
- Center for Lattice Defectronics, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Jeonghun Suh
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea
- Center for Lattice Defectronics, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Ho-Hyun Nahm
- Graduate School of Nanoscience and Technology, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Sang-Woo Kim
- Pohang Accelerator Laboratory, POSTECH, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Byeong-Gwan Cho
- Pohang Accelerator Laboratory, POSTECH, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Tae Yeong Koo
- Pohang Accelerator Laboratory, POSTECH, Pohang, Gyeongbuk 37673, Republic of Korea
| | - Eunjip Choi
- Department of Physics, University of Seoul, Seoul 02504, Republic of Korea
| | - Yong-Hyun Kim
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea.
- Graduate School of Nanoscience and Technology, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Chan-Ho Yang
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea.
- Center for Lattice Defectronics, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
- KAIST Institute for the NanoCentury, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea
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15
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Campanini M, Gradauskaite E, Trassin M, Yi D, Yu P, Ramesh R, Erni R, Rossell MD. Imaging and quantification of charged domain walls in BiFeO 3. NANOSCALE 2020; 12:9186-9193. [PMID: 32297890 DOI: 10.1039/d0nr01258k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Charged domain walls in ferroelectrics hold great promise for the design of novel electronic devices due to their enhanced local conductivity. In fact, charged domain walls show unique properties including the possibility of being created, moved and erased by an applied voltage. Here, we demonstrate that the charged domain walls are constituted by a core region where most of the screening charge is localized and such charge accumulation is responsible for their enhanced conductivity. In particular, the link between the local structural distortions and charge screening phenomena in 109° tail-to-tail domain walls of BiFeO3 is elucidated by a series of multiscale analysis performed by means of scanning probe techniques, including conductive atomic force microscopy (cAFM) and atomic resolution differential phase contrast scanning transmission electron microscopy (DPC-STEM). The results prove that an accumulation of oxygen vacancies occurs at the tail-to-tail domain walls as the leading charge screening process. This work constitutes a new insight in understanding the behavior of such complex systems and lays down the fundaments for their implementation into novel nanoelectronic devices.
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Affiliation(s)
- Marco Campanini
- Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstr. 129, 8600 Dübendorf, Switzerland.
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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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Song Q, Wu P, Sarkar S, Zhao Y, Liu Z. Bi 3TaO 7 film: a promising photoelectrode for photoelectrochemical water splitting. Dalton Trans 2020; 49:147-155. [PMID: 31793580 DOI: 10.1039/c9dt03953h] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Most of the transition metal bismuth salts have excellent visible absorption range and carrier transport properties due to their unique structure capable of orbits and s-p bonds. As one of the transition metal bismuth salts, Bi3TaO7 is firstly directly prepared on fluorine-doped SnO2 transparent conductive glass (FTO) as a photoanode for photoelectrochemical (PEC) water oxidation via a simple hydrothermal method using a special precursor solution. The growth mechanism of the Bi3TaO7 film is investigated in detail. Besides, the Bi3TaO7 photoanode exhibits a wide visible light response range with an optical band gap of 2.88 eV, which is useful for its PEC properties. Bi3TaO7 achieves an excellent PEC performance by tuning the calcination temperature, producing a photocurrent density of 23.0 μA cm-2 at 1.23 V vs. RHE and showing excellent stability that decays by only 2% after illumination for 6000 s. The above results indicate that Bi3TaO7 has broad application prospects in the field of PEC water oxidation.
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Affiliation(s)
- Qinggong Song
- College of Science, Civil Aviation University of China, Tianjin, 300300, China.
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18
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Feng Y, Wu J, Chi Q, Li W, Yu Y, Fei W. Defects and Aliovalent Doping Engineering in Electroceramics. Chem Rev 2020; 120:1710-1787. [DOI: 10.1021/acs.chemrev.9b00507] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Yu Feng
- Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, P. R. China
- State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P. R. China
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Jiagang Wu
- Department of Materials Science, Sichuan University, Chengdu 610064, P. R. China
| | - Qingguo Chi
- Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, P. R. China
| | - Weili Li
- State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P. R. China
| | - Yang Yu
- Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, P. R. China
| | - Weidong Fei
- State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P. R. China
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Yin L, Mi W. Progress in BiFeO 3-based heterostructures: materials, properties and applications. NANOSCALE 2020; 12:477-523. [PMID: 31850428 DOI: 10.1039/c9nr08800h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
BiFeO3-based heterostructures have attracted much attention for potential applications due to their room-temperature multiferroic properties, proper band gaps and ultrahigh ferroelectric polarization of BiFeO3, such as data storage, optical utilization in visible light regions and synapse-like function. Here, this work aims to offer a systematic review on the progress of BiFeO3-based heterostructures. In the first part, the optical, electric, magnetic, and valley properties and their interactions in BiFeO3-based heterostructures are briefly reviewed. In the second part, the morphologies of BiFeO3 and medium materials in the heterostructures are discussed. Particularly, in the third part, the physical properties and underlying mechanism in BiFeO3-based heterostructures are discussed thoroughly, such as the photovoltaic effect, electric field control of magnetism, resistance switching, and two-dimensional electron gas and valley characteristics. The fourth part illustrates the applications of BiFeO3-based heterostructures based on the materials and physical properties discussed in the second and third parts. This review also includes a future prospect, which can provide guidance for exploring novel physical properties and designing multifunctional devices.
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Affiliation(s)
- Li Yin
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology, School of Science, Tianjin University, Tianjin 300354, China.
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20
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Design and Preparation of Chitosan-Crosslinked Bismuth Ferrite/Biochar Coupled Magnetic Material for Methylene Blue Removal. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 17:ijerph17010006. [PMID: 31861304 PMCID: PMC6981408 DOI: 10.3390/ijerph17010006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 12/08/2019] [Accepted: 12/16/2019] [Indexed: 01/31/2023]
Abstract
Biochar obtained by pyrolysis of the fiber plant kenaf was mixed with bismuth ferrite (BiFeO3) in a chitosan-containing acetic acid solution, magnetized, and modified to prepare a chitosan-crosslinked BiFeO3/biochar coupled magnetic material. The adsorption properties of the composite were investigated using methylene blue dissolved in water, and the effects of external conditions, such as pH, methylene blue concentration, reaction time, and temperature, on the adsorption performance were studied. The adsorption data were fitted and analyzed with kinetic and isotherm models, and the results showed that the BiFeO3/biochar coupled magnetic material effectively adsorbed methylene blue. The amounts adsorbed onto this magnetic material increased with increasing initial methylene blue concentration, reaction time, and temperature, and the adsorption performance improved under neutral and alkaline conditions. The pseudo-first-order kinetic and Langmuir isotherm models satisfactorily fitted the adsorption data, showing that the adsorption of methylene blue involved both chemical and physical adsorption. The maximum adsorption capacity of methylene blue onto the BiFeO3/biochar coupled magnetic material reached 18.942 mg·g−1 at 25 °C, confirming the excellent dye binding activity of this material.
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Hachtel JA, Idrobo JC, Chi M. Sub-Ångstrom electric field measurements on a universal detector in a scanning transmission electron microscope. ADVANCED STRUCTURAL AND CHEMICAL IMAGING 2018; 4:10. [PMID: 30221126 PMCID: PMC6132373 DOI: 10.1186/s40679-018-0059-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 08/09/2018] [Indexed: 11/25/2022]
Abstract
Scanning transmission electron microscopy (STEM) excels in accessing atomic-scale structure and chemistry. Enhancing our ability to directly image the functionalities of local features in materials has become one of the most important topics in the future development of STEM. Recently, differential phase contrast (DPC) imaging has been utilized to map the internal electric and magnetic fields in materials from nanoscale features such as p-n junctions, skyrmions, and even from individual atoms. Here, we use an ultra-low noise SCMOS detector in as the diffraction plane camera to collect four-dimensional (4D) datasets. The high angular resolution, efficient high-SNR acquisition, and modifiability of the camera allow it to function as a universal detector, where STEM imaging configurations, such as DPC, bright field, annular bright field, and annular dark field can all be reconstructed from a single 4D dataset. By examining a distorted perovskite, DyScO3, which possesses projected lattice spacings as small as 0.83 Å, we demonstrate DPC spatial resolution almost reaching the information limit of a 100 keV electron beam. In addition, the perovskite has ordered O-coordinations with alternating octahedral tilts, which can be quantitatively measured with single degree accuracy by taking advantage of DPC's sensitivity to light atoms. The results, acquired on a standard Ronchigram camera as opposed to a specialized DPC detector, open up new opportunities to understand and design functional materials and devices that involve lattice and charge coupling at nano- and atomic-scales.
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Affiliation(s)
- Jordan A. Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Juan Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Miaofang Chi
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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