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Ojha SK, Hazra S, Bera S, Gogoi SK, Mandal P, Maity J, Gloskovskii A, Schlueter C, Karmakar S, Jain M, Banerjee S, Gopalan V, Middey S. Quantum fluctuations lead to glassy electron dynamics in the good metal regime of electron doped KTaO 3. Nat Commun 2024; 15:3830. [PMID: 38714672 PMCID: PMC11076559 DOI: 10.1038/s41467-024-47956-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 04/15/2024] [Indexed: 05/10/2024] Open
Abstract
One of the central challenges in condensed matter physics is to comprehend systems that have strong disorder and strong interactions. In the strongly localized regime, their subtle competition leads to glassy electron dynamics which ceases to exist well before the insulator-to-metal transition is approached as a function of doping. Here, we report on the discovery of glassy electron dynamics deep inside the good metal regime of an electron-doped quantum paraelectric system: KTaO3. We reveal that upon excitation of electrons from defect states to the conduction band, the excess injected carriers in the conduction band relax in a stretched exponential manner with a large relaxation time, and the system evinces simple aging phenomena-a telltale sign of glassy dynamics. Most significantly, we observe a critical slowing down of carrier dynamics below 35 K, concomitant with the onset of quantum paraelectricity in the undoped KTaO3. Our combined investigation using second harmonic generation technique, density functional theory and phenomenological modeling demonstrates quantum fluctuation-stabilized soft polar modes as the impetus for the glassy behavior. This study addresses one of the most fundamental questions regarding the potential promotion of glassiness by quantum fluctuations and opens a route for exploring glassy dynamics of electrons in a well-delocalized regime.
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Affiliation(s)
- Shashank Kumar Ojha
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India.
| | - Sankalpa Hazra
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Surajit Bera
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India
| | - Sanat Kumar Gogoi
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India
- Department of Physics, Digboi College, Digboi, 786171, India
| | - Prithwijit Mandal
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India
| | - Jyotirmay Maity
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India
| | | | | | - Smarajit Karmakar
- Tata Institute of Fundamental Research, 36/P, Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad, 500107, India
| | - Manish Jain
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India
| | - Sumilan Banerjee
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India.
| | - Venkatraman Gopalan
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Srimanta Middey
- Department of Physics, Indian Institute of Science, Bengaluru, 560012, India.
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2
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Degerman D, Goodwin CM, Lömker P, García-Martínez F, Shipilin M, Gloskovskii A, Nilsson A. Demonstrating Pressure Jumping as a Tool to Address the Pressure Gap in High Pressure Photoelectron Spectroscopy of CO and CO 2 Hydrogenation on Rh(211). Chemphyschem 2024; 25:e202300523. [PMID: 37877432 DOI: 10.1002/cphc.202300523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 10/24/2023] [Accepted: 10/25/2023] [Indexed: 10/26/2023]
Abstract
Operando probing by x-ray photoelectron spectroscopy (XPS) of certain hydrogenation reactions are often limited by the scattering of photoelectrons in the gas phase. This work describes a method designed to partially circumvent this so called pressure gap. By performing a rapid switch from a high pressure (where acquisition is impossible) to a lower pressure we can for a short while probe a "remnant" of the high pressure surface as well as the time dynamics during the re-equilibration to the new pressure. This methodology is demonstrated using the CO2 and the CO hydrogenation reaction over Rh(211). In the CO2 hydrogenation reaction, the remnant surface of a 2 bar pressure shows an adsorbate distribution which favors chemisorbed CHx adsorbates over chemisorbed CO. This contrasts against previous static operando spectra acquired at lower pressures. Furthermore, the pressure jumping method yields a faster acquisition and more detailed spectra than static operando measurements above 1 bar. In the CO hydrogenation reaction, we observe that CHx accumulated faster during the 275 mbar low pressure regime, and different hypotheses are presented regarding this observation.
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Affiliation(s)
- David Degerman
- Department of Physics, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, 114 21, Stockholm, Sweden
| | - Christopher M Goodwin
- Department of Physics, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, 114 21, Stockholm, Sweden
- Present Address: ALBA Synchrotron Light Facility, Carrer de la Llum 2, 26, 08290, Cerdanyola del Vallés, Spain
| | - Patrick Lömker
- Department of Physics, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, 114 21, Stockholm, Sweden
| | | | - Mikhail Shipilin
- Department of Physics, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, 114 21, Stockholm, Sweden
| | - Andrei Gloskovskii
- Deutsches Elektronen Synchrotron DESY, Notkestraße 85, 226 07, Hamburg, Germany
| | - Anders Nilsson
- Department of Physics, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, 114 21, Stockholm, Sweden
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3
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Mondal D, Mahapatra SR, Derrico AM, Rai RK, Paudel JR, Schlueter C, Gloskovskii A, Banerjee R, Hariki A, DeGroot FMF, Sarma DD, Narayan A, Nukala P, Gray AX, Aetukuri NPB. Modulation-doping a correlated electron insulator. Nat Commun 2023; 14:6210. [PMID: 37798279 PMCID: PMC10556139 DOI: 10.1038/s41467-023-41816-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 09/13/2023] [Indexed: 10/07/2023] Open
Abstract
Correlated electron materials (CEMs) host a rich variety of condensed matter phases. Vanadium dioxide (VO2) is a prototypical CEM with a temperature-dependent metal-to-insulator (MIT) transition with a concomitant crystal symmetry change. External control of MIT in VO2-especially without inducing structural changes-has been a long-standing challenge. In this work, we design and synthesize modulation-doped VO2-based thin film heterostructures that closely emulate a textbook example of filling control in a correlated electron insulator. Using a combination of charge transport, hard X-ray photoelectron spectroscopy, and structural characterization, we show that the insulating state can be doped to achieve carrier densities greater than 5 × 1021 cm-3 without inducing any measurable structural changes. We find that the MIT temperature (TMIT) continuously decreases with increasing carrier concentration. Remarkably, the insulating state is robust even at doping concentrations as high as ~0.2 e-/vanadium. Finally, our work reveals modulation-doping as a viable method for electronic control of phase transitions in correlated electron oxides with the potential for use in future devices based on electric-field controlled phase transitions.
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Affiliation(s)
- Debasish Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Smruti Rekha Mahapatra
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | | | - Rajeev Kumar Rai
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, Karnataka, India
| | - Jay R Paudel
- Department of Physics, Temple University, Philadelphia, PA, USA
| | | | | | - Rajdeep Banerjee
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Atsushi Hariki
- Department of Physics and Electronics, Graduate School of Engineering, Osaka Metropolitan University, Osaka, Japan
| | - Frank M F DeGroot
- Utrecht University, Inorganic Chemistry and Catalysis Group Universiteitsweg 99, Utrecht, The Netherlands
| | - D D Sarma
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Awadhesh Narayan
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India
| | - Pavan Nukala
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, Karnataka, India
| | - Alexander X Gray
- Department of Physics, Temple University, Philadelphia, PA, USA.
| | - Naga Phani B Aetukuri
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India.
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4
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Datta S, Prakash Pandeya R, Bikash Dey A, Gloskovskii A, Schlueter C, Peixoto TRF, Singh A, Thamizhavel A, Maiti K. Layer-resolved electronic behavior in a Kondo lattice system, CeAgAs 2. J Phys Condens Matter 2023; 35:235601. [PMID: 36940482 DOI: 10.1088/1361-648x/acc5c9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 03/20/2023] [Indexed: 06/18/2023]
Abstract
We investigate the electronic structure of an antiferromagnetic Kondo lattice system CeAgAs2employing hardx-ray photoemission spectroscopy. CeAgAs2, an orthorhombic variant of HfCuSi2structure, exhibits antiferromagnetic ground state, Kondo like resistivity upturn and compensation of magnetic moments at low temperatures. The photoemission spectra obtained at different photon energies suggest termination of the cleaved surface at cis-trans-As layers. The depth-resolved data show significant surface-bulk differences in the As and Ce core level spectra. The As 2pbulk spectrum shows distinct two peaks corresponding to two different As layers. The peak at higher binding energy correspond to cis-trans-As layers and is weakly hybridized with the adjacent Ce layers. The As layers between Ce and Ag-layers possess close to trivalent configuration due to strong hybridization with the neighboring atoms and the corresponding feature appear at lower binding energy. Ce 3dcore level spectra show multiple features reflecting strong Ce-As hybridization and strong correlation. Intensef0peak is observed in the surface spectrum while it is insignificant in the bulk. In addition, we observe a features at binding energy lower than the well-screened feature indicating the presence of additional interactions. This feature becomes more intense in the bulk spectra suggesting it to be a bulk property. Increase in temperature leads to a spectral weight transfer to higher binding energies in the core level spectra and a depletion of spectral intensity at the Fermi level as expected in a Kondo material. These results reveal interesting surface-bulk differences, complex interplay of intra- and inter-layer covalency, and electron correlation in the electronic structure of this novel Kondo lattice system.
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Affiliation(s)
- Sawani Datta
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Ram Prakash Pandeya
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Arka Bikash Dey
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - A Gloskovskii
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - C Schlueter
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - T R F Peixoto
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Ankita Singh
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - A Thamizhavel
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Kalobaran Maiti
- Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
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5
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Kohantorabi M, Wagstaffe M, Creutzburg M, Ugolotti A, Kulkarni S, Jeromin A, Krekeler T, Feuerherd M, Herrmann A, Ebert G, Protzer U, Guédez G, Löw C, Thuenauer R, Schlueter C, Gloskovskii A, Keller TF, Di Valentin C, Stierle A, Noei H. Adsorption and Inactivation of SARS-CoV-2 on the Surface of Anatase TiO 2(101). ACS Appl Mater Interfaces 2023; 15:8770-8782. [PMID: 36723177 DOI: 10.1021/acsami.2c22078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
We investigated the adsorption of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), the virus responsible for the current pandemic, on the surface of the model catalyst TiO2(101) using atomic force microscopy, transmission electron microscopy, fluorescence microscopy, and X-ray photoelectron spectroscopy, accompanied by density functional theory calculations. Three different methods were employed to inactivate the virus after it was loaded on the surface of TiO2(101): (i) ethanol, (ii) thermal, and (iii) UV treatments. Microscopic studies demonstrate that the denatured spike proteins and other proteins in the virus structure readsorb on the surface of TiO2 under thermal and UV treatments. The interaction of the virus with the surface of TiO2 was different for the thermally and UV treated samples compared to the sample inactivated via ethanol treatment. AFM and TEM results on the UV-treated sample suggested that the adsorbed viral particles undergo damage and photocatalytic oxidation at the surface of TiO2(101) which can affect the structural proteins of SARS-CoV-2 and denature the spike proteins in 30 min. The role of Pd nanoparticles (NPs) was investigated in the interaction between SARS-CoV-2 and TiO2(101). The presence of Pd NPs enhanced the adsorption of the virus due to the possible interaction of the spike protein with the NPs. This study is the first investigation of the interaction of SARS-CoV-2 with the surface of single crystalline TiO2(101) as a potential candidate for virus deactivation applications. Clarification of the interaction of the virus with the surface of semiconductor oxides will aid in obtaining a deeper understanding of the chemical processes involved in photoinactivation of microorganisms, which is important for the design of effective photocatalysts for air purification and self-cleaning materials.
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Affiliation(s)
- Mona Kohantorabi
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
| | - Michael Wagstaffe
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
| | - Marcus Creutzburg
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
| | - Aldo Ugolotti
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, Via Cozzi 55, Milano 20125, Italy
| | - Satishkumar Kulkarni
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
| | - Arno Jeromin
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
| | - Tobias Krekeler
- Electron Microscopy Unit, Hamburg University of Technology, Eissendorfer Strasse 42, Hamburg 21073, Germany
| | - Martin Feuerherd
- Institute of Virology, Technical University of Munich/Helmholtz Munich, Munich 81675, Germany
- Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States
| | - Alexander Herrmann
- Institute of Virology, Helmholtz Munich, Ingolstädter Landstraße 1, Neuherberg 85764, Germany
| | - Gregor Ebert
- Institute of Virology, Technical University of Munich/Helmholtz Munich, Munich 81675, Germany
| | - Ulrike Protzer
- Institute of Virology, Technical University of Munich/Helmholtz Munich, Munich 81675, Germany
| | - Gabriela Guédez
- Centre for Structural Systems Biology (CSSB), Deutsches Elektronen-Synchrotron (DESY), EMBL Hamburg, Notkestr. 85, Hamburg 22607, Germany
| | - Christian Löw
- Centre for Structural Systems Biology (CSSB), Deutsches Elektronen-Synchrotron (DESY), EMBL Hamburg, Notkestr. 85, Hamburg 22607, Germany
| | - Roland Thuenauer
- Technology Platform Light Microscopy and Image Analysis (TP MIA), Leibniz Institute for Experimental Virology (HPI), Hamburg 20251, Germany
- Centre for Structural Systems Biology (CSSB), Notkestr. 85, Hamburg 22607, Germany
| | - Christoph Schlueter
- Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
| | - Andrei Gloskovskii
- Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
| | - Thomas F Keller
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
- Department of Physics, University of Hamburg, Notkestraße 9-11, Hamburg 22607, Germany
| | - Cristiana Di Valentin
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, Via Cozzi 55, Milano 20125, Italy
| | - Andreas Stierle
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
- Department of Physics, University of Hamburg, Notkestraße 9-11, Hamburg 22607, Germany
| | - Heshmat Noei
- Center for X-ray and Nano Science (CXNS), Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, Hamburg 22607, Germany
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6
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Telang P, Bandyopadhyay A, Mishra K, Rout D, Bag R, Gloskovskii A, Matveyev Y, Singh S. X-ray photoemission and absorption study of the pyrochlore iridates (Eu1-xBi x) 2Ir 2O 7, 0 ⩽ x ⩽ 1. J Phys Condens Matter 2022; 34:395601. [PMID: 35817027 DOI: 10.1088/1361-648x/ac8038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 07/11/2022] [Indexed: 06/15/2023]
Abstract
The pyrochlore iridates (Eu1-xBix)2Ir2O7(0⩽x⩽1) undergo an anomalous negative lattice expansion for small Bi-doping (x⩽0.035) (region I) and a normal lattice expansion forx⩾0.1(region II); this is accompanied by a transition from an insulating (and magnetically ordered) to a metallic (and with no magnetic ordering) ground state. Here, we investigate (Eu1-xBix)2Ir2O7(0⩽x⩽1) using hard x-ray photoemission spectroscopy and x-ray absorption fine structure (XAFS) spectroscopy. By analyzing the Eu-L3, Ir-L3and Bi-L2&L3edges x-ray absorption near edge structure spectra and Eu-3dcore-level XPS spectra, we show that the metal cations retain their nominal valence, namely, Ir4+, Bi3+and Eu3+, respectively, throughout the series. The Ir-4fand Bi-4fcore-level XPS spectra consist of screened and unscreened doublets. The unscreened component is dominant In the insulating range (x⩽0.035), and in the metallic region (x⩾0.1), the screened component dominates the spectra. The Eu-3dcore-level spectra remain invariant under Bi doping. The extended XAFS data show that the coordination around the Ir remains well preserved throughout the series. The evolution of the valence band spectra near the Fermi energy with increasing Bi doping indicates the presence of strong Ir(5d)-Bi(6p) hybridization which drives the metal-to-insulator transition.
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Affiliation(s)
- Prachi Telang
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - Abhisek Bandyopadhyay
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - Kshiti Mishra
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - Dibyata Rout
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - Rabindranath Bag
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
| | - A Gloskovskii
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Yu Matveyev
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Surjeet Singh
- Department of Physics, Indian Institute of Science Education and Research, Pune, Maharashtra 411008, India
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7
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Serrano-Sanchez F, Yao M, He B, Chen D, Gloskovskii A, Fedorov A, Auffermann G, Liu E, Burkhardt U, Fecher GH, Fu C, Felser C, Pan Y. Electronic structure and low-temperature thermoelectric transport of TiCoSb single crystals. Nanoscale 2022; 14:10067-10074. [PMID: 35791918 PMCID: PMC9302267 DOI: 10.1039/d2nr02556f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 06/20/2022] [Indexed: 06/15/2023]
Abstract
Band structure engineering has a strong beneficial impact on thermoelectric performance, where theoretical methods dominate the investigation of electronic structures. Here, we use angle-resolved photoemission spectroscopy (ARPES) to analyze the electronic structure and report on the thermoelectric transport properties of half-Heusler TiCoSb high-quality single crystals. High degeneracy of the valence bands at the L and Γ band maximum points was observed, which provides a band-convergence scenario for the thermoelectric performance of TiCoSb. Previous efforts have shown how crystallographic defects play an important role in TiCoSb transport properties, while the intrinsic properties remain elusive. Using hard X-ray photoelectron spectroscopy (HAXPES), we discard the presence of interstitial defects that could induce in-gap states near the valence band in our crystals. Contrary to polycrystalline reports, intrinsic TiCoSb exhibits p-type transport, albeit defects still affect the carrier concentration. In two initially identical p-type TiCoSb crystal batches, distinct metallic and semiconductive behaviors were found owing to defects not noticeable by elemental analysis. A varying Seebeck effective mass is consistent with the change at the Fermi level within this band convergence picture. This report tackles the direct investigation of the electronic structure of TiCoSb and reveals new insights and the strong impact of point defects on the optimization of thermoelectric properties.
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Affiliation(s)
| | - Mengyu Yao
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
| | - Bin He
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
| | - Dong Chen
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
| | | | - Alexander Fedorov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
- Institute for Solid State Research, Leibniz IFW Dresden, 01069 Dresden, Germany
| | - Gudrun Auffermann
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
| | - Enke Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
| | - Ulrich Burkhardt
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
| | - Gerhard H Fecher
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
| | - Chenguang Fu
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, 310027 Hangzhou, China
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
| | - Yu Pan
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
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8
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Shimura Y, Wörl A, Sundermann M, Tsuda S, Adroja DT, Bhattacharyya A, Strydom AM, Hillier AD, Pratt FL, Gloskovskii A, Severing A, Onimaru T, Gegenwart P, Takabatake T. Antiferromagnetic Correlations in Strongly Valence Fluctuating CeIrSn. Phys Rev Lett 2021; 126:217202. [PMID: 34114835 DOI: 10.1103/physrevlett.126.217202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 04/29/2021] [Indexed: 06/12/2023]
Abstract
CeIrSn with a quasikagome Ce lattice in the hexagonal basal plane is a strongly valence fluctuating compound, as we confirm by hard x-ray photoelectron spectroscopy and inelastic neutron scattering, with a high Kondo temperature of T_{K}∼480 K. We report a negative in-plane thermal expansion α/T below 2 K, which passes through a broad minimum near 0.75 K. Volume and a-axis magnetostriction for B∥a are markedly negative at low fields and change sign before a sharp metamagnetic anomaly at 6 T. These behaviors are unexpected for Ce-based intermediate valence systems, which should feature positive expansivity. Rather they point towards antiferromagnetic correlations at very low temperatures. This is supported by muon spin relaxation measurements down to 0.1 K, which provide microscopic evidence for a broad distribution of internal magnetic fields. Comparison with isostructural CeRhSn suggests that these antiferromagnetic correlations emerging at T≪T_{K} result from geometrical frustration.
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Affiliation(s)
- Y Shimura
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | - A Wörl
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - M Sundermann
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - S Tsuda
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | - D T Adroja
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon OX11 0QX, United Kingdom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - A Bhattacharyya
- Department of Physics, Ramakrishna Mission Vivekananda Educational and Research Institute, Belur Math, Howrah 711202, West Bengal, India
| | - A M Strydom
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, PO Box 524, Auckland Park 2006, South Africa
| | - A D Hillier
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon OX11 0QX, United Kingdom
| | - F L Pratt
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot Oxon OX11 0QX, United Kingdom
| | - A Gloskovskii
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - A Severing
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Institute of Physics II, University of Cologne, 50937 Cologne, Germany
| | - T Onimaru
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | - P Gegenwart
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - T Takabatake
- Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
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9
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Schönhense G, Kutnyakhov D, Pressacco F, Heber M, Wind N, Agustsson SY, Babenkov S, Vasilyev D, Fedchenko O, Chernov S, Rettig L, Schönhense B, Wenthaus L, Brenner G, Dziarzhytski S, Palutke S, Mahatha SK, Schirmel N, Redlin H, Manschwetus B, Hartl I, Matveyev Y, Gloskovskii A, Schlueter C, Shokeen V, Duerr H, Allison TK, Beye M, Rossnagel K, Elmers HJ, Medjanik K. Suppression of the vacuum space-charge effect in fs-photoemission by a retarding electrostatic front lens. Rev Sci Instrum 2021; 92:053703. [PMID: 34243258 DOI: 10.1063/5.0046567] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 04/04/2021] [Indexed: 06/13/2023]
Abstract
The performance of time-resolved photoemission experiments at fs-pulsed photon sources is ultimately limited by the e-e Coulomb interaction, downgrading energy and momentum resolution. Here, we present an approach to effectively suppress space-charge artifacts in momentum microscopes and photoemission microscopes. A retarding electrostatic field generated by a special objective lens repels slow electrons, retaining the k-image of the fast photoelectrons. The suppression of space-charge effects scales with the ratio of the photoelectron velocities of fast and slow electrons. Fields in the range from -20 to -1100 V/mm for Ekin = 100 eV to 4 keV direct secondaries and pump-induced slow electrons back to the sample surface. Ray tracing simulations reveal that this happens within the first 40 to 3 μm above the sample surface for Ekin = 100 eV to 4 keV. An optimized front-lens design allows switching between the conventional accelerating and the new retarding mode. Time-resolved experiments at Ekin = 107 eV using fs extreme ultraviolet probe pulses from the free-electron laser FLASH reveal that the width of the Fermi edge increases by just 30 meV at an incident pump fluence of 22 mJ/cm2 (retarding field -21 V/mm). For an accelerating field of +2 kV/mm and a pump fluence of only 5 mJ/cm2, it increases by 0.5 eV (pump wavelength 1030 nm). At the given conditions, the suppression mode permits increasing the slow-electron yield by three to four orders of magnitude. The feasibility of the method at high energies is demonstrated without a pump beam at Ekin = 3830 eV using hard x rays from the storage ring PETRA III. The approach opens up a previously inaccessible regime of pump fluences for photoemission experiments.
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Affiliation(s)
- G Schönhense
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - D Kutnyakhov
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - F Pressacco
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - M Heber
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - N Wind
- University of Hamburg, Institut für Experimentalphysik, D-22761 Hamburg, Germany
| | - S Y Agustsson
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - S Babenkov
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - D Vasilyev
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - O Fedchenko
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - S Chernov
- Departments of Chemistry and Physics, Stony Brook University, Stony Brook, New York 11790-3400, USA
| | - L Rettig
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin, Germany
| | - B Schönhense
- Department of Bioengineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - L Wenthaus
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - G Brenner
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - S Dziarzhytski
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - S Palutke
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - S K Mahatha
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - N Schirmel
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - H Redlin
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - B Manschwetus
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - I Hartl
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - Yu Matveyev
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - A Gloskovskii
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - C Schlueter
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - V Shokeen
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - H Duerr
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 75120 Uppsala, Sweden
| | - T K Allison
- Departments of Chemistry and Physics, Stony Brook University, Stony Brook, New York 11790-3400, USA
| | - M Beye
- Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - K Rossnagel
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, D-22607 Hamburg, Germany
| | - H J Elmers
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - K Medjanik
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
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10
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Agustsson SY, Chernov SV, Medjanik K, Babenkov S, Fedchenko O, Vasilyev D, Schlueter C, Gloskovskii A, Matveyev Y, Kliemt K, Krellner C, Demsar J, Schönhense G, Elmers HJ. Temperature-dependent change of the electronic structure in the Kondo lattice system YbRh 2Si 2. J Phys Condens Matter 2021; 33:205601. [PMID: 33561846 DOI: 10.1088/1361-648x/abe479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 02/09/2021] [Indexed: 06/12/2023]
Abstract
The heavy-fermion behavior in intermetallic compounds manifests itself in a quenching of local magnetic moments by developing Kondo spin-singlet many-body states combined with a drastic increase of the effective mass of conduction electrons, which occurs below the lattice Kondo temperatureTK. This behavior is caused by interactions between the strongly localized 4felectrons and itinerant electrons. A controversially discussed question in this context is how the localized electronic states contribute to the Fermi surface upon changing the temperature. One expects that hybridization between the local moments and the itinerant electrons leads to a transition from a small Fermi surface in a non-coherent regime at high temperatures to a large Fermi surface once the coherent Kondo lattice regime is realized belowTK. We demonstrate, using hard x-ray angle-resolved photoemission spectroscopy that the electronic structure of the prototypical heavy fermion compound YbRh2Si2changes with temperature between 100 and 200 K, i.e. far above the Kondo temperature,TK= 25 K, of this system. Our results suggest a transition from a small to a large Fermi surface with decreasing temperature. This result is inconsistent with the prediction of the dynamical mean-field periodic Anderson model and supports the idea of an independent energy scale governing the change of band dispersion.
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Affiliation(s)
- S Y Agustsson
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - S V Chernov
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - K Medjanik
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - S Babenkov
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - O Fedchenko
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - D Vasilyev
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - C Schlueter
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - A Gloskovskii
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Yu Matveyev
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - K Kliemt
- Physikalisches Institut, Goethe Universität Frankfurt, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - C Krellner
- Physikalisches Institut, Goethe Universität Frankfurt, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - J Demsar
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - G Schönhense
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
| | - H-J Elmers
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, 55128 Mainz, Germany
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11
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Sahoo L, Mondal S, Beena NC, Gloskovskii A, Manju U, Topwal D, Gautam UK. 3D Porous Polymeric-Foam-Supported Pd Nanocrystal as a Highly Efficient and Recyclable Catalyst for Organic Transformations. ACS Appl Mater Interfaces 2021; 13:10120-10130. [PMID: 33617231 DOI: 10.1021/acsami.1c00497] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The efficient recovery of noble metal nanocrystals used in heterogeneous organic transformations has remained a significant challenge, hindering their use in industry. Herein, highly catalytic Pd nanoparticles (NPs) were first prepared having a yield of >98% by a novel hydrothermal method using PVP as the reducing cum stabilizing agent that exhibited excellent turnover frequencies of ∼38,000 h-1 for Suzuki-Miyaura cross-coupling and ∼1200 h-1 for catalytic reduction of nitroarene compounds in a benign aqueous reaction medium. The Pd NPs were more efficient for cross-coupling of aryl compounds with electron-donating substituents than with electron-donating ones. Further, to improve their recyclability, a strategy was developed to embed these Pd NPs on mechanically robust polyurethane foam (PUF) for the first time and a "dip-catalyst" (Pd-PUF) containing 3D interconnected 100-500 μm pores was constructed. The PUF was chosen as the support with an expectation to reduce the fabrication cost of the "dip-catalyst" as the production of PUF is already commercialized. Pd-PUF could be easily separated from the reaction aliquot and reused without any loss of activity because the leaching of Pd NPs was found to be negligible in the various reaction mixtures. We show that the Pd-PUF could be reused for over 50 catalytic cycles maintaining a similar activity. We further demonstrate a scale-up reaction with a single-reaction 1.5 g yield for the Suzuki-Miyaura cross-coupling reaction.
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Affiliation(s)
- Lipipuspa Sahoo
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, Sector 81, Mohali, SAS, Nagar, Punjab 140306, India
| | - Sanjit Mondal
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, Sector 81, Mohali, SAS, Nagar, Punjab 140306, India
| | - Nayana Christudas Beena
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, Sector 81, Mohali, SAS, Nagar, Punjab 140306, India
| | - A Gloskovskii
- DESY Photon Science, Deutsches Elektronen-Synchrotron, 22603 Hamburg, Germany
| | - Unnikrishnan Manju
- CSIR -Institute of Minerals and Materials Technology, Bhubaneswar 751013, India
| | - D Topwal
- Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, India
- Training School Complex, Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400094, India
| | - Ujjal K Gautam
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, Sector 81, Mohali, SAS, Nagar, Punjab 140306, India
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12
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Swekis P, Sukhanov AS, Chen YC, Gloskovskii A, Fecher GH, Panagiotopoulos I, Sichelschmidt J, Ukleev V, Devishvili A, Vorobiev A, Inosov DS, Goennenwein STB, Felser C, Markou A. Magnetic and Electronic Properties of Weyl Semimetal Co 2MnGa Thin Films. Nanomaterials (Basel) 2021; 11:251. [PMID: 33477868 PMCID: PMC7832844 DOI: 10.3390/nano11010251] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 11/18/2022]
Abstract
Magnetic Weyl semimetals are newly discovered quantum materials with the potential for use in spintronic applications. Of particular interest is the cubic Heusler compound Co2MnGa due to its inherent magnetic and topological properties. This work presents the structural, magnetic and electronic properties of magnetron co-sputtered Co2MnGa thin films, with thicknesses ranging from 10 to 80 nm. Polarized neutron reflectometry confirmed a uniform magnetization through the films. Hard x-ray photoelectron spectroscopy revealed a high degree of spin polarization and localized (itinerant) character of the Mn d (Co d) valence electrons and accompanying magnetic moments. Further, broadband and field orientation-dependent ferromagnetic resonance measurements indicated a relation between the thickness-dependent structural and magnetic properties. The increase of the tensile strain-induced tetragonal distortion in the thinner films was reflected in an increase of the cubic anisotropy term and a decrease of the perpendicular uniaxial term. The lattice distortion led to a reduction of the Gilbert damping parameter and the thickness-dependent film quality affected the inhomogeneous linewidth broadening. These experimental findings will enrich the understanding of the electronic and magnetic properties of magnetic Weyl semimetal thin films.
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Affiliation(s)
- Peter Swekis
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
| | - Aleksandr S. Sukhanov
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
| | - Yi-Cheng Chen
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
| | | | - Gerhard H. Fecher
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
| | - Ioannis Panagiotopoulos
- Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece;
| | - Jörg Sichelschmidt
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
| | - Victor Ukleev
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland;
| | - Anton Devishvili
- Institut Laue Langevin, 38000 Grenoble, France;
- Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden;
| | - Alexei Vorobiev
- Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden;
| | - Dmytro S. Inosov
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
| | - Sebastian T. B. Goennenwein
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
- Center for Transport and Devices of Emergent Materials, Technische Universität Dresden, 01062 Dresden, Germany
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
| | - Anastasios Markou
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
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13
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Elmers HJ, Chernov SV, D'Souza SW, Bommanaboyena SP, Bodnar SY, Medjanik K, Babenkov S, Fedchenko O, Vasilyev D, Agustsson SY, Schlueter C, Gloskovskii A, Matveyev Y, Strocov VN, Skourski Y, Šmejkal L, Sinova J, Minár J, Kläui M, Schönhense G, Jourdan M. Néel Vector Induced Manipulation of Valence States in the Collinear Antiferromagnet Mn 2Au. ACS Nano 2020; 14:17554-17564. [PMID: 33236903 DOI: 10.1021/acsnano.0c08215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The coupling of real and momentum space is utilized to tailor electronic properties of the collinear metallic antiferromagnet Mn2Au by aligning the real space Néel vector indicating the direction of the staggered magnetization. Pulsed magnetic fields of 60 T were used to orient the sublattice magnetizations of capped epitaxial Mn2Au(001) thin films perpendicular to the applied field direction by a spin-flop transition. The electronic structure and its corresponding changes were investigated by angular-resolved photoemission spectroscopy with photon energies in the vacuum-ultraviolet, soft, and hard X-ray range. The results reveal an energetic rearrangement of conduction electrons propagating perpendicular to the Néel vector. They confirm previous predictions on the origin of the Néel spin-orbit torque and anisotropic magnetoresistance in Mn2Au and reflect the combined antiferromagnetic and spin-orbit interaction in this compound leading to inversion symmetry breaking.
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Affiliation(s)
- H J Elmers
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - S V Chernov
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - S W D'Souza
- New Technologies-Research Centre, University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic
| | - S P Bommanaboyena
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - S Yu Bodnar
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - K Medjanik
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - S Babenkov
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - O Fedchenko
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - D Vasilyev
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - S Y Agustsson
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - C Schlueter
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - A Gloskovskii
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Yu Matveyev
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - V N Strocov
- Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen-PSI, Switzerland
| | - Y Skourski
- Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - L Šmejkal
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
- Institute of Physics Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic
| | - J Sinova
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
- Institute of Physics Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic
| | - J Minár
- New Technologies-Research Centre, University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic
| | - M Kläui
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - G Schönhense
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
| | - M Jourdan
- Institut für Physik, Johannes Gutenberg-Universität, Staudingerweg 7, D-55099 Mainz, Germany
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14
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Amorese A, Sundermann M, Leedahl B, Marino A, Takegami D, Gretarsson H, Gloskovskii A, Schlueter C, Haverkort MW, Huang Y, Szlawska M, Kaczorowski D, Ran S, Maple MB, Bauer ED, Leithe-Jasper A, Hansmann P, Thalmeier P, Tjeng LH, Severing A. From antiferromagnetic and hidden order to Pauli paramagnetism in U M 2Si 2 compounds with 5 f electron duality. Proc Natl Acad Sci U S A 2020; 117:30220-30227. [PMID: 33203673 PMCID: PMC7720184 DOI: 10.1073/pnas.2005701117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Using inelastic X-ray scattering beyond the dipole limit and hard X-ray photoelectron spectroscopy we establish the dual nature of the U [Formula: see text] electrons in U[Formula: see text] (M = Pd, Ni, Ru, Fe), regardless of their degree of delocalization. We have observed that the compounds have in common a local atomic-like state that is well described by the U [Formula: see text] configuration with the [Formula: see text] and [Formula: see text] quasi-doublet symmetry. The amount of the U 5[Formula: see text] configuration, however, varies considerably across the U[Formula: see text] series, indicating an increase of U 5f itineracy in going from M = Pd to Ni to Ru and to the Fe compound. The identified electronic states explain the formation of the very large ordered magnetic moments in [Formula: see text] and [Formula: see text], the availability of orbital degrees of freedom needed for the hidden order in [Formula: see text] to occur, as well as the appearance of Pauli paramagnetism in [Formula: see text] A unified and systematic picture of the U[Formula: see text] compounds may now be drawn, thereby providing suggestions for additional experiments to induce hidden order and/or superconductivity in U compounds with the tetragonal body-centered [Formula: see text] structure.
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Affiliation(s)
- Andrea Amorese
- Institute of Physics II, University of Cologne, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Martin Sundermann
- Institute of Physics II, University of Cologne, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Brett Leedahl
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Andrea Marino
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Daisuke Takegami
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Hlynur Gretarsson
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Positron-Elektron-Tandem-Ring-Anlage III (PETRA III), Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Andrei Gloskovskii
- Positron-Elektron-Tandem-Ring-Anlage III (PETRA III), Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Christoph Schlueter
- Positron-Elektron-Tandem-Ring-Anlage III (PETRA III), Deutsches Elektronen-Synchrotron, 22607 Hamburg, Germany
| | - Maurits W Haverkort
- Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Yingkai Huang
- van der Waals-Zeeman Institute, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Maria Szlawska
- Institute of Low Temperature & Structure Research, Polish Academy of Science, 50-950 Wroclaw, Poland
| | - Dariusz Kaczorowski
- Institute of Low Temperature & Structure Research, Polish Academy of Science, 50-950 Wroclaw, Poland
| | - Sheng Ran
- Department of Physics, University of California San Diego, La Jolla, CA 92093
| | - M Brian Maple
- Department of Physics, University of California San Diego, La Jolla, CA 92093
| | - Eric D Bauer
- MPA-Q, Los Alamos National Laboratory, Los Alamos, NM 87545
| | | | - Philipp Hansmann
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Department of Physics, University of Erlangen-Nuremberg, 91058 Erlangen, Germany
| | - Peter Thalmeier
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Liu Hao Tjeng
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Andrea Severing
- Institute of Physics II, University of Cologne, 50937 Cologne, Germany;
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
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15
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Matveyev Y, Mikheev V, Negrov D, Zarubin S, Kumar A, Grimley ED, LeBeau JM, Gloskovskii A, Tsymbal EY, Zenkevich A. Polarization-dependent electric potential distribution across nanoscale ferroelectric Hf 0.5Zr 0.5O 2 in functional memory capacitors. Nanoscale 2019; 11:19814-19822. [PMID: 31624822 DOI: 10.1039/c9nr05904k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The emergence of ferroelectricity in nanometer-thick films of doped hafnium oxide (HfO2) makes this material a promising candidate for use in Si-compatible non-volatile memory devices. The switchable polarization of ferroelectric HfO2 controls functional properties of these devices through the electric potential distribution across the capacitor. The experimental characterization of the local electric potential at the nanoscale has not so far been realized in practice. Here, we develop a new methodology which allows us, for the first time, to experimentally quantify the polarization-dependent potential profile across few-nanometer-thick ferroelectric Hf0.5Zr0.5O2 thin films. Using a standing-wave excitation mode in synchrotron based hard X-ray photoemission spectroscopy, we depth-selectively probe TiN/Hf0.5Zr0.5O2/W prototype memory capacitors and determine the local electrostatic potential by analyzing the core-level line shifts. We find that the electric potential profile across the Hf0.5Zr0.5O2 layer is non-linear and changes with in situ polarization switching. Combined with our scanning transmission electron microscopy data and theoretical modeling, we interpret the observed non-linear potential behavior in terms of defects in Hf0.5Zr0.5O2, at both interfaces, and their charge state modulated by the ferroelectric polarization. Our results provide an important insight into the intrinsic electronic properties of HfO2 based ferroelectric capacitors and are essential for engineering memory devices.
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Affiliation(s)
- Yury Matveyev
- Deutsches Elektronen-Synchrotron, 85 Notkestraße, Hamburg, D-22607, Germany and Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Vitalii Mikheev
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Dmitry Negrov
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Sergei Zarubin
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Abinash Kumar
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA
| | - Everett D Grimley
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA
| | - James M LeBeau
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA
| | - Andrei Gloskovskii
- Deutsches Elektronen-Synchrotron, 85 Notkestraße, Hamburg, D-22607, Germany
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588, USA and Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Andrei Zenkevich
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
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16
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Medjanik K, Babenkov SV, Chernov S, Vasilyev D, Schönhense B, Schlueter C, Gloskovskii A, Matveyev Y, Drube W, Elmers HJ, Schönhense G. Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording. J Synchrotron Radiat 2019; 26:1996-2012. [PMID: 31721745 PMCID: PMC6853377 DOI: 10.1107/s1600577519012773] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 09/13/2019] [Indexed: 05/27/2023]
Abstract
An alternative approach to hard-X-ray photoelectron spectroscopy (HAXPES) has been established. The instrumental key feature is an increase of the dimensionality of the recording scheme from 2D to 3D. A high-energy momentum microscope detects electrons with initial kinetic energies up to 8 keV with a k-resolution of 0.025 Å-1, equivalent to an angular resolution of 0.034°. A special objective lens with k-space acceptance up to 25 Å-1 allows for simultaneous full-field imaging of many Brillouin zones. Combined with time-of-flight (ToF) parallel energy recording this yields maximum parallelization. Thanks to the high brilliance (1013 hν s-1 in a spot of <20 µm diameter) of beamline P22 at PETRA III (Hamburg, Germany), the microscope set a benchmark in HAXPES recording speed, i.e. several million counts per second for core-level signals and one million for d-bands of transition metals. The concept of tomographic k-space mapping established using soft X-rays works equally well in the hard X-ray range. Sharp valence band k-patterns of Re, collected at an excitation energy of 6 keV, correspond to direct transitions to the 28th repeated Brillouin zone. Measured total energy resolutions (photon bandwidth plus ToF-resolution) are 62 meV and 180 meV FWHM at 5.977 keV for monochromator crystals Si(333) and Si(311) and 450 meV at 4.0 keV for Si(111). Hard X-ray photoelectron diffraction (hXPD) patterns with rich fine structure are recorded within minutes. The short photoelectron wavelength (10% of the interatomic distance) `amplifies' phase differences, making full-field hXPD a sensitive structural tool.
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Affiliation(s)
- K. Medjanik
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - S. V. Babenkov
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - S. Chernov
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - D. Vasilyev
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - B. Schönhense
- Department of Bioengineering, Imperial College London, UK
| | - C. Schlueter
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - A. Gloskovskii
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - Yu. Matveyev
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - W. Drube
- DESY Photon Science, Notkestrasse 85, 22607 Hamburg, Germany
| | - H. J. Elmers
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
| | - G. Schönhense
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz, Germany
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17
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Hamed MH, Hinz RA, Lömker P, Wilhelm M, Gloskovskii A, Bencok P, Schmitz-Antoniak C, Elnaggar H, Schneider CM, Müller M. Tunable Magnetic Phases at Fe 3O 4/SrTiO 3 Oxide Interfaces. ACS Appl Mater Interfaces 2019; 11:7576-7583. [PMID: 30672270 DOI: 10.1021/acsami.8b20625] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We demonstrate the emergence and control of magnetic phases between magnetite (Fe3O4), a ferrimagnetic halfmetal, and SrTiO3, a transparent nonmagnetic insulator considered the bedrock of oxide-based electronics. The Verwey transition ( TV) was detected to persist from bulk-like down to ultrathin Fe3O4 films, decreasing from 117 ± 4 K (38 nm) to 25 ± 4 K (2 nm), respectively. Element-selective electronic and magnetic properties of the ultrathin films and buried interfaces are studied by angle-dependent hard X-ray photoelectron spectroscopy and X-ray magnetic circular dichroism techniques. We observe a reduction of Fe2+ ions with decreasing film thickness, accompanied by an increase of Fe3+ ions in both tetrahedral and octahedral sites and conclude on the formation of a magnetically active ferrimagnetic 2 u.c. γ-Fe2O3 intralayer. To manipulate the interfacial magnetic phase, a postannealing process causes the controlled reduction of the γ-Fe2O3 that finally leads to stoichiometric and ferrimagnetic Fe3O4/SrTiO3(001) heterointerfaces.
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Affiliation(s)
- Mai Hussein Hamed
- Peter-Grünberg-Institut (PGI-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
- Faculty of Science , Helwan University , 11795 Cairo , Egypt
| | - Ronja Anika Hinz
- Peter-Grünberg-Institut (PGI-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
| | - Patrick Lömker
- Peter-Grünberg-Institut (PGI-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
| | - Marek Wilhelm
- Peter-Grünberg-Institut (PGI-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
| | - Andrei Gloskovskii
- Photon Science, Deutsches Elektronen-Synchrotron DESY , 22607 Hamburg , Germany
| | | | | | - Hebatalla Elnaggar
- Debye Institute for Nanomaterials Science , 3584 CG Utrecht , The Netherlands
| | - Claus M Schneider
- Peter-Grünberg-Institut (PGI-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
- Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE) , 47048 Duisburg , Germany
| | - Martina Müller
- Peter-Grünberg-Institut (PGI-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
- Experimentelle Physik I , Technische Universität Dortmund , 44227 Dortmund , Germany
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18
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Sahoo L, Rana M, Mondal S, Mittal N, Nandi P, Gloskovskii A, Manju U, Topwal D, Gautam UK. Self-immobilized Pd nanowires as an excellent platform for a continuous flow reactor: efficiency, stability and regeneration. Nanoscale 2018; 10:21396-21405. [PMID: 30427026 DOI: 10.1039/c8nr06844e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Despite extensive use of Pd nanocrystals as catalysts, the realization of a Pd-based continuous flow reactor remains a challenge. Difficulties arise due to ill-defined anchoring of the nanocrystals on a substrate and reactivity of the substrate under different reaction conditions. We demonstrate the first metal (Pd) nanowire-based catalytic flow reactor that can be used across different filtration platforms, wherein, reactants flow through a porous network of nanowires (10-1000 nm pore sizes) and the product can be collected as filtrate. Controlling the growth parameters and obtaining high aspect ratio of the nanowires (diameter = ∼13 nm and length > 8000 nm) is necessary for successful fabrication of this flow reactor. The reactor performance is similar to a conventional reactor, but without requiring energy-expensive mechanical stirring. Synchrotron-based EXAFS studies were used to examine the catalyst microstructure and Operando FT-IR spectroscopic studies were used to devise a regenerative strategy. We show that after prolonged use, the catalyst performance can be regenerated up to 99% by a simple wash-off process without disturbing the catalyst bed. Thus, collection, regeneration and redispersion processes of the catalyst in conventional industrial reactors can be avoided. Another important advantage is avoiding specific catalyst-anchoring substrates, which are not only expensive, but also non-universal in nature.
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Affiliation(s)
- Lipipuspa Sahoo
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER)-Mohali, Sector 81, Mohali, SAS Nagar, Punjab 140306, India.
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19
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Schlueter C, Gloskovskii A, Ederer K, Piec S, Sing M, Claessen R, Wiemann C, Schneider C, Medjanik K, Schönhense G, Amann P, Nilsson A, Drube W. New HAXPES Applications at PETRA III. ACTA ACUST UNITED AC 2018. [DOI: 10.1080/08940886.2018.1483656] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- C. Schlueter
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | - A. Gloskovskii
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | - K. Ederer
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | - S. Piec
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
| | - M. Sing
- Physikalisches Institut and Röntgen Center for Complex Materials Systems, Universität Würzburg, Würzburg, Germany
| | - R. Claessen
- Physikalisches Institut and Röntgen Center for Complex Materials Systems, Universität Würzburg, Würzburg, Germany
| | - C. Wiemann
- Peter Grünberg Institut, Jülich, Germany
| | | | - K. Medjanik
- Institut für Physik, Johannes Gutenberg-Universität, Mainz, Germany
| | - G. Schönhense
- Institut für Physik, Johannes Gutenberg-Universität, Mainz, Germany
| | - P. Amann
- Department of Physics, AlbaNova University Center, Stockholm University, Stockholm, Sweden
| | - A. Nilsson
- Department of Physics, AlbaNova University Center, Stockholm University, Stockholm, Sweden
| | - W. Drube
- Photon Science, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
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20
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Matveyev Y, Negrov D, Chernikova A, Lebedinskii Y, Kirtaev R, Zarubin S, Suvorova E, Gloskovskii A, Zenkevich A. Effect of Polarization Reversal in Ferroelectric TiN/Hf 0.5Zr 0.5O 2/TiN Devices on Electronic Conditions at Interfaces Studied in Operando by Hard X-ray Photoemission Spectroscopy. ACS Appl Mater Interfaces 2017; 9:43370-43376. [PMID: 29160064 DOI: 10.1021/acsami.7b14369] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Because of their compatibility with modern Si-based technology, HfO2-based ferroelectric films have recently attracted attention as strong candidates for applications in memory devices, in particular, ferroelectric field-effect transistors or ferroelectric tunnel junctions. A key property defining the functionality of these devices is the polarization dependent change of the electronic band alignment at the metal/ferroelectric interface. Here, we report on the effect of polarization reversal in functional ferroelectric TiN/Hf0.5Zr0.5O2/TiN capacitors on the potential distribution across the stack and the electronic band line-up at the interfaces studied in operando by hard X-ray photoemission spectroscopy. By tracking changes in the position of Hf0.5Zr0.5O2 core-level lines with respect to those of the TiN electrode in both short- and open-circuit configurations following in situ polarization reversal, we derive the conduction band offset to be 0.7 (1.0) eV at the top and 1.7 (1.0) eV at the bottom interfaces for polarization, pointing up (down), respectively. Energy dispersive X-ray spectroscopy profiling of the sample cross-section in combination with the laboratory X-ray photoelectron spectroscopy reveal the presence of a TiOx/TiON layer at both interfaces. The observed asymmetry in the band line-up changes in the TiN/Hf0.5Zr0.5O2/TiN memory stack is explained by different origin of these oxidized layers and effective pinning of polarization at the top interface. The described methodology and first experimental results are useful for the optimization of HfO2-based ferroelectric memory devices under development.
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Affiliation(s)
- Yury Matveyev
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
| | - Dmitry Negrov
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
| | - Anna Chernikova
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
| | - Yury Lebedinskii
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
| | - Roman Kirtaev
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
| | - Sergei Zarubin
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
| | - Elena Suvorova
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
- A.V. Shubnikov Institute of Crystallography , Leninsky pr. 59, Moscow 119333, Russia
| | - Andrei Gloskovskii
- Deutsches Elektronen-Synchrotron , 85 Notkestraße, Hamburg D-22607, Germany
| | - Andrei Zenkevich
- Moscow Institute of Physics and Technology , 9, Institutskiy Lane, Dolgoprudny, Moscow region, 141701, Russia
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21
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Patt M, Wiemann C, Weber N, Escher M, Gloskovskii A, Drube W, Merkel M, Schneider CM. Bulk sensitive hard x-ray photoemission electron microscopy. Rev Sci Instrum 2014; 85:113704. [PMID: 25430117 DOI: 10.1063/1.4902141] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Hard x-ray photoelectron spectroscopy (HAXPES) has now matured into a well-established technique as a bulk sensitive probe of the electronic structure due to the larger escape depth of the highly energetic electrons. In order to enable HAXPES studies with high lateral resolution, we have set up a dedicated energy-filtered hard x-ray photoemission electron microscope (HAXPEEM) working with electron kinetic energies up to 10 keV. It is based on the NanoESCA design and also preserves the performance of the instrument in the low and medium energy range. In this way, spectromicroscopy can be performed from threshold to hard x-ray photoemission. The high potential of the HAXPEEM approach for the investigation of buried layers and structures has been shown already on a layered and structured SrTiO3 sample. Here, we present results of experiments with test structures to elaborate the imaging and spectroscopic performance of the instrument and show the capabilities of the method to image bulk properties. Additionally, we introduce a method to determine the effective attenuation length of photoelectrons in a direct photoemission experiment.
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Affiliation(s)
- M Patt
- Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich, Germany
| | - C Wiemann
- Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich, Germany
| | - N Weber
- Focus GmbH, Neukirchner Str. 2, D-65510 Hünstetten, Germany
| | - M Escher
- Focus GmbH, Neukirchner Str. 2, D-65510 Hünstetten, Germany
| | - A Gloskovskii
- DESY Photon Science, Deutsches Elektronen-Synchrotron, D-22603 Hamburg, Germany
| | - W Drube
- DESY Photon Science, Deutsches Elektronen-Synchrotron, D-22603 Hamburg, Germany
| | - M Merkel
- Focus GmbH, Neukirchner Str. 2, D-65510 Hünstetten, Germany
| | - C M Schneider
- Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich, Germany
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22
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Calka P, Sowinska M, Bertaud T, Walczyk D, Dabrowski J, Zaumseil P, Walczyk C, Gloskovskii A, Cartoixà X, Suñé J, Schroeder T. Engineering of the chemical reactivity of the Ti/HfO₂ interface for RRAM: experiment and theory. ACS Appl Mater Interfaces 2014; 6:5056-60. [PMID: 24625458 DOI: 10.1021/am500137y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The Ti/HfO2 interface plays a major role for resistance switching performances. However, clear interface engineering strategies to achieve reliable and reproducible switching have been poorly investigated. For this purpose, we present a comprehensive study of the Ti/HfO2 interface by a combined experimental-theoretical approach. Based on the use of oxygen-isotope marked Hf*O2, the oxygen scavenging capability of the Ti layer is clearly proven. More importantly, in line with ab initio theory, the combined HAXPES-Tof-SIMS study of the thin films deposited by MBE clearly establishes a strong impact of the HfO2 thin film morphology on the Ti/HfO2 interface reactivity. Low-temperature deposition is thus seen as a RRAM processing compatible way to establish the critical amount of oxygen vacancies to achieve reproducible and reliable resistance switching performances.
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Affiliation(s)
- Pauline Calka
- IHP , Im Technologiepark 25, 15236 Frankfurt an der Oder, Germany
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23
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Nayak J, Maniraj M, Rai A, Singh S, Rajput P, Gloskovskii A, Zegenhagen J, Schlagel DL, Lograsso TA, Horn K, Barman SR. Bulk electronic structure of quasicrystals. Phys Rev Lett 2012; 109:216403. [PMID: 23215602 DOI: 10.1103/physrevlett.109.216403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 09/26/2012] [Indexed: 06/01/2023]
Abstract
We use hard x-ray photoemission to resolve a controversial issue regarding the mechanism for the formation of quasicrystalline solids, i.e., the existence of a pseudogap at the Fermi level. Our data from icosahedral fivefold Al-Pd-Mn and Al-Cu-Fe quasicrystals demonstrate the presence of a pseudogap, which is not observed in surface sensitive low energy photoemission because the spectrum is affected by a metallic phase near the surface. In contrast to Al-Pd-Mn, we find that in Al-Cu-Fe the pseudogap is fully formed; i.e., the density of states reaches zero at E(F) indicating that it is close to the metal-insulator phase boundary.
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Affiliation(s)
- J Nayak
- UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, India
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24
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Gray AX, Cooke DW, Krüger P, Bordel C, Kaiser AM, Moyerman S, Fullerton EE, Ueda S, Yamashita Y, Gloskovskii A, Schneider CM, Drube W, Kobayashi K, Hellman F, Fadley CS. Electronic structure changes across the metamagnetic transition in FeRh via hard X-ray photoemission. Phys Rev Lett 2012; 108:257208. [PMID: 23004654 DOI: 10.1103/physrevlett.108.257208] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Indexed: 06/01/2023]
Abstract
Stoichiometric FeRh undergoes a temperature-induced antiferromagnetic (AFM) to ferromagnetic (FM) transition at ~350 K. In this Letter, changes in the electronic structure accompanying this transition are investigated in epitaxial FeRh thin films via bulk-sensitive valence-band and core-level hard x-ray photoelectron spectroscopy with a photon energy of 5.95 keV. Clear differences between the AFM and FM states are observed across the entire valence-band spectrum and these are well reproduced using density-functional theory. Changes in the 2p core levels of Fe are also observed and interpreted using Anderson impurity model calculations. These results indicate that significant electronic structure changes over the entire valence-band region are involved in this AFM-FM transition.
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Affiliation(s)
- A X Gray
- Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94029, USA
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25
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Graf T, Barth J, Jung V, Gloskovskii A, Balke B, Felser C. Magnetic and Structural Properties of Heusler Compounds with 27.8 Valence Electrons. Z Anorg Allg Chem 2010. [DOI: 10.1002/zaac.200900576] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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26
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Barth J, Schoop M, Gloskovskii A, Shkabko A, Weidenkaff A, Felser C. Investigation of the Thermoelectric Properties of the Series TiCo1-xNixSnxSb1-x. Z Anorg Allg Chem 2010. [DOI: 10.1002/zaac.200900349] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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27
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Cinchetti M, Gloskovskii A, Nepjiko SA, Schönhense G, Rochholz H, Kreiter M. Photoemission electron microscopy as a tool for the investigation of optical near fields. Phys Rev Lett 2005; 95:047601. [PMID: 16090841 DOI: 10.1103/physrevlett.95.047601] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Indexed: 05/03/2023]
Abstract
Photoemission electron microscopy was used to image the electrons photoemitted from specially tailored Ag nanoparticles deposited on a Si substrate (with its native oxide SiO(x)). Photoemission was induced by illumination with a Hg UV lamp (photon energy cutoff homega(UV) = 5.0 eV, wavelength lambda(UV) = 250 nm) and with a Ti:sapphire femtosecond laser (homega(l) = 3.1 eV, lambda(l) = 400 nm, pulse width below 200 fs), respectively. While homogeneous photoelectron emission from the metal is observed upon illumination at energies above the silver plasmon frequency, at lower photon energies the emission is localized at tips of the structure. This is interpreted as a signature of the local electrical field therefore providing a tool to map the optical near field with the resolution of emission electron microscopy.
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Affiliation(s)
- M Cinchetti
- Johannes Gutenberg-Universität, Institut für Physik, Mainz, Germany
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28
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Nepijko SA, Gloskovskii A, Sedov NN, Schönhense G. Measurement of the electric field distribution and potentials on the object surface in an emission electron microscope without restriction of the electron beams. J Microsc 2003; 211:89-94. [PMID: 12839555 DOI: 10.1046/j.1365-2818.2003.01199.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An emission electron microscope without restriction of the electron beams was used to visualize and measure the distribution of electric fields and potentials on the surface under study. Investigations of this kind can be performed in an emission electron microscope without any aperture diaphragm. The potentialities of this method have been demonstrated using measurements with a silicon p-n junction to which a voltage has been applied in the reverse direction. The quantitative analysis becomes more complicated if the specimen is characterized by a heterogeneous intensity distribution of the electron emission from different areas of its surface. In the latter case two images obtained at different accelerating voltages (i.e. different voltages of the microscope extractor) provide the information necessary for an analysis of electric field and potential distributions.
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Affiliation(s)
- S A Nepijko
- Institute of Physics, University Mainz, Staudingerweg 7, 55099 Mainz, Germany.
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