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Pfannstiel A, Hehemann T, Schäfer NA, Sanna S, Suhak Y, Vittadello L, Sauerwein F, Dömer N, Koelmann J, Fritze H, Imlau M. Small electron polarons bound to interstitial tantalum defects in lithium tantalate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:355701. [PMID: 38759682 DOI: 10.1088/1361-648x/ad4d47] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 05/17/2024] [Indexed: 05/19/2024]
Abstract
The absorption features of optically generated, short-lived small bound electron polarons are inspected in congruent lithium tantalate, LiTaO3(LT), in order to address the question whether it is possible to localize electrons at interstitial TaV:VLidefect pairs by strong, short-range electron-phonon coupling. Solid-state photoabsorption spectroscopy under light exposure and density functional theory are used for an experimental and theoretical access to the spectral features of small bound polaron states and to calculate the binding energies of the small bound TaLi4+(antisite) and TaV4+:VLi(interstitial site) electron polarons. As a result, two energetically well separated (ΔE≈0.5 eV) absorption features with a distinct dependence on the probe light polarization and peaking at 1.6 eV and 2.1 eV are discovered. We contrast our results to the interpretation of a single small bound TaLi4+electron state with strong anisotropy of the lattice distortion and discuss the optical generation of interstitial TaV4+:VLismall polarons in the framework of optical gating of TaV4+:TaTa4+bipolarons. We can conclude that the appearance of carrier localization at TaV:VLimust be considered as additional intermediate state for the 3D hopping transport mechanisms at room temperature in addition to TaLi, as well, and, thus, impacts a variety of optical, photoelectrical and electrical applications of LT in nonlinear photonics. Furthermore, it is envisaged that LT represents a promising model system for the further examination of the small-polaron based photogalvanic effect in polar oxides with the unique feature of two, energetically well separated small polaron states.
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Affiliation(s)
- Anton Pfannstiel
- Institut für Physik, Fachbereich Mathematik/Informatik/Physik, Universität Osnabrück, Barbarastraße 7, D-49076 Osnabrück, Germany
| | - Tobias Hehemann
- Institut für Physik, Fachbereich Mathematik/Informatik/Physik, Universität Osnabrück, Barbarastraße 7, D-49076 Osnabrück, Germany
| | - Nils A Schäfer
- Institut für Theoretische Physik and Center for Materials Research (ZfM/LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, D-35392 Gießen, Germany
| | - Simone Sanna
- Institut für Theoretische Physik and Center for Materials Research (ZfM/LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, D-35392 Gießen, Germany
| | - Yuriy Suhak
- Institut für Energieforschung und Physikalische Technologien, Technische Universität Clausthal, Am Stollen 19 B, D-38640 Goslar, Germany
| | - Laura Vittadello
- Institut für Physik, Fachbereich Mathematik/Informatik/Physik, Universität Osnabrück, Barbarastraße 7, D-49076 Osnabrück, Germany
- Zentrum für zelluläre Nanoanalytik Osnabrück (CellNanOs), Universität Osnabrück, Barbarastraße 11, D-49076 Osnabrück, Germany
| | - Felix Sauerwein
- Institut für Physik, Fachbereich Mathematik/Informatik/Physik, Universität Osnabrück, Barbarastraße 7, D-49076 Osnabrück, Germany
| | - Niklas Dömer
- Institut für Physik, Fachbereich Mathematik/Informatik/Physik, Universität Osnabrück, Barbarastraße 7, D-49076 Osnabrück, Germany
| | - Julian Koelmann
- Institut für Physik, Fachbereich Mathematik/Informatik/Physik, Universität Osnabrück, Barbarastraße 7, D-49076 Osnabrück, Germany
| | - Holger Fritze
- Institut für Energieforschung und Physikalische Technologien, Technische Universität Clausthal, Am Stollen 19 B, D-38640 Goslar, Germany
| | - Mirco Imlau
- Institut für Physik, Fachbereich Mathematik/Informatik/Physik, Universität Osnabrück, Barbarastraße 7, D-49076 Osnabrück, Germany
- Zentrum für zelluläre Nanoanalytik Osnabrück (CellNanOs), Universität Osnabrück, Barbarastraße 11, D-49076 Osnabrück, Germany
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Pilyak FS, Kulikov AG, Pisarevsky YV, Blagov AE, Kovalchuk MV. Separation of the Mechanisms of Photoinduced Deformations in Crystals Using Time-Resolved X-ray Diffractometry. CRYSTALLOGR REP+ 2022. [DOI: 10.1134/s1063774522050121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
The recent Special Issue on lithium niobate (LiNbO3) is dedicated to Prof. Schirmer and his topics and contains nineteen papers, out of which seven review various aspects of intrinsic and extrinsic defects in single crystals, thin films, and powdered phases; six present brand-new results of basic research, including two papers on Li(Nb,Ta)O3 mixed crystals; and the remaining six are related to various optical and/or thin film applications.
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Petrenko A, Novikova N, Blagov A, Kulikov A, Pisarevskii Y, Verin I, Kovalchuk M. Lateral deformations of a crystal of potassium acid phthalate in an external electric field. J Appl Crystallogr 2021. [DOI: 10.1107/s1600576721007366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The anisotropy of deformations in potassium acid phthalate crystals arising under the action of an external electric field up to 1 kV mm−1 applied along the [001] polar axis was studied using X-ray diffraction methods at room temperature. Electrical conductivity was measured and rocking curves for reflections 400, 070 and 004 were obtained by time-resolved X-ray diffractometry in Laue and Bragg geometries. Two saturation processes were observed from the time dependences of the electrical conductivity. A shift in the diffraction peaks and a change in their intensity were found, which indicated a deformation of the crystal structure. Rapid piezoelectric deformation and reversible relaxation-like deformation, kinetically similar to the electrical conductivity of a crystal, were revealed. The deformation depended on the polarity and strength of the applied field. The deformation was more noticeable in the [100] direction and was practically absent in the [001] direction of the applied field. X-ray diffraction analysis revealed a disordered arrangement of potassium atoms, i.e. additional positions and vacancies. The heights of potential barriers between the positions of K+ ions and the paths of their possible migration in the crystal structure of potassium acid phthalate were determined. The data obtained by time-resolved X-ray diffractometry and X-ray structure analysis, along with additional electrophysical measurements, allow the conclusion that the migration of charge carriers (potassium cations) leads to lateral deformation of the crystal structure of potassium phthalate in an external electric field.
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‘Horror Vacui’ in the Oxygen Sublattice of Lithium Niobate Made Affordable by Cationic Flexibility. CRYSTALS 2021. [DOI: 10.3390/cryst11070764] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The present review is intended for a broader audience interested in the resolution of the several decades-long controversy on the possible role of oxygen-vacancy defects in LiNbO3. Confronting ideas of a selected series of papers from classical experiments to brand new large-scale calculations, a unified interpretation of the defect generation and annealing mechanisms governing processes during thermo- and mechanochemical treatments and irradiations of various types is presented. The dominant role of as-grown and freshly generated Nb antisite defects as traps for small polarons and bipolarons is demonstrated, while mobile lithium vacancies, also acting as hole traps, are shown to provide flexible charge compensation needed for stability. The close relationship between LiNbO3 and the Li battery materials LiNb3O8 and Li3NbO4 is pointed out. The oxygen sublattice of the bulk plays a much more passive role, whereas oxygen loss and Li2O segregation take place in external or internal surface layers of a few nanometers.
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