UV light-induced absorption in pure KTaO3 at low temperature
Autor(en): | Kapphan, S.E. Gubaev, A.I. Vikhnin, V.S. |
Stichwörter: | Absorption spectroscopy; Charge transfer; Crystal defects; Ferroelectricity; Laser beam effects; Photoluminescence; Potassium compounds; Second harmonic generation; Ultraviolet radiation, Charge transfer vibronic exilons (CTVE); Cubic symmetry; Oxygen vacancies; UV-illumination, Crystal symmetry | Erscheinungsdatum: | 2005 | Journal: | Physica Status Solidi C: Conferences | Volumen: | 2 | Ausgabe: | 1 | Startseite: | 128 | Seitenende: | 131 | Zusammenfassung: | Pure KTaO3 with cubic symmetry down to lowest temperatures is a model incipient ferroelectric exhibiting the existence of intrinsic inversion symmetry breaking defects in a wide range of experiments. At low temperature a strong second harmonic generation (SHG) of Nd:YAG laser light is observed, despite the overall cubic symmetry of the crystal. Under excitation with UV-light in the band gap region (about 330 nm (3.7 eV)) a strong green luminescence (GL, at 510 run (2.43 eV)) appears with excitation maximum near 330 nm (3.7 eV). Both, SHG and GL depend strongly on previous oxidation/reduction treatments, increasing with the reduction. In absorption at low temperature broad bands peaking at 1.2 eV and at 1.5 eV are observed in reduced KTaO 3 samples. Additional UV-illumination in the band gap region at low temperature gives rise to broad light-induced absorption bands in the same 1-2 eV region. These observations are being discussed on the basis of polaronic holes, of charge transfer vibronic exilons (CTVEs) and of CTVE clusters interacting with oxygen vacancies. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
ISSN: | 16101634 | DOI: | 10.1002/pssc.200460128 | Externe URL: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-27344442241&doi=10.1002%2fpssc.200460128&partnerID=40&md5=825a41fe25fa31284f7dd232d9579153 |
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geprüft am 29.05.2024