Lifetime of small polarons in strontium-barium-niobate single crystals doped with cerium or chromium

Autor(en): Woike, T
Berben, D
Imlau, M 
Buse, K
Pankrath, R
Kratzig, E
Stichwörter: ABSORPTION; ACTIVATION; NB4+; Physics; Physics, Applied
Erscheinungsdatum: 2001
Herausgeber: AMER INST PHYSICS
Journal: JOURNAL OF APPLIED PHYSICS
Volumen: 89
Ausgabe: 10
Startseite: 5663
Seitenende: 5666
Zusammenfassung: 
Small polarons are excited by pulsed illumination (lambda =532 nm) of strontium-barium-niobate single crystals doped with 0.66 mol % cerium or with 0.025 mol % chromium. The dark decay of the polarons is observed by monitoring the light-induced absorption at lambda =632.8 nm and at lambda =785 nm. The relaxation fulfills a stretched-exponential behavior over at least five decades. Using the Arrhenius law the temperature dependence yields the activation energy E-A=(0.58 /-0.02) eV and a frequency factor of Z=(5 /-3)x10(13) s(-1). Delayed double-pulse technique (lambda =532 nm pulse followed by a lambda =1064 nm pulse) reveals a distance dependent recombination rate of the small polarons, i.e., the lifetime of a created polaron is a function of the distance to the next available deep electron trap. In SBN:Cr the R branch can be excited by pulses of lambda =1064 nm with energy transfer via an unknown X center. Excitation and recombination show a single-exponential temporal evolution without any significant temperature dependence. (C) 2001 American Institute of Physics.
ISSN: 00218979
DOI: 10.1063/1.1328779

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