Polaron-mediated luminescence in lithium niobate and lithium tantalate and its domain contrast

Philipp Reichenbach, Thomas Kämpfe, Alexander Haußmann, Andreas Thiessen, Theo Woike, Robin Steudtner, Laura Kocsor, Zsuzsanna Szaller, L. Kovács, Lukas M. Eng

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Abstract

In this review article, we discuss photoluminescence phenomena mediated by polarons in lithium niobate (LNO). At first we present the fundamentals on polaron states in LNO and their energy levels, i.e., on free and bound electron polarons, on hole polarons as well as on bipolarons. We discuss the absorption measurements on reduced as well as on doped LNO that made the characterization of the formed polaron states possible by their absorption bands. Next, we proceed by reporting on the two polaron-mediated photoluminescence bands that have been observed in LNO: (1) A near-infrared luminescence band in the range of 1.5 eV shows a mono-exponential decay and a strong dependence on iron doping. This luminescence is emitted by bound polarons returning from an excited state to the ground state. (2) A luminescence band at visible wavelengths with a maximum at 2.6 eV shows a stretched-exponential decay and is strongly enhanced by optical damage resistant doping around the doping threshold. This luminescence stems from the recombination of free electron and hole polarons. The next major topic of this review are domain contrasts of the visible photoluminescence that have been observed after electrical poling of the substrate, as singly inverted domains show a slightly reduced and faster decaying luminescence. Subsequent annealing results in an exponential decrease of that domain contrast. We show that this contrast decay is strongly related to the mobility of lithium ions, thus confirming the role of polar defect complexes, including lithium vacancies, for these domain contrasts. Finally we discuss the extension of our investigations to lithium tantalate (LTO) samples. While the results on the domain contrast and its decay are similar to LNO, there are remarkable differences in their luminescence spectra.

Original languageEnglish
Article number214
JournalCrystals
Volume8
Issue number5
DOIs
Publication statusPublished - May 1 2018

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Keywords

  • Defect
  • Defect complex
  • Domain contrast
  • Doping threshold
  • Ferroelectric
  • Lithium niobate
  • Lithium tantalate
  • Multiphoton luminescence
  • Polaron
  • Thermal relaxation

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Inorganic Chemistry

Cite this

Reichenbach, P., Kämpfe, T., Haußmann, A., Thiessen, A., Woike, T., Steudtner, R., Kocsor, L., Szaller, Z., Kovács, L., & Eng, L. M. (2018). Polaron-mediated luminescence in lithium niobate and lithium tantalate and its domain contrast. Crystals, 8(5), [214]. https://doi.org/10.3390/cryst8050214