Dresden 2026 – scientific programme
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FM: Fachverband Funktionsmaterialien
FM 11: Poster Session Functional Materials
FM 11.30: Poster
Tuesday, March 10, 2026, 18:00–20:30, P4
A high-temperature optical spectroscopy study of congruent LiTaO3 — •Ludmila Eisner1, Angélique Hoffmann2, Ani Manucharyan2, Sebastian Inckemann2, Yuriy Suhak1, Steffen Ganschow2, Holger Fritze1, and Klaus.-D. Becker3 — 1Clausthal University of Technology, Germany — 2Leibniz-Institut für Kristallzüchtung, Germany — 3Technische Universität Braunschweig, Germany
Spectroscopic studies of congruent lithium tantalate (cLT) were performed to analyze the optical absorption edge under different thermal treatments in air and to relate its changes to band gap variations with temperature. At room temperature, the material exhibits an absorption edge near 4.45 eV. Thermal measurements, extending up to 900∘C, show a systematic shift of about 0.138 eV toward lower photon energies per 100 K with increasing temperature. The treatments at reducing conditions (Ar/5% H2) were found to induce significant changes in the spectra after cooling down to room temperature. These spectra show the formation of extended absorption tails down to photon energies of about 2.5 eV. This may suggest enhanced occupation or reconfiguration of intrinsic defect states, including polaronic states, vacancies, and antisite-related centers. These spectral changes largely evade observation under high-temperature in-situ conditions due to the redshift of the absorption edge. Comparison of spectra recorded after thermal cycling shows partial reversibility of these defect-related features. The present results provide a picture of how temperature and reduction-induced defect chemistry impact the optical response of cLT.
Keywords: congruent lithium tantalate; optical absorption edge; spectroscopy