Berlin 2015 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 11: Small Polarons in LiNbO₃

DF 11.9: Vortrag

Mittwoch, 18. März 2015, 12:20–12:40, EB 133C

Protons in doped LiNbO₃ crystals resistant to photorefractive damage — •Krisztián Lengyel, László Kovács, Viktor Szalay, and Gábor Corradi — Wigner Research Centre for Physics, Budapest, Hungary

Protons are common impurities in LiNbO₃ forming OH⁻ ions in the lattice. The characteristic spectrum in the 3400–3600 cm⁻¹ wavenumber range due to stretching vibrations of O–H is very sensitive to neighbouring defects (e.g. antisite Nb_0.7Li, various dopants, polarons, etc). Studying the details of OH⁻ incorporation is also helpful for understanding the behavior of neighboring defects. Proton dynamics can be investigated by the SIESTA quantum chemical software package as already successfully demonstrated for undoped stoichiometric and congruent LiNbO₃. Dopants like Mg, Zn, Sc, In, Hf, Zr or Sn leading to photorefractive optical damage resistance (ODR ions) can change the polaronic behavior of LiNbO₃ crystals as well. ODR-doping of LiNbO₃ crystals above a threshold concentration also leads to substantially modified OH absorption bands which can be explained by assuming the existence of ODR_0.7Nbⁿ⁺–OH defect complexes. In the present work this model will be discussed using the results of theoretical calculations of OH⁻ ions incorporated into ODR-doped LiNbO₃ crystals. This project has been supported by the Hungarian Scientific Research Fund (OTKA) K83390.