Lattice location of Hf and its interaction with other impurities in LiNbO3: a review

Abstract

Abstract. Lithium niobate, LiNbO3, exists in a wide range of compositions, from congruent to stoichiometric. Undoped congruent LiNbO3 suffers from a relatively low optical damage threshold that constitutes its major disadvantage for optoelectronic devices. The optical damage threshold is dependent on the amount of intrinsic defects and is considerably increased in stoichiometric material and in congruent material doped with specific impurities, such as Mg, In, Sc, and Zn. It has been recently shown that the doping with Hf leads to a significant increase of the photorefractive resistance at a threshold concentration of about 3 mol%. The study of the lattice location of Hf in LiNbO3 and its interaction with other impurities and intrinsic defects started more than a decade before the discovery of the role of this impurity, as Hf was a convenient probe for combined studies using the nuclear techniques perturbed angular correlations and Rutherford backscattering spectrometry/channeling. An integrated review of the main results obtained with these techniques is presented. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.OE.53.6.060901

Unveiling the Defect Structure of Lithium Niobate with Nuclear Methods

“…The angular PIXE/C scans for various axial directions confirm clearly that Ti occupies only Li sites at this concentration level and that no off-axis sites are occupied. The PAC measurements show a single QIF, ν Q = 15.4(2) MHz, which scales up very well with the results obtained with other probes occupying Li sites [34]. These findings led to the conclusion that Ti occupies solely Li-sites for lower concentrations while for higher concentrations a mixture of Li-and Nb-sites has to be assumed.…”

“…Two frequencies of the same magnitude were also observed in 181 Hf PAC measurements done in polycrystalline LN samples [50]. These QIF were later detailed as ν Q1 = 1154 (12) MHz and ν Q2 = 1213(12) MHz, with asymmetry parameters in the 0.2-0.3 range, from new measurements in single-crystals [34]. NMR studies [51,52] confirm an asymmetry parameter of 0.2 for congruent material.…”

“…Although much progress has been made in the calculation of EFG [33] this is still time-consuming and far from generalized. Nevertheless, one can compare EFG values obtained with different probes in LN [34].…”