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

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 which 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 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 had 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.