Site spectroscopy of Hf doping in Hf-doped crystals

By means of Raman scattering spectroscopy we determine the site location occupied by Hf ions in photorefractive damage resistant Hf-doped LiNbO3. At room temperature the two lowest frequency phonons are related to sites B (Nb) and A (Li), and are used to directly probe the dopant ion. For the low concentration range, the Hf ions go into the sites A whereas, for high concentration, Hf ions occupy both sites A and B. Results are compared with data obtained for pure congruent and stoichiometric crystals, and the proposed mechanism of incorporation of Hf ions in the LiNbO3 lattice explains the threshold in the behaviour of photorefractive properties.