LOCALIZED VIBRATION IN PROTON-EXCHANGED LINBO3 AND LITAO3 CRYSTALS

Raman spectra of LiNbO3 and LiTaO3 crystals with different proton-exch anged time were examined. Two new vibrational modes at 38 and 58cm(-1) were found. The 38cm(-1) mode shows a line spectrum and its intensity changes with proton-exchanged time. The 58cm(-1) mode, which exists o nly in the Raman spectrum of protonated LiNbO3 crystal with 14 hours t reatment, shows a large intensity and a broad line. We attribute the 3 8 and 58cm(-1) modes to a localized vibrational mode resulted from def ect-induced disorder and a second-order Raman scattering mode, respect ively. The properties of the two modes really reflect the microstructu re change of the protonated samples.