Resonant Raman of O-H/O-D vibrations and photoluminescence studies in LiTaO₃ thin film

Abstract

Resonant Raman spectra (RRS) of O-H and O-D vibration and libration modes, their combinations, and higher harmonics have been observed in LiTaO₃ polycrystalline thin films. RRS peaks are superimposed on photoluminescence (PL) spectrum. Monochromatic light from a xenon lamp is used as excitation source. PL spectrum shows two broad peaks: first near the band gap in UV (4.4-4.8 eV) and another in the sub-band-gap region («4.0 eV). Band gap PL along with RRS peaks are reported for the first time. PL excitation spectrum shows a peak at 4.8 eV. Peak positions and full width at half maximum of RRS peaks depend on the excitation energy. Dispersions of the fundamental and the third harmonic of the stretching mode of O-H with excitation energy are about 800 and 2000 cm^-1/eV, respectively. This dispersion is much higher than reported in any other material.