Resonant Raman of OH/OD vibrations and photoluminescence studies in LiTaO3 thin film

TL;DR

This study investigates resonant Raman scattering and photoluminescence in LiTaO3 thin films, revealing unique vibrational modes and their interaction with electronic states, including the first observation of band gap related PL.

Contribution

It reports the first observation of band gap photoluminescence along with resonant Raman peaks in LiTaO3 thin films, and details the high dispersion of vibrational modes with excitation energy.

Findings

Resonant Raman peaks are superimposed on photoluminescence spectrum.

Band gap photoluminescence observed for the first time in LiTaO3 thin films.

High dispersion of vibrational modes with excitation energy, exceeding other materials.

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 (4.4-4.8eV) and another in the sub band gap region (< 4.0 eV). Band gap PL along with RRS peaks are reported for the first time. Photoluminescence excitation spectrum (PLE) shows a peak at 4.8 eV. Peak positions and full width at half maximum (FWHM) of RRS peaks depend upon the excitation energy. Dispersions of the fundamental and the third harmonic of the stretching mode of O-H with excitation energy are about 800 cm-1/eV and 2000 cm-1/eV respectively. This dispersion is much higher than reported in any other material.