Structural and optical characterization of oriented LiTaO₃ thin films deposited by sol-gel technique

¹ Institut d'Électronique du Sud IES – Université Montpellier II, UMR CNRS 5214, Place E. Bataillon, 34095 Montpellier, France
² Département de Sciences et Technologie, Faculté des Sciences et de Génie Informatique, Université Saint-Esprit de Kaslik, BP 446 Jounieh, Liban

Corresponding author: sami.youssef@ies.univ-montp2.fr

Received: 16 January 2008
Revised: 21 March 2008
Accepted: 23 April 2008
Published online: 24 June 2008

Abstract

This paper reports the characterization of lithium tantalite (LiTaO₃) thin films deposited by sol gel process. Thin films were deposited on (001) sapphire substrates by spin coating. In order to study the effect of annealing temperature on the structural and optical properties, the films were annealed at several heating temperatures, ranging from 600 to 750 °C. From X-ray diffraction measurements it is confirmed that LiTaO₃ films are highly c-axis oriented, the line width and the intensity of the (006) peak are sensitive to the variation of the annealing temperature and the best results were found at 700 °C. From SEM pictures it is found that the grain size increases from 100 to 200 nm when the annealing temperature is increased to 700 °C. From the optical transmittance and absorbance measurements, the band gap energy was extrapolated at about 4.6 eV which closely agrees with the LiTaO₃ bulk value. Fourier transform infrared (FTIR) reflectivity and Raman backscattering were used as two complementary experiments to probe the zone center optical phonons in the lithium tantalite thin films.