Chemical and Strain Engineering of Functional Oxides

Abstract

LiNbO₃ and LiTaO₃ are the two of the most important crystals, being the equivalent in the field of optics, nonlinear optics and optoelectronics to silicon in electronics. Thus, the studies about epitaxial ferroelectric LiNbO₃ and LiTaO₃ thin films are of great interest because of their potential application as miniaturized and integrated elements in acoustic delay lines, resonators, pyroelectric sensors, optical waveguides, etc. Although LiNbO₃ and LiTaO₃ films have been fabricated by different techniques, many electrical and electro-optical properties reported are not comparable for those of LiNbO₃ and LiTaO₃ single-crystals. The growth of high quality LiNbO₃/LiTaO₃ films is far from being a routine due to a difficulty to estimate the phase composition and Li stoichiometry. Thus, the deposited films are hardly reproducible, often contain undesirable phases (for example, LiNb₃O₈ or Li₃NbO₄) or are stoichiometrically inhomogeneous. This inhibits the applications of the materials in the thin film form. The indirect methods, used to estimate Li concentration in the single crystals, cannot be applied directly due to the presence of strain, size effects or other defects in the films, which influences also the structural, optical and other physical properties.