Étude ab initio des propriétés électroniques et optiques du niobate de lithium (LiNbO3) stoechiométrique

Abstract : Lithium niobate (LN) has piezoelectric, electro-optics, nonlinear optical and photorefractive properties, which are rich in mature (surface acoustic filters, EO modulators, frequency converters) or potential (holographic memories, photo-induced waveguide) applications. Using the density functional theory (DFT) combined with the full potential linearized augmented plane waves (FP- LAPW) method implemented in the WIEN2k_12 code, we investigated - with more details - the electronic properties of stoichiometric LN (SLN) such as the band structure, the density of states, the charge density, the effective masses, the hopping integral for Nb-Nb and O-O, as well as different optical properties derived from the dielectric function like the refractive index, the extinction index, the absorption coefficient ...etc. In our study, we also tried to analyze and interpret some disagreements that appear in the results of ab initio calculations of an author to another. These disagreements due to the methods of calculation employed may be very sensitive for the SLN material without any defects. The experimental value of the energy band gap (3.78 eV) corresponding to LN nearly stoichiometric (NSLN) - frequently cited in the literature - was suggested to be largest for SLN according to recent ab inito studies. For this reason, we have tried to correct it by using a new approach (referring to the value of the experimental refractive index of SLN). Thus, we propose a new theoretical value Eg for pure LN and we bring correction of some energy's peaks of excited states of the optical spectra
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Souheyla Mamoun. Étude ab initio des propriétés électroniques et optiques du niobate de lithium (LiNbO3) stoechiométrique. Autre [cond-mat.other]. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0273⟩. ⟨tel-01750618⟩

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