Spin coated La2CuO4 thin film: An extensive study on optical dispersion parameters

Abstract

In this paper, a layered perovskite-type La2CuO4 thin film was deposited on quartz substrate using sol-gel spin coating technique. Though it is a well-studied material, the novelty of the proposed work is the technology adopted for the preparation of this thin film and extensive studies on optical dispersion parameters. The structural characterizations revealed the formation of pure phase ternary La2CuO4 compound with orthorhombic structure. The chemical state analysis detects the valance state of the constituent elements, La, Cu, and O as + 3, (+2,+1) and − 2 respectively. The average grain size was found to be nearly 115 nm from the FESEM images. The surface topography was studied using Atomic Force Microscopy and the root mean square roughness of the film was estimated as 20 nm. The optical studies indicated the semiconducting nature of the compound with a bandgap of 1.6 eV. The refractive index and extinction coefficient have been evaluated from the reflectance data. The linear and non-linear optical dispersion parameters are thoroughly studied using the Wemple and DiDomenico (WDD) single oscillator model. The linear dispersion parameters like the effective single oscillator energy, zero frequency refractive index, optical oscillator strength, and zero frequency dielectric constant have been estimated. Moreover, the nonlinear refractive index, optical susceptibility and optical moments were evaluated. The refractive index and third-order nonlinear susceptibility of La2CuO4 thin film were observed to be higher than some other materials reported in the literature. Thus, this study may be useful in designing La2CuO4-based high-performance devices for optical communications and integrated circuits.