Optical properties of aluminum oxide thin films and colloidal nanostructures

•Optical properties of alumina thin films and nanocolloids were investigated.•New theoretical depiction of transmission and reflection from the thin films was evaluated.•Interference in reflection from thin films was studied.•Real and imaginary parts of the dielectric constant for alumina nanoparticles were calculated.•Using a novel method, evaluation of optical dispersion and UV–visible absorption were performed.

In this work, we prepared thin films of aluminum oxide (Al2O3) with different thicknesses, using a wet chemical process. The Al2O3 nanoparticles with an average size of 40 nm were dispersed in water and deposited on soda glass substrates. The morphology of the resulting thin films was characterized by means of scanning electron microscopy. The optical properties of the thin films were studied by measuring reflectance and transmittance. A theoretical description of the reflection and transmission mechanism of the films was developed by measuring the thickness and spectral behavior of the refractive index. Numerical evaluations were used for modeling the optical spectra of the thin films of alumina. By fitting numerical curves to the experimental data, the extinction coefficient and refractive index were obtained. The dielectric constant and optical properties of the colloidal solution of the particles were also studied.