Interconnections between electronic structure and optical properties of multilayer nanolaminate TiAlN/Ag and Al2O3/Ag coatings

Multilayer nanolaminate TiAlN/Ag and Al2O3/Ag metal-insulator-metal (MIM) coatings with thicknesses of individual layers from a few to several hundreds of nanometers were fabricated by direct current magnetron sputtering. Their optical transmittance and reflectance spectra were measured for photon energies 1–5 eV (1240–248 nm). The spectra were non-monotonous as their transmission and reflection bands were strongly dependent on the coating architecture. A set of advanced electron spectroscopy methods was used to analyse the electronic structure of the coatings controlling optical properties. Energies of plasmons peaks and the distribution of their intensities are functions of the Ag layers thickness as well as the composition and thickness of the dielectric nanolayers in the MIM nanocomposite. Statistical analysis established the cross-correlations between geometrical parameters of the coatings, transmissions and reflection bands on the optical spectra and parameters of the electronic structure. Particularly, the blue side of the transmittance band is controlled by plasmons while the dielectric band gap determines the transmittance of the red side. The obtained experimental results allowed us to fulfil the computed architectural design of a multilayer Al2O3/Ag coating with a narrow bandwidth in the visible light region and strong reflection in the infrared and ultraviolet regions.