Influence of the bilayer thickness on the optical properties of Al2O3-Y2O3 dielectric nanolaminate films grown by thermal atomic layer deposition

Abstract

This work focuses on the study of the optical properties of nanolaminate films of Al2O3-Y2O3 bilayers. Nanolaminates were grown by means of thermal atomic layer deposition (ALD). The multilayer thickness, refractive index and optical bandgap were studied via spectroscopic ellipsometry. Ellipsometric data revealed an increase of the refractive index from 1.9 to 2.2 at 190nm wavelength when the bilayer thickness varies between 4 and 10nm. These results demonstrate that the refractive index can be modulated by varying the nanolaminate thickness. Optical bandgap values, obtained by the Wemple and DiDomenico model, indicate that the bilayer thickness decrease leads to an increase of the optical bandgap (ΔEg=0.8eV), as well as Eg modulation as a function of the bilayer thickness. The optical properties show that this material could be exploited for designing optical multilayered coatings suitable for nanoscale optoelectronic devices.