Ellipsometric characterization on multi-layered thin film systems during hydrogenation

Ellipsometric characterization on the basis of multi-layered modeling is proposed to describe the optical and electrical property transients of hydrogenated films. In particular, two-step modeling is developed to make ellipsometric characterization on the yttrium film and the palladium capped yttrium film deposited on the SiO₂ glass substrate. In the former, Y₂O₃ film deposited on SiO₂ substrate is prepared to estimate the dielectric response of yttrium oxide layer as the first step. These data are further utilized in the second step to determine optical and electric properties of yttrium-base multi-layers which are composed of metallic yttrium, composite of metallic yttrium and Y₂O₃, and Y₂O₃ layer with surface roughness. In the latter, a palladium film deposited on SiO₂ substrate is prepared to investigate the dielectric response of palladium hydrides. The estimated dispersion functions are further used in the multi-layered modeling for hydrogenated Pd-capped yttrium films on the SiO₂ substrate. Under the ambient hydrogen pressure, palladium coated yttrium films have low resistivity and hydrogenated yttrium is still metallic. This palladium coating works as a top capping layer for yttrium film during hydrogenation and de-hydrogenation.