Electrode effects on the dielectric permittivity of SiO2 thin films

The dielectric permittivity of amorphous SiO2 thin films could be remarkably increased by the evaporation of palladium electrodes. The evaporation of gold electrodes does not show a comparable effect. Gold electrodes reproduce the value for the dielectric permittivity of SiO2, which is expected from literature. Because the preparation processes of both types of electrodes have been carried out in the same manner, the detected increase of the dielectric permittivity must be caused by the physical properties of the used evaporated material. A significant difference between gold and palladium is the ability of palladium to absorb large amounts of hydrogen. Therefore we assume in case of evaporated Pd-electrodes a diffusion process of protons into the insulator, which cause additional relaxation centres. The contribution of these relaxation centres to the polarization is measured as an enhanced dielectric permittivity of the SiO2 thin film.