Surface characteristics of silver oxide thin film electrodes for supercapacitor applications

In this paper the preparation of nano-structured silver oxide thin films with different oxidation states with promise as electrode materials for supercapacitors by reactive magnetron sputtering is investigated. The chemical, structural, surface morphological dependence of the films on oxygen gas flow rate and deposition power were examined by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The average thickness of the films was controlled in the range of ≈50–330 nm. The XRD spectra of the films indicated the formation of bi-phase films comprised of silver and silver oxides with different oxidation states. The wettability of the films in contact with different probing liquids was investigated by measuring the contact angles using a goniometer. It was shown that the silver oxide films are relatively hydrophilic and increasing oxygen flow rate increases the wettability of the films toward water as a result of an increase in the oxidation state of the films and consequently clustering of electrons in polar molecules of water around the oxides at higher oxidation states. This is further confirmed by the analysis of the surface energy measurements.