Scanning Transmission Electron Microscopy Characterization of Nanostructured Palladium Film Formed by Dealloying with Citric Acid from Al–N–Pd Mother Alloy Film

Abstract

A high-purity palladium film with a three-dimensional nanoporous structure was fabricated from a reactive sputtered Al–N–Pd alloy film by a dealloying method that used citric acid chelation. Its characteristic porous structure could be controlled by the concentration of nitrogen gas in the Ar sputtering gas. The added nitrogen gas inhibited the formation of the intermetallic Al₄Pd phase in the as-deposited film, thereby improving the purity of Pd in the dealloyed nanoporous Pd film up to 99 at%. Furthermore, the formed structure of the dealloyed film changed with the nitrogen gas concentration during initial sputtering, i.e., the structure of the film could be controlled from a three-dimensional nano-network to an aggregated nanoparticle-like structure with increasing N₂ gas concentration.