Development of a spontaneous immersion process for deposition of cerium oxide coatings on copper substrates

A spontaneous immersion process has been developed to deposit cerium oxide/hydroxide coatings on copper foil substrates. The immersion process selectively deposits adherent cerium oxide/hydroxide coatings on exposed copper areas using an aqueous, room temperature process. The development and optimization of process parameters that result in film deposition and the characterization of the coatings are described. The effect of process parameters and bath additives with respect to coating morphology and formation are discussed. Cerium oxide/hydroxide coatings on copper foils were found to consist primarily of tetravalent cerium compounds by X-ray photoelectron spectroscopy, exhibiting a previously unreported crystal structure by X-ray and selected area electron diffraction. The coatings were composed solely of cerium and oxygen with no copper incorporated within the coating by Auger electron spectroscopy. Deposition was very sensitive to process parameters, in particular pH and hydrogen peroxide concentration. Millimolar additions of chloride ion were found to increase the deposition rate. Uniform, adherent coatings ranging from 40 to 250 nm were produced under optimum conditions.