Elucidation of the thickness inside the niobium anodic oxide film and its effect on adhesion to polyimide film

Abstract

Niobium oxide films prepared via anodic oxidation are known to exhibit various colors. These colors are affected by the voltage during anodizing treatment to produce such thick film. The anodic oxidation reaction stops when the applied voltage reaches its saturation value. At this point the film stops growing, its thickness of the internal oxide layer being proportional to the applied voltage. Therefore, this study aims to clarify the relationship between the oxidation state inside the anodized film and its thickness.We also attempted to anodize a polyimide (PI) film, which is a flexible resin material. Because such a PI film is nonconductive, it was sputter-coated with an intermediate layer of niobium before anodization. To enable adhesion to the PI film, the Nb-sputtered film was subjected to surface modification via oxygen plasma treatment. Finally, the Nb-coated PI film was subjected to anodization. Detailed optical comparison was performed between the anodized Nb-coated PI substrate and anodized Nb plate substrate.