Study of Structural Colors of Anodic Alumina Thin Films Prepared by a Point Electrode

Abstract

For this study, porous anodic alumina thin films with annular structural colors were fabricated in a phosphoric acid electrolyte by the one-step oxidation of an aluminum (Al) sheet. In this case, small carbon balls were used as the cathode and an Al sheet used as the anode, with the distance between cathode and anode remaining adjustable. Electron microscopy shows that the different parts of films are different in microstructure. Results additionally reveal that the depth and aperture of nano-holes diminished symmetrically outward from the center of the films. It is possible to control ring density by changing the oxidation time and voltage. These experimental results, conducted using point electrode, are consistent with a theoretical study of the oxidation process and formation mechanism of anodic alumina thin films with annular structural colors.