BRIEF DESCRIPTION OF THE DRAWINGS [0064] In the accompanying drawings: [0065]FIGS. 1A and 1B are a SEM photograph view and a schematic diagram, respectively, of the anodic oxidation of the present invention; [0066]FIG. 2 is a diagram showing the relationship between the applied voltage and the current in the anodic oxidation process of the present invention; [0067]FIGS. 3A to 3D are diagrams showi