Fabrication of porous silica with three-dimensional periodicity by Si anodization

Ordered nanoporous silica has been fabricated using self-assembled polystyrene beads as a template for the anodization of a Si substrate in an aqueous solution. The closely packed structure of the nanospheres formed on the Si substrate could act as a template during anodization without additional fixation of beads onto the underlying substrate. The obtained porous silica with spatially ordered features up to a thickness of 5 mum, which could be produced only in the voids between the beads on the substrate, had a structure inverse to the colloidal crystal structure used as a template. The hole interval of porous silica, which was in good agreement with the diameter of the nanospheres, was slightly lower than that achieved by a conventional dry process.