The fabrication of high-quality periodic porous alumina templates

Porous alumina films can be achieved by anodizing an ultra pure aluminum sheet in proper conditions. Both the distribution and the size of the pores are regular. The depths of the pores are uniquely limited by the anodization time thus very deep pores can be obtained, in the order of mm. Such a porous structure can be employed to serve as the templates for nano-sized materials. The Oxalic acid of 0.3 mol/L was used in our experiments with the applied DC voltage 40 V. The two-step method was involved to fabricate the templates. The resultant templates exhibit regular porous section. The pore size is similar to 40-70 nm and the pore-pore spacing is similar to 110 nm. The depth is similar to 0.4 mm. The dependence of the template quality on the solution ( oxalic acid) temperature was analyzed and the comparison between the single-step and two-step anodization was made. The results indicate that low solution temperature and two-step method are necessary.