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Anodic Aluminum Oxide (AAO) has attracted considerable interest as a non-lithographic technique that utilizes the self-formed and ordered nano-structures because of its unique electric, optic, magnetic and optoelectronic characteristics. AAO can be obtained easily by anodizing high purity aluminum and the interpore distance and pore diameter can be controlled through the adjustment of the anodizing conditions such as electrolyte concentration, voltage, and temperature. Currently, phosphoric, oxalic and sulfuric acid are usually used as electrolyte for anodization. However, the periodicity of AAO obtained in these acids is limited in the range of 40 - 500 nm and it is difficult to obtain the periodicity of AAO under 50 nm. In this work, we used sulfuric/phosphoric acid mixture as new electrolyte to fabricate AAO which has a smaller periodicity than previous reports. We were able to fabricate AAO patterns with mean pore distance of 27 nm and mean pore diameter of 7 nm at 5 V at 5 °C. The present results suggest that the ordered AAO nano structures with small pore distance under 30 nm could be fabricated by adjusting the ratio of the different acids properly and we expect it could be utilized for uniform and high density quantum dots with increased quantum effect. |