Efficient fabrication of ordered alumina through-hole membranes using a TiO2 protective layer prepared by atomic layer deposition

Abstract

Ordered alumina through-hole membranes were obtained by a combination of the anodization of Al, formation of a TiO₂ protective layer, and subsequent etching. Two-layered anodic porous alumina materials composed of TiO₂-coated and noncoated alumina were prepared by the combination of the anodization of Al and the formation of a TiO₂ protective layer by atomic layer deposition (ALD). The obtained two layers of anodic porous alumina have different solubilities because the TiO₂ thin layer formed by ALD acts as a protective layer that prevents the dissolution of the alumina layer during wet etching of the sample in an etchant. After the selective dissolution of the bottom layer of porous alumina without the TiO₂ layer, an ordered alumina through-hole membrane could be detached from the Al substrate. This process allows the repeated preparation of ordered alumina through-hole membranes from a single Al substrate. By this process, ordered alumina through-hole membranes with large interhole distances could also be obtained. The obtained alumina through-hole membrane can be used in various applications.