The generation of hole array architectures with, for example, square or triangular patterns (see Figure) is achieved by controlling the spatial definition of the indentation sites for hole development in anodic porous alumina. The technique has potential for the fabrication of two‐dimensional photonic crystals, or carbon nanotubes with triangular or square cross section.

The conditions for the fabrication of ideally ordered anodic porous alumina with a high aspect ratio were examined using pretextured Al in oxalic acid solution. The obtained anodic porous alumina has a defect-free array of straight parallel channels perpendicular to the surface. The channel interval could be controlled by changing the interval of the pretextured pattern and the applied voltage. However, the depth at which perfect ordering could be maintained depended on the anodizing conditions, that is, the hole array with a high aspect ratio could be obtained only under the appropriate anodizing voltage, which corresponded to that of the long-range ordering conditions in the oxalic acid solution. Under the most appropriate condition, ideally ordered channels with an aspect ratio of over 500 could be obtained. From these results, it was concluded that the long-range ordering conditions significantly influenced the growth of channels in anodic porous alumina even in/on the pretextured Al.

Dot—or multiple dot—arrays of nanometer dimensions have applications in nanodevices. Control of the size and site of each dot is essential as variations can alter the optical or catalytic properties of the composite metal nanoparticles. A method is presented in which anodic porous alumina, a typical self‐organized structure, is used as an evaporation mask for the shadow evaporation of a metal beam, enabling the spatially resolved deposition of the metal—or several different metals—at the bottom of the apertures of the mask. Each dot in the array is composed of two or three deposits of one or more metals.

Nanochannel arrays with an ideally ordered hole configuration with a 63 nm hole periodicity and 15–40 nm hole diameter were fabricated using anodization of the pretextured Al in sulfuric acid solution. The SiC mold with an array of convexes, which was prepared by electron beam lithography, was used for the nanoindentation of the Al. The periodicity of convexes was adjusted to the self-organized periodicity in sulfuric acid solution. The obtained concaves on Al initiated the hole development during the anodization and generated the ideally ordered hole configuration with a 63 nm period. Under the appropriate anodization conditions, anodic porous alumina with an aspect ratio of over 20 was obtained.

We have fabricated arrays of 60-nm-size magnetic Fe nanodots over a 1-cm2-size area using nanoporous alumina membranes as shadow masks. The size and size distribution of the nanodots correlate very well with that of the membrane pores. By placing an antiferromagnetic FeF2 layer underneath the Fe nanodots, an exchange anisotropy can be introduced into the Fe/FeF2 system. We have observed an increase in the magnetic hysteresis loop squareness in biased nanodots, suggesting that exchange bias may be used as a tunable source of anisotropy to stabilize the magnetization in such nanodots.

The self-repair of an ordered pattern of nanometer dimensions based on the self-compensation properties of anodic porous alumina is demonstrated. In a pretextured pattern formed on Al using the nanoindentation process with an array of convexes, the deficiency sites of the pattern were found to be compensated automatically during the anodization. Combining the self-compensation properties of the pore configuration of the anodic porous alumina with the preparation of a replica of the compensated porous structure allowed us to develop a process which has the capability of self-repairing the imperfections in the starting pattern. It was confirmed that deficiencies in the starting pattern could be repaired automatically in the Ni pattern regenerated using the self-compensated anodic porous alumina as a template.

Anti-reflection (AR) structures composed of an ordered array of tapered pillars were formed on the surfaces of two types of lens, microlens and Fresnel lens, through the nanoimprinting of polymer using molds prepared from anodic porous alumina. The use of anodic porous alumina for the preparation of mold for nanoimprinting allows the formation of AR structures on the curved surface of the lens, and could effectively suppress the reflectance of incident light. The process enables the high-throughput production of polymer lenses with AR structures and will be useful for the preparation of various types of functional optical devices.

Two-dimensional (2D) photonic crystals were fabricated using anodic porous alumina with a highly ordered air-hole array of triangular lattice with a high aspect ratio of over 200. The transmission properties of the obtained ordered air-hole array in the alumina matrix exhibited a stop band in the spectrum which corresponds to the band gap in 2D photonic crystals.