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Fabrication of nanostructures has so far been extensively studied in order to develop electronic or photonicdevices that work with new operating principles such as quantum effects. There are generally two complementaryapproaches to fabrication of nanostructures on solid substrates. One is the top-down process which is typified by theconventional lithographic technique widely used in Si LSI technology, and the other is the bottom-up process in whichself-organization or self-ordering is used. For a lithographic technique, it is not easy to fabricate nanostructures, whilewe can put elemental devices at desired positions on solid substrates such as silicon crystals. For a self-organizationprocess, on the other hand, it is not easy to put nanostructures at desired positions on substrates, while we can easilyform nano-scaled structures. Therefore, it is required for the fabrication of practical nano-scaled electronic devices touse a so-called "hybrid" process in which these complementary techniques are combined.
It is well-known that on anodization in suitable electrolytes, the so-called "valve" metals such as aluminium,tantalum, zirconium and titanium, undergo formation of porous anodic oxides with the self-ordered structures. Thoseself-ordered nanostructures may be utilized as the fundamental elements of nanoelectronic devices. In this study, wehave tried to fabricate single-electron-transistors (SETs), dye-sensitized solar cells (DSCs), and biosensing devices, byusing the hybrid process in which anodization for formation of porous anodic oxides is combined with the conventionalphotolithographic technique. We used porous alumina nanohole arrays for the fabrication of SETs and biosensors, andTiO2 nanotubes for the fabrications of DSCs. We demonstrate that porous alumina-based SETs we fabricated with ourhybrid process, exhibit an extremely large Coulomb energy, approximately 2 eV, and operate at room temperature [1].
References
1. Y. Kimura, K. Itoh, R. Yamaguchi, K. Ishibashi, K. Itaya, and M. Niwano, Appl. Phys. Lett. 90, 093119 (2007).
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