Life is supported by highly sophisticated organisms composed of assemblies of proteins and nucleic acids, which work as molecular machines. Molecular machines show many interesting characteristics, among which are self-assembly and highly efficient energy transduction. Self-assembly would also be essential in engineering application, when one would try to handle molecules for nanometer-scale fabrication. Self-assembling proteins provide a way to realizing important break through in making nanometer-size devices or functional structures based on principles completely different from what the present technologies are base on.
As a trial of fabricating nanometer-size functional structures, we employed ferritin particle assembly to make nano-dots for quantum electronic devices. Ferritin consists of a protein shell with a diameter of 12 nm, which surrounds the core of Fe2O3 with a diameter of 6 nm. It is possible to make two dimensional crystals of protein molecule on a Si wafer using the method by Furuno et al. (Thin Solid Films 180, 23-30,1989). We treated ferritin crystals on Si wafer at around 400 C in a nitrogen atmosphere. This treatment burned out the protein shell and yielded two dimensional arrays of inorganic iron oxide dots on the Si wafer. The size and repeat distance of the dots were 6 and 12 nm, respectively, as measure by FE-SEM and AFM. As the diameter of the iron oxide dots is only 6 nm, this two dimensional array of inorganic iron oxide dots has a potential to be used as quantum dots. Feasibility study of the application of this dot array to the structure of semiconductor memory is now in progress.
Central Research Laboratories, Matsushita Electric Industrial Co., Ltd.
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