Research on precise artificial structure and position control of ultra-small nanodots, nanorods, and nanolines

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The research has aimed at the development of new artificial control technology for size, shape and position of low dimensional nanostructures, with which novel device applications are expected. The results are summarized as follows ;1.The basic idea, that is, substrate nanopatterning with focused ion beam(FIB) and successive growth of semiconductors, is proposed for the purpose.2.Formation of nanolines on substrates by FIB resulted in selective growth of ZnO nanodots along the line. At the certain growth conditions, the periodical arrangement of the nanodots was performed.3.A novel technique to form nanoholes on the SiO2 surface over the wide area with the separation smaller than 1 μm has been developed. The growth of ZnO on the substrate resulted in one nanodot on one nanohole, that is, the complete control of position of a nanodot was achieved. The almost complete control was domonstrated even the separation between the nanodots was smaller than 200 nm.4.The mechanism of the selective formation of nanodots on nanohole was attributed to the interation between Ga implanted by the FIB process and precursors for growing ZnO. Liquids of Ga at the growth temperature may react with the precursors and form a nucleus center in the nanohole.5.Cathodoluminescence from single ZnO nanodot was confiremed and quantum effects in nanodots were evidenced, suggesting that the nanodots are of high optical quality capable of being applied to practical devices.6.Formation of ZnO nanodots along the step edge of sapphire substrate was observed. This was followed by the formation of nanolines. These phenomena have not been often observed near the atmospheric pressure under which the MOCVD growth has been done.In conclusion, artificial control of nanostructures has been successfully carried out by nanopatterning the substrate surface by FIB or by forming clear step edge on the surface. The results are highlighted as a novel technology to allow various nanostructure devices.