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

本研究旨在发展低维纳米结构尺寸、形状和位置的人工控制新技术，以期在器件上有新的应用。结果总结如下：1。为此提出了一种基本思路，即利用聚焦离子束（FIB）对衬底进行纳米图形化并连续生长半导体。FIB在衬底上形成纳米线，导致ZnO纳米点沿着纳米线选择性生长。在一定的生长条件下，纳米点呈周期性排列。本文提出了一种在SiO2表面大面积形成纳米孔的新方法，纳米孔的间距小于1 μm。ZnO在衬底上的生长导致一个纳米点在一个纳米孔上，即实现了纳米点位置的完全控制。即使纳米点之间的间距小于200nm，也几乎完全控制。在纳米孔上选择性形成纳米点的机制归因于FIB工艺注入的Ga与生长ZnO的前驱体之间的相互作用。在生长温度下，Ga液体与前驱体发生反应，在纳米孔中形成核中心。证实了单个ZnO纳米点的阴极发光，并证明了纳米点中的量子效应，表明纳米点具有高光学质量，可以应用于实际器件。观察到沿蓝宝石衬底阶梯边缘形成ZnO纳米点。随后是纳米线的形成。在MOCVD生长所处的大气压附近，这些现象并不常见。综上所述，通过FIB在衬底表面形成纳米图案或在表面形成清晰的阶梯边缘，成功地实现了对纳米结构的人工控制。该结果被强调为一种新的技术，允许各种纳米结构器件。

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.