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

该研究旨在开发新的人工控制技术，以控制低维纳米结构的尺寸、形状和位置，并有望实现新的器件应用。主要研究结果如下：1.提出了聚焦离子束（FIB）衬底纳米图案化和半导体连续生长的基本思路; 2.通过FIB在衬底上形成纳米线，实现了ZnO纳米点沿着线的选择性生长。在一定的生长条件下，纳米点呈周期性排列。3.提出了一种在SiO2表面大面积形成纳米孔的新方法，孔间距小于1 μm。ZnO在衬底上的生长导致一个纳米点在一个纳米孔上，即实现了对纳米点位置的完全控制。即使纳米点之间的间距小于200 nm，也几乎可以完全控制。4.纳米孔上选择性形成纳米点的机制是通过FIB注入的Ga与ZnO生长前体之间的相互作用实现的。在生长温度下，Ga的液相可以与前驱体反应，在纳米孔中形成核中心。5.确认了单个ZnO纳米点的阴极发光，证实了纳米点中的量子效应，表明纳米点具有高的光学质量，可以应用于实际器件。随后是纳米线的形成。这些现象在大气压附近并不常见，而MOCVD生长是在大气压下进行的。总之，通过FIB对衬底表面进行纳米图案化或在表面上形成清晰的台阶边缘，已经成功地实现了对纳米结构的人工控制。结果突出显示为一种新的技术，允许各种纳米结构设备。

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.