Study of Nano-fabrication and Tunneling Phenomenon of Nanowires at Tip-Surface studied by UHV electron microscoopy

在超高真空电子显微镜下制备金属纳米线，研究纳米线的结构。此外，我们还对金属纳米线的高分辨率电子显微镜图像进行了计算机模拟。研究了纳米线的结构与电导之间的关系。我们发现，对于金纳米线，金纳米线表现出不同于晶体结构的特殊结构。新结构具有同轴管状结构，类似于碳纳米管。然而，与碳纳米管的石墨片不同，金管由三角形网络组成。因此，金纳米线的结构有望拥有决定纳米线稳定结构的神奇数字。我们发现最外层的纳米管的神奇数字是7,11,13,14。最精细的纳米线是由原子的线性链组成的单原子排。我们发现金原子可以形成一个悬浮的单行链，键长为4A。我们模拟了金链的图像，并验证了该链中分离的4A金原子之间没有胶原子。综上所述，我们发现金纳米线具有同轴管状结构，单链断裂前的键长为4A。然而，这些特定纳米线的电导率在未来仍有待研究。

We made metal nanowires in ultra-high-vacuum electron microscope to study the structues of nanowires. In addition, we made computer simulation of the high-resolution electron microscope images of metal nanowires. Also we investigated relationship between the structure and conductance of the nanowires. We found for gold nanowires that the gold nanowires exhibit specific structure that is different from the crystaline structure. The new structures had co-axial tube structure, similar to carbon nanotubes. The gold tube, however, consists of the triangular network, dissimilar to graphite sheet of the carbon nanotubes. The structure of gold nanowires, then, expected to have the magic number that determine the stable structure of the nanowire. We found the magic number of the outer-most tube is 7, 11, 13, 14 for the fine nanotubes. The finest nanowire is a single atomic row, of a linear chain of atoms. We found that gold atoms could form a suspended single row chain, with a large bond length of 4A. We simulated the image of gold chain, and verified that the chain has no glue atoms between the 4A separated gold atoms.In summary, we found gold nanowires have co-axial tube structure, and a single chain has even 4A bond length before its break. Conductance of these specific nanowires, however, have remained to be investigated in future.