原子尺度金属纳米线的结构和性质

当物质尺度减少到几层原子时，形成超细的纳米结、纳米线、或者纳米团簇，原有凝聚态物质的结构和物理性质将不再保持，而呈现出许多令人惊奇的奇异特性。本文重点讨论直径大约3nm以下，具有足够长度的、原子结构往往不同于体材料的准一维金属纳米结构，我们称之为原子尺度金属纳米线或超细金属纳米线（也称为金属原子线）。近年来实验上已经制备和表征出在超高真空中悬挂在两个顶针尖端的Au、Pt、Cu等金属纳米线和纳米管，金属线直径达到1nm以下而长度为6nm以上。通过高分辩电子显微镜观察，它们是同轴圆管（或壳）组成的、类似纳米碳管的单壳或多壳结构，管由绕着线轴的螺旋原子绳构成。理论工作围绕这种新奇结构形态的形成机制、奇异的物理性质和可能的应用前景而同时展开。这是一个崭新的纳米世界，无论是对基础的低维物理还是未来分子电子设备的应用，都将产生深远的影响，有许多奇妙的现象正等待人们去发现。本文将对最近几年原子尺度金属纳米线研究工作的主要进展和发展趋势作一个概述，并重点介绍本组有关的具有螺旋结构的纳米线的各类新奇结构和物理性质。

STRUCTURES AND PROPERTIES OF METALLIC NANOWIRES IN ATOMIC SCALE

When matter is reduced to just a few layers of atoms, being ultrathin nanocontact, nanowires, or nanoclusters, the structures and properties of solid matter often do not remain. Their novel structures and properties are surprising. We focus upon the metal nanowires with diameters less than 3.0 nm. Recently, very thin Au, Pt and Cu wires and tubes with a helical structure have fabricated experimentally. The metal nanowires with more than 6 nm in length and diameters down to 1 nm were successfully prepared and characterized. By using the ultrahigh vacuum transmission electron microscopy, these nanowires with structures consisting of coaxial cylindrical tubes, or shells are observed, similar to the single and multishell structures of carbon nanotubes. Each shell shows helical atom rows coiled round the wire axis. Theoretically, structural mechanisms, physical properties and technological applications of ultrathin metal nanowires are investigated at the same time. It is a new nanofield from newpoint of both low dimensional physics and technological applications. In this review, after summaring experimental results, we have discussed recent theoretical progress and development trends on studies of metal nanowires in atomic scale, especially, based on our own works, the novel structures and physical properties of nanowires.