Molecular Dynamics Simulation on Forming Process of Nano Contact

随着电子设备小型化的努力，元件尺寸接近纳米级。特别是元件间接触的形成过程是未来电子工业的关键技术之一，本课题的目的是通过原子模拟来阐明机械形成过程的机理和机理以及变形特性。(1)（2）对单晶体进行了从头算和EMT（Effective Media Theory）模拟，以评价EMT势的有效性;（3）利用EMT模拟对细丝进行了拉伸模拟。模拟（1）揭示了原子链的理想强度约为1 nN，并且链表现出比本体更高的强度和更低的伸长率。根据模拟（2），EMT模拟非常好地再现了无序原子结构（例如晶界）以及拉伸中的单晶的拉伸性质。模拟（3）揭示了纳米线的细化过程。由于位错从表面形核和快速弛豫，金属丝在拉伸时容易变形。在拉伸后期，原子的旋转控制变形过程。讨论了初始晶向对减薄过程的影响。

As the effort is made on the downsizing of electronic devices, the element size is approaching the nano-meter scale. Especially, the forming process of contact between the elements is one of key technologies in the future electronic industry.The purpose of this project is to elucidate the mechanism and mechanics of the mechanically forming process as well as the deformation property by atomic simulations.The following simulation of aluminum contact is carried out. (1) Ab initio simulation of atomic chain where atoms aline on a direction, (2) Ab initio and EMT (Effective Medium Theory) simulation on single crystal in order to evaluate the validity of EMT potential, and (3) tensile simulation of thin wire by means of the EMT simulation. The simulation (1) reveals that the ideal strength of atomic chain is about 1nN, and the chain shows higher strength and lower elongation than the bulk. From the simulation (2), the EMT simulation reproduces very well the tensile property of disordered atomic structure (e.g. grain boundary) as well as single crystal in tension. The simulation (3) reveals the thinning process of the nano-wire. The wire deforms easily in tension by dislocations nucleation from the surface and quick relaxation. At late stage of tension, the rotation of atoms governs the deformation process. The effect of initial crystal orientation on the thinning process is also discussed.