Thermal Properties of Nanobridges


Ho Jung Hwang Chung-Ang University

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As the scale of electronic devices continues to shrink, fundamental interest has focused on the nature of the mechanical, optical, and electrical behavior of one-dimensional nanometer-scale channels such as quantum wires and carbon nanotubes. The development of new experimental techniques such as mechanically controllable break junctions (MCBJs) and scanning tunneling microscopy (STM) has made it possible to form and to study atomic-sized junctions or contacts between macroscopical metals. The mechanical and electrical properties of nanocontacts between metallic bodies have been a subject of intensive research. Quantum point contacts are structures in which a ‘neck’ of atoms, of just a few atomic diameters, bridges two electrical contacts. The results prepared by contacting a metal surface with an STM and by other methods have typically displayed a conductance quantized in steps of 2e2/h, where e is the electron charge and h is Planck's constant. The mechanical properties of nanocontacts have shown that before the first yielding, nanowires preserve the elastic stage and, after that, the elongation deformation proceeds in alternating quasi-elastic and yielding stages.

The thermal properties of infinite nanowires with periodical boundary conditions (PBCs) along the nanowire axis have been investigated using molecular dynamics (MD) simulations. For example, the MD methods were used to investigate the premelting of infinite Pb nanowires with the axis along a (110) direction and the melting of infinite Au nanowires with a multishelled structure. However, previous works have not been enough to provide the thermal properties of nanocontacts and nanobridges, such as the melting and the breaking of nanobridges. Nanobridges can be sustained by supporting layers in contact with both ends of the nanobridges. This condition is considered as a similar situation to that in which a string, such as a guitar string, is connected between two clamps separated by a fixed distance. Therefore the nanobridge can also make an oscillation at a resonant frequency to set up a standing wave pattern. Copper is an important engineering material, so in this investigation, we use MD simulations to investigate ultrathin Cu nanobridges. In this paper, we show the thermal properties of nanobridges in Sections “Oscillations of Nanobridges” and “Melting and Breaking of Nanobridges,” using a classical MD simulation.