The Molecular Study on Size and Vacancy Density Effects of Cu Nanowires
I-L Chang, C-Y Tsai and Y-C Chen
National Chung Cheng University, TW
nanowire, elastic moduli, vacancy density
In current research, the molecular method is applied to study the mechanical and thermal properties of copper nanowires for their wide application in semiconductor industry. An approach that could be employed to realize the simple tension stress state is adopted and subsequently applied to investigate the effect of characteristic sizes, crystal orientations, and loading conditions on the material properties of nanowires. Embedded-atom-method (EAM) potential has been adopted to describe the interactions between atoms for face-cubic-center single crystal copper. The cross-sectional dimensions of the nanowires vary from 4 to 40 lattice spacings (or 1.4-14.4 nm). The periodic boundary condition is applied in the length direction to represent an infinite long wire. Moreover, vacancy is one of the commonly observed point defects inside materials. In our research, the effects of vacancy densities on the physical properties of copper nanowires are also considered. Two different types of vacancy configurations are taken into consideration. One is that the vacancy sites are randomly chosen based on the various defect densities. The other is to arrange the vacancy sites so that the surface to volume ratio is maximized.
Our research systematically analyzed the effects of nanowire sizes, crystal orientations, and vacancy densities on the material behaviors of nanowires. It is shown that the physical properties of nanowires (i.e., Young’s modulus, Poisson’s ratio, thermal expansion coefficient, etc) depend on the lateral size of nanowires and the trend of size dependence is significantly influenced by the crystal orientations. It is also learned that the vacancy densities affect the mechanical behaviors of the nanowires.
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Nanotech 2006 Conference Program Abstract