School of Chemistry, Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and Bioengineering Research (AMBER), Trinity College Dublin, Dublin 2, Ireland.
Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
Science. 2017 Jul 28;357(6349):397-400. doi: 10.1126/science.aan4797.
We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy.
我们使用扫描隧道显微镜研究了近乎平面的铜纳米晶（111）薄膜表面的低角度晶界。晶界的存在及其在薄膜表面的出现形成了由离解边缘位错组成的山谷和部分位错重新组合的脊。几何分析和模拟表明，山谷和脊是由晶界能降低驱动的面外晶粒旋转形成的。这些结果表明，一般来说，不可能形成具有小堆垛层错能和/或大弹性各向异性的铜和其他金属的平整二维纳米晶薄膜，这会导致位错线能量的各向异性很大。
