Twin-Boundary Reduced Surface Diffusion on Electrically Stressed Copper Nanowires

Surface diffusion is intimately correlated with crystal orientation and surface structure. Fast surface diffusion accelerates phase transformation and structural evolution of materials. Here, through in situ transmission electron microscopy observation, we show that a copper nanowire with dense nanoscale coherent twin-boundary (CTB) defects evolves into a zigzag configuration under electric-current driven surface diffusion. The hindrance at the CTB-intercepted concave triple junctions decreases the effective surface diffusivity by almost 1 order of magnitude. The energy barriers for atomic migration at the concave junctions and different faceted surfaces are computed using density functional theory. We proposed that such a stable zigzag surface is shaped not only by the high-diffusivity facets but also by the stalled atomic diffusion at the concave junctions. This finding provides a defect-engineering route to develop robust interconnect materials against electromigration-induced failures for nanoelectronic devices.

Automated summary

Surface diffusion is closely related to crystal orientation and surface structure, and fast surface diffusion accelerates phase transformation and structural evolution of materials. In this study, researchers observed that a copper nanowire with dense coherent twin-boundary (CTB) defects evolved into a zigzag configuration under electric-current driven surface diffusion. The hindrance at the CTB-intercepted concave triple junctions reduced the effective surface diffusivity significantly. This finding offers a defect-engineering method for developing robust interconnect materials against electromigration-induced failures in nanoelectronic devices.