Fast Diffusion and Void Formation in a Two-Segment Copper-Tin Lead-Free Nanowire System with One-Dimensional Confinement

We present experimental observations of electron-beam irradiation induced diffusion and void formation confined in a one-dimensional two-segment copper-tin (Cu-Sn) nanowire system. The two segmented Cu-Sn nanowires were synthesized by a layer-by-layer electrodeposition method using a nanoporous template. The structure and morphology of the nanowires were characterized by SEM, STEM, TEM, EDS and elemental mapping. Under e-beam irradiation, it is found that the nanowire surface oxide effectively confined the movement of metallic copper and tin atoms and the void regions were formed due to anisotropic diffusion rates and/or Sn melting. It is also seen that Cu/Sn alloy nanoparticles were formed on the oxide layer in the void regions. Such 1-D cylindrical nanowire structure presents an ideal system for understanding dimensionally confined transport phenomena and alloy formation at the nanometer scale.