High-resolution ultrahigh-vacuum electron microscopy of helical gold nanowires: junction and thinning process.

Helical multishell (HMS) gold nanowires were observed in situ by ultra-high-vacuum electron microscopy. During thinning of the helical nanowire, a junction was formed between two nanowires of different diameter. The structure of the gold junction is proposed in comparison with the multiwall carbon nanotube. The gold junction has a dislocation-like core to accommodate the number difference of the atomic rows that compose the HMS nanowires, while the carbon junction has a pair of five- and seven-membered rings. Thinning of the helical gold nanowire by electron-beam radiation can be caused by the climbing motion of the dislocation-like core along the nanowire.