In situ observation of structural rearrangement of a Cu nanotwin particle

Cu nanotwin particles were successfully obtained on SiO₂ films through Ar ion beam to bombard the copper transmission electron microscopy (TEM) grid. The structural rearrangement of a large Cu nanotwin particle was observed in situ using high-resolution TEM under long-time electron beam irradiation. The rotation of the whole nanotwin particle was also observed. The Cu nanotwin particle possessed some independent subgrains. The crystal facets of the subgrains tended to be parallel to each other after rearrangement during electron beam irradiation. The deformation of the Cu nanotwin particle started from the central subgrains to the side subgrains. Structural rearrangement in single subgrain occurred in the opposite direction, from outside to inside. Strain fields in Cu nanotwin particle was mapped using geometric phase analysis, which displayed the decrease in the space between crystal facets and the change from tensile strain to compressive strain.