Fusion behaviour and mechanism of ultrafine Ag-Cu nanoparticles induced by electron beam irradiation

Understanding the thermal evolution mechanisms of metal nanoparticles (NPs) at the quantum-dot-scale is arrestive and meaningful for utilization of nanomaterials. Herein, an interesting fusion evolution phenomenon of Ag-Cu NPs induced by in-situ TEM high-energy electron beam illumination has been observed and investigated. It turned out that a rapid fusion process was in progress as reflected by the significant morphological change as the electron beam illumination time increased. The Ag-Cu NPs clusters tended to shrink their overall surface area along with the increase of sintering neck radii and decrease of neck curvature which was dominated by lattice diffusion mechanism. In addition, the necks among three Ag-Cu NPs continuously grew until the three particles became a short nanorod with a relatively uniform lateral diameter of about 20 nm after 300 sʹ illumination. It was also worthy of note that the smaller particles disappeared faster than bigger ones due to their highest surface energy.