Fabrication of conductive interconnects by Ag migration in Cu–Ag core-shell nanoparticles

Fabrication of conductive nanoparticle films is observed in Cu–Ag core-shell nanoparticles by fast diffusion of Ag at 220 °C from particle surfaces, leading to the formation of sintered necks of Ag at the initial particle-particle contacts. Transmission electron microscopy showed that the necks were pure Ag and that particle surfaces away from the contacts were nearly Ag-free. The extent of neck formation is controllable by the choice of initial Ag thickness. Analysis of the thermodynamics of the Ag–Cu system and the relative diffusivities of Ag and Cu provide criteria for fabrication of other core-shell two-phase systems by the same mechanism.