Coalescence between Au nanoparticles as induced by nanocurvature effect and electron beam athermal activation effect

Abstract

The coalescence of two single-crystalline Au nanoparticles on surface of amorphous SiO_x nanowire, as induced by electron beam irradiation, was in situ studied at room temperature in a transmission electron microscope. It was observed that along with shrinkage of the SiO_x nanowire during irradiation, adjacent Au nanoparticles moved around and migrated close to each other. Once the two nanoparticles contacted with each other, a fast, massive atom transportation took place along their contact surface, where a neck region was created. With a further irradiation, the two nanoparticles rotated, aligning their crystal orientations, and gradually coalesced into a larger single-crystalline nanoparticle. The above coalescence process demonstrated an intriguing surface nanowetting ability and nanograin boundary dislocation climb and slip of Au NPs at room temperature as driven by the non-uniformly distributed nanocurvature over the surface of the two contacting nanoparticles as well as the beam-induced instability and soft mode of atomic vibration, which have been underestimated or neglected in the existing theoretical descriptions or simulations.