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

The coalescence of two single-crystalline Au nanoparticles on surface of amorphous SiOx 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 SiOx 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.