Substrate and size effects on the coalescence of small particles

Here we present experimental results, using high-resolution electron microscopy and real time video recording, on the liquid-like coalescence of small gold particles supported on silica. We report that particles that are few nanometers in size, and decoupled from substrate interactions, coalesce extremely fast, in fractions of a second. When the particles are properly supported on a substrate, coalescence is orders of magnitude slower, depending on the particle size, and influenced by the diffusion of atoms on the substrate surface. Necks are seen to develop distinctly during coalescence only for particles above certain size.