Thermal fragmentation of nano-size clusters on surfaces

Nano-size silver clusters deposited on a silicon surface with a native-oxide layer undergo rapid thermal annealing, and after fast cooling a partial fragmentation into smaller clusters is observed. The observations are explained by a simple model where the behavior of a liquid droplet on a surface is characterized by the surface tension for a free droplet and the surface tension at the interface with the silicon surface. A method is suggested for the determination of the ratio of these parameters. Within the framework of this model cluster fragmentation into several smaller droplets is caused by thermal fluctuations due to droplet oscillations. The model could prove useful for controlling the size of nano-particles on a surface.