Graphene layer number dependent size distribution of silver nanoparticles

We observe that silver atoms deposited by thermal evaporation deposition onto n-layer graphene films condense upon annealing to form nanoparticles with an average diameter and density that is determined by the layer numbers of graphene films. The optical microscopy and Raman spectroscopy were utilized to identify the number of the graphene layers and the SEM (scanning electron microscopy) was used to observe the morphologies of the particles. Systematic analysis revealed that the average sizes of the nanoparticles increased with the number of graphene layers. The density of nanoparticles decreased as the number of graphene layers increased, revealing a large variation in the surface diffusion strength of nanoparticles on the different substrates. The mechanisms of formation of these layer-dependent morphologies of silver nanoparticles are related to the surface free energy and surface diffusion of the n-layer graphenes.