Determination of structural features of silver nanoparticles synthesized by vacuum thermal evaporation on a carbon substrate

Silver is one of the most promising nanomaterials for plasmonic applications, but it has become clear that the shape and internal symmetry of nanoparticles can significantly affect the scattering and absorption of light waves. Therefore, for the use of silver nanoclusters in plasmonic applications, it is very important to determine the conditions of stability of the structure and form of Ag nanoparticles. To this end high-resolution electron microscopy was used to examine initial and annealed arrays of silver nanoparticles with diameters ranging from 0.8 to 9.4 nm, formed on a carbon substrate by vacuum thermal evaporation. It was found that small Ag nanoparticles (D < 3.0 nm) have almost perfect FCC structure, while nanoparticles of larger diameter unexpectedly have predominantly icosahedral or decahedral facets. To explain this contradiction from the perspective of standard crystallographic theory, molecular dynamics simulations using the TB-SMA potential were conducted to study the stability limits of structural modifications of silver nanoclusters of similar diameters, and possible atomic rearrangement mechanisms that could lead to such experimental results were found. Based on the results of the computer analysis, conclusions were drawn about the technological possibilities of creating the desired crystal structure of Ag nanoparticles when preparing SERS substrates.