Beam generation and structural optimization of size-selected Au923 clusters
Size selected beam of Au923±20 clusters are generated in a gas-phase condensation cluster source equipped with a lateral time-of-flight mass selector. The beam current reaches up to 9.13 nA for small clusters and 80 pA for the Au923±20 clusters, which are then analyzed by a scanning transmission electron microscope. Four types of metastable structures are observed for the Au923±20 clusters including ino-decahedron (Dh), cuboctahedron and icosahedron (Ih) etc. The bulk-favorable cuboctahedron (i.e. face center cubic, Fcc) structure is found with only 10-20 percent, while the penta-rotating symmetrical structures (Dh / Ih) are dominant over three quarters. Changing the beam condition may optimize the clusters from Dh-dominant to Ih-dominant phase. This paves the way towards nanoparticles control beyond the diameters.