Two-dimensional magic Ag nanopucks on Pb quantum islands

Periodic patterns of electronic origin found on Pb quantum islands can be employed as the templates to grow self-organized nanopucks of various materials. Owing to a strong interaction existing between Ag and the template, nearly perfect two-dimensional arrays of Ag nanopucks can be grown from 70 K to 150K. Not only is the notable site-selected feature of Ag nanopucks observed on Pb islands but their size distribution also registers a remarkable abundance variation. Those nanopucks with significantly enhanced intensity are denoted as two dimensional magic Ag nanoclusters. Detailed calculations based on \textit{ab initio} density functional theory have been made to illuminate how the size and shape effects related to electronic confinement influence the formation of two-dimensional metal nanostructures. Furthermore, when the Ag nanopuck grows to a certain size, the geometrical effect takes hold from the electronic effect as the major attribute, which drive the Ag nanopucks towards well defined hexagonal crystalline structures.