Metallic quantum dots

In a quantum dot, the electrons are confined in all three dimensions to a length scale of the order of the electron Fermi wavelength. Due to the confinement, quantum effects will dominate over the bulk properties and the energy spectrum becomes discrete, similar to that of an atom. In this review, we present a short introduction to electron confinement in nanosize structures and properties related to quantum size effects. Furthermore, we present a model for calculation of the electronic structure of adsorbed quantum dots, where we have focused on the system of Na on Cu(111). Our results are compared to experimental results from scanning tunnelling microscopy and photoemission spectroscopy. In addition, we present a study of CO adsorption on a small Na quantum dot. The resulting charge transfer turns out to depend critically on the size of the quantum dot, and the results are discussed in terms of electron structure and symmetry of relevant electron orbitals.