title: Quantum well states in two-dimensional gold clusters on MgO thin films.
abstract: The electronic structure of ultrasmall Au clusters on thin MgO/Ag(001) films has been analyzed by scanning tunneling spectroscopy and density functional theory. The clusters exhibit two-dimensional quantum well states, whose shapes resemble the eigenstates of a 2D electron gas confined in a parabolic potential. From the symmetry of the highest occupied (HOMO) and lowest unoccupied molecular orbital (LUMO) of a particular cluster, its electron filling and charge state is determined. In accordance with a Bader charge analysis, aggregates containing up to 20 atoms accumulate one to four extra electrons due to a charge transfer from the MgO/Ag interface. The HOMO-LUMO gap is found to close for clusters containing between 70 and 100 atoms.
authors.affiliation: Fritz-Haber Institut der MPG, D14195 Berlin, Germany.
authors.forename: X
authors.initials: X
authors.lastname: Lin
authors.forename: N
authors.initials: N
authors.lastname: Nilius
authors.forename: H-J
authors.initials: HJ
authors.lastname: Freund
authors.forename: M
authors.initials: M
authors.lastname: Walter
authors.forename: P
authors.initials: P
authors.lastname: Frondelius
authors.forename: K
authors.initials: K
authors.lastname: Honkala
authors.forename: H
authors.initials: H
authors.lastname: Häkkinen