Quantum well states in two-dimensional gold clusters on MgO thin films.
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.
Lin
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X
Fritz-Haber Institut der MPG, D14195 Berlin, Germany.
Nilius
N
N
Freund
H-J
HJ
Walter
M
M
Frondelius
P
P
Honkala
K
K
Häkkinen
H
H