Condensed
Matter & Surface Sciences
COLLOQUIUM
Stefan Fölsch
Paul Drude Institute for
Quantum
confinement in surface-supported metal nanostructures
Aside from local surface characterization,
low-temperature scanning tunneling microscopy (LT-STM) is capable of
manipulating adsorbed atoms and molecules with atomic-scale precision. This
combined approach makes LT-STM a powerful experimental tool to explore
fundamental electronic processes in nanometric model
systems. The experiments discussed in this talk employ a Cu(111)
surface onto which perfect nanostructures are assembled by means of STM-based
manipulation. Using single Cu adatoms as building
blocks, we obtain zero-, one-, and two-dimensional quantum objects
(corresponding to the discrete adatom, monatomic adatom chains, and compact adatom
assemblies) with intriguing electronic properties. Depending on the shape of
the structure and the number of incorporated atoms we observe the formation of
characteristic quantum levels which merge into the sp-derived Shockley surface
state in the limit of extended 2D islands; this state exists on many surfaces,
such as Cu(111). Our results reveal the natural
linkage between this traditional surface property, the quantum confinement in
compact adatom structures, and the quasi-atomic state
associated with the single adatom. LT-STM provides
direct insight into how electronic properties evolve when building artificial
surface structures atom by atom. A detailed understanding of such a scenario is
an essential step towards the ultimate goal of tailoring magnetic and
electronic surface properties by controlling size, geometry, and composition at
the atomic level.