Web Release Date: January 15,
Hexa-peri-hexabenzocoronene on Ag(111): Monolayer/Multilayer Transition of Molecular Orientation and Electronic Structure
and
Humboldt-Universität zu Berlin, Institut f. Physik, Newtonstr. 15, D-12489 Berlin, Germany, Technische Universität Chemnitz, Institut f. Physik, Reichenhainer Str. 70, D-09126 Chemnitz, Germany, Universität Hamburg, Institut f. Experimentalphysik, D-22761 Hamburg, Germany, and Max Planck Institut für Polymerforschung, D-55021 Mainz, Germany
Received: September 17, 2007
In Final Form: November 4, 2007
Abstract:
The molecular orientation and electronic structure of hexa-peri-hexabenzocoronene (HBC) deposited on Ag(111) was investigated in the mono- and multilayer regime by near edge X-ray absorption fine structure
spectroscopy (NEXAFS), scanning tunneling and scanning force microscopy (STM and SFM), and ultraviolet
photoelectron spectroscopy (UPS). We found that the molecular orientation changed as a function of coverage,
exhibiting a transition from flat lying HBC in the monolayer to molecules being 43
inclined relative to the
substrate plane in the multilayer. This structural transition was accompanied by a rigid shift of molecular
energy levels by 0.3 eV toward higher binding energy between mono- and multilayer. In addition, broadening
of the highest molecular levels by ca. 0.35 eV was observed in the multilayer, suggesting the formation of
extended intermolecular energy bands.
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