Electronic Structure of Organic Films on Metal Surfaces
Gina M. Florio, Department of Chemistry and the Department of Physics, St. John’s College of Liberal Arts and Sciences
Elio Vescovo, National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY
Abstract
The electronic structure of thin films of conjugated organic molecules adsorbed on graphite surfaces has been investigated using ultraviolet photoelectron spectroscopy. Ultraviolet photoelectron spectroscopy gives information about how the electronic structure of the molecule is altered upon adsorption to the metal surface. Specifically, the signatures of the highest occupied molecular orbitals are obtained relative to the Fermi level of the metal, providing direct information about changes in molecular electronic structure upon adsorption. Thin films of chrysene, naphthalocyanine, and pentacene were individually prepared in situ by vapor deposition on the basal plane of graphite and characterized by photoelectron spectroscopy under ultrahigh vacuum conditions. The spectral dependence on film thickness and the incident angle were investigated. Finally, the structural properties of the films are investigated using scanning tunneling spectroscopy and atomic force microscopy. The ability to characterize the structure and electronic properties of the metal-molecule interface is crucial to achieving a thorough understanding of nanoscale charge transport, and as such, this work is relevant to a variety of fields including molecular electronics, nanotechnology, and basic energy science.