Orientation of pentacene molecules on SiO{sub 2}: From a monolayer to the bulk
- Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
Near edge x-ray absorption fine structure (NEXAFS) spectroscopy is used to study the orientation of pentacene molecules within thin films on SiO{sub 2} for thicknesses ranging from monolayers to the bulk (150 nm). The spectra exhibit a strong polarization dependence of the {pi}{sup *} orbitals for all films, which indicates that the pentacene molecules are highly oriented. At all film thicknesses the orientation varies with the rate at which pentacene molecules are deposited, with faster rates favoring a thin film phase with different tilt angles and slower rates leading to a more bulklike orientation. Our NEXAFS results extend previous structural observations to the monolayer regime and to lower deposition rates. The NEXAFS results match crystallographic data if a finite distribution of the molecular orientations is included. Damage to the molecules by hot electrons from soft x-ray irradiation eliminates the splitting between nonequivalent {pi}{sup *} orbitals, indicating a breakup of the pentacene molecule.
- OSTI ID:
- 20991250
- Journal Information:
- Journal of Chemical Physics, Vol. 126, Issue 15; Other Information: DOI: 10.1063/1.2717161; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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