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Author Capelli, R. ♦ Koshmak, K. ♦ Giglia, A. ♦ Mukherjee, S. ♦ Nannarone, S. ♦ Mahne, N. ♦ Doyle, B. P. ♦ Pasquali, L.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ ANISOTROPY ♦ CROSS SECTIONS ♦ DENSITY FUNCTIONAL METHOD ♦ DIELECTRIC MATERIALS ♦ EXPERIMENTAL DATA ♦ FILMS ♦ GOLD ♦ LAYERS ♦ SIMULATION ♦ SOFT X RADIATION
Abstract Resonant soft X-ray reflectivity at the carbon K edge, with linearly polarized light, was used to derive quantitative information of film morphology, molecular arrangement, and electronic orbital anisotropies of an ultrathin 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) film on Au(111). The experimental spectra were simulated by computing the propagation of the electromagnetic field in a trilayer system (vacuum/PTCDA/Au), where the organic film was treated as an anisotropic medium. Optical constants were derived from the calculated (through density functional theory) absorption cross sections of the single molecule along the three principal molecular axes. These were used to construct the dielectric tensor of the film, assuming the molecules to be lying flat with respect to the substrate and with a herringbone arrangement parallel to the substrate plane. Resonant soft X-ray reflectivity proved to be extremely sensitive to film thickness, down to the single molecular layer. The best agreement between simulation and experiment was found for a film of 1.6 nm, with flat laying configuration of the molecules. The high sensitivity to experimental geometries in terms of beam incidence and light polarization was also clarified through simulations. The optical anisotropies of the organic film were experimentally determined and through the comparison with calculations, it was possible to relate them to the orbital symmetry of the empty electronic states.
ISSN 00219606
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-07-14
Publisher Place United States
Journal Journal of Chemical Physics
Volume Number 145
Issue Number 2


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