NEXAFS investigations on ordered adsorbate layers of large aromatic molecules

Taborski, J.; Väterlein, P.; Dietz, Hendrik; Zimmermann, Uwe; Umbach, E.

doi:10.1016/0368-2048(95)02397-6

Cited by 158 publications

(102 citation statements)

References 21 publications

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“…Such a resonance can be easily identified in the whole family of perylene derivatives. From the experimental point of view, our spectrum is consistent with former NEXAFS spectra measured on single crystals 15,17 and on multilayer films, 16 even if our higher resolution allows us to resolve clearly the fine structure of the LUMO (whose splitting was first resolved in the crystalline phase 15 ) and higher energy resonances.…”

Section: Carbon K-edge Nexafssupporting

confidence: 88%

“…[12][13][14] From the experimental point of view, the spectroscopic characterization of the molecular orbitals of the free PTCDI molecule, as well as of perylene, is largely outdated or limited. [15][16][17][18] In this context, the knowledge of the molecular orbital symmetry and energy, as measured in NEXAFS, is fundamental to understand the key parameters that govern the performances of an archetypal device, such as the orientation of the molecules on the surfaces 19 and the mechanism of charge transfer to the substrate. 20 In their extended review, Zahn and coworkers reported a comparative study of the electronic and vibrational properties of PTCDA and dimethyl-PTCDI, 2 however their analysis of NEXAFS spectra was limited to the comparison with previous calculations for naphthalene-tetracarboxylic dianhydride (NTCDA), 21 thus a clearcut disentanglement between initial and final state effects in the PTCDI NEXAFS is still missing.…”

Section: Introductionmentioning

confidence: 99%

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High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

Fratesi

Lanzilotto

Stranges

et al. 2014

Phys. Chem. Chem. Phys.

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We made use of synchrotron radiation to perform near edge X-ray absorption fine structure spectroscopy, NEXAFS, at the carbon K-edge of perylene and perylene-tetracarboxylic-diimide, PTCDI. Reference spectra measured for isolated molecules in the gas phase are compared with polarization dependent NEXAFS spectra measured on highly oriented thin films in order to study the symmetry of the molecular orbitals. The molecular overlayers are grown onto the rutile TiO 2 (110) surface for which the large anisotropic corrugation effectively drives the molecular orientation, while its dielectric nature prevents the rehybridization of the molecular orbitals. We employed density functional theory, DFT, calculations to disentangle the contribution of specific carbon atoms to the molecular density of states. Numerical simulations correctly predict the observed NEXAFS azimuthal dichroism of the s* resonances above the ionization threshold, from which we determine the full geometric orientation of the overlayer molecules. A discrepancy observed for the spectral contribution of the imide carbon atom to the calculated unoccupied molecular orbitals has been explained in terms of initial state effects, as determined by Hartree-Fock corrections and in full agreement with the corresponding shift of the C 1s core level measured by X-ray photoelectron spectroscopy, XPS.

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Section: Carbon K-edge Nexafssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

Fratesi

Lanzilotto

Stranges

et al. 2014

Phys. Chem. Chem. Phys.

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“…The strongest * resonant peak is asymmetric with a dominant component (labeled 1) and a subtle shoulder (labeled 2) at slightly higher photon energy. Peaks 1 and 2 are assigned to the transitions of carbonyl oxygen atoms (C=O) to the lowest unoccupied molecular orbital (LUMO) and higher orbitals (LUMO+1 and LUMO+2), respectively [19]. Resonant peak 3 is attributed to the transition from the bridging O atoms (C─O─C) to the LUMO+1 (and perhaps LUMO+2 and LUMO+3) [19].…”

Section: Resultsmentioning

confidence: 99%

Angular dependent NEXAFS study of the molecular orientation of PTCDA multilayers on Au (111) surface

et al. 2011

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“…parallel to the surface. 9,22 Because of their integral character, most of the experiments were insensitive to low concentrations of inhomogeneities like, e.g., 3D islands or defects which may play an important role for the electronic and optical properties. The SMART microscope with several different operation modes (see Section 2.3) enables new and deeper insights into organic layer growth.…”

mentioning

confidence: 99%

Direct observation of epitaxial organic film growth: temperature-dependent growth mechanisms and metastability

Marchetto

Schmidt

Groh

et al. 2015

Phys. Chem. Chem. Phys.

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The growth of the first ten layers of organic thin films on a smooth metallic substrate has been investigated in real-time using the model system PTCDA on Ag(111). The complex behaviour is comprehensively studied by electron microscopy, spectroscopy and diffraction in a combined PEEM/LEEM instrument revealing several new phenomena and yielding a consistent picture of this layer growth. PTCDA grows above room temperature in a Stranski-Krastanov mode, forming three-dimensional islands on a stable bi-layer, in competition with metastable 3rd and 4th layers. Around room temperature this growth mode changes into a quasi layer-by-layer growth, while at temperatures below about 250 K a Vollmer-Weber-like behaviour is observed. By means of laterally resolved soft X-ray absorption spectroscopy the orientation of all adsorbed molecules is found to be homogeneously flat lying on the surface, even during the growth process. The films grow epitaxially, showing long-range order with rotational domains. For the monolayer these domains could be directly analysed, showing an average size of several micrometers extending over substrate steps.

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NEXAFS investigations on ordered adsorbate layers of large aromatic molecules

Cited by 158 publications

References 21 publications

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis

Angular dependent NEXAFS study of the molecular orientation of PTCDA multilayers on Au (111) surface

Direct observation of epitaxial organic film growth: temperature-dependent growth mechanisms and metastability

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