Comparison of ultraviolet photoelectron spectroscopy and scanning tunneling spectroscopy measurements on highly ordered ultrathin films of hexa-<i>peri</i>-hexabenzocoronene on Au(111)

Proehl, Holger; Toerker, M.; Sellam, F.; Fritz, Torsten; Leo, Karl; Simpson, Christopher D.; Müllen, Kläus

doi:10.1103/physrevb.63.205409

Cited by 57 publications

(58 citation statements)

References 31 publications

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“…the value of the HOMO-LUMO gap View Article Online for phenylenes is B5 eV, 38 for pentacene 4.1 eV 39 and for hexa-peri-hexabenzocoronene 3.2 eV (2.8 eV as measured by UV-Vis absorption). 40 Our results are in agreement with cyclic voltammetry measurements which demonstrated that the phenylthio-substitution of the central aromatic core leads to an effective delocalization of charge throughout the molecular system. 13 For DPTC deposited on the HOPG(0001) surface, we obtained an orbital mediated tunneling through HOMO and LUMO molecular states which is similar to the measured characteristics for the single, non-aggregated molecules on Au(111).…”

Section: Scanning Tunneling Spectroscopy (Sts)supporting

confidence: 90%

Columnar self-assembly of a 3D-persulfurated coronene asterisk. The dominant role of aryl-sulfur bonds

et al. 2012

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The synthesis, adsorption behavior, surface structure, and the charge transport properties of a persulfurated coronene asterisk with a 3D-polyaromatic system, namely dodecakis(phenylthio)coronene (DPTC), deposited on HOPG(0001) and Au(111) surfaces, are investigated by means of scanning tunneling microscopy (STM) and spectroscopy (STS). DPTC molecules adsorbed on HOPG (0001) show an orbital mediated tunneling through mainly undisturbed frontier molecular states. DPTC molecules self-assemble on Au(111) into a highly ordered p-stacked columnar ''edge-on pattern. The columnar stacking is a gold surface mediated process, as ascertained by fluorescence correlation spectroscopy (FCS). DPTC was monomeric in the precursor solution before assembly. The tunneling spectra of ordered DPTC stacks on Au (111) show an energetic splitting of the frontier molecular states, indicating orbital overlap and supramolecular p-p interactions of adjacent molecules. DPTCs are sufficiently flexible to facilitate dense 1D stacks. The multiple aryl-sulfur bonds play a dominant role in the modulation of the self-assembly properties of the coronenes which in turn affect their electronic properties. Our results encourage further applications in dendrimer chemistry toward molecular electronics, by using the functionalized coronene core and its multidirectional 3D properties.

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Section: Scanning Tunneling Spectroscopy (Sts)supporting

confidence: 90%

Columnar self-assembly of a 3D-persulfurated coronene asterisk. The dominant role of aryl-sulfur bonds

et al. 2012

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“…These levels include the workfunctions of the metal electrodes, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the organic semiconducting materials. Besides ✉ Fax: +31-50/363-4879, E-mail: jonkman@phys.rug.nl the absolute values of these energy levels, also their mutual alignment at interfaces is important, since it was recently shown that the use of the so-called vacuum-level alignment principle may lead to erroneous results [1][2][3][4]. The misalignment of the vacuum levels is caused by interfacial dipole layers whose mechanism is not completely understood.…”

Section: Introductionmentioning

confidence: 99%

On interface dipole layers between C 60 and Ag or Au

Veenstra

Heeres

Hadziioannou

et al. 2002

Applied Physics A: Materials Science & Processing

103

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C 60 layers on polycrystalline Ag and Au are studied by photoelectron spectroscopy. At these metal/C 60 interfaces an electron transfer occurs from the metal to the lowest unoccupied orbital of C 60 . We found in the case of the polycrystalline Ag/C 60 interface a dipolar layer with its associated electric field in the direction corresponding to the charge transfer, so pointing from the substrate to the adsorbent. Yet, at the Au/C 60 interface we observed an overall electric field pointing from C 60 towards the metal. We discuss our observations in terms of charge transfer, screening and hybridization effects and propose the occurrence of a hybridization mechanism similar to back-bonding at the Au/C 60 interface. We show that the alignment of energy levels at the metal/C 60 interface cannot simply be deduced using the metal workfunction and the frontier orbitals of C 60 , including screening effects, since hybridization effects may strongly alter the interfacial energy level structure. Our experimental findings on the polycrystalline metal/C 60 interfaces indicate an at-most weak dependence of the Fermi level of the C 60 overlayer on the workfunction of the polycrystalline metal substrate. These interfaces are found in donoracceptor-based organic photovoltaic devices and our results may help to understand the electrical characteristics of these devices.

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“…Hexa-peri-hexabenzocoronene ͑HBC͒ is a large conjugated planar hydrocarbon that is often considered as a model system in the context of organic electronics. [1][2][3][4][5] While, in a closed monolayer ͑ML͒, HBC mostly grows planar in a hexagonal arrangement, recently also studies of HBC on Au͑111͒ at very low coverage have been performed showing a nonplanar adsorption at step edges in face-centered-cubic regions. 6,7 In addition, HBC on Au͑111͒ has also been used as template for the heteroepitaxial growth of different organic species.…”

Section: Introductionmentioning

confidence: 99%

Repulsion between molecules on a metal: Monolayers and submonolayers of hexa-peri-hexabenzocoronene on Au(111)

et al. 2010

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We investigate the growth of hexa-peri-hexabenzocoronene ͑HBC͒ on Au͑111͒ for monolayer ͑ML͒ and sub-ML coverage by scanning tunneling microscopy and low-energy electron diffraction. A transition from a disordered isotropic phase at low coverage to a highly ordered phase with a coverage-dependent lattice constant at higher coverage is found and attributed to a repulsive intermolecular force. To deduce the origin of this repulsion a model is set up, containing the Coulomb interaction between molecules and between localized dipoles from the push-back effect, as well as the intermolecular van der Waals potential. The modeling of the van der Waals interaction is done on a force field level. We find that the observed repulsion can only be explained when assuming a certain screening of the attractive London forces by the presence of the metal substrate.

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Comparison of ultraviolet photoelectron spectroscopy and scanning tunneling spectroscopy measurements on highly ordered ultrathin films of hexa-peri-hexabenzocoronene on Au(111)

Cited by 57 publications

References 31 publications

Columnar self-assembly of a 3D-persulfurated coronene asterisk. The dominant role of aryl-sulfur bonds

Columnar self-assembly of a 3D-persulfurated coronene asterisk. The dominant role of aryl-sulfur bonds

On interface dipole layers between C 60 and Ag or Au

Repulsion between molecules on a metal: Monolayers and submonolayers of hexa-peri-hexabenzocoronene on Au(111)

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