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Rubidium doped Metal-free Phthalocyanine monolayer structures on Au(111)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
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2010 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 28, 12166-12172 p.Article in journal (Refereed) Published
Abstract [en]

Scanning tunneling microscopy (STM) studies of monolayer of metal-free phthalocyanine (H2Pc) adsorbed on Au(111) have shown ordered arrangement of the molecules on the surface. Evaporation of H2Pc onto the Au(111) surface and post annealing of the sample to 670 K results in a densely packed structure of the molecules. The monolayer is characterized by molecules adsorbed with the molecular plane parallel to the substrate surface in a square adsorption unit cell. Furthermore, the high resolution images revealed the orientation of individual molecules. The H2Pc/Au(111) system has also been doped by rubidum and compared to the undoped layers. The Rb affects the molecular adsorption geometry, and a hexagonal unit cell is found for the coadsorption of H2Pc and Rb. Upon doping, highly ordered Rb-induced protrusions are observed at the benzene site of adsorbed molecules.

Place, publisher, year, edition, pages
2010. Vol. 114, no 28, 12166-12172 p.
National Category
Natural Sciences Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-96204DOI: 10.1021/jp910180yISI: 000279787600017OAI: oai:DiVA.org:uu-96204DiVA: diva2:170699
Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Phthalocyanines on Surfaces: Monolayers, Films and Alkali Modified Structures
Open this publication in new window or tab >>Phthalocyanines on Surfaces: Monolayers, Films and Alkali Modified Structures
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Phthalocyanines (Pc’s) are a group of macro-cyclic molecules, widely investigated due to the possibility to use them in a variety of applications. Electronic and geometrical structure investigations of molecular model systems of Pc’s adsorbed on surfaces are important for a deeper understanding of the functionality of different Pc-based devices.

Here, Pc’s monolayers and films, deposited on different surfaces, were investigated by X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS) and Scanning Tunneling Microscopy (STM). In addition Density Functional Theory (DFT) simulations were performed.

For molecular films of Metal-free (H2Pc) and Iron (FePc) Pc’s, on surfaces, it is found that the intermolecular interaction is weak and the molecules arrange with their molecular plane mainly perpendicular to the surface.

Several monolayer systems were characterized, namely H2Pc and FePc adsorbed on Graphite, ZnPc on InSb(001)-c(8x2), H2Pc on Al(110) and on Au(111). For all the studied monolayers it was found that the molecules are oriented with their molecular plane parallel to the surface. The electronic structure of the molecules is differently influenced by interaction with the surfaces. For H2Pc adsorbed on Graphite the nearly negligible effect of the surface on the molecular electronic structure allowed STM characterization of different molecular orbitals. A strong interaction is instead found in the case of H2Pc on Al(110) resulting in molecules strongly adsorbed, and partly dissociated.

Modifications of the electronic and geometrical structure induced by alkali doping of H2Pc films and monolayers were characterized. It is found both for the H2Pc film on Al(110) and monolayer adsorbed on Au(111), that the molecular arrangement is changed upon doping by Potassium and Rubidium, respectively.

Potassium doping of the H2Pc films results in a filling of previously empty molecular orbitals by a charge transfer from the alkali to the molecule, with significant modification of the molecular electronic structure.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 61 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 342
Keyword
Atomic and molecular physics, Phthalocyanines, Surface Science, X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS), Scanning Tunneling Microscopy (STM), Density Functional Theory (DFT), Metal-free Phthalocyanine, Iron Phthalocyanine, Zinc Phthalocyanine, Gold, Graphite, Aluminium, Indium Antimony, Molecular adsorption, Monolayer, Film, Alkali, Geometrical structure, Electronic structure, Doping, Atom- och molekylfysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-8209 (URN)978-91-554-6966-5 (ISBN)
Public defence
2007-10-12, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2011-07-08Bibliographically approved
2. Electronic and Geometric Structure of Phthalocyanines on Metals
Open this publication in new window or tab >>Electronic and Geometric Structure of Phthalocyanines on Metals
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Adsorption of monolayers and multilayers of metal-free and metal phthalocyanines molecules on metal surfaces has been investigated using complementary microscopic and synchrotron-based spectroscopic techniques. It was observed by STM measurements that at monolayer coverage the adsorption direction of the metal-free phthalocyanine molecules with respect to the gold surface vary as a function of temperature, i.e. at room temperature (RT) and low temperature (LT). It was explained by the difference in strength of intermolecular and adsorbate-substrate interactions at room and low temperatures. Nature of the interaction between adsorbed species and the surfaces as a function of coverage has been further characterized by XPS measurements. Binding energy shifts as a function of coverage have been attributed to initial- and final-state effects, the latter being due to different core-hole screening for the different molecular coverage. The alignment of molecular films at both monolayer and multilayer coverages, which has been determined by XAS measurements in several cases, is also dependent upon the relative strength of molecule-molecule versus molecule-substrate interaction. Parallel alignment of the molecular film with respect to the surface is the result of significant interaction between the adsorbate and the substrate, whilst standing geometry of the molecular film is due to more significant intermolecular interactions. DFT simulations have provided further information on the nature of the adsorbate-substrate interaction as well as contribution of different molecular orbitals in XPS and XAS spectra. Moreover, investigation of alkali interaction with the phthalocyanine films revealed a significant modification in their geometric and electronic structures due to charge transfer from the alkali metal to the molecular film. However, no sign of metallization of the molecules has been observed by spectroscopic and microscopic studies.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 64 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 941
Keyword
monolayer, multilayer, metal-free phthalocyanine, metal phthalocyanine, interaction, intermolecular, adsorbate-substrate, XPS, XAS, STM, DFT, alkali, metallization
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-173505 (URN)978-91-554-8382-1 (ISBN)
Public defence
2012-06-08, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2012-05-16 Created: 2012-04-25 Last updated: 2012-09-18Bibliographically approved

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