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Electronic and Geometric Structure of Phthalocyanines on Metals
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
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 [en]
monolayer, multilayer, metal-free phthalocyanine, metal phthalocyanine, interaction, intermolecular, adsorbate-substrate, XPS, XAS, STM, DFT, alkali, metallization
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-173505ISBN: 978-91-554-8382-1 (print)OAI: oai:DiVA.org:uu-173505DiVA: diva2:523657
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
List of papers
1. Rubidium doped Metal-free Phthalocyanine monolayer structures on Au(111)
Open this publication in new window or tab >>Rubidium doped Metal-free Phthalocyanine monolayer structures on Au(111)
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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.

National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-96204 (URN)10.1021/jp910180y (DOI)000279787600017 ()
Available from: 2007-09-21 Created: 2007-09-21 Last updated: 2017-12-14Bibliographically approved
2. Photelectron spectroscopy studies of metal-free phthalocyanine on Au(111)
Open this publication in new window or tab >>Photelectron spectroscopy studies of metal-free phthalocyanine on Au(111)
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(English)Manuscript (preprint) (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-173389 (URN)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2016-04-29Bibliographically approved
3. Charge transfer and chemical interaction of ZnPc and FePc with Au(111)
Open this publication in new window or tab >>Charge transfer and chemical interaction of ZnPc and FePc with Au(111)
(English)Manuscript (preprint) (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-173502 (URN)
Available from: 2012-04-25 Created: 2012-04-25 Last updated: 2012-08-01
4. Valence band photoelectron spectra of metal-free and ion phthalocayanine: atomic contributions to the HOMO and HOMO-1 features
Open this publication in new window or tab >>Valence band photoelectron spectra of metal-free and ion phthalocayanine: atomic contributions to the HOMO and HOMO-1 features
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(English)Manuscript (preprint) (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-173394 (URN)
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2012-09-18
5. Potassium-intercalated H2Pc films: Alkali-induced electronic and geometrical modifications
Open this publication in new window or tab >>Potassium-intercalated H2Pc films: Alkali-induced electronic and geometrical modifications
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2012 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 4, 044708- p.Article in journal (Refereed) Published
Abstract [en]

X-ray spectroscopy studies of potassium intercalated metal-free phthalocyanine multilayers adsorbed on Al(110) have been undertaken. Photoelectron spectroscopy measurements show the presence of several charge states of the molecules upon K intercalation, due to a charge transfer from the alkali. In addition, the comparison of valence band photoemission spectra with the density functional theory calculations of the density of states of the H2Pc anion indicates a filling of the formerly lowest unoccupied molecular orbital by charge transfer from the alkali. This is further confirmed by x-ray absorption spectroscopy (XAS) studies, which show a decreased density of unoccupied states. XAS measurements in different experimental geometries reveal that the molecules in the pristine film are standing upright on the surface or are only slightly tilted away from the surface normal but upon K intercalation, the molecular orientation is changed in that the tilt angle of the molecules increases.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-173385 (URN)10.1063/1.4738755 (DOI)000307611500056 ()
Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved

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