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Electronic structure of a vapor-deposited metal-free phthalocyanine thin film
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2005 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, no 21, 214723- p.Article in journal (Refereed) Published
Abstract [en]

The electronic structure of a vapor-sublimated thin film of metal-free phthalocyanine(H2Pc) is studied experimentally and theoretically. An atom-specific picture of the occupied and unoccupied electronic states is obtained using x-ray-absorption spectroscopy (XAS), core- and valence-level x-ray photoelectron spectroscopy (XPS), and density-functional theory (DFT) calculations. The DFT calculations allow for an identification of the contributions from individual nitrogen atoms to the experimental N1sXAS and valence XPS spectra. This comprehensive study of metal-free phthalocyanine is relevant for the application of such molecules in molecular electronics and provides a solid foundation for identifying modifications in the electronic structure induced by various substituent groups.

Place, publisher, year, edition, pages
2005. Vol. 122, no 21, 214723- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96196DOI: 10.1063/1.1924539OAI: oai:DiVA.org:uu-96196DiVA: diva2:170691
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 Geometrical Structure of Phthalocyanines on Surfaces: An Electron Spectroscopy and Scanning Tunneling Microscopy Study
Open this publication in new window or tab >>Electronic and Geometrical Structure of Phthalocyanines on Surfaces: An Electron Spectroscopy and Scanning Tunneling Microscopy Study
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Core- and Valence Photoelectron Spectroscopy (PES), X-ray- and Ultraviolet-Visible Absorption Spectroscopy (XAS and UV-Vis), Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) calculations are used to study the electronic and geometrical structure of a class of macro-cyclic molecules, Phthalocyanines (Pc), on surfaces. These molecules are widely studied due to their application in many different fields.

Multilayer and monolayer coverages of Iron Phthalocyanine (FePc) and metal-free Phthalocyanine (H2Pc) deposited on different surfaces are investigated in order to get insight in the electronic and geometrical structure of the obtained overlayers, of crucial importance for the understanding of the film functionality. Sublimation of molecular thick films on Si(100) and on conducting glass results in films with molecules mainly oriented with their molecular plane orthogonal to the surface. Ex-situ deposited H2Pc films on conductive glass show different molecular orientation and morphology with respect to the vacuum sublimated films.

We study the monolayer adsorption structure of FePc and H2Pc and compare our results with other Pc’s adsorbed on graphite. We find that the molecular unit cell and the superstructure is characteristic for each Pc adsorbed on graphite, even if the geometrical size of the compared molecules is the same. The PE- and XA- spectra of FePc on graphite are essentially identical for the mono- and multilayer preparations, evidencing weak intermolecular and molecular-substrate interactions of van der Waals nature.

Furthermore, we characterize Pc’s on InSb (001)-c(8x2). The substrate In rows are observed to be the adsorption site for Pc’s. We find that the growth of the two-dimensional islands of FePc is prolonged in the [-110] direction, in contrast to ZnPc adsorbed on the same substrate at room temperature. We interpret this result as an indication that the adsorption is controlled by the substrate corrugation observed at 70 K.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 67 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 291
Keyword
Physics, PhotoElectron Spectroscopy (PES), X-ray Absorption Spectroscopy (XAS), UltraViolet-Visible absorption spectroscopy (UV-Vis), Scanning Tunneling Microscopy (STM), Phthalocyanine (Pc), Iron Phthalocyanine (FePc), metal-free Phthalocyanine (H2Pc), Zinc Phthalocyanine (ZnPc), Graphite (HOPG), Indium Antimony (InSb), Surface science, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-7802 (URN)978-91-554-6856-9 (ISBN)
Public defence
2007-05-04, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2007-04-13 Created: 2007-04-13 Last updated: 2012-03-28Bibliographically approved
3. Electronic and Structural Properties of Thin Films of Phthalocyanines and Titanium Dioxide
Open this publication in new window or tab >>Electronic and Structural Properties of Thin Films of Phthalocyanines and Titanium Dioxide
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is based on experimental studies in chemical physics. Titanium dioxide (TiO2) and phthalocyanine’s (Pc’s), interesting in many future perspectives, have been deposited as thin films and studied as follows. Information has been obtained on e.g. molecular orientation, crystal structure, depth profile of the chemical composition, electrochemical properties and electronic structure. This has been achieved by means of a combination of techniques: X-ray photoelectron spectroscopy (XPS), near edge x-ray absorption fine structure (NEXAFS), density functional theory calculations (DFT), UV-visible absorption spectroscopy (UVVIS) and cyclic voltammetry (CV).

Metal-free phthalcyanine (H2Pc) has been shown to form films with different crystal structure and molecular orientation depending on deposition method, evaporation/sublimation or powder deposition, on commercial conducting glass (fluorine doped tin oxide, FTO), which is used e.g. in solar cells and organic light emitting devices (OLEDs). The unoccupied molecular orbitals are divided in x, y and z space coordinates of the molecule and also divided in inequivalent nitrogen components.

The electronic structure is also studied for a sublimated titanyl phthalocyanine (TiOPc) film and related to the metal-free phthalocyanine. The ligand field around the titanium atom in TiOPc is compared with that of TiO2 to delineate the unoccupied levels recorded by means of x-ray absorption spectroscopy.

Nanostructured TiO2 films were manufactured by screen printing/doctor blading on FTO. Such films were additionally covered with lutetium diphthalocyanine (LuPc2) by means of surface assembly from solution. LuPc2-, LuPc2+ and LuPc2H were identified and the stability of the electrochromic reactions in this system was monitored.

Chemical vapor deposition (CVD) has been used to grow nanometer sized anatase TiO2 crystals on pre-oxidized Si (111) without formation of interfacial carbon and with an interface layer of the size of 15- 25Å. The interface layer was found to be amorphous TiSixOy with graded stoichiometry.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 51 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 16
Keyword
Physics, photoelectron spectroscopy, x-ray absorption spectroscopy, phthalocyanine, titanium dioxide, electronic structure, electrochromic reactions, thin films, chemical vapor deposition, evaporation, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-4802 (URN)91-554-6155-7 (ISBN)
Public defence
2005-03-18, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2005-02-25 Created: 2005-02-25 Last updated: 2013-05-21Bibliographically approved

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Alfredsson, YlviBrena, BarbaraNilson, KatharinaÅhlund, JohnMårtensson, NilsSandell, AndersPuglia, CarlaSiegbahn, Hans

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