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Fundamental aspects of the self-assembly behavior and electronic properties of corannulenes


Bauert, T. Fundamental aspects of the self-assembly behavior and electronic properties of corannulenes. 2011, University of Zurich, Faculty of Science.

Abstract

Surface modifications with functionalized molecules are a key feature for electronic applications with organic molecules. The self-assembly behavior of these molecules is of fundamental interest regarding the driving forces and processes involved. Corannulene (COR) and pentamethyl substituated COR (Me5COR) on Cu(111) were investigated with X-Ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM) and temperature programmed desorption (TPD). Me5COR exhibits a C5 symmetry, which is incompatible with periodic tessellations of the plane. Combined LEED and STM studies show, that the fivefold symmetric molecules adapt two packing motifs known from macroscopic pentagons, while COR assembles in a hexagonal lattice at room temperature. Other phases of Me5COR are identified, including a high temperature phase, which forms through surface chemistry. The previously reported enantiotropic phase transition of COR is confirmed with LEED and in uenced by filling free space around a high density phase, thus blocking a phase transition. Putting chiral molecules on top of the room temperature phase leads to suppression of mirror domains of the next phase during phase transition. Self-assembly of D- and L- tartaric acid (TA) as well as the racemic mixture were investigated with LEED. UPS measurements on COR and Me5COR on Cu(111) reveal the electronic structure of the adsorbates, as well as confirmation of the COR HOMO participating in surface binding. From work function change measurements the interfacial dipole moment of COR /Cu(111) and Me5COR/Cu(111) is determined and found to be unusually high at over 8 debye. The maximum work function change is in the order of -1.5 eV. Finally the efiect of Cs doping on the two molecules was investigated with UPS. Both molecules show occupation of the LUMO and thick films of Cs/COR and
Cs/Me5COR proved to be very stable far beyond room temperature. XPS studies of Cs/COR indicate coordination of four Cs atoms per COR molecule.

Abstract

Surface modifications with functionalized molecules are a key feature for electronic applications with organic molecules. The self-assembly behavior of these molecules is of fundamental interest regarding the driving forces and processes involved. Corannulene (COR) and pentamethyl substituated COR (Me5COR) on Cu(111) were investigated with X-Ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), low-energy electron diffraction (LEED), scanning tunneling microscopy (STM) and temperature programmed desorption (TPD). Me5COR exhibits a C5 symmetry, which is incompatible with periodic tessellations of the plane. Combined LEED and STM studies show, that the fivefold symmetric molecules adapt two packing motifs known from macroscopic pentagons, while COR assembles in a hexagonal lattice at room temperature. Other phases of Me5COR are identified, including a high temperature phase, which forms through surface chemistry. The previously reported enantiotropic phase transition of COR is confirmed with LEED and in uenced by filling free space around a high density phase, thus blocking a phase transition. Putting chiral molecules on top of the room temperature phase leads to suppression of mirror domains of the next phase during phase transition. Self-assembly of D- and L- tartaric acid (TA) as well as the racemic mixture were investigated with LEED. UPS measurements on COR and Me5COR on Cu(111) reveal the electronic structure of the adsorbates, as well as confirmation of the COR HOMO participating in surface binding. From work function change measurements the interfacial dipole moment of COR /Cu(111) and Me5COR/Cu(111) is determined and found to be unusually high at over 8 debye. The maximum work function change is in the order of -1.5 eV. Finally the efiect of Cs doping on the two molecules was investigated with UPS. Both molecules show occupation of the LUMO and thick films of Cs/COR and
Cs/Me5COR proved to be very stable far beyond room temperature. XPS studies of Cs/COR indicate coordination of four Cs atoms per COR molecule.

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Additional indexing

Item Type:Dissertation
Referees:Ernst K H
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:7 March 2011
Deposited On:05 Mar 2012 11:10
Last Modified:07 Dec 2017 11:52
Related URLs:http://opac.nebis.ch/F/?local_base=NEBIS&CON_LNG=GER&func=find-b&find_code=SYS&request=006497495

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