Interfacial Electronic Structure of Dipolar Vanadyl Naphthalocyanine Thin Films

Persistent Link:
http://hdl.handle.net/10150/203477
Title:
Interfacial Electronic Structure of Dipolar Vanadyl Naphthalocyanine Thin Films
Author:
Steele, Mary P.
Issue Date:
2011
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The studies presented in this work are aimed towards a better understanding of the fundamental physics of the electrode/organic molecule interface in both the ground and excited state manifolds. Systematic investigations of single systems using two-photon photoemission (TPPE) and ultraviolet photoelectron spectroscopy (UPS) were undertaken in order to assess the evolution of the electronic structure and molecular organization at the interface. The adsorbate molecule vanadyl naphthalocyanine (VONc) was used whose properties are well-suited to this purpose. Interfacial electronic states of thin films of VONc were studied with two different substrates: highly ordered pyrolytic graphite (HOPG) and Au(111).The substrate of HOPG is a surface which does not possess reactive dangling bonds and the electron density close to the Fermi edge is very low, permitting high resolution spectroscopic band analysis of VONc and revealing subtle changes to the electronic structure. From interfacial studies of this weakly interacting substrate/ adsorbate system, it is shown in this work that molecular electronic levels in both the ground and excited state manifolds can shift independently of the vacuum level. Further, electron transfer between close lying electron donor and acceptor energy levels may be influenced by energy level shifts caused by depolarization effects as a function of dipole density.The VONc/Au(111) interface is investigated in order to examine energy level alignment in a system with the additional complexity of molecule/substrate interactions. The electron rich Au(111) surface leads to a strong interface dipole upon addition of VONc. Joint experimental and computational data is presented showing that the underlying cause of this interface dipole is Pauli repulsion. Additionally, investigations of energy level alignment in the excited state manifold are presented and the possibility of quantum interference is discussed.The interfacial electronic structure is quite different among these two model systems. The interfacial alignment observed in the HOPG/VONc system was largely due to depolarization of the intrinsic molecular dipole as a function of density, whereas the Au(111)/VONc interface is dominated by interfacial Pauli repulsion interactions.
Type:
text; Electronic Dissertation
Keywords:
interface; naphthalocyanine; two-photon photoemission; ultraviolet photoelectron spectroscopy; Chemistry; Au(111); HOPG
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemistry
Degree Grantor:
University of Arizona
Advisor:
Monti, Oliver L. A.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleInterfacial Electronic Structure of Dipolar Vanadyl Naphthalocyanine Thin Filmsen_US
dc.creatorSteele, Mary P.en_US
dc.contributor.authorSteele, Mary P.en_US
dc.date.issued2011-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe studies presented in this work are aimed towards a better understanding of the fundamental physics of the electrode/organic molecule interface in both the ground and excited state manifolds. Systematic investigations of single systems using two-photon photoemission (TPPE) and ultraviolet photoelectron spectroscopy (UPS) were undertaken in order to assess the evolution of the electronic structure and molecular organization at the interface. The adsorbate molecule vanadyl naphthalocyanine (VONc) was used whose properties are well-suited to this purpose. Interfacial electronic states of thin films of VONc were studied with two different substrates: highly ordered pyrolytic graphite (HOPG) and Au(111).The substrate of HOPG is a surface which does not possess reactive dangling bonds and the electron density close to the Fermi edge is very low, permitting high resolution spectroscopic band analysis of VONc and revealing subtle changes to the electronic structure. From interfacial studies of this weakly interacting substrate/ adsorbate system, it is shown in this work that molecular electronic levels in both the ground and excited state manifolds can shift independently of the vacuum level. Further, electron transfer between close lying electron donor and acceptor energy levels may be influenced by energy level shifts caused by depolarization effects as a function of dipole density.The VONc/Au(111) interface is investigated in order to examine energy level alignment in a system with the additional complexity of molecule/substrate interactions. The electron rich Au(111) surface leads to a strong interface dipole upon addition of VONc. Joint experimental and computational data is presented showing that the underlying cause of this interface dipole is Pauli repulsion. Additionally, investigations of energy level alignment in the excited state manifold are presented and the possibility of quantum interference is discussed.The interfacial electronic structure is quite different among these two model systems. The interfacial alignment observed in the HOPG/VONc system was largely due to depolarization of the intrinsic molecular dipole as a function of density, whereas the Au(111)/VONc interface is dominated by interfacial Pauli repulsion interactions.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectinterfaceen_US
dc.subjectnaphthalocyanineen_US
dc.subjecttwo-photon photoemissionen_US
dc.subjectultraviolet photoelectron spectroscopyen_US
dc.subjectChemistryen_US
dc.subjectAu(111)en_US
dc.subjectHOPGen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMonti, Oliver L. A.en_US
dc.contributor.committeememberBrown, Michael F.en_US
dc.contributor.committeememberLichtenberger, Dennis L.en_US
dc.contributor.committeememberCorrales, L. Renéen_US
dc.contributor.committeememberMonti, Oliver L. A.en_US
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