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TY  - THES
AU  - Henneke, Caroline
TI  - Kinetic and thermodynamic considerations on the formation of heteromolecular layers on metal surfaces
PB  - RWTH Aachen University
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2016-06249
SP  - 1 Online-Ressource (vii, 157, XIV Seiten) : Illustrationen, Diagramme
PY  - 2015
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2016
N1  - Dissertation, RWTH Aachen University, 2015
AB  - A systematic study of the growth of a heteromolecular adsorbate system consisting of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and copper phthalocyanine (CuPc) on the substrates Ag(111) and Cu(001) in the submonolayer regime is presented.The key finding is the phase diagram of the PTCDA-CuPc system on Ag(111) in the complete coverage regime up to 1 ML at 300 K. It contains eight different regions with one or two different crystalline phases which coexist with areas of a disordered phase of both molecules. Only the disordered phase is present on the surface in a ninth region. The reason for this complicated phase diagram is the complex interplay between energetic aspectsof the island formation (adhesion energy) and the involved entropic effects which are both investigated in detail.The phase formation is strongly influenced by the deposition parameters for the PTCDA-CuPc system on Cu(001). Heteromolecular phases only grow when PTCDA is deposited on a submonolayer film of CuPc, while the PTCDA islands remain unchanged for the reversed deposition sequence when CuPc is deposited on a submonolayer film of PTCDA. This is different on Ag(111). PTCDA islands are transformed into three different heteromolecular phases with increasing CuPc:PTCDA stoichiometry during the deposition of CuPc on a submonolayer film of PTCDA. It is found that the phases are in thermodynamic equilibrium since they only depend on coverage (of CuPc and PTCDA) and temperature, but (in contrast to Cu(001)) not on other deposition parameters. This allows the determination of the above mentioned phase diagram. Its form can be explained by an ab-initio model without any fit parameters. It is based on the model for an intermetallic compound at 1 ML coverages and includes the additional assumption that critical densities of CuPc in the disordered phase must be exceeded for the growth of each heteromolecular phase. The existence of such critical densities of CuPc can be explained by the interplay between the intermolecular PTCDA-CuPc interactions and the entropy of the entire system. Both homomolecular systems were characterized in a prefixed part of the work since their understanding is essential for a successful analysis of the heteromolecular system. Here, it is found that the strong attractive intermolecular interaction dominates the growth of PTCDA, while entropic effects can influence the growth of CuPc molecules due to their weakly repulsive interaction.The characterization of both homo- and heteromolecular systems shows that an improved understanding of the self-assembly of molecules on surfaces enables the selective fabrication of heteromolecular thin films with desired properties which potentially influences the production of commercially used organic layers.
LB  - PUB:(DE-HGF)11
UR  - https://publications.rwth-aachen.de/record/667469
ER  -