title: Self-Assembled Monolayers Get Their Final Finish via a Quasi-Langmuir-Blodgett Transfer.
abstract: The growth of self-assembled monolayers (SAMs) of octadecylphosphonic acid (ODPA) molecules on α-Al2O3(0001) and subsequent dewetting of the SAMs were studied with a combination of in situ sum-frequency generation (SFG) and molecular dynamics (MD) simulations. Although SAM growth after deposition times >8 h reduces to nearly negligible values, the resultant ODPA SAMs in solution are still not in a well-ordered state with the alkyl chains in all-trans configurations. In fact, in situ SFG spectroscopy revealed a comparatively high concentration of gauche defects of the SAM in the ODPA 2-propanol solution even after a growth time of 16 h. Here, results of the MD simulations strongly suggest that defects can be caused by ODPA molecules which are not attached to the substrate but are incorporated into the SAM layer with the polar headgroup oriented into the 2-propanol solvent. This inverted adsorption geometry of additional ODPA molecules blocks adsorption sites and thus stabilizes the SAM without improving ordering to an extent that all molecules are in the all-trans configuration. While persistent in solution, the observed defects can be healed out when the SAMs are transferred from the solvent to a gas phase. During this process, a quasi-Langmuir-Blodgett transfer of molecules takes place which drives the SAM into a higher conformational state and significantly improves its quality.
authors.affiliation: †Institute of Particle Technology (LFG), ‡Erlangen Graduate School in Advanced Optical Technologies (SAOT), §Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, ∥Chair of Theoretical Chemistry, and ⊥Cluster of Excellence - Engineering of Advanced Materials (EAM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Meltzer
authors.affiliation: †Institute of Particle Technology (LFG), ‡Erlangen Graduate School in Advanced Optical Technologies (SAOT), §Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, ∥Chair of Theoretical Chemistry, and ⊥Cluster of Excellence - Engineering of Advanced Materials (EAM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany.
authors.forename: Hanno
authors.initials: H
authors.lastname: Dietrich
authors.affiliation: †Institute of Particle Technology (LFG), ‡Erlangen Graduate School in Advanced Optical Technologies (SAOT), §Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, ∥Chair of Theoretical Chemistry, and ⊥Cluster of Excellence - Engineering of Advanced Materials (EAM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Zahn
authors.affiliation: †Institute of Particle Technology (LFG), ‡Erlangen Graduate School in Advanced Optical Technologies (SAOT), §Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, ∥Chair of Theoretical Chemistry, and ⊥Cluster of Excellence - Engineering of Advanced Materials (EAM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Peukert
authors.affiliation: †Institute of Particle Technology (LFG), ‡Erlangen Graduate School in Advanced Optical Technologies (SAOT), §Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, ∥Chair of Theoretical Chemistry, and ⊥Cluster of Excellence - Engineering of Advanced Materials (EAM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Braunschweig