| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThA |
| Session: | Self-assembled Monolayers and Organic/Inorganic Interface Engineering |
| Presenter: | Sven Pletincx, Vrije Universiteit Brussel, Belgium |
| Authors: | S. Pletincx, Vrije Universiteit Brussel, Belgium L. Trotochaud, Lawrence Berkeley Lab, University of California, Berkeley A.R. Head, Lawrence Berkeley Lab, University of California, Berkeley O. Karslıoğlu, Lawrence Berkeley Lab, University of California, Berkeley L.I. Fockaert, TU Delft, Netherlands J.M.C. Mol, TU Delft, Netherlands H. Bluhm, Lawrence Berkeley Lab, University of California, Berkeley H. Terryn, Vrije Universiteit Brussel, Belgium T. Hauffman, Vrije Universiteit Brussel, Belgium |
| Correspondent: | Click to Email |
Stability in aqueous and corrosive environments of formed bonds between carboxylic acid functional groups of a polymer and a hydroxylated surface of aluminium oxide has a great relevance to a broad range of applications. One of the most important industrial problems of adhesion phenomena includes the loss of desired chemical interactions at the interface as a result of humidity and ionic compounds present in the atmosphere. Conventional vacuum techniques do not permit analysis under atmospheric conditions or can nullify the influence of ex-situ atmospheric modifications upon exposure of the sample to an ultra-high vacuum environment. Also, because of the relatively thick polymer layer present in conventional hybrid systems, a buried interface exists, which is difficult to characterize with surface-sensitive analytical techniques. Recent developments in the field of ambient-pressure x-ray photoelectron spectroscopy (APXPS) enable a novel approach to probe these interfaces. A broad range of relative humidities can be reached in the analysis chamber, making it possible to unravel interfacial chemistry changes operando.
The amount of bonds formed at the hybrid interface and their binding mechanism (monodentate, bidentate, Brønsted interactions, Lewis interactions) are largely determined by oxide properties such as surface hydroxyl content, acid/base character, and dielectric properties. In this work, aluminium oxide is synthesized by electropolishing and anodizing pretreatment steps to carefully control oxide properties on the nanoscale and fully characterized by different analysis techniques. Polyacrylic acid coatings are made sufficiently thin to access the interface with surface analysis techniques with probing depths between 5-10 nm.
Complementary to APXPS, a vibrational spectroscopy technique using the so-called Kretschmann configuration is used to characterize the formed bonds at the metal oxide/polymer interface. An Al layer is sputtered on an IR transparent crystal, with the Al thickness selected such that the FTIR signal from the oxide/polymer interface is amplified as a result of the Kretschmann effect, and thus an interface-specific spectrum of the oxide/polymer surface is attained. This way, we have direct access to the interface, and the influence of an above-the-polymer electrolyte (i.e. H2O) can be probed. Preliminary results show an increase in the amount of bonds at the oxide/polymer interface, together with an increase in water content directly at this interface. It seems that water, at least during the first 24 hours of interaction, triggers an increased wet adhesion.