Regensburg 2010 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 16: Interfaces II
MM 16.3: Talk
Monday, March 22, 2010, 16:45–17:00, H5
Dielectric anti-reflective coatings for attenuated total reflection spectroscopy through metal films
— •Martina Reithmeier and Andreas Erbe —
MPI für Eisenforschung, Düsseldorf, Deutschland
In order to obtain insight into structural transformation during an electrochemical reaction, attenuated total reflection (ATR) infrared spectroscopy has proven to be a useful tool. The applicability is, however, limited when applied on continuous metal films, because of the metal’s high reflectivity. In order to overcome this limitation, we introduce a novel system of stratifications.
On the incidence media (silicon, calcium fluoride or zinc selenide), a thin layer of germanium with a thickness ∼1 µm is evaporated, followed by a 20 nm gold layer.
For certain wave numbers the reflectivity of the system is significantly lowered compared to a reference system. Calculations show that a higher absorption of the investigated material is expected at these wavenumbers.
Experiments based on calculations were performed on Si-Ge-Au-H2O, CaF2-Ge-Au-acetonitrile and ZnSe-Ge-Au-acetonitrile and -acetone systems.
In acetonitrile, a splitting of most vibrational absorptions is observed in contact with gold, which could originate from the strong interaction with gold.
The experiments so far show qualitative agreement with the computations. The regions with lower reflectivity are found and can be modelled. They show a strong sensitivity towards the presence of material close to the interface. Current problems are holes in the 20 nm Au film, which have been observed by scanning electron microscopy.