Abstract

A metal-overlayer infrared ATR technique proposed by Ishino and Ishida is one of the infrared reflection spectroscopies comprising the Ge prism/thin film/metal overlayer sample system and is expected to be a powerful tool for studying ultrathin organic films because of its high sensitivity. Since, in this case, the surface selection rule is valid, as in the case of conventional infrared reflection-absorption (RA) spectroscopy, it is also useful in providing information on the molecular structure and orientation in the films. Using this technique, Ishino and Ishida succeeded in obtaining high-quality infrared spectra of a thin (10-nm thick) cast film of poly(vinyl acetate) (PVAc) as well as a two-monolayer Langmuir-Blodgett (LB) film of cadmium arachidate directly deposited on a Ge prism, followed by a vacuum evaporation of a silver overlayer (20-nm thick) on the sample films. The signal-to-noise (S/N) ratio thus obtained was estimated to be five times better than that achieved by RA spectroscopy.

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