Fourier Transform Infrared Reflection Spectroscopy Studies of Organic Films Formed on Inorganic Substrates

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Abstract
Reflection absorption spectroscopy on metal surfaces has been applied to reflection spectroscopy on nonmetallic inorganic materials with Fourier transform infrared spectroscopy. The optimal measurement conditions—polarization of incident light and angle of incidence—are discussed on the basis of a calculation using a model of a three-phase system consisting of air, an organic film, and an inorganic substrate. Reflection spectra of stearic acid films on glass substrates were obtained for both perpendicular and parallel polarized incident lights. The optimal measurement condition was for perpendicular polarization, at angle of incidence of 70°, although the signal-to-noise ratio (S/N) of reflection spectra under this condition was ten times less than the S/N of reflection absorption spectra. Reflection spectra on indium tin oxide substrates were obtained for only parallel polarized incident light, and the optimal angle of incidence was 73°. These results were in good agreement with the calculation results.