ANALYSIS OF INTERFACIAL WATER AT A HYDROPHILIC SILICON SURFACE BY IN-SITU FTIR INTERNAL REFLECTION SPECTROSCOPY/

In-situ FTIR/internal reflection spectroscopy (FTIR/IRS) has been used to spectroscopically characterize interfacial water near the hydrophi lic surface of a silicon single-crystal internal reflection element. I nterfacial water was examined spectroscopically over certain distances from the surface by appropriate design of the geometry and optics of the internal reflection system, thus creating an integrated depth prof ile of the water structure. The in-situ FTIR/IRS spectra were characte rized by consideration of the O-H stretching region (3000-3800 cm(-1)) associated with the vibrational spectra of interfacial water. The bro ad peak in this region was deconvoluted in order to isolate overlappin g spectral features that indicate the nature of hydrogen bonding in in terfacial water. Three distinct bands were found: similar to 3600 cm(- 1) (free OH), similar to 3400 cm(-1) (incomplete tetrahedral coordinat ion), and similar to 3240 cm(-1) (complete tetrahedral coordination). Preliminary analysis of these spectral bands indicates the presence of an icelike water structure (similar to 3240 cm(-1)) at the hydrophili c silicon surface. This icelike structure decreases in significance aw ay from the interface, as established from spectroscopic depth profile measurements.