Mr. Yalamanchili et al., ANALYSIS OF INTERFACIAL WATER AT A HYDROPHILIC SILICON SURFACE BY IN-SITU FTIR INTERNAL REFLECTION SPECTROSCOPY/, Langmuir, 12(17), 1996, pp. 4176-4184
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.