RAMAN-SPECTROSCOPIC INVESTIGATION OF THE ADSORPTION OF ACETONITRILE AND METHANOL ON SI(100)-2X1

We report the coverage dependent Raman spectra of acetonitrile and methanol on Si(100)-2 × 1 at 100 K in UHV. First, we demonstrate that unenhanced Raman spectroscopy can be used as an in-vacuo surface vibrational probe with monolayer sensitivity on a substrate that itself possesses Raman active modes. Second, we obtain qualitative information about the orientation of both methanol and acetonitrile on this surface. Our results indicate that acetonitrile is oriented with its primary axis roughly parallel and methanol with its primary axis roughly perpendicular to the surface normal. The sensitivity of our current spectrometer did not allow the detection of monolayer amounts of methanol. In light of these results, we comment briefly on the requirements of a next generation surface Raman spectrometer. © 1990 Elsevier Science Publishers B.V. (North-Holland).