ADSORPTION OF BENZENE AND PYRIDINE ON SI- CRYSTAL SURFACE - MEASUREMENTS OF ADSORBED LAYER THICKNESS BY ELLIPSOMETRY

Ellipsometry is used for measuring adsorption layer thicknesses of ben zene and pyridine on silicon crystal surface (001). Variations of the, thickness with specific pressures are shown to be correlated well by the BET multilayer adsorption isotherm equation, which allows us to es timate the thicknesses of saturated monomolecular layer and molecular occupied areas. It was found that the monomolecular layer thickness of pyridine is about 40 percent greater than that of benzene, while the occupied area of a pyridine molecule is about 60 percent less than tha t of a benzene molecule. These conclusions are coincident with spectro scopic results reported for adsorbate-surface interaction by means of UV photoemission and Raman spectroscopy. Ellipsometry has been proved to be an effective method for evaluating adsorption equilibrium charac teristics.