Gas adsorption studies by ellipsometry in combination with low energy electron diffraction and mass spectrometry

Abstract

Isotherms for physical adsorption on a silver single crystal surface from ultrahigh vacuum have been determined by ellipsometry. Molecular volumes, derived from the optically determined monolayer film thickness, indicate that the classical macroscopic theory of ellipsometry for film covered surfaces is surprisingly well suited for physically adsorbed coverages of molecular dimensions. For a fractional monolayer coverage, the electron diffraction pattern has been found to remain characteristic of the clean substrate surface. The results also show the difficulties in the preparation and definition of clean solid surfaces, and indicate a sensitivity of the ellipsometer to surface roughness on an atomic level.