A study of the optical properties and of the physical adsorption of gases on silver single crystal surfaces by low energy electron diffraction and ellipsometry

Abstract

The physical adsorption of Kr, Xe, O 2, CH 4, C 2H 2, C 2H 4, n- C 4H 10 on the (110) and (100) faces of silver single crystals has been studied by low energy electron diffraction (LEED) and ellipsometry in the temperature range from −195 °C to 0°C and pressure range 10 −10 to 10 −6 Torr. Adsorption isotherms in terms of optical thickness have been measured and from these data, heats of adsorption, the cross sectional areas of the adsorbed molecules and coverage ratios have been derived. LEED measurements indicate that the adsorbed phase is disordered on the silver surface. Ellipsometry is sensitive to the presence of the adsorbed gases in fractional monolayer coverages, while the LEED diffraction patterns were rather insensitive to this disordered adsorption below and up to the monolayer in the beam voltage range 50 to 150 eV.