Adsorption and Diffusion of Oxygen on Tungsten

摘要: The surface diffusion and adsorption of oxygen on tungsten have been studied by a field emission technique, utilizing the high sticking coefficient, negligible vapor pressure O2 at 4.2–20°K. Three types migration were noted. At ∼27°K occurs with sharp boundary an activation energy Ed≈0.9 kcal. This is believed to be physically adsorbed over chemisorbed layer, precipitation bare surface. distance traversed was found limited desorption above ∼40°K. A study this effect yielded estimate 2.3 kcal for heat adsorption, Ha, in physisorbed layer. 400–500°K coverages, within monolayer energies 23–25 Boundaries moving radially outward from close‐packed faces are observed, result O atoms trap sites rough regions low coverages free Ed≃30 observed i...