Chemisorption of O2 and N2O on Cu/Ru(001)

The interaction of O₂ and N₂O are compared on the basal plane of Ru as a function of the coverage of copper. Dissociative N₂O uptake (N₂O(g) → O(a) + N₂(g)) on clean Ru was measured using AES and transient partial pressures. The initial dissociative reaction probability is a steadily declining function of temperature while the saturation uptake of oxygen remains constant from 300–900 K. The saturation oxygen AES signal for N₂O chemisorption was one half that observed for O₂ chemisorption. The presence of 0.02 monolayers of Cu retards the initial dissociative adsorption of N₂O by 40% but has little effect on the total uptake of oxygen. The initial dissociative sticking coefficient for O₂ is not retarded significantly by small amounts of copper. Deposition of larger amounts of Cu leads to the completion of a 2D overlayer before growth in 3D begins. Surfaces covered with less than 3 monolayers of Cu exhibit larger O₂ sticking coefficients and greater oxygen stability than pure Cu.