Enhanced selectivity towards O2 and H2 dissociation on ultrathin Cu films on Ru(0001)

The reactivity of Cu monolayer (ML) and bilayer films grown on Ru(0001) towards O-2 and H-2 has been investigated. O-2 initial sticking coefficients were determined using the King and Wells method in the incident energy range 40-450 meV, and compared to the corresponding values measured on clean Ru(0001) and Cu(111) surfaces. A relative large O-2 sticking coefficient (similar to 0.5-0.8) was measured for 1 ML Cu and even 2 ML Cu/Ru(0001). At low incident energies, this is one order of magnitude larger than the value observed on Cu(111). In contrast, the corresponding reactivity to H-2 was near zero on both Cu monolayer and bilayer films, for incident energies up to 175 meV. Water adsorption on 2 ML Cu/Ru(0001) was found to behave quite differently than on the Ru(0001) and Cu(111) surfaces. Our study shows that Cu/Ru(0001) is a highly selective system, which presents a quite different chemical reactivity towards different species in the same range of collision energies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746942]