Kinetics and dynamics of the initial dissociative chemisorption of oxygen on Ru(001)

Abstract

We have used supersonic molecular beam techniques to measure the initial dissociative chemisorption probability S 0 of O 2 on Ru͑001͒ as a function of incident kinetic energy E i , surface temperature T s , and angle of incidence i . We observe different behavior in the adsorption dynamics in two separate kinetic energy regimes: the value of S 0 decreases with incident energy in the low kinetic energy regime, and the value increases with incident energy in a higher kinetic energy regime. In the low energy regime, we observe a large inverse dependence of S 0 on surface temperature which is consistent with a trapping-mediated mechanism. Moreover, adsorption in the low energy regime can be accurately modeled by a trapping-mediated mechanism, with a surface temperature independent trapping probability ␣ into a physically adsorbed state followed by a temperature dependent kinetic competition between desorption and dissociation. The barrier to dissociation from the physically adsorbed state is ϳ28 meV below the barrier to desorption from this state as determined by analysis of kinetic data. In the high kinetic energy regime, values of the initial adsorption probability scale with normal kinetic energy, and S 0 approaches a value of unity for the highest incident energies studied. However, we report an unusual surface temperature dependence of S 0 in the high energy regime that is inconsistent with a simple direct mechanism. Indeed, in this higher energy regime the value of S 0 rises as the surface temperature is increased. We suggest a mechanism involving electron transfer from the ruthenium surface to account for this phenomena.

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

“…3, our results for clean Ru(0001) are in very good agreement with the data taken from Ref. 30, which were obtained at a surface temperature of 500 K and normal incidence (normal energy scaling has been also verified in Ref. 30).…”

“…The crystal temperature is 300 K, and the angle of incidence is i = 15 • . The data reported by Wheeler et al 30 for Ru(0001) under similar incident conditions are also shown. For 1 ML Cu and 2 ML Cu, we observe a monotonic increase of the initial sticking probability with incident beam energy, with progressively reduced values as the thickness of the layer increases and for energies lower than 200 meV.…”

“…30, which were obtained at a surface temperature of 500 K and normal incidence (normal energy scaling has been also verified in Ref. 30). This gives confidence on the use of Eq.…”

Carbonate Formation and Decomposition on Atomic Oxygen Precovered Au(111)

“…[11][12][13] Here we present experimental evidence with supporting density functional theory (DFT) calculations of carbonate formation and decomposition from the adsorption of oxygen-labeled carbon dioxide (C 18 O 2 ) on an atomic oxygen ( 16 O) precovered Au(111) surface. We studied the effects of CO 2 exposure, surface temperature, and oxygen coverage on carbonate formation and decomposition and also estimated reaction probabilities (∼10 -3 -10 -4 ) and activation energies as a function of conditions.Our experiments were performed in a UHV chamber that has been described elsewhere, [14][15][16][17][18][19] but details specific to this study are briefly summarized here. The Au(111) single crystal sample is mounted to a tantalum plate that can be resistively heated and is in thermal contact with a liquid nitrogen bath.…”

Growth and thermal oxidation of Ru and ZrO2 thin films as oxidation protective layers

“…212,218 In the case of adsorption of O2 on Ru, which undergoes via a limited precursormediated dissociative chemisorption, there are several studies on kinetics of O2 adsorption on monocrystalline Ru. 215,216,219,220,221 However, to the best of our knowledge, there is no reported data for oxygen adsorption kinetics on polycrystalline Ru at room temperature. Polycrystalline Ru is relevant due to that the structure of Ru thin films used as oxidation resistant protective layers for DRAMs, CMOS devices, solar cells, or EUVL optics is either polycrystalline or amorphous rather than monocrystalline.…”