This study shows direct experimental evidence of the catalytic activity of bimetallic ruthenium/manganese surfaces toward oxygen and determines how this activity impacts the thermodynamic stability of Ru/Mn-based copper diffusion barrier layers for advanced microelectronic devices. X-ray photoemission spectroscopy (XPS) analysis, as part of a fully in situ experimental procedure, showed the thermal dissociation of manganese monoxide (MnO) and the desorption of oxygen in the presence of Ru at 500 C. This is in contrast with the thermal stability of MnO in the absence of Ru at temperatures up to 700 C and suggests that the presence of Ru increases the catalytic activity of Mn surfaces by reducing the MnO dissociation energy and the oxygen desorption energy. XPS analysis showed no evidence of a change in the chemical composition of the Ru layer, consistent with previously proposed mechanisms for oxygen catalysis on bimetallic surfaces. Further studies investigated the impact of the presence of Ru on the chemical composition and thermodynamic stability of Mn-O-based copper diffusion barrier layers, which were preformed in situ in ultra high vacuum. Results from separate experiments show that the presence of Ru liner layers (∼2 nm) causes the partial dissociation of both MnO and MnSiO3 barrier layers (∼5 nm) following 500 C thermal annealing. This result is again attributed to the catalytic activity of Ru/Mn surfaces reducing the dissociation energy of the Mn-O bond within the barrier layer region. © 2013 American Chemical Society.