Oxygen incorporation into Fe-doped SrTiO3: Mechanistic interpretation of the surface reaction

The surface part of the oxygen incorporation reaction into the model material Fe-doped SrTiO3 is investigated by in situ optical spectroscopy. Experiments close to and far from equilibrium ( small and large pO(2) changes) and the effect of UV irradiation on the reaction rate allow us to draw the following conclusions with respect to the kinetic processes at the surface: (i) molecular oxygen species participate in or before the rate determining step (RDS), and (ii) a single conduction band electron participates in or before the RDS of the incorporation reaction even though the bulk is p-type conducting. Probable reaction mechanisms comprising chemisorption, charge transfer, dissociation and oxygen ion transfer steps are discussed.