Detection of filament formation in forming-free resistive switching SrTiO3 devices with Ti top electrodes

We investigated the influence of Ti top electrodes on the resistive switching properties of SrTiO3 thin film devices. Above a Ti layer thickness of 5 nm, the initial resistance is strongly reduced, giving rise to forming-free devices. Hard x-ray photoemission experiments reveal the Ti layer to be composed of several oxide phases, induced by the redox-reaction at the Ti/SrTiO3 interface. Grazing incidence small angle x-ray scattering measurements indicate that the reduction of the SrTiO3 thin film occurs in a filamentary way. We attribute this behavior to the preferential reduction of SrTiO3 thin films along highly defective areas.