Insulator-metal transition associated with resistive switching in real SrTiO3 and TiO2 crystals

Among the various concepts for future data storage, the resistive switching phenomenon (memristive effect) in transition metal oxides has attracted much attention since it would allow fast non-volatile and energy-efficient memory devices to be designed. As prototype materials for transition metal oxides SrTiO₃ and TiO₂ have been established and were investigated intensively. It was found that in these materials conducting filaments channel the current flow during switching which implies a change of paradigm in understanding insulator-metal transitions. Instead of assuming a current flow in the whole bulk, the electronic transport in metal oxides has to be described from a local perspective taking into account the role of conducting filaments. Here, we present investigations of the insulator-metal transition induced by reduction or extrinsic donor doping in SrTiO₃ and TiO₂ on the macro- and nanoscale revealing a strong interplay between the conducting filaments and extended defects such as dislocations and secondary phases.