Cluster-like resistive switching of SrTiO3: Nb surface layers

The understanding of the resistive switching mechanisms in perovskites is of particular importance for the development of novel non-volatile memories. Nanoscale investigations recently revealed that in the model material SrTiO3 a filamentary type of switching is present. In this paper, we show that upon donor doping with Nb the switching type changes fundamentally. We report on the observation of conducting clusters that can be switched independently between a high resistance and a low resistance state when applying a voltage. Furthermore, we show that the resistive switching takes place in a semiconducting surface layer on top of the metallic bulk of SrTiO3: Nb single crystals, which can change its properties easily under external gradients. Based on various measurements, we postulate that ionic movements leading to the creation of secondary phases as nano-filaments between the clusters have to be taken into account in modelling the resistive switching.