Inhomogeneity and Segregation Effect in the Surface Layer of Fe-Doped SrTiO3 Single Crystals

Abstract

The effect of Fe doping on SrTiO3 single crystals was investigated in terms of crystal and electronic structure over a wide temperature range in both oxidizing and reducing conditions. The electrical properties were thoroughly studied with a special focus on the resistive switching phenomenon. Contrary to the undoped SrTiO3 crystals, where isolated filaments are responsible for resistive switching, the iron-doped crystals showed stripe-like conducting regions at the nanoscale. The results showed a non-uniform Fe distribution of as-received crystals and the formation of new phases in the surface layer of reduced/oxidized samples. The oxidation procedure led to a separation of Ti(Fe) and Sr, while the reduction resulted in the tendency of Fe to agglomerate and migrate away from the surface as seen from the time of flight mass spectroscopy measurements. Moreover, a clear presence of Fe-rich nano-filament in the reduced sample was found.