Resistance switching properties in Pt/SrTiO3:Nb Schottky junctions studied by admittance spectroscopy

We have investigated the resistance switching behavior of Pt/Nb-doped SrTiO3 (STO:Nb) Schottky junctions, which were fabricated using STO:Nb single crystals with an as-polished surface, a thermally treated surface, and a freshly cleaved surface. The largest and smallest I–V curve hystereses were found in the samples with the cleaved and thermally treated surfaces, respectively. The I–V curves’ temperature dependence showed a steep increase of leakage current in reverse bias mode with decreasing temperature for all samples. Also cooling enhanced the magnitude of the hysteresis. The frequency dependence of the junction admittance indicated that the fundamental structure of the Pt/STO:Nb junction can be described by a parallel connection of a depletion layer (capacitance) and a leakage path. Furthermore, the leakage path seemed to be a simple conduction path without any obvious frequency dependency in conductance.