The oxygen content and associated structural changes in SFO films significantly modify the electrical properties. The room temperature dielectric and leakage current properties of SFO films with various anneal treatments are shown in Fig. 2. A metal-insulator-metal (MIM) structure was employed with Au top circular electrodes of area approximately 0.3 mm2 sputtered on the SFO/Nb:STO samples. In samples with O2 anneal and no anneal, the dielectric constant is higher than that of the vacuum annealed samples, but the loss is also significantly greater, with dissipation factor, D, of 0.547 and 0.409 for SFO at 100 kHz without anneal and O2 annealed, respectively (see Fig. 2a,c and e). The dissipation factor of SFO annealed in vacuum is a magnitude of order lower, with a value of 0.064 at 100 kHz. The lower loss is due to the increased formation of the semiconducting SrFeO2.5 brownmillerite phase in the vacuum annealed SFO, which can also be seen in the trend of leakage current behavior in Fig. 2b,d and f. The phase transition between the semiconducting SrFeO2.5 phase and metallic SrFeO3 phase has been used to design filament type resistive switching devices31. The formation of conducting filaments in SFO is possibly related to the migration of oxygen vacancies within SrFeO3−δ., under application of electric field, which allows metallic SrFeO3 channels to flow current within the semiconducting matrix. As a result, the hysteretic behavior related to this filament formation is directly related to the density and mobility of oxygen vacancies within the SFO bulk. The asymmetry of leakage behavior between positive and negative applied bias is a product of the difference between conduction activity at the Au/SFO and Nb:STO/SFO interfaces3334. By applying fields in both directions in the MIM structure, the Schottky diode behavior allows for investigation in the dominant I-V characteristics at either of the metal-semiconductor contact interfaces35.