Resistive switching in multiferroic BiFeO3 films: Ferroelectricity versus vacancy migration

Abstract We studied the voltage-induced resistive switching (RS) in ferroelectric/metal (BiFeO 3 /Nb:SrTiO 3 ) vertical devices. We found switching with R ON and R OFF ratios of ΔR = 1-R ON /R OFF  = 0.82 at voltages starting at V SET, RESET  = ±2 V. Upon increasing voltage, ΔR also increases until dielectric breakdown is reached. Interestingly, the V SET, RESET values at which the RS becomes significant, coincides with the coercive voltage of the ferroelectric polarization, as measured by piezoelectric force microscopy in similar BiFeO 3 films. This suggests that the driving mechanism of the RS effect in our films is connected to the BiFeO 3 ferroelectricity. However, the increase of the RS effect after complete ferroelectric saturation points to an additional mechanism that may be related to vacancy displacements. This is further supported by forming process necessary to induce resistance bi-stability, typical of an RS effect.