Kinetics and relaxation of electroresistance in transition metal oxides: model for resistive switching

The kinetics of electric-field-induced resistive switching across metal ͑Ag͒-Pr0.7Ca0.3MnO3 interfaces has been investigated. The resistance hysteresis ⌬R varies with the pulse amplitude V0 roughly as a step function with existence of a threshold voltage Vt for a fixed switching pulses width Tw. On the other hand, the ⌬R varies with the pulse width ͑Tw͒ as a two-stage sequence at a fixed V0: an initial exponential rise with a time constant ␶SϷ2ϫ10−7 s and a slow linearly increasing tail. The slow linear part is dominant only in the quasi-dc switch ͑pulse widthϳa few seconds͒ below Vt but negligibly small above it. The retentions of the ⌬R corresponding to the two stages are also extremely different, indicating that different underlying processes are involved. The relaxation time ͑␶R͒ is 108 s ͑ϳyear͒ or higher for the sub-␮s switching, in strong contrast with the total disappearance of the ⌬R after a few days for subthreshold ͑V0ӶVt͒ quasi-dc switch. Different mechanisms, therefore, dominate the two different stages. More results obtained from time dependence study and impedance spectroscopy suggest that defect creation/annihilation, such as broken bonds under field, is likely the mecha-nism for the sub-␮s switching and that a slow accumulative process ͑like diffusion͒ of defects may be responsible for the subthreshold quasi-dc switch. Many observations further suggest that the accumulative process is much more complicated than simple migration/diffusion of the pre-existing defects.