Electric Field Induced Resistive Switch in Transition Metal Oxides: A ``Model'' for Future Non-Volatile Memory Devices

The kinetics of resistive switching in metal (Ag)--Pr$_{0.7}$Ca $_{0.3}$MnO$_{3}$ interfaces has been investigated. The resistance hysteresis $\Delta R $varies with the pulse amplitude $V_{0}$ roughly as a step function with existence of a threshold voltage $V_{t}$. On the other hand, the $\Delta R $varies with the pulse width ($T_{w})$ as a two-stage sequence: an initial exponential rise with a time constant $\tau _{S}\approx $ 2 X10$^{7}$ s and a slow linearly increasing tail. The slow linear part is dominant only in the quasi-dc switch (pulse width $\sim $ a few seconds) below $V_{t}$. The retentions of the $\Delta R $corresponding to the two stages are also extremely different, indicating that different underlying processes are involved. The relaxation time ($\tau _{R})$ is 10$^{8}$ s ($\sim $year) or higher for the sub-$\mu $s switching, in strong contrast with the total disappearance of the $\Delta R $after a few days for sub-threshold ($V_{0}<< \quad V_{t})$ switch. More results obtained suggest that defect creation/annihilation is likely the mechanism for the sub-$\mu $s switching and that a slow accumulative process (like diffusion) of defects may be responsible for the quasi-dc switch.