Pulse length and amplitude dependent resistive switching mechanisms in Pt-Pr0.67Ca0.33MnO3-Pt sandwich structures

We report here on the presence of two different nonvolatile resistive switching mechanisms in Pt-Pr0.67Ca0.33MnO3-Pt sandwich structures based on pulsed electrical transport measurements. As a function of pulse length, amplitude and temperature, the devices show two different switching regimes. The first is positive switching (PS) where a high resistance state (HRS) evolves at positive bias at the top electrode in the voltage range of U???0.5?1.2 V and pulse lengths tp???10?7 s. In addition, we observe a cross over to negative switching (NS) for U?>?1 V and tp???10?3 s. Here, the HRS evolves at negative bias applied at the top electrode. We present strong evidence that both switching mechanisms take place at the interface between Pr0.67Ca0.33MnO3 and the top electrode. Based on finite element simulations of the temperature evolution during the electrical pulses, we show that the onset of Joule heating is characteristic of the PS regime, whereas drastic temperature increases of several hundred Kelvin evolve during NS. Based on the observed different timescales, pulse amplitudes and temperature dependences of PS and NS, respectively, we suggest that two different switching mechanisms are involved: a fast, short range exchange of oxygen at the interface with the metallic electrode for PS and a slower, long range redistribution of oxygen in the entire PCMO film for the NS.