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Register a new userIn situ TEM investigation of oxygen migration as a key mechanism for resistive switching in Pr0.7Ca0.3MnO3
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Low temperature growth Pr0.7Ca0.3MnO3 (PCMO) thin film showed high performance in electric field induced resistance switching (RS). To understand the micro-mechanism of RS in Metal/PCMO/Metal devices, structure evolution of PCMO under external electric field monitored inside transmission electron microscope (TEM) were performed. Evolution of the modulation stripe in as-grown PCMO sample was investigated when applying electric field. The new-generated modulation stripe gradually disappeared. These results indicate that oxygen ion migration plays a key role in RS.
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The polarity-dependent resistive-switching across metal-Pr0.7Ca0.3MnO3 interfaces is investigated. The data suggest that shallow defects in the interface dominate the switching. Their density and fluctuation, therefore, will ultimately limit the device size. While the defects generated/annihilated by the pulses and the associated carrier depletion seem to play the major role at lower defect density, the defect correlations and their associated hopping ranges appear to dominate at higher defect density. Therefore, the switching characteristics, especially the size-scalability, may be altered through interface treatments.
Deformation twinning in hexagonal crystals is often considered as a way to palliate the lack of independent slip systems. This mechanism might be either exacerbated or shut down in small-scale crystals whose mechanical behavior can significantly deviate from bulk materials. Here, we show that sub-micron beryllium fibers initially free of dislocation and tensile tested in-situ in a transmission electron microscope (TEM) deform by a ${ 10bar{1}2 }$ $langle 10bar{1}1 rangle$ twin thickening. The propagation speed of the twin boundary seems to be entirely controlled by the nucleation of twinning dislocations directly from the surface. The shear produced is in agreement with the repeated lateral motion of twinning dislocations. We demonstrate that the activation volume ($V$) associated with the twin boundary propagation can be retrieved from the measure of the twin boundary speed as the stress decreases as in a classical relaxation mechanical test. The value of $V approx 8.3 pm 3.3 times 10^{-29}m^3$ is comparable to the value expected from surface nucleation.
We study the effect of external noise on resistive switching. Experimental results on a manganite sample are presented showing that there is an optimal noise amplitude that maximizes the contrast between high and low resistive states. By means of numerical simulations, we study the causes underlying the observed behavior. We find that experimental results can be related to general characteristics of the equations governing the system dynamics.
Superlattices may play an important role in next generation electronic and spintronic devices if the key-challenge of the reading and writing data can be solved. This challenge emerges from the coupling of low dimensional individual layers with macroscopic world. Here we report the study of the resistive switching characteristics of a of hybrid structure made out of a superlattice with ultrathin layers of two ferromagnetic metallic oxides, La0.7Sr0.3MnO3 (LSMO) and SrRuO3 (SRO). Bipolar resistive switching memory effects are measured on these LSMO/SRO superlattices, and the observed switching is explainable by ohmic and space charge-limited conduction laws. It is evident from the endurance characteristics that the on/off memory window of the cell is greater than 14, which indicates that this cell can reliably distinguish the stored information between high and low resistance states. The findings may pave a way to the construction of devices based on nonvolatile resistive memory effects.
We extend results by Stotland and Di Ventra on the phenomenon of resistive switching aided by noise. We further the analysis of the mechanism underlying the beneficial role of noise and study the EPIR (Electrical Pulse Induced Resistance) ratio dependence with noise power. In the case of internal noise we find an optimal range where the EPIR ratio is both maximized and independent of the preceding resistive state. However, when external noise is considered no beneficial effect is observed.
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