Reversible Resistance Switching Effect Research Articles

Bi-stable resistive switching characteristics in Ti-doped ZnO thin films

Ti-doped ZnO (ZnO/Ti) thin films were grown on indium tin oxide substrates by a facile electrodeposition route. The morphology, crystal structure and resistive switching properties were examined, respectively. The morphology reveals that grains are composed of small crystals. The (002) preferential growth along c-axis of ZnO/Ti could be observed from structural analysis. The XPS study shows the presence of oxygen vacancies in the prepared films. Typical bipolar and reversible resistance switching effects were observed. High ROFF/RON ratios (approximately 14) and low operation voltages within 100 switching cycles are obtained. The filament theory and the interface effect are suggested to be responsible for the resistive switching phenomenon.

Reversible resistance switching properties in Ti-doped polycrystalline Ta2O5 thin films

Unipolar reversible resistance switching effects were found in 5 at% Ti-doped polycrystalline Ta2O5 films with the device structure of Pt/Ti–Ta2O5/Pt. Results suggest that the recovery/rupture of the conductive filaments which are involved in the participation of oxygen vacancies and electrons leads to the resistance switching process. Ti-doped Ta2O5 thin films possess higher resistance whether in low-resistance state or high-resistance state and higher resistance switching ratio than Ta2O5 thin films, where Ti addition plays an important role in the resistance switching process by suppressing the migration of oxygen vacancies via forming an electrically inactive Ti/O–vacancy complex. Excellent retention properties of the high and low resistances under constant stress of applied voltage were obtained.

Effect of incorporating copper on resistive switching properties of ZnO films

Undoped and copper-doped ZnO (ZnO:Cu) thin films of wurtzite structure with c-axis orientation were grown on F-doped SnO2 (FTO) substrates by pulsed laser deposition. Typical bipolar and reversible resistance switching effects were observed in these films, and the ratio of high and low resistance state (ON/OFF ratio) increases abruptly by introducing Cu. Based on the impedance spectra of ZnO and ZnO:Cu films, the change of resistance at high and low resistance states is found to be accompanied with the variance of depletion width. Furthermore, the depletion width of ZnO films changes little, while that of ZnO:Cu films varies greatly under different resistance states, which is consistent with the result of that ZnO:Cu films show a much larger ON/OFF ratio than ZnO films. Therefore, the resistance switchings are supposed to be due to the change of depletion width of Schottky barrier.

Reversible resistance switching in La0.225Pr0.4Ca0.375MnO3: The Joule-heat-assisted phase transition

The reversible resistance switching (RS) controlled by current pulse pairs, accompanied with an overshooting relaxation, is observed in bulk La0.225Pr0.4Ca0.375MnO3. We demonstrate that the reversible RS effect is not the result of current-induced intrinsic transition of charge-ordered insulator (COI) into ferromagnetic metal (FMM) phase, but the outcome of Joule-heat-assisted transition between the FMM and COI phases. A local thermal-cycle assisted rearrangement of the FMM phase in the COI matrix is controllable by a current pulse, opening a possibility for multistate memory applications.

Reversible Resistance Switching Effect in Amorphous Ge1Sb4Te7 Thin Films without Phase Transformation

We demonstrate a reversible resistance switching effect that does not rely on amorphous-crystalline phase transformation in a nanoscale capacitor-like cell using Ge1Sb4Te7 films as the working material. The polarity and amplitude of the applied electric voltage switches the cell resistance between low- and high-resistance states, as revealed in the current-voltage characteristics of the film by conductive atomic force microscopy (CAFM). This reversible SET/RESET switching effect is induced by voltage pulses and their polarity. The change of electrical resistance due to the switching effect is approximately two orders of magnitude.

Occurrence of Both Unipolar Memory and Threshold Resistance Switching in a NiO Film

We observed two types of reversible resistance switching (RS) effects in a NiO film: memory RS at low temperature and threshold RS at high temperature. We were able to control the type of RS effects by thermal cycling. These phenomena were explained using a new dynamic percolation model that can describe the rupture and formation of conducting filaments. We showed that the RS effects are governed by the thermal stability of the filaments, which arise from competition between Joule heating and thermal dissipation. This work provides us understandings on basic mechanism of the RS effects and their interrelation.

“Positive” and “negative” electric-pulse-induced reversible resistance switching effect in Pr0.7Ca0.3MnO3 films

“Negative” electric-pulse-induced reversible resistance (EPIR) switching phenomenon was found in In/PCMO/Pt sandwich, in which the high resistance can be written with positive voltage pulses, and the low resistance can be reset using negative voltage pulses (the positive voltage direction is defined as going from the top electrode to the bottom electrode). This is just the opposite from the “positive” EPIR effect in Ag/PCMO/Pt sandwich, in which the high resistance can be written only with negative voltage pulses, and the low resistance can be reset using positive voltage pulses. The I–V hysteresis curves of In/PCMO/Pt and Ag/PCMO/Pt sandwiches also show opposite directions, i.e., counterclockwise and clockwise under a negative voltage region for indium and Ag electrode systems, respectively. C–V characteristics show that the barrier does not exist in Ag/PCMO/Pt sandwich, while In/PCMO/Pt sandwich exhibits an obvious Schottky-like barrier. We suggest that in the negative EPIR behavior in In/PCMO/Pt structure, the resistance states are mainly controlled changing the Schottky-like barrier at the interface with the weak effect of carrier trapping process, while the positive EPIR behavior in Ag/PCMO/Pt sandwich mainly depends on the carrier trapping process at the interface.

Spatially extended nature of resistive switching in perovskite oxide thin films

The authors report the direct observation of the electric pulse induced resistance-change effect at the nanoscale on La1−xSrxMnO3 thin films by the current measurement of the atomic force microscopy (AFM) technique. After a switching voltage of one polarity is applied across the sample by the AFM tip, the conductivity in a local nanometer region around the AFM tip is increased, and after a switching voltage of the opposite polarity is applied, the local conductivity is reduced. This reversible resistance switching effect is observed under both continuous and short-pulse-voltage switching conditions. It is important for future nanoscale nonvolatile memory device applications.