Improved Resistance Switching Research Articles

Resistive switching, endurance and retention properties of ZnO/HfO2 bilayer heterostructure memory device

This work reports the fabrication of resistive memory device with a bilayer ZnO/HfO2 structure. Highly stable and uniform bipolar resistance switching (RS) characteristics were attained when HfO2 interfacial layer is introduced in ZnO device. The bilayer device attains good resistive switching with increased resistance ON-OFF ratio of the order of ∼102, better dc endurance of > 102 cycles and retention of >104 s at room temperature. X-ray Photoelectron Spectroscopy (XPS) investigation is also done and it is confirmed that oxygen vacancies in ZnO thin film are responsible for improved resistance switching. The current-voltage (I–V) relationship reveals that switching behavior of these devices is mainly dominated by Space-Charge-Limited-Current mechanism (SCLC) regulated due to localized oxygen vacancies. Effect of temperature on the electrical conductivity has also been investigated to analyze the behavior of Low Resistance States (LRS) and High Resistance States (HRS). The findings imply that the bilayer ZnO/HfO2 device structure is a promising one for upcoming non-volatile memory applications.

Resistance Switching and Failure Behavior of the MoOx/Mo2C Heterostructure.

With the rapid demand for high-performance and power-efficient memristive and synaptic systems, more 2D heterostructures with improved resistance switching (RS) properties are still urgently in need for next-generation devices. Here, we report the RS behaviors of vertical MoOx/Mo2C heterostructures fabricated by controllable thermal oxidation and uncover the failure behavior for the first time. It is found that the MoOx/Mo2C heterostructure exhibits bipolar RS with a low set/reset voltage of +0.5/-0.3 V, an ultralow power consumption of 5 × 10-8 W, and an on/off ratio of 102, which is ascribed to the transport of the internal oxygen ions of MoOx. Furthermore, the failure behavior of RS behaviors of the MoOx/Mo2C heterostructure under a higher work voltage is revealed. It indicates that the amorphization of the pristine crystalline MoOx layer could block the movement of the internal oxygen ions in the vertical direction. The excellent RS performance induced by the synergy of MoOx and Mo2C and the demonstration of the failure behavior enable the potential applications of the 2D heterostructure in related memory devices and biological neural networks.

Improved Resistance Switching Characteristics of BiFeO3 Thin Film by Increasing the Annealing Temperature

We have fabricated BiFeO3 thin film deposited on Pt/Ti/SiO2/Si substrates by the chemical solution deposition method. The effects of annealing temperature on the thin film structure, resistance switching (RS) properties, conduction mechanisms are investigated. It exhibits improved RS window with high ON/OFF ratio ([Formula: see text]104) for the sample annealed at 650[Formula: see text]C. XPS characterization indicates that cation ratio of Fe[Formula: see text]/Fe[Formula: see text] is increased with increasing annealing temperature. Crystal lattice distortion generated by Fe[Formula: see text] cations, along with oxygen vacancies, commonly contribute to opening the RS window and the increment of conductive filaments. The film’s conduction mechanisms under different annealing temperatures are fully discussed. The RS properties of this system can be effectively improved by increasing the annealing temperature, which is crucial prerequisite for future applications of BFO-based thin film device in resistance random access memory.

Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region.

Improved Resistance Switching Characteristics in Ti-Doped $\hbox{Yb}_{2}\hbox{O}_{3}$ for Resistive Nonvolatile Memory Devices

A conventional approach of doping to control the bistable resistance switching in Yb2O3 was investigated for nonvolatile memory applications. With the help of Ti doping into oxide films during the process, better cycle-to-cycle resistance distribution and switching voltage uniformity were found due to modulation of current conduction mechanism from space-charge-limited current in Yb2O3 to Schottky type in YbTiOx. The program/erase cycles with successive readout operation over 105 cycles can be achieved without any degradation. No data loss was found upon continuous readout process at both room temperature and 85°C. The Ni/YbTiOx/TaN memory is a promising candidate to be integrated into future memory processes.

Areal and Structural Effects on Oxide-Based Resistive Random Access Memory Cell for Improving Resistive Switching Characteristics

A new technical improvement in understanding the resistive switching characteristics of unipolar resistive random access memory (RRAM) is investigated. It is possible to minimize reset current (IRESET), set voltage variation, and forming voltage (VFORMING), which results in a wide sensing margin and high density applications by using a conducting filament (CF) minimized structure up to a 10 nm technology node. Its structural advantages enable IRESET to be tuned with excellent manufacturability. Numerical simulation is also performed using a random circuit breaker (RCB) model, showing that the proposed structure elucidates the resistive switching improvement.

Areal and Structural Effects on Oxide-Based Resistive Random Access Memory Cell for Improving Resistive Switching Characteristics

Areal and Structural Effects on Oxide-Based Resistive Random Access Memory Cell for Improving Resistive Switching Characteristics

Improved resistance switching in ZnO-based devices decorated with Ag nanoparticles

ZnO is especially attractive among the materials showing resistance switching because of its excellent properties such as light emitting and transparency for visible light. Unfortunately, the resistance switching in a ZnO-based device is usually unstable. By dispersing Ag particles of size ∼20 nm at the electrode–ZnO interface, we significantly improved the resistance uniformity, set/reset repeatability of Ag–ZnO–Pt devices. Conducting atomic force microscope analysis revealed the appearance of micro-regions where resistance switching, with an improved stability, is more easily triggered. It is suggested that Ag particles act as seeds for conducting filaments, leading to depressed randomness and reduced diameter of the conducting paths.

Fabication of one-diode-one-resistor memory cell structure of Pt/CuO/Pt/TiN/Pt/CuO/InZnO x/Pt and the effect of TiN layer on the improved resistance switching characteristics

We investigated the electrical properties of oxide-based one diode/one resistor (1D-1R) memory cells for resistance switching memory device application employing NiO as a storage element and p-CuO/ n-InZnO x diode as a steering element. The electrical property of the 1D-1R memory cells was significantly affected by the repetitive resistance switching operation of the NiO layer. It appears that oxygen vacancy movement from NiO layer leads to the degradation of the oxide diode. We introduced a conducting TiN layer as a diffusion barrier between the diode and the NiO. As a result, the reliability of the 1D-1R memory cells was significantly improved.

Novel U-Shape Resistive Random Access Memory Structure for Improving Resistive Switching Characteristics

Novel U-Shape Resistive Random Access Memory Structure for Improving Resistive Switching Characteristics

Novel U-Shape Resistive Random Access Memory Structure for Improving Resistive Switching Characteristics

We firstly propose a novel U-shape resistive cell structure which is the best fit for generating low power resistive random access memory (RRAM) with forming-less process. We find that irregular resistive switching behavior in the initial transition and the characteristics associated with it. Controlling the conducting filament (CF) dimension and deposition orientation of resistive material are expected to reduce the distribution and forming voltage, which enables low power RRAM to be feasible without forming state. Simple fabrication flow and device performances are also evaluated in the aspect of forming-less process. Numerical simulation is performed using random circuit breaker model (RCB) to confirm the proposed structure.

Improved switching characteristics of perovskite oxide‐based resistance random access memory by high‐pressure oxygen annealing at low temperature

AbstractWe successfully fabricated perovskite oxide‐based resistance random access memory (RRAM) with improved resistance switching characteristics, at a low temperature. A high‐pressure oxygen‐annealed (HPOA) W/Al/Pr0.7Ca0.3MnO3 (PCMO)/Pt device shows good memory characteristics such as device uniformity, endurance, and improved switching speed. X‐ray photoelectron spectroscopy reveals large amounts of oxygen effectively incorporated into the PCMO layer during HPOA, enhancing the crystallization of PCMO at low temperature. X‐ray diffraction analysis confirmed that an amorphous PCMO layer was converted to a polycrystalline structure. These results suggest that HPOA is a promising method for fabricating reliable perovskite oxide‐based RRAM at a low temperature.

Nonvolatile Resistive Switching Devices Based on Nanoscale Metal/Amorphous Silicon/Crystalline Silicon Junctions

AbstractM/a-Si:H/c-Si based nonvolatile resistive switching devices with active areas down to 50 nm×50 nm have been fabricated and explored. Close to 100% device yield was achieved without necessity of high voltage forming process. Both rectifying switching and non-rectifying switching were demonstrated in a controllable fashion. The potential for this structure as nanoscale nonvolatile memory devices was investigated in terms of scalability, retention time, endurance and switching speed. The device showed switching speed faster than 5 ns, endurance cycles more than 106 and retention time longer than 150 days without any degradation of stored data. The devices exhibit improved resistance switching ratio when scaled down.

HPHA Effect on Reversible Resistive Switching of Pt∕Nb-Doped SrTiO[sub 3] Schottky Junction for Nonvolatile Memory Application

We investigated the effect of high-pressure hydrogen annealing (HPHA) on a Pt/Nb-doped SrTiO 3 Schottky junction for nonvolatile memory applications. Hysteretic current-voltage (I-V) characteristic curves reveal that the HPHA-treated Schottky junction interface has a higher resistance ratio than the control sample in dc bias sweep. The HPHA sample also exhibits switching behavior by pulsed voltage stress with excellent electrical characteristics including voltage pulse duration as short as 1 μs, endurance cycles of up to 10 6 times, and retention time as long as 10 5 s. These indicate that HPHA improved resistance switching characteristics of the Schottky junction.