Switching Memory Effect Research Articles

Reconfigurable Low-Voltage Hexagonal Boron Nitride Nonvolatile Switches for Millimeter-Wave Wireless Communications.

Recently, nonvolatile resistive switching memory effects have been actively studied in two-dimensional (2D) transition metal dichalcogenides and boron nitrides to advance future memory and neuromorphic computing applications. Here, we report on radiofrequency (RF) switches utilizing hexagonal boron nitride (h-BN) memristors that afford operation in the millimeter-wave (mmWave) range. Notably, silver (Ag) electrodes to h-BN offer outstanding nonvolatile bipolar resistive switching characteristics with a high ON/OFF switching ratio of 1011 and low switching voltage below 0.34 V. In addition, the switch exhibits a low insertion loss of 0.50 dB and high isolation of 23 dB across the D-band spectrum (110 to 170 GHz). Furthermore, the S21 insertion loss can be tuned through five orders of current compliance magnitude, which increases the application prospects for atomic switches. These results can enable the switch to become a key component for future reconfigurable wireless and 6G communication systems.

Nano-analytical investigation of the forming process in an HfO2-based resistive switching memory

Metal oxide-based resistive random access memory devices are highly attractive candidates for next-generation nonvolatile memories, but the resistive switching phenomena remain poorly understood. This article focuses on the microscopic understanding of the initial forming step, which is decisive for the switching process. The integrated resistive switching memory effect in Ti/HfO2/TiWN metal insulator metal structures is studied. After forming, transmission electron microscopy investigations pointed out the presence of a funnel-shaped region, in the ON state of the cell, where slightly oxidized Ti (TiOx) was present within HfO2 dielectric. Modeling of the measured ON state conductance of the cell with the semi-classical approximation is consistent with a conductive nanometric TiOx filament (or a sum of sub-nanometric TiOx filaments) present in the funnel-shaped region. The conductive area is likely formed by diffusion after the dielectric breakdown.

Quantum conductors formation and resistive switching memory effects in zirconia nanotubes

The prospects of the development of non-volatile memory elements that involve memristive metal-dielectric-metal sandwich structures are due to the possibility of reliably implementing sustained functional states with quantized conductance. In the present paper, we have explored the properties of Zr/ZrO2/Au memristors fabricated based on an anodic zirconia layer that consists of an ordered array of vertically oriented non-stoichiometric nanotubes with an outer diameter of 30 nm. The operational stability of the designed memory devices has been analyzed in unipolar and bipolar resistive switching modes. The resistance ratio ≥105 between high-resistance (HRS) and low-resistance (LRS) states has been evaluated. It has been found that the LRS conductivity is quantized over a wide range with a fundamental minimum of 0.5G 0 = 38.74 μS due to the formation of quantum conductors based on oxygen vacancies (VO). For Zr/ZrO2/Au memristors, resistive switching mechanisms to be sensitive to the migration of VO in an applied electric field have been proposed. It has been shown that the ohmic type and space-charge-limited conductivities are realized in the LRS and HRS, respectively. Besides, we have offered a brief review of parameters for functional metal/zirconia/metal nanolayered structures to create effective memristors with multiple resistive states and a high resistance ratio.

A Novel Poly-N-Epoxy Propyl Carbazole Based Memory Device.

Generally, polymer-based memory devices store information in a manner distinct from that of silicon-based memory devices. Conventional silicon memory devices store charges as either zero or one for digital information, whereas most polymers store charges by the switching of electrical resistance. For the first time, this study reports that the novel conducting polymer Poly-N-Epoxy-Propyl Carbazole (PEPC) can offer effective memory storage behavior. In the current research, the electrical characterization of a single layer memory device (metal/polymer/metal) using PEPC, with or without doping of charge transfer complexes 7,7,8,8-tetra-cyanoquino-dimethane (TCNQ), was investigated. From the current–voltage characteristics, it was found that PEPC shows memory switching effects in both cases (with or without the TCNQ complex). However, in the presence of TCNQ, the PEPC performs faster memory switching at relatively lower voltage and, therefore, a higher ON and OFF ratio (ION/IOFF ~ 100) was observed. The outcome of this study may help to further understand the memory switching effects of conducting polymer.

A Visible Light Modulated Resistive Switching Memory Behaviors in the Ta/BiFeO3/Carbon/BaTiO3/Si Device

A bipolar resistance switching memory effect is observed in the Ta/BiFeO3/carbon/BaTiO3/Si structure. The resistance switching (RS) behavior can be modulated by an optical signal. The HRS/LRS resistance ratio and threshold voltage change remarkably under white-light irradiation. The trap-based charges in the Schottky-like depletion layers excited by the white light are responsible for the white-light controlled RS memory behaviors. This research is useful in exploring multi-functional materials and applications in optical-controlled nonvolatile memory devices.

Compositional tuning of negative differential resistance in a bulk silver iodide memristor

Silver iodide a negative differential resistance (NDR) memristor

Resistive switching memory effects in p-type hydrogen-treated CuO nanowire

Nanowire (NW)-based resistive switching device offers an ideal platform to develop a nanoscale-memristive device for next-generation memory and computing. The present study developed a p-type hydrogen-treated CuO NW memory device by using hydrogen annealing. The hydrogen-treated CuO NW, which is mainly composed of Cu2O, exhibited a resistive switching non-volatile memory effect and demonstrated low electric-field device operation with ∼3 × 106 V/m and high ON/OFF ratio up to 107. The hole conduction path formation/rapture mechanism based on the redox reaction of CuO was proposed as a resistive switching mechanism.

Surface traps-related nonvolatile resistive switching memory effect in a single SnO2:Sm nanowire

For nanostructure SnO2, it is very difficult for its electric properties to accurately control due to the presence of abundant surface states. The introduction of Sm can improve the traps in surface space charge region of SnO2 nanowires, resulting in a controllable storage charge effect. For the single nanowire-based two-terminal device, two surface state-related back-to-back diodes are formed. At a relatively large voltage, electrons can be injected into the traps in surface space charge region from negative electrode, resulting in a decrease of surface barrier connected with negative electrode, and contrarily electrons can be extracted from the traps in surface space charge region into positive electrode, resulting in an increase of surface barrier connected with positive electrode. The reversible injection and extraction induce a nonvolatile resistive switching memory effect.

Effect of anodic oxidation time on resistive switching memory behavior based on amorphous TiO2 thin films device

Resistance random access memory (RRAM) is a promising memory technology in the applications of memory device. Herein, the amorphous TiO2 thin film was grown onto titanium (Ti) foil by anodic oxidation. Further, the Ag/TiO2/Ti sandwich structure device was prepared, which displays a resistive switching memory effect with a high HRS/LRS resistance ratio with ∼27 at room temperature when the TiO2 film was oxidized ∼5 min. Finally, the formation/rupture models of Ag conductive filaments are suggested to explain the resistive switching memory behavior. This work open a new way for preparing the RRAM device for memory applications in the future.

Tunneling of carrier at the interface barrier induced nonvolatile resistive switching memory behaviors

The mechanism of resistance switching memory effect has always been a focused scientific topic. In this work, a new resistance conversion mechanism is put forward in a resistance switching device with sandwich structure, in which the Cu2ZnSnSe4 (CZTSe) is used as active layer and the F-doped SnO2 (FTO) and Al-doped ZnO (AZO) acts the top and bottom electrode, respectively. Through further in-depth study, an optimal memory effect in the FTO/CZTSe/AZO device is observed when the thickness of CZTSe film is ∼200 nm (dCZTSe = 200 nm). Finally, the memory characteristics of the resistance switching device is clarified in detail by using a physical model based on the tunneling of carrier at the Schottky barrier which are formed on the FTO/CZTSe and CZTSe/AZO interfaces.

Electroformed silicon nitride based light emitting memory device

The resistive memory switching effect of an electroformed nanocrystal silicon nitride thin film light emitting diode (LED) is demonstrated. For this purpose, current-voltage (I-V) characteristics of the diode were systematically scanned, paying particular attention to the sequence of the measurements. It was found that when the voltage polarity was changed from reverse to forward, the previously measured reverse I-V behavior was remembered until some critical forward bias voltage. Beyond this critical voltage, the I-V curve returns to its original state instantaneously, and light emission switches from the OFF state to the ON state. The kinetics of this switching mechanism was studied for different forward bias stresses by measuring the corresponding time at which the switching occurs. Finally, the switching of resistance and light emission states was discussed via energy band structure of the electroformed LED.

Flexible nonvolatile resistive memory devices based on SrTiO3 nanosheets and polyvinylpyrrolidone composites

A non-volatile resistive switching memory effect was observed in flexible memory device based on SrTiO3 nanosheets and polyvinylpyrrolidone composites.

Resistance switching characteristics of core–shell γ-Fe2O3/Ni2O3 nanoparticles in HfSiO matrix

Core–shell γ-Fe2O3/Ni2O3 nanoparticles are synthesized by chemical co-precipitation method. Resistive switching memory behaviors, which have resistance ON/OFF ratio of ∼102 and excellent retention property, are observed in the Au/HfSiO/γ-Fe2O3/Ni2O3/HfSiO/Pt structure. Space charge limited current (SCLC) mechanism, which is supported by the fitting current–voltage results, is employed to know the resistive switching memory effects. The transportation of Oxygen vacancy Vo2+, oxygen ion O2−, recombination of oxygen atom and drive of external electric field are responsible for the ON or OFF states observed in device.

Surface-type nonvolatile electric memory elements based on organic-on-organic CuPc-H2Pc heterojunction**Project supported by the GIK Institute of Engineering Science and Technology, Pakistan and Physical Technical Institute of Academy of Sciences of Tajikistan.

A novel surface-type nonvolatile electric memory elements based on organic semiconductors CuPc and H2Pc are fabricated by vacuum deposition of the CuPc and H2Pc films on preliminary deposited metallic (Ag and Cu) electrodes. The gap between Ag and Cu electrodes is 30–40 μm. For the current–voltage (I–V) characteristics the memory effect, switching effect, and negative differential resistance regions are observed. The switching mechanism is attributed to the electric-field-induced charge transfer. As a result the device switches from a low to a high-conductivity state and then back to a low conductivity state if the opposite polarity voltage is applied. The ratio of resistance at the high resistance state to that at the low resistance state is equal to 120–150. Under the switching condition, the electric current increases ∼ 80–100 times. A comparison between the forward and reverse I–V characteristics shows the presence of rectifying behavior.

Resistive switching memory characteristics of single MoSe2 nanorods

Resistive switching memory effect in metal–oxide–metal structures is a fascinating phenomenon toward next generation universal nonvolatile memories. Herein, the MoSe2 nanorods were prepared by hydrothermal method. Further, a resistive switching memory device of single MoSe2 nanorods is demonstrated. The device presents stable resistive switching memory behaviors with on–off ratio (memory window) of ∼50 at room temperature. Moreover, the origin of switching behavior in these devices on the basis of formation and annihilation of conducting filaments is addressed. This study is useful for exploring the multifunctional materials and their applications in nonvolatile memory devices.

Chemical linkage functions of poly(ether imide)s on the resistive switching memory effects

A series of aromatic poly(ether imide)s, AZTA-PEIs containing triphenylamine and 1,2,4-triazole moieties are prepared and characterized. All the polymers with inherent viscosity from 0.58 to 1.1dL/g show glass transition temperatures in the range of 250–278°C. Resistive switching memory devices are constructed based on the processable poly(ether imide) (AZTA-PEIa). The device can be switched from the initial OFF state to the ON state under either positive or negative electrical sweep at about ±3.2V. The ON state is nonvolatile and can maintain the high conducting state even turning off the electrical power and applying a reverse bias. The device fulfills the requirements of a write-once read-many times memory (WORM) with a high ON/OFF current ratio up to 105 and a long retention time in both ON and OFF states. The bistable switching effects of the polymer result from the conformation-coupled charge transfer from electron donors (triazole-substituted triphenylamine moieties) to electron acceptors (phthalimide moieties). By comparing with the memory behaviors of analogue polymers, the functions of ether and imide in the chemical polymer structure on the memory behaviors are discussed.

Resistive switching in ultra-thin La0.7Sr0.3MnO3/SrRuO3 superlattices

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 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.

Resistive Switching in a Printed Nanolayer of Poly(4-vinylphenol)

Resistive switching in organic resistive switches fabricated with a sandwich structure of indium tin oxide (ITO)-coated polyethylene terephthalate (PET)/poly(4-vinylphenol) (PVP)/silver (Ag) is reported. A single layer of PVP was used as an active layer in the sandwich structure between the two electrodes. The active layer of the polymer was atomized with the electrohydrodynamic atomization technique on the ITO-coated PET. The film thickness of the PVP polymeric layer on the ITO-coated PET was measured to be 110 nm. The surface morphology was characterized by field-emission scanning electron microscopy, and the purity of the film was examined by x-ray photoelectron spectroscopy analysis. Electrical current–voltage (I–V) measurements confirmed the memristive behavior of the sandwich device. The effect of the current compliance (CC) on resistive switching in the fabricated sandwich structure was also explored. The PVP-based organic resistive switch showed a CC-dependent OFF/ON ratio and memory window. Resistive switching memory effects were prominent at low CC up to nanoamps. The as-fabricated device was operated with low operational voltages for both polarities with OFF/ON ratio greater than 100:1. The robustness of the fabricated memristor was checked with multiple voltage sweeps, and the retention time is reported to be over 100 min.

Tunneling characteristics of graphene

Negative differential conductance and tunneling characteristics of two-terminal graphene devices are observed before and after electric breakdown, respectively. The former is caused by the strong scattering under a high E-field, and the latter is due to the appearance of a tunneling barrier in graphene channel induced by a structural transformation from crystalline graphene to disordered graphene because of the breakdown. Using Raman spectroscopy and imaging, the presence of nonuniform disordered graphene is confirmed. A memory switching effect of 100 000% ON/OFF ratio is demonstrated in the tunneling regime, which can be employed in various applications.

Bistable resistance memory switching effect in amorphous InGaZnO thin films

We report a bistable resistance switching effect in amorphous InGaZnO (a-IGZO) thin films deposited by a pulsed laser deposition method. The electrical properties of a-IGZO thin films were controlled by the oxygen partial pressure during deposition and this determined the resistance switching effect. We also observed the resistance switching effect with various electrodes such as Pt, Au, and Al. We suggest that the resistance switching effect is related to the formation of a conducting path by metal and/or oxygen vacancy defects in the a-IGZO matrix.