Search Results (127)

Ba_0.6Sr_0.4TiO₃ (BST) thin films were deposited on ITO substrates via rf magnetron sputtering, followed by structural and morphological characterization using XRD and FE-SEM. Metal–insulator–metal (MIM) RRAM devices were fabricated by depositing Al top electrodes, and their electrical properties were examined through I–V measurements. The optimized BST films deposited at 40% oxygen concentration exhibited stable resistive switching, with an operating voltage of 3 V, an on/off ratio of 1, and a leakage current of 10⁻⁸ A. After rapid thermal annealing at 500 °C, the on/off ratio improved to 2 but leakage increased to 10⁻³ A. Incorporating an electron transport layer (ETL) effectively suppressed the leakage current to 10⁻⁵ A while maintaining the on/off ratio at 2. Moreover, a transition from bipolar to unipolar switching was observed at higher oxygen concentration (60%). These results highlight the role of ETLs in reducing leakage and stabilizing switching characteristics, providing guidance for the development of transparent, low-power, and high-reliability BST-based RRAM devices. This study aims to investigate the role of Ba_0.6Sr_0.4TiO₃ (BST) ferroelectric oxide as a functional switching layer in resistive random-access memory (RRAM) and to evaluate how interface engineering using an electron transport layer (ETL) can improve resistive switching stability, leakage suppression, and device reliability. Full article

Work investigates the doping of molybdenum oxide (MoO_x) with tungsten (W). The successful incorporation of W into the MoO_x lattice was confirmed through X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS). Structural and optical analysis revealed the presence of oxygen vacancies within the W-MoO_x film, which are known to facilitate resistive switching (RS) in memristive devices. Based on this, a flexible memristor with the structure PET/ITO/W-MoO_x/polymethyl methacrylate (PMMA)/Al was fabricated. PMMA was strategically introduced between the W-MoO_x layer and the aluminum electrode to modulate interfacial properties that influence RS behavior. The W-MoO_x/PMMA-based memristor exhibited good resistive switching characteristics, with a memory window of approximately 12 and a retention time exceeding 2 × 10⁴ s, demonstrating a non-volatile memory behavior. In the high-resistance state (HRS), the conduction mechanism under higher applied voltages follows a space-charge-limited current (SCLC) model, indicating that the RS process is primarily governed by charge trapping and de-trapping at the interface. Overall, the consistent and robust switching performance of the W-MoO_x/PMMA heterostructure underlines its potential as a reliable functional layer for next-generation resistive random-access memory (ReRAM) devices. Full article

Thin films of nickel oxide (NiO) were deposited on a 5° miscut magnesium oxide (MgO)(100) substrate using electron-beam evaporation to pursue morphology-directed resistive switching. The atomic force microscope (AFM) confirmed a stepped surface with a terrace width of ~85 nm and a step height of ~7 nm. After deposition, the film resistance decreased from 200 MΩ to 25 MΩ by annealing under ambient air at 400 °C, attributed to the increase in the p-type conductivity through nickel vacancy formation. Top electrodes of Ag (500 nm width, 180 nm gap) were patterned parallel or perpendicular to the substrate steps using UV and electron-beam lithography. Devices aligned parallel to the step showed reproducible unipolar switching with 100% yield between forming voltages 20–70 V and HRS/LRS~10² at ±5 V. In contrast, devices formed perpendicular to the steps (8/8) subsequently failed catastrophically during electroforming, with scanning electron microscopy (SEM) showing breakdown holes on the order of ~100 nm at the step crossings. The anisotropic electrodynamic response is due to step-guided electric field distribution and directional nickel vacancy migration, illustrating how substrate morphology can deterministically influence filament nucleation. These results highlighted stepped MgO as a template to engineer the anisotropic charge transport of NiO, exhibiting a reliable ReRAM as well as directional electrocatalysis for energy applications. Full article

In this study, silicon carbide (SiC) thin films for resistive random-access memory (RRAM) devices were successfully prepared using the radio-frequency magnetron sputtering method at deposition powers of 50 and 75 W for 1 h. The aluminum (Al) top electrode of the RRAM devices was also fabricated using thermal evaporator deposition. Additionally, the electrical properties of the SiC thin film RRAM devices were determined using a B2902A mechanism. The current–voltage (I–V) curves of the as-deposited SiC thin films at 50 and 75 W power levels were measured and analyzed. Specifically, the set and reset voltages for the RRAM devices deposited at 50 and 75 W were approximately 1.2 and −1.5 V, respectively. For the annealed samples, the memory windows of the 75 W SiC thin film RRAM devices treated at 300 °C were found to be around 10⁵. Full article

Resistive switching (RS) phenomena are nowadays one of the most studied topics in the area of microelectronics. It can be observed in Metal–Insulator–Metal (MIM) structures that are the basis of resistive switching random-access memories (RRAMs). In the case of commercial use of RRAMs, it is beneficial that the applied materials would have to be compatible with Complementary Metal-Oxide-Semiconductor (CMOS) technology. Fabricating methods of these materials can determine their stoichiometry and structural composition, which can have a detrimental impact on the electrical performance of manufactured devices. In this study, we present the influence of the Ar/N₂ ratio during reactive magnetron sputtering of titanium nitride (TiN) electrodes on the resistive switching behavior of MIM devices. We used silicon oxide (SiOx) as a dielectric layer, which was characterized by the same properties in all fabricated MIM structures. The composition of TiN thin layers was controlled by tuning the Ar/N₂ ratio during the deposition process. The fabricated conductive materials were characterized in terms of chemical and structural properties employing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis. Structural characterization revealed that increasing the Ar content during the reactive sputtering process affects the crystallite size of the deposited TiN layer. The resulting crystallite sizes ranged from 8 Å to 757.4 Å. The I-V measurements of fabricated devices revealed that tuning the Ar/N₂ ratio during the deposition of TiN electrodes affects the RS behavior. Our work shows the importance of controlling the stoichiometry and structural parameters of electrodes on resistive switching phenomena. Full article

In this study, tin oxide (SnO₂) resistive random-access memory (RRAM) thin films were fabricated using the thermal evaporation and radiofrequency and dc frequency sputtering techniques for metal–insulator–metal (MIM) structures. The fabrication process began with the deposition of a silicon dioxide (SiO₂) layer onto a silicon (Si) substrate, followed by the deposition of a titanium nitride (TiN) layer to serve as the bottom electrode. Subsequently, the tin oxide (SnO₂) layer was deposited as the resistive switching insulator. Two types of top electrodes were developed to investigate the influence of different oxygen concentrations on the bipolar switching, electrical characteristics, and performance of memory devices. An aluminum (Al) top electrode was deposited using thermal evaporation, while a platinum (Pt) top electrode was deposited via dc sputtering. As a result, two distinct metal–insulator–metal (MIM) memory RRAM device structures were formed, i.e., Al/SnO₂/TiN/SiO₂/Si and Pt/SnO₂/TiN/SiO₂/Si. In addition, the symmetry bipolar switching characteristics, electrical conduction mechanism, and oxygen concentration factor of the tin oxide-based memory devices using rapid thermal annealing and different top electrodes were determined and investigated by ohmic, space-charge-limit-current, Schottky, and Poole–Frenkel conduction equations in this study. Full article

Two-dimensional (2D) material-based resistive random-access memory (RRAM) has emerged as a promising solution for neuromorphic computing and computing-in-memory architectures. Compared to conventional metal-oxide-based RRAM, the novel 2D material-based RRAM devices demonstrate lower power consumption, higher integration density, and reduced performance variability, benefiting from their atomic-scale thickness and ultra-flat surfaces. Remarkably, 2D layered metal oxides retain these advantages while preserving the merits of traditional metal oxides, including their low cost and high environmental stability. Through a multi-step dry transfer process, we fabricated a Pd-MoO₃-Ag RRAM device featuring 2D α-MoO₃ as the resistive switching layer, with Pd and Ag serving as inert and active electrodes, respectively. Resistive switching tests revealed an excellent operational stability, low write voltage (~0.5 V), high switching ratio (>10⁶), and multi-bit storage capability (≥3 bits). Nevertheless, the device exhibited a limited retention time (~2000 s). To overcome this limitation, we developed a Gr-MoO₃-Ag heterostructure by substituting the Pd electrode with graphene (Gr). This modification achieved a fivefold improvement in the retention time (>10⁴ s). These findings demonstrate that by controlling the type and thickness of 2D materials and resistive switching layers, RRAM devices with both high On/Off ratios and long-term data retention may be developed. Full article

This work investigates the impact of reset pulse width on multilevel conductance programming in Al₂O₃/TiO_x-based resistive random access memory. A 32 × 32 cross-point array of Ti (12 nm)/Pt (62 nm)/Al₂O₃ (3 nm)/TiO_x (32 nm)/Ti (14 nm)/Pt (60 nm) devices (2.5 µm × 2.5 µm active area) was fabricated via e-beam evaporation, atomic layer deposition, and reactive sputtering. Following an initial forming step and a stabilization phase of five DC reset–set cycles, devices were programmed using an incremental step pulse programming (ISPP) scheme. Reset pulses of fixed amplitude were applied with widths of 100 µs, 10 µs, 1 µs, and 100 ns, and the programming sequence was terminated when the read current at 0.2 V exceeded a 45 µA target. At a 100 µs reset pulse width, most cycles exhibited abrupt current jumps that exceeded the target current, whereas at a 100 ns width, the programmed current increased gradually in all cycles, enabling precise conductance tuning. Cycle-to-cycle variation decreased by more than 50% as the reset pulse width was reduced, indicating more uniform filament disruption and regrowth. These findings demonstrate that controlling reset pulse width offers a straightforward route to reliable, linear multilevel operation in Al₂O₃/TiO_x-based RRAM. Full article

Resistive random-access memory (RRAM) has been attractive as an emerging memory that can be used for computing-in-memory (CIM) and storage-class memory (SCM). However, achieving gradual resistive switching (RS) characteristics and minimizing the variability remain critical challenges. In this work, we investigate the wake-up effect in Al₂O₃-based RRAM and its role in improving RS properties. Two types of wake-up effects were found: HRS variation improvement and gradual switching during set operation. First, a reduction in current variation in the high-resistance state (HRS), which indicates improvement of filament stability and uniformity. Second, gradual switching during the set voltage sweep, suggesting a more gradual modulation of the conduction mechanism, likely related to interface conductive filament (CF) generation. By harnessing the wake-up effect, it is possible to overcome the limitations of RRAM, which allows writing only during the reset voltage sweep, to enable writing during the set voltage sweep as well. Full article

In this manuscript, strontium barium titanate (BST) ferroelectric memory film materials for applications in the feasibility of applying to non-volatile RAM devices were obtained and compared. Solutions were synthesized with a proportional ratio and through the deposition of BST films on titanium nitride/silicon substrates using the sol–gel method, using rapid thermal annealing for defect repair and re-crystallization processing. The crystallization structure and surface morphology of annealed and as-deposited BST films were obtained by XPS, XRD, and SEM measurements. Additionally, the ferroelectric and resistive switching properties for the memory window, the maximum capacitance, and the leakage current were examined for Al/BST/TiN and Cu/BST/TiN structure memory devices. In addition, the first-order reaction equation of the decay reaction behavior for the BST film RRAM devices in the reset state revealed that $r=0.19{[O^{2-}]}^1$. Finally, the Cu/BST/TiN and Al/BST/TiN structures of the ferroelectric BST films RRAM devices exhibited good memory window properties, bipolar switching properties, and non-volatile properties for applications in non-volatile memory devices. Full article

In this study, the bipolar resistance switching behavior and electrical conduction transport properties of a neodymium oxide film’s resistive random access memory (RRAM) devices for using different top electrode materials were observed and discussed. Different related electrical properties and transport mechanisms are important factors in applications in a film’s RRAM devices. For aluminum top electrode materials, the electrical conduction mechanism of the neodymium oxide film’s RRAM devices all exhibited hopping conduction behavior, with 1 mA and 10 mA compliance currents in the set state for low/high voltages applied. For TiN and ITO (Indium tin oxide) top electrode materials, the conduction mechanisms all exhibited ohmic conduction for the low voltage applied, and all exhibited hopping conduction behavior for the high voltage applied. In addition, the electrical field strength simulation resulted in an increase in the reset voltage, indicating that oxygen ions have diffused into the vicinity of the ITO electrode during the set operation. This was particularly the case in the three physical models proposed, and based on the relationship between different ITO electrode thicknesses and the oxygen ion concentration distribution effect of the neodymium oxide film’s RRAM devices, they were investigated and discussed. To prove the oxygen concentration distribution expands over the area of the ITO electrode, the simulation software was used to analyze and simulate the distribution of the electric field for the Poisson equation. Finally, the neodymium oxide film’s RRAM devices for using different top electrode materials all exhibited high memory window properties, bipolar resistance switching characteristics, and non-volatile properties for incorporation into next-generation non-volatile memory device applications in this study. Full article

In the era of artificial intelligence and Internet of Things, data storage has an important impact on the future development direction of data analysis. Resistive random-access memory (RRAM) devices are the research hotspot in the era of artificial intelligence and Internet of Things. Perovskite-type rare-earth metal oxides are common functional materials and considered promising candidates for RRAM devices because their interesting electronic properties depend on the interaction between oxygen ions, transition metals, and rare-earth metals. LaCoO₃, NdCoO₃, and SmCoO₃ are typical rare-earth cobaltates (RCoO₃). These perovskite materials were fabricated by electrospinning and the calcination method. The aim of this study was to investigate the resistive switching effect in the RCoO₃ structure. The oxygen vacancies in RCoO₃ are helpful to form conductive filaments, which dominates the resistance transition mechanism of Pt/RCoO₃/Pt. The electronic properties of RCoO₃ were investigated, including the barrier height and the shape of the conductive filaments. This study confirmed the potential application of LaCoO₃, NdCoO₃, and SmCoO₃ in memory storage devices. Full article

Aluminum nitride (AlN) with a wide band gap (approximately 6.2 eV) has attractive characteristics, including high thermal conductivity, a high dielectric constant, and good insulating properties, which are suitable for the field of resistive random access memory. AlN thin films were deposited on ITO substrate using the radio-frequency magnetron sputtering technique. Al’s and Au’s top electrodes were deposited on AlN thin films to make a Au/Al/AlN/ITO sandwich structure memristor. The effects of the Al₂O₃ film on the on/off window and voltage characteristics of the device were investigated. The deposition time and nitrogen content in the sputtering atmosphere were changed to adjust the thickness and composition of AlN films, respectively. The possible mechanism of resistive switching was examined via analyses of the electrical resistive switching characteristics, forming voltage, and switching ratio. Full article

In this study, we prepared a strontium ferrite titanate (STF) thin film using a sol–gel process to insulate resistive random-access memory (RRAM) applications. Compared to the typical strontium titanate (STO) RRAM, the improvement in the resistive switching characteristics in STF RRAM is obvious. The Al/STO/ITO/Glass RRAM set/reset voltages of −1.4 V/+3.3 V and the Al/STF/ITO/Glass RRAM set/reset voltages of −0.45 V/+1.55 V presented a memory window larger than 10³, a low operating voltage and device stability of more than 104 s. In this study, the influence of Fe on the conducting paths and the bipolar resistive switching properties of Al/STF/ITO/Glass RRAM devices is investigated. Full article

Memristor devices for resistive-switching memory and artificial synapses have emerged as promising solutions for overcoming the technological challenges associated with the von Neumann bottleneck. Recently, due to their unique optoelectronic properties, solution processability, fast switching speeds, and low operating voltages, quantum dots (QDs) have drawn substantial research attention as candidate materials for memristors and artificial synapses. This review covers recent advancements in QD-based resistive random-access memory (RRAM) for resistive memory devices and artificial synapses. Following a brief introduction to QDs, the fundamental principles of the switching mechanism in RRAM are introduced. Then, the RRAM materials, synthesis techniques, and device performance are summarized for a relative comparison of RRAM materials. Finally, we introduce QD-based RRAM and discuss the challenges associated with its implementation in memristors and artificial synapses. Full article