High-performance Resistive Random Access Memory Research Articles

Stable and repeatable ZrO2 RRAM achieved by NiO barrier layer for negative set phenomenon elimination

Resistive random-access memory (RRAM) is a promising non-volatile memory technology due to its fast operation, low power consumption, and high reliability. However, the negative set phenomenon remains a challenge for RRAM, which can lead to the deterioration of device switching parameters. In this study, we successfully addressed this issue by inserting a NiO blocking layer between the ZrO2 and Ag top electrodes in ZrO2-based RRAM. In addition, the resistive switching characteristics of the device are significantly enhanced by the incorporation of a p-type oxide NiO layer. Compared to single-layer ZrO2 devices, the double-layer Ag/NiO/ZrO2/ITO RRAM exhibits improved cycling durability (>500 cycles) and good retention time (3 × 104s). Our analysis of the device conduction mechanism and proposed resistive switching model suggest that oxygen vacancies play a connecting role in the reset process, leading to failed reset behavior. Through the incorporation of a p-type semiconductor NiO layer into ZrO2-based RRAMs, the interference of oxygen vacancies on the reset process can be effectively impeded. This approach not only provides an effective resolution to the unforeseen negative set phenomenon in RRAM devices, but it also holds paramount significance for the advancement of high-performance RRAMs.

Heterogeneous integrated InP/SiC high-performance multilevel RRAM

With the advent of the Age of Big Data, resistive random-access memory (RRAM) shows considerable potential for next generation nonvolatile storage technologies owing to its simplified structure, high switching speed, and low power consumption. However, mainstream prepared materials, such as oxides and halide perovskite, face critical issues for practical applications such as switching uniformity and long-term environmental stability. In this work, we report that high carrier mobility material indium phosphide (InP) is prepared as an RRAM medium and is directly bonded to the high thermal conductivity substrate silicon carbide (SiC) at 200 °C, overcoming large (14.9%) lattice mismatch. Importantly, the bonding strength reaches 9.3 MPa, and this high-performance stable RRAM exhibits nonvolatile and reliable switching characteristics including stable endurance (200 cycles) and long data retention (2000 s). Moreover, multilevel storage is also available by modulating RESET stop voltages. This work provides broad possibilities for high-performance RRAM with structures based on traditional semiconductors in the field of nonvolatile storage.

High-performance resistive random access memory using two-dimensional electron gas electrode and its switching mechanism analysis

In this study, a two-dimensional electron gas (2DEG), which is a conductive layer formed at the interface of Al2O3 and TiO2, was used as an electrode for resistive random access memory (RRAM) and implemented in a cell size down to 30 nm. For an RRAM device comprising W/2DEG/TiO2/W, we confirmed that the dominant switching mechanism changed from interfacial to filamentary as the cell size decreased from 500 nm to 30 nm. Through analyses of changes in forming characteristics and conduction mechanisms in the low resistive state depending on the cell size, it was identified that the 2DEG acted as an oxygen-scavenging layer of TiO2 during the resistive switching process. By comparing the switching characteristics of RRAM devices with and without 2DEG for a 30 nm cell size, we confirmed that a high-performance 2DEG RRAM was realized, with highly uniform current–voltage characteristics, a low operating voltage (∼1 V), and a high on/off ratio (>102). Finally, the applicability of the proposed device to a crossbar array was validated by evaluating 1S1R operation with an NbO2-based selector. Considering the improved switching uniformity, the 2DEG RRAM shows promise for high-density memory applications.

Organic-2D composite material-based RRAM with high reliability for mimicking synaptic behavior

The field of artificial intelligence and neural computing has been rapidly expanding due to the implementation of resistive random-access memory (RRAM) based artificial synaptic. However, the low flexibility of conventional RRAM materials hinders their ability to mimic synaptic behavior accurately. To overcome such limitation, organic-2D composites with high mechanical properties are proposed as the active layer of RRAM. Moreover, we enhance the reliability of the device by ZrO2 insertion layer, resulting in stable synaptic performance. The Ag/PVA:h-BN/ZrO2/ITO devices show stable bipolar resistive switching behavior with an ON/OFF ratio of over 5 × 102, a ∼2 400 cycles endurance and a long retention time (>6 × 103s), which are essential for the development of high-performance RRAMs. We also study the possible synaptic mechanism and dynamic plasticity of the memory device, observing the transition from short-term potentiation (STP) to long-term potentiation (LTP) under the effect of continuous voltage pulses. Moreover, the device exhibits both long-term depression (LTD) and paired-pulse facilitation (PPF) properties, which have significant implications for the design of organic-2D composite material RRAMs that aim to mimic biological synapses, representing promising avenues for the development of advanced neuromorphic computing systems.

High-performance Ta2O5-based resistive random-access memory with embedded graphene quantum dots and Pt–Ag composite active layer

Resistive random-access memory (RRAM) has garnered significant interest in developing nonvolatile memory systems due to its ability to provide external field tunable resistive states with fast speed and low power consumption. This tunable resistive state primarily results from the formation and breakage of conductive pathways triggered by active ion migration. However, due to the stochastic nature of ion migration, the stability of the switching process is a long-standing bottleneck. Here, we investigate the impact of device kinetic parameters on the stability of resistive switching behavior and propose a high-performance RRAM with a Pt–Ag/Ta2O5/GQDs/Pt structure. Incorporating quantum dots can regulate the direction of Ag ion migration, while the Pt–Ag composite electrode can manipulate the oxidation rate of Ag atoms. Compared to the Ag/Ta2O5/GQDs/Pt device, the Pt–Ag/Ta2O5/GQDs/Pt device exhibited a 15-fold reduction in operating voltage, a 10-fold increase in on/off ratio, and superior endurance and uniformity. These findings demonstrate that tuning kinetic parameters has the potential to enhance resistive switching performance, which offers an effective pathway for designing high-performance memory systems.

Resistive switching behavior of TiO2/(PVP:MoS2) nanocomposite hybrid bilayer in rigid and flexible RRAM devices

Resistive switching (RS) behavior of bilayer of poly(4-vinylphenol) (PVP): molybdenum disulfide (MoS2) nanocomposite (NC) and TiO2 in resistive random-access memory (RRAM) devices were explored. Devices were demonstrated on indium tin oxide (ITO) coated glass and polyethylene naphtholate (PEN) substrates, with ITO acting as bottom electrode and Ag as top electrode for both rigid and flexible RRAM devices. The rigid devices exhibited excellent RS with very low SET and RESET voltages of ∼1 V and ∼−1.2 V, whereas the flexible devices showed average SET and RESET voltages of 1.5 V and −0.7 V. A decent repeatability was demonstrated with high on/off current ratios of more than 103 at reading voltage of 0.2 V for both types of devices. The flexible devices exhibited decent switching behavior even after bending up to a radius of 7 mm, indicating that PVP:MoS2 NC bilayer can be a promising candidate for the demonstration of high-performance RRAM devices for flexible electronics.

Facilitation of the thermochemical mechanism in NiO-based resistive switching memories via tip-enhanced electric fields

Transition metal oxides have attracted considerable attention as a switching material for resistive random access memory (RRAM) based on the thermochemical mechanism (TCM). However, the heat energy required for resistance switching is applied to the entire area of the RRAM without position selectivity, causing random growth of conductive filaments (CFs) and degrading device performance. This study showed that structured electrodes can promote the TCM in nickel oxide (NiO)-based RRAM by enhancing the electric field within the switching material and controlling Joule heat generation locally. Pyramid-structured electrodes with an extremely sharp tip prepared by the template-stripping method achieve an electric field in the tip region that is ∼5 times larger than that of conventional planar electrodes. The tip-enhanced electric field can induce a local temperature rise, which facilitates the TCM for nucleation and CF growth. The resulting RRAMs exhibit low and reliable forming, SET and RESET voltages (1.96±0.14V, 1.44±0.12V, and 0.64±0.05V, respectively). Moreover, their retention time and resistance ratio (RHRS/RLRS) are greatly improved, by 10 and 102 times, respectively, compared to planar devices. This approach can achieve position selectivity in TCM-based resistance switching, and could lead to the development of high-performance RRAM.

Improvement of durability and switching speed by incorporating nanocrystals in the HfOx based resistive random access memory devices

Resistive random access memory (RRAM) has attracted significant interest for next-generation nonvolatile memory applications. However, it is somehow difficult to design a high speed RRAM device with enhanced data reliability. This paper deals with the improvement of high speed durable switching in nanocrystals based RRAM (NC-RRAM) devices. The high performance RRAM devices were prepared by incorporating the NCs into the HfOx oxide layer. As compared to the without (w/o) NC devices, the NC-RRAM devices are capable to execute uniform switching with higher set speed of 100 ns and reset speed of 150 ns, longer retention time and higher endurance of 108 cycles at 85 °C. The possible switching mechanism is due to the formation and rupture of the conductive filaments (CFs) inside the oxide film. The improvement of the NC-RRAM devices is due to the enhanced electric field intensity on the surface of the NCs, which can effectively facilitate the formation and rupture of the CFs.

Improved resistive switching reliability by using dual-layer nanoporous carbon structure

We optimized the diameter and microgeometry of preformed conductive filaments (CFs) to improve the switching reliability of copper/nanoporous amorphous carbon (a-C)/platinum memory devices. Forming-free devices were obtained because of the introduction of preformed CFs into the nanoporous layer during the copper electrode evaporation process. The switching fluctuation decreased with the increasing preformed CF size in a certain range; however, the device with stronger preformed CFs suffered from high current in the first RESET process. Furthermore, to achieve both high switching uniformity and low power consumption, a dual-layer structure was proposed to regulate the microgeometry of preformed CFs. Compared with those of a pristine device and single-layer nanoporous device, the fluctuation of high/low resistance values was further suppressed to 26% and 21%, respectively. In addition, Resistive random access memory (RRAM) devices exhibited a fast switching speed (<50 ns), excellent endurance (>105 cycles), and long retention time (>105 s at 85 °C). These results reveal the key role of preformed CF optimization in resistive switching performance improvement, providing an effective approach to develop high-performance RRAM devices.

Demonstration of Logic Operations in High-Performance RRAM Crossbar Array Fabricated by Atomic Layer Deposition Technique

In this paper, resistive random access memory (RRAM)-based crossbar arrays with the cell structure of Pt/[AlOy/HfOx]m/TiN were fabricated by using atomic layer deposition (ALD) technique. The RRAM devices in the arrays show excellent performances such as good uniformity and high reliability. Based on the fabricated RRAM array, a complete set of basic logic operations including NOR and XNOR were successfully demonstrated.

Design of high-performance memristor cell using W-implanted SiO2 films

Highly reproducible bipolar resistance switching was demonstrated in a composite material of W-implanted silicon dioxide. Because of its excellent dielectric properties, SiO2 was selected as the sole active material for fabricating the resistance switching devices. The device employed a metal-insulator-semiconductor structure, showing an excellent resistance switching performance (the ON/OFF ratio is close to ∼106). In addition, this sandwich structure device shows a forming-free resistance switching behavior. The overall device performance of the SiO2-based memristor has the potential to open up a new avenue to a large-scale high-performance resistive random access memory, which could significantly impact their existing applications.

Nonlinear Switching With Ultralow Reset Power in Graphene-Insulator-Graphene Forming-Free Resistive Memories

A high-performance resistive random access memory with graphene top and bottom electrodes and TiO x /Al 2 O 3 /TiO 2 dielectric stacks is reported. The devices exhibit forming-free switching with stable operation at sub-μA operating current. The switching is highly nonlinear with rectifying characteristics in the sub-μA regime. As a result, the reset current is orders of magnitude smaller than the current compliance. Due to the increasing nonlinearity with decreasing current compliance, the reset current is ~100 pA or less for the current compliance of 180 nA. Overall, the devices demonstrate sub-μA operating current, sub-nW reset power, ON/OFF ratio of ~10 4 , stable dc endurance for more than 200 dc cycles, and stable retention up to 10 4 s. The rectifying characteristic offers potential to reduce sneak-currents in cross-bar architectures.