Journal articles: 'RRAM'

1

Lee, Doowon, and Hee-Dong Kim. "Effect of Hydrogen Annealing on Performances of BN-Based RRAM." Nanomaterials 13, no. 10 (May 18, 2023): 1665. http://dx.doi.org/10.3390/nano13101665.

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BN-based resistive random-access memory (RRAM) has emerged as a potential candidate for non-volatile memory (NVM) in aerospace applications, offering high thermal conductivity, excellent mechanical, and chemical stability, low power consumption, high density, and reliability. However, the presence of defects and trap states in BN-based RRAM can limit its performance and reliability in aerospace applications. As a result, higher set voltages of 1.4 and 1.23 V were obtained for non-annealed and nitrogen-annealed BN-based RRAM, respectively, but lower set voltages of 1.06 V were obtained for hydrogen-annealed BN-based RRAM. In addition, the hydrogen-annealed BN-based RRAM showed an on/off ratio of 100, which is 10 times higher than the non-annealed BN-based RRAM. We observed that the LRS changed to the HRS state before 10,000 s for both the non-annealed and nitrogen-annealed BN-based RRAMs. In contrast, the hydrogen-annealed BN-based RRAM showed excellent retention characteristics, with data retained up to 10,000 s.

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Kim, Kyoungdu, Woongki Hong, Changmin Lee, Won-Yong Lee, Do Won Kim, Hyeon Joong Kim, Hyuk-Jun Kwon, Hongki Kang, and Jaewon Jang. "Sol-gel-processed amorphous-phase ZrO₂ based resistive random access memory." Materials Research Express 8, no. 11 (November 1, 2021): 116301. http://dx.doi.org/10.1088/2053-1591/ac3400.

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Abstract In this study, sol–gel-processed amorphous-phase ZrO2 was used as an active channel material to improve the resistive switching properties of resistive random access memories (RRAMs). ITO/ZrO2/Ag RRAM devices exhibit the properties of bipolar RRAMs. The effect of the post-annealing temperature on the electrical properties of the ZrO2 RRAM was investigated. Unlike the ZrO2 films annealed at 400 and 500 °C, those annealed at 300 °C were in amorphous phase. The RRAM based on the amorphous-phase ZrO2 exhibited an improved high-resistance state (HRS) to low-resistance state ratio (over 106) as well as promising retention and endurance characteristics without deterioration. Furthermore, its disordered nature, which causes efficient carrier scattering, resulted in low carrier mobility and the lowest leakage current, influencing the HRS values.

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Lin, Wu, and Chen. "Effects of Sm2O3 and V2O5 Film Stacking on Switching Behaviors of Resistive Random Access Memories." Crystals 9, no. 6 (June 19, 2019): 318. http://dx.doi.org/10.3390/cryst9060318.

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: In this work, the resistive switching characteristics of resistive random access memories (RRAMs) containing Sm2O3 and V2O5 films were investigated. All the RRAM structures made in this work showed stable resistive switching behavior. The High-Resistance State and Low-Resistance State of Resistive memory (RHRS/RLRS) ratio of the RRAM device containing a V2O5/Sm2O3 bilayer is one order of magnitude higher than that of the devices containing a single layer of V2O5 or Sm2O3. We also found that the stacking sequence of the Sm2O3 and V2O5 films in the bilayer structure can affect the switching features of the RRAM, causing them to exhibit both bipolar resistive switching (BRS) behavior and self-compliance behavior. The current conduction mechanisms of RRAM devices with different film structures were also discussed.

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Lonn, Eija, Esa Koskela, Tapio Mappes, Mikael Mokkonen, Angela M. Sims, and Phillip C. Watts. "Balancing selection maintains polymorphisms at neurogenetic loci in field experiments." Proceedings of the National Academy of Sciences 114, no. 14 (March 21, 2017): 3690–95. http://dx.doi.org/10.1073/pnas.1621228114.

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Most variation in behavior has a genetic basis, but the processes determining the level of diversity at behavioral loci are largely unknown for natural populations. Expression of arginine vasopressin receptor 1a (Avpr1a) and oxytocin receptor (Oxtr) in specific regions of the brain regulates diverse social and reproductive behaviors in mammals, including humans. That these genes have important fitness consequences and that natural populations contain extensive diversity at these loci implies the action of balancing selection. In Myodes glareolus, Avpr1a and Oxtr each contain a polymorphic microsatellite locus located in their 5′ regulatory region (the regulatory region-associated microsatellite, RRAM) that likely regulates gene expression. To test the hypothesis that balancing selection maintains diversity at behavioral loci, we released artificially bred females and males with different RRAM allele lengths into field enclosures that differed in population density. The length of Avpr1a and Oxtr RRAMs was associated with reproductive success, but population density and the sex interacted to determine the optimal genotype. In general, longer Avpr1a RRAMs were more beneficial for males, and shorter RRAMs were more beneficial for females; the opposite was true for Oxtr RRAMs. Moreover, Avpr1a RRAM allele length is correlated with the reproductive success of the sexes during different phases of reproduction; for males, RRAM length correlated with the numbers of newborn offspring, but for females selection was evident on the number of weaned offspring. This report of density-dependence and sexual antagonism acting on loci within the arginine vasopressin–oxytocin pathway explains how genetic diversity at Avpr1a and Oxtr could be maintained in natural populations.

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Ansh and Mayank Shrivastava. "Superior resistance switching in monolayer MoS₂ channel-based gated binary resistive random-access memory via gate-bias dependence and a unique forming process." Journal of Physics D: Applied Physics 55, no. 8 (November 12, 2021): 085102. http://dx.doi.org/10.1088/1361-6463/ac3281.

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Abstract Resistance switching (RS) in 2D molybdenum disulfide (MoS2) was recently discovered. Since the discovery, many reports demonstrating MoS2 resistive random-access memory (RRAM) with synapse-like behavior have been published. These reports strongly justify applications of MoS2 RRAM in neuromorphic hardware as well as an alternative to conventional binary memories. In this work, we unveil the effect of RS, induced by current–voltage hysteresis cycles across CVD-grown monolayer MoS2-based gated RRAM, on its transistor’s electrical and reliability characteristics. A unique gate voltage dependence on the RS is identified which has a remarkable impact on the switching performance of MoS2 RRAM. RS behavior was found to be significantly dependent on the charge conduction in the channel. Moreover, we have shown a potential device-forming event when MoS2-gated RRAMs were subjected to a steady-state electrical stress. Both hysteresis and steady-state electrical stress were found to disturb the transistor action of these gated RRAMs, which can in fact be used as a signature of RS. Interestingly, current–voltage hysteresis resulted in unipolar RS, whereas steady-state electrical stress before RS measurement led to bipolar RS. Moreover, successive stress cycles of such electrical stress lead to multiple resistance states, a behavior similar to synaptic properties such as long-term potentiation and long-term depression, typically found in memristors. We find that the charge transport mechanism dominant in the MoS2 FET, in conjunction with steady-state stress-induced device forming, determine the extent of RS induced in thes MoS2-based gated RRAMs. Finally, on the basis of insights developed from the dependence on the charge transport mechanism and steady-state stress-induced forming of the MoS2 channel, we propose a certain steady-state electrical stress condition which can be used as a ‘forming’ process, employed prior to the use of MoS2-based binary RRAMs for improved switching performance.

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Xie, Hao, Jun Hu, Zhili Wang, Xiaohui Hu, Hong Liu, Wei Qi, and Shuo Zhang. "Multiphysics Simulation of Crosstalk Effect in Resistive Random Access Memory with Different Metal Oxides." Micromachines 13, no. 2 (February 6, 2022): 266. http://dx.doi.org/10.3390/mi13020266.

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Based on the electrical conductivity model built for graphene oxide, the thermal crosstalk effects of resistive random access memory (RRAM) with graphene electrode and Pt electrode are simulated and compared. The thermal crosstalk effects of Pt-RRAM with different metal oxides of TiOx, NiOx, HfOx, and ZrOx are further simulated and compared to guide its compatibility design. In the Pt-RRAM array, the distributions of oxygen vacancy density and temperature are obtained, and the minimum spacing between adjacent conduction filaments to avoid device operation failure is discussed. The abovementioned four metal oxides have different physical parameters such as diffusivity, electrical conductivity, and thermal conductivity, from which the characters of the RRAMs based on one of the oxides are analyzed. Numerical results reveal that thermal crosstalk effects are severe as the spacing between adjacent conduction filaments is small, even leading to the change of logic state and device failure.

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Tsai, Jeff T. H., Chia-Yun Hsu, Chia-Hsiang Hsu, Chu-Shou Yang, and Tai-Yuan Lin. "Fabrication of Resistive Random Access Memory by Atomic Force Microscope Local Anodic Oxidation." Nano 10, no. 02 (February 2015): 1550028. http://dx.doi.org/10.1142/s1793292015500289.

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The fabrication of gallium, zinc and nickel oxide nanodots for application of resistive random access memory (RRAM) was demonstrated using the atomic force microscopy (AFM) local anodic oxidation technique. Thin metal films were deposited on indium tin oxide conductive glass substrates. In the atmospheric environment, using AFM equipped with an Ag -coated probe can generate metal oxide nanodots locally on the metal films. These nanodots act as an insulator layer in a single unit cell of the RRAM. The voltage-biased method allows devices to reset from a low-resistance state (LRS) to a high-resistance state (HRS) at 0.9 V. These results show the ability of the AFM local anodic oxidation to produce 50 nm NiO nanodots on glass substrates for potentially high-density RRAMs. As we developed the characteristics of the structure, we found that a lateral NiO nanobelt RRAM performs very low power operation from such experimental manufacturing process. Using a current-biased method, the lateral device switches from a HRS to a LRS with a low writing voltage of 0.64 V.

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Alimkhanuly, Batyrbek, Sanghoek Kim, Lok-won Kim, and Seunghyun Lee. "Electromagnetic Analysis of Vertical Resistive Memory with a Sub-nm Thick Electrode." Nanomaterials 10, no. 9 (August 20, 2020): 1634. http://dx.doi.org/10.3390/nano10091634.

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Resistive random access memories (RRAMs) are a type of resistive memory with two metal electrodes and a semi-insulating switching material in-between. As the persistent technology node downscaling continues in transistor technologies, RRAM designers also face similar device scaling challenges in simple cross-point arrays. For this reason, a cost-effective 3D vertical RRAM (VRRAM) structure which requires a single pivotal lithography step is attracting significant attention from both the scientific community and the industry. Integrating an extremely thin plane electrode to such a structure is a difficult but necessary step to enable high memory density. In addition, experimentally verifying and modeling such devices is an important step to designing RRAM arrays with a high noise margin, low resistive-capacitive (RC) delays, and stable switching characteristics. In this work, we conducted an electromagnetic analysis on a 3D vertical RRAM with atomically thin graphene electrodes and compared it with the conventional metal electrode. Based on the experimental device measurement results, we derived a theoretical basis and models for each VRRAM design that can be further utilized in the estimation of graphene-based 3D memory at the circuit and architecture levels. We concluded that a 71% increase in electromagnetic field strength was observed in a 0.3 nm thick graphene electrode when compared to a 5 nm thick metal electrode. Such an increase in the field led to much lower energy consumption and fluctuation range during RRAM switching. Due to unique graphene properties resulting in improved programming behavior, the graphene-based VRRAM can be a strong candidate for stacked storage devices in new memory computing platforms.

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9

Arumí, Daniel, Salvador Manich, Álvaro Gómez-Pau, Rosa Rodríguez-Montañés, Víctor Montilla, David Hernández, Mireia Bargalló González, and Francesca Campabadal. "Impact of Laser Attacks on the Switching Behavior of RRAM Devices." Electronics 9, no. 1 (January 20, 2020): 200. http://dx.doi.org/10.3390/electronics9010200.

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The ubiquitous use of critical and private data in electronic format requires reliable and secure embedded systems for IoT devices. In this context, RRAMs (Resistive Random Access Memories) arises as a promising alternative to replace current memory technologies. However, their suitability for this kind of application, where the integrity of the data is crucial, is still under study. Among the different typology of attacks to recover information of secret data, laser attack is one of the most common due to its simplicity. Some preliminary works have already addressed the influence of laser tests on RRAM devices. Nevertheless, the results are not conclusive since different responses have been reported depending on the circuit under testing and the features of the test. In this paper, we have conducted laser tests on individual RRAM devices. For the set of experiments conducted, the devices did not show faulty behaviors. These results contribute to the characterization of RRAMs and, together with the rest of related works, are expected to pave the way for the development of suitable countermeasures against external attacks.

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10

Zhang, Yuhang, Guanghui He, Feng Zhang, Yongfu Li, and Guoxing Wang. "The study of lithographic variation in resistive random access memory." Journal of Semiconductors 45, no. 5 (May 1, 2024): 052303. http://dx.doi.org/10.1088/1674-4926/45/5/052303.

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Abstract Reducing the process variation is a significant concern for resistive random access memory (RRAM). Due to its ultra-high integration density, RRAM arrays are prone to lithographic variation during the lithography process, introducing electrical variation among different RRAM devices. In this work, an optical physical verification methodology for the RRAM array is developed, and the effects of different layout parameters on important electrical characteristics are systematically investigated. The results indicate that the RRAM devices can be categorized into three clusters according to their locations and lithography environments. The read resistance is more sensitive to the locations in the array (~30%) than SET/RESET voltage (<10%). The increase in the RRAM device length and the application of the optical proximity correction technique can help to reduce the variation to less than 10%, whereas it reduces RRAM read resistance by 4×, resulting in a higher power and area consumption. As such, we provide design guidelines to minimize the electrical variation of RRAM arrays due to the lithography process.

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11

Kim, Minjae, Yue Wang, Dong-eun Kim, Qingyi Shao, Hong-Sub Lee, and Hyung-Ho Park. "Resistive switching properties for fluorine doped titania fabricated using atomic layer deposition." APL Materials 10, no. 3 (March 1, 2022): 031105. http://dx.doi.org/10.1063/5.0076669.

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This study demonstrates a new resistive switching material, F-doped TiO2 (F:TiO2), fabricated by atomic layer deposition (ALD) with an in-house fluorine source for resistive random access memory (RRAM) devices. Controlling oxygen vacancies is required since RRAM uses resistive switching (RS) characteristics by redistributing oxygen ions in oxide, and poor oxygen defect control has been shown to significantly reduce RRAM reliability. Therefore, this study designed an F based RRAM device using fluorine anions rather than oxygen defect for the main agent of RS behavior. We developed the F:TiO2 RRAM material using a novel in situ doping method in ALD and investigated its RS behaviors. The Pt/F:TiO2/Pt device exhibited forming-less bipolar RS and self-rectifying behavior by fluorine anion migration, effectively reducing the sneak current in crossbar array architecture RRAM. The doped fluorine passivated and reduced oxygen related defects in TiO2, confirmed by x-ray photoelectron spectroscopy analysis. Adopting the F-based RS material by ALD provides a viable candidate for high reliability RRAM.

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Wong, H. S. Philip, Heng-Yuan Lee, Shimeng Yu, Yu-Sheng Chen, Yi Wu, Pang-Shiu Chen, Byoungil Lee, Frederick T. Chen, and Ming-Jinn Tsai. "Metal–Oxide RRAM." Proceedings of the IEEE 100, no. 6 (June 2012): 1951–70. http://dx.doi.org/10.1109/jproc.2012.2190369.

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13

Kim, Hae-In, Taehun Lee, Won-Yong Lee, Kyoungdu Kim, Jin-Hyuk Bae, In-Man Kang, Sin-Hyung Lee, Kwangeun Kim, and Jaewon Jang. "Improved Environment Stability of Y2O3 RRAM Devices with Au Passivated Ag Top Electrodes." Materials 15, no. 19 (October 2, 2022): 6859. http://dx.doi.org/10.3390/ma15196859.

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In this study, we fabricated sol-gel-processed Y2O3-based resistive random-access memory (RRAM) devices. The fabricated Y2O3 RRAM devices exhibited conventional bipolar RRAM device characteristics and did not require the forming process. The long-term stability of the RRAM devices was investigated. The Y2O3 RRAM devices with a 20 nm thick Ag top electrode showed an increase in the low resistance state (LRS) and high resistance state (HRS) and a decrease in the HRS/LRS ratio after 30 days owing to oxidation and corrosion of the Ag electrodes. However, Y2O3 RRAM devices with inert Au-passivated Ag electrodes showed a constant RRAM device performance after 30 days. The 150 nm-thick Au passivation layer successfully suppressed the oxidation and corrosion of the Ag electrode by minimizing the chance of contact between water or oxygen molecules and Ag electrodes. The Au/Ag/Y2O3/ITO RRAM devices exhibited more than 300 switching cycles with a decent resistive window (>103). They maintained constant LRS and HRS resistances for up to 104 s, without significant degradation of nonvolatile memory properties for 30 days while stored in air.

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Liu, Li Feng, Wei Bing Zhang, Yi Ran Wang, Wen Jia Ma, Guo Hui Wang, Bing Sun, Sheng Kai Wang, and Hong Gang Liu. "Effect of Rapid Thermal Annealing on Resistive Switching Uniformity of HfAlO_x Based RRAM Devices." Applied Mechanics and Materials 665 (October 2014): 136–39. http://dx.doi.org/10.4028/www.scientific.net/amm.665.136.

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HfAlOx based RRAM devices were fabricated using atomic layer deposition by modulating deposition cycles for HfO2 and Al2O3. The effect of rapid thermal annealing (RTA) on the resistive switching uniformity of HfAlOx based RRAM devices was investigated. Compared to the as-deposited devices, the resistive switching uniformity of HfAlOx based RRAM devices after RTA treatment are remarkably improved. The uniformity improvement of HfAlOx based RRAM after RTA treatment is related to microstructure change in the resistive switching film.

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Fedotov, Mikhail, Viktor Korotitsky, and Sergei Koveshnikov. "Modeling of Self-Aligned Selector Based on Ultra-Thin Metal Oxide for Resistive Random-Access Memory (RRAM) Crossbar Arrays." Nanomaterials 14, no. 8 (April 12, 2024): 668. http://dx.doi.org/10.3390/nano14080668.

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Resistive random-access memory (RRAM) is a crucial element for next-generation large-scale memory arrays, analogue neuromorphic computing and energy-efficient System-on-Chip applications. For these applications, RRAM elements are arranged into Crossbar arrays, where rectifying selector devices are required for correct read operation of the memory cells. One of the key advantages of RRAM is its high scalability due to the filamentary mechanism of resistive switching, as the cell conductivity is not dependent on the cell area. Thus, a selector device becomes a limiting factor in Crossbar arrays in terms of scalability, as its area exceeds the minimal possible area of an RRAM cell. We propose a tunnel diode selector, which is self-aligned with an RRAM cell and, thus, occupies the same area. In this study, we address the theoretical and modeling aspects of creating a self-aligned selector with optimal parameters to avoid any deterioration of RRAM cell performance. We investigate the possibilities of using a tunnel diode based on single- and double-layer dielectrics and determine their optimal physical properties to be used in an HfOx-based RRAM Crossbar array.

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Veksler, D., and G. Bersuker. "Advances in RRAM Technology: Identifying and Mitigating Roadblocks." International Journal of High Speed Electronics and Systems 25, no. 01n02 (March 2016): 1640006. http://dx.doi.org/10.1142/s0129156416400061.

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Superior scalability, endurance, low power operation, retention, and operating speed of filamentary crystalline HfOx-based resistive random access memory (RRAM) makes this technology promising for implementation in exascale neuromorphic computing systems. Challenges, roadblocks for the implementation, and possible resolutions are discussed. Technological solutions to overcome RRAM variability (both device-to-device and cycle-to-cycle) and read instability are discussed. Major material properties and operation conditions controlling performance of the crystalline HfOx-based RRAM devices are linked to physical processes determining RRAM characteristics.

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17

Liu, Lifeng, Yi Hou, Weibing Zhang, Dedong Han, and Yi Wang. "Ozone Treatment Improved the Resistive Switching Uniformity of HfAlO2Based RRAM Devices." Advances in Condensed Matter Physics 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/714097.

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HfAlO2based resistive random access memory (RRAM) devices were fabricated using atomic layer deposition by modulating deposition cycles for HfO2and Al2O3. Effect of ozone treatment on the resistive switching uniformity of HfAlO2based RRAM devices was investigated. Compared to the as-fabricated devices, the resistive switching uniformity of HfAlO2based RRAM devices with the ozone treatment is significantly improved. The uniformity improvement of HfAlO2based RRAM devices is related to changes in compositional and structural properties of the HfAlO2resistive switching film with the ozone treatment.

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18

Zhang, Donglin, Bo Peng, Yulin Zhao, Zhongze Han, Qiao Hu, Xuanzhi Liu, Yongkang Han, et al. "Sensing Circuit Design Techniques for RRAM in Advanced CMOS Technology Nodes." Micromachines 12, no. 8 (July 30, 2021): 913. http://dx.doi.org/10.3390/mi12080913.

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Resistive random access memory (RRAM) is one of the most promising new nonvolatile memories because of its excellent properties. Moreover, due to fast read speed and low work voltage, it is suitable for seldom-write frequent-read applications. However, as technology nodes shrink, RRAM faces many issues, which can significantly degrade RRAM performance. Therefore, it is necessary to optimize the sensing schemes to improve the application range of RRAM. In this paper, the issues faced by RRAM in advanced technology nodes are summarized. Then, the advantages and weaknesses in the novel design and optimization methodologies of sensing schemes are introduced in detail from three aspects, the reference schemes, sensing amplifier schemes, and bit line (BL)-enhancing schemes, according to the development of technology in especially recent years, which can be the reference for designing the sensing schemes. Moreover, the waveforms and results of each method are illustrated to make the design easy to understand. With the development of technology, the sensing schemes of RRAM become higher speed and resolution, low power consumption, and are applied at advanced technology nodes and low working voltage. Now, the most advanced nodes the RRAM applied is 14 nm node, the lowest working voltage can reach 0.32 V, and the shortest access time can be only a few nanoseconds.

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Koohzadi, Pooria, Mohammad Taghi Ahmadi, Javad Karamdel, and Truong Khang Nguyen. "Graphene band engineering for resistive random-access memory application." International Journal of Modern Physics B 34, no. 18 (July 10, 2020): 2050171. http://dx.doi.org/10.1142/s0217979220501714.

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Emerging memory technologies promise new memories to store more data at less cost. On the other hand, the scaling of silicon-based chips approached its physical limits. Nonvolatile memory technologies, such as resistive random-access memory (RRAM), are trying to solve this problem. The fundamental study in RRAM devices still needs to be moved further. In this regard, conduction mechanism of RRAM is focused in this study. The RRAM conductance varies considerably depending on the material used in the dielectric layer and selection of electrodes. To formulate the conductance mechanism, new materials with notable conductivity such as graphene oxide (GO) sheets has been employed by researchers. In the GO-based RRAM, pristine of GO due to the presence of sp3-hybridized oxygen functional groups(hydroxyl) leads to electrically insulating layers in the device. However, by applying the voltage, the conductive path can be formed with the redox of GO layer in to graphene. This phenomenon is known as RRAM set process which can be explained due to the conversion of sp3 to sp2 oxygen functionalities, which make the RRAM to move in to the ON state. Also, in this paper, variation of the ON state resistance by the voltage in the nondegenerate mode is described and the reset process by degeneracy variation is reported.

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Qiu, Wen Wen, Hong Deng, Mi Li, Min Wei, Xue Ran Deng, Jian Qiang Yao, Guang Jun Wen, Rong Tang, Jian Yang, and Guang Jun Wen. "The Recent Progress of Research on Resistive Random Access Memory." Advanced Materials Research 685 (April 2013): 372–77. http://dx.doi.org/10.4028/www.scientific.net/amr.685.372.

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Resistive random access memory (RRAM) has attracted comprehensive attention from academia and industry as a new-type of nonvolatile memory. This memory has many advantages, such as high-speed, low power consumption, simple structure, high-density integration, etc. Therefore, it has a strong potential to replace DRAM. This paper summarizes the recent progress of the studies on RRAM. Although the achievement obtained has been summarized, there is still a long way from the real application. We also discuss the principle and related properties of RRAM and forecast the preparation trends of RRAM

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Peng, Bo, Qiqiao Wu, Zhongqiang Wang, and Jianguo Yang. "A RRAM-Based True Random Number Generator with 2T1R Architecture for Hardware Security Applications." Micromachines 14, no. 6 (June 8, 2023): 1213. http://dx.doi.org/10.3390/mi14061213.

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Resistance random access memory (RRAM) based true random number generator (TRNG) has great potential to be applied to hardware security owing to its intrinsic switching variability. Especially the high resistance state (HRS) variation is usually taken as the entropy source of RRAM-based TRNG. However, the small HRS variation of RRAM may be introduced owing to fabrication process fluctuations, which may lead to error bits and be vulnerable to noise interference. In this work, we propose an RRAM-based TRNG with a 2T1R architecture scheme, which can effectively distinguish the resistance values of HRS with an accuracy of 1.5 kΩ. As a result, the error bits can be corrected to a certain extent while the noise is suppressed. Finally, a 2T1R RRAM-based TRNG macro is simulated and verified using the 28 nm CMOS process, which suggests its potential for hardware security applications.

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Jang, DongJun, and Min-Woo Kwon. "Self-Rectifying Resistive Switching Memory Based on Molybdenum Disulfide for Reduction of Leakage Current in Synapse Arrays." Electronics 12, no. 22 (November 15, 2023): 4650. http://dx.doi.org/10.3390/electronics12224650.

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Resistive random-access memory has emerged as a promising non-volatile memory technology, receiving substantial attention due to its potential for high operational performance, low power consumption, temperature robustness, and scalability. Two-dimensional nanostructured materials play a pivotal role in RRAM devices, offering enhanced electrical properties and physical attributes, which contribute to overall device improvement. In this study, the self-rectifying switching behavior in RRAM devices is analyzed based on molybdenum disulfide nanocomposites decorated with Pd on SiO2/Si substrates. The switching layer integration of Pd and MoS2 at the nanoscale effectively mitigates leakage currents decreasing from cross-talk in the RRAM array, eliminating the need for a separate selector device. The successful demonstration of the expected RRAM switching operation and low switching dispersion follows the application of a Pd nanoparticle embedding method. The switching channel layer is presented as an independent (Pd nanoparticle coating and MoS2 nanosheet) nanocomposite. The switching layer length (4000 μm) and width (7000 μm) play an important role in a lateral-conductive-filament-based RRAM device. Through the bipolar switching behavior extraction of RRAM, the formation of the conductive bridges via electronic migration is explained. The fabricated Pd-MoS2 synaptic RRAM device results in a high resistive current ratio for a forward/reverse current higher than 60 at a low resistance state and observes a memory on/off ratio of 103, exhibiting stable resistance switching behavior.

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Bature, Usman Isyaku, Illani Mohd Nawi, Mohd Haris Md Khir, Furqan Zahoor, Abdullah Saleh Algamili, Saeed S. Ba Hashwan, and Mohd Azman Zakariya. "Statistical Simulation of the Switching Mechanism in ZnO-Based RRAM Devices." Materials 15, no. 3 (February 5, 2022): 1205. http://dx.doi.org/10.3390/ma15031205.

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Resistive random access memory (RRAM) has two distinct processes, the SET and RESET processes, that control the formation and dissolution of conductive filament, respectively. The laws of thermodynamics state that these processes correspond to the lowest possible level of free energy. In an RRAM device, a high operating voltage causes device degradation, such as bends, cracks, or bubble-like patterns. In this work, we developed a statistical simulation of the switching mechanism in a ZnO-based RRAM. The model used field-driven ion migration and temperature effects to design a ZnO-based RRAM dynamic SET and RESET resistance transition process. We observed that heat transport within the conducting filament generated a great deal of heat energy due to the carrier transport of the constituent dielectric material. The model was implemented using the built-in COMSOL Multiphysics software to address heat transfer, electrostatic, and yield RRAM energy. The heat energy increased with the increase in the operating power. Hence, the reliability of a device with high power consumption cannot be assured. We obtained various carrier heat analyses in 2D images and concluded that developing RRAM devices with low operating currents through material and structure optimization is crucial.

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Chen, Kai-Huang, Chien-Min Cheng, Na-Fu Wang, and Ming-Cheng Kao. "Activation Energy and Bipolar Switching Properties for the Co-Sputtering of ITOX:SiO2 Thin Films on Resistive Random Access Memory Devices." Nanomaterials 13, no. 15 (July 26, 2023): 2179. http://dx.doi.org/10.3390/nano13152179.

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Activation energy, bipolar resistance switching behavior, and the electrical conduction transport properties of ITOX:SiO2 thin film resistive random access memory (RRAM) devices were observed and discussed. The ITOX:SiO2 thin films were prepared using a co-sputtering deposition method on the TiN/Si substrate. For the RRAM device structure fabrication, an Al/ITOX:SiO2/TiN/Si structure was prepared by using aluminum for the top electrode and a TiN material for the bottom electrode. In addition, grain growth, defect reduction, and RRAM device performance of the ITOX:SiO2 thin film for the various oxygen gas flow conditions were observed and described. Based on the I-V curve measurements of the RRAM devices, the turn on-off ratio and the bipolar resistance switching properties of the Al/ITOX:SiO2/TiN/Si RRAM devices in the set and reset states were also obtained. At low operating voltages and high resistance values, the conductance mechanism exhibits hopping conduction mechanisms for set states. Moreover, at high operating voltages, the conductance mechanism behaves as an ohmic conduction current mechanism. Finally, the Al/ITOX:SiO2/TiN/Si RRAM devices demonstrated memory window properties, bipolar resistance switching behavior, and nonvolatile characteristics for next-generation nonvolatile memory applications.

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Kim, Kyoungdu, Changmin Lee, Won-Yong Lee, Do Won Kim, Hyeon Joong Kim, Sin-Hyung Lee, Jin-Hyuk Bae, In-Man Kang, and Jaewon Jang. "Enhanced switching ratio of sol–gel-processed Y₂O₃ RRAM device by suppressing oxygen vacancy formation at high annealing temperatures." Semiconductor Science and Technology 37, no. 1 (December 9, 2021): 015007. http://dx.doi.org/10.1088/1361-6641/ac3dd3.

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Abstract Sol–gel-processed Y2O3 films were used as an active-channel layer for resistive switching memory (RRAM) devices. The influence of post-annealing temperature on structural, chemical, and electrical properties was studied. Y2O3-RRAM devices comprising electrochemically active metal electrodes, Ag, and indium tin oxide (ITO) electrodes exhibited the conventional bipolar RRAM device operation. The fabricated Ag/Y2O3/ITO RRAM devices, which included 500 °C-annealed Y2O3 films, exhibited less oxygen vacancy and defect sites, reduced the leakage current, increased the high-/low-resistance state ratio of more than 105, and provided excellent nonvolatile memory properties without significant deterioration for 100 cycles and 104 s.

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Lee, Ke-Jing, Wei-Shao Lin, Li-Wen Wang, Hsin-Ni Lin, and Yeong-Her Wang. "Resistive Switching Memory Cell Property Improvement by Al/SrZrTiO3/Al/SrZrTiO3/ITO with Embedded Al Layer." Nanomaterials 12, no. 24 (December 10, 2022): 4412. http://dx.doi.org/10.3390/nano12244412.

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The SrZrTiO3 (SZT) thin film prepared by sol-gel process for the insulator of resistive random-access memory (RRAM) is presented. Al was embedded in the SZT thin film to enhance the switching characteristics. Compared with the pure SZT thin-film RRAM, the RRAM with the embedded Al in SZT thin film demonstrated outstanding device parameter improvements, such as a resistance ratio higher than 107, lower operation voltage (VSET = −0.8 V and VRESET = 2.05 V), uniform film, and device stability of more than 105 s. The physical properties of the SZT thin film and the embedded-Al SZT thin-film RRAM devices were probed.

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Lee, Taehun, Hae-In Kim, Yoonjin Cho, Sangwoo Lee, Won-Yong Lee, Jin-Hyuk Bae, In-Man Kang, Kwangeun Kim, Sin-Hyung Lee, and Jaewon Jang. "Sol–Gel-Processed Y2O3 Multilevel Resistive Random-Access Memory Cells for Neural Networks." Nanomaterials 13, no. 17 (August 27, 2023): 2432. http://dx.doi.org/10.3390/nano13172432.

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Yttrium oxide (Y2O3) resistive random-access memory (RRAM) devices were fabricated using the sol–gel process on indium tin oxide/glass substrates. These devices exhibited conventional bipolar RRAM characteristics without requiring a high-voltage forming process. The effect of current compliance on the Y2O3 RRAM devices was investigated, and the results revealed that the resistance values gradually decreased with increasing set current compliance values. By regulating these values, the formation of pure Ag conductive filament could be restricted. The dominant oxygen ion diffusion and migration within Y2O3 leads to the formation of oxygen vacancies and Ag metal-mixed conductive filaments between the two electrodes. The filament composition changes from pure Ag metal to Ag metal mixed with oxygen vacancies, which is crucial for realizing multilevel cell (MLC) switching. Consequently, intermediate resistance values were obtained, which were suitable for MLC switching. The fabricated Y2O3 RRAM devices could function as a MLC with a capacity of two bits in one cell, utilizing three low-resistance states and one common high-resistance state. The potential of the Y2O3 RRAM devices for neural networks was further explored through numerical simulations. Hardware neural networks based on the Y2O3 RRAM devices demonstrated effective digit image classification with a high accuracy rate of approximately 88%, comparable to the ideal software-based classification (~92%). This indicates that the proposed RRAM can be utilized as a memory component in practical neuromorphic systems.

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Wang, Yue, Kyung-Mun Kang, Minjae Kim, Hong-Sub Lee, Rainer Waser, Dirk Wouters, Regina Dittmann, J. Joshua Yang, and Hyung-Ho Park. "Mott-transition-based RRAM." Materials Today 28 (September 2019): 63–80. http://dx.doi.org/10.1016/j.mattod.2019.06.006.

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Hsieh, E. Ray, Yi Xiang Huang, You Hung Ye, and Zih Ying Wang. "A three-bit-per-cell via-type resistive random access memory gated metal-oxide semiconductor field-effect transistor non-volatile memory with the FORMing-free characteristic." Semiconductor Science and Technology 36, no. 12 (November 17, 2021): 124002. http://dx.doi.org/10.1088/1361-6641/ac33c3.

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Abstract We present an embedded memory for possible neuromorphic computing applications using a via-type resistive random access memory (RRAM) gated metal-oxide semiconductor field-effect transistor (MOSFET). By this arrangement, the threshold voltage (V th) of the MOSFET is modulated by the resistance of the via-type RRAM. When the resistance of the via-type RRAM is in a high-resistance state (HRS), the word-line voltage (V WL) is consumed mostly across the via-type RRAM and little is left on the gate dielectric layer of the MOSFET; the V th of the MOSFET is boosted. In contrast, when the resistance of the via-type RRAM is in a low-resistance state (LRS), with the resistance value much smaller than that of the gate dielectric of the MOSFET, the VWL will be dropped majorly on the gate dielectric of the MOSFET, and the V th of the MOSFET will be much reduced than that of the MOSFET gated by the via-type RRAM in a HRS. The experimental results show that, in a direct-current mode, the memory window achieves 1 V between a LRS and a HRS of the via-type RRAM gated MOSFET. In an alternating current mode, the LRS can be SET at 10 nanoseconds; the HRS can be RESET at 5 nanoseconds. Furthermore, three-bit-per-cell operation of the via-type RRAM gated MOSFET is demonstrated. The eight conductance states are distributed evenly between 100 micro- and 100 picosiemens with almost isometric gaps in between. The endurance tests were executed for eight conductance states with one million cycles for four pairs. Finally, the retention tests of eight states were kept under 125 °C for one month.

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Hao, Yunxia, Ying Zhang, Zuheng Wu, Xumeng Zhang, Tuo Shi, Yongzhou Wang, Jiaxue Zhu, Rui Wang, Yan Wang, and Qi Liu. "Uniform, fast, and reliable CMOS compatible resistive switching memory." Journal of Semiconductors 43, no. 5 (May 1, 2022): 054102. http://dx.doi.org/10.1088/1674-4926/43/5/054102.

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Abstract Resistive switching random access memory (RRAM) is considered as one of the potential candidates for next-generation memory. However, obtaining an RRAM device with comprehensively excellent performance, such as high retention and endurance, low variations, as well as CMOS compatibility, etc., is still an open question. In this work, we introduce an insert TaO x layer into HfO x -based RRAM to optimize the device performance. Attributing to robust filament formed in the TaO x layer by a forming operation, the local-field and thermal enhanced effect and interface modulation has been implemented simultaneously. Consequently, the RRAM device features large windows (> 103), fast switching speed (~ 10 ns), steady retention (> 72 h), high endurance (> 108 cycles), and excellent uniformity of both cycle-to-cycle and device-to-device. These results indicate that inserting the TaO x layer can significantly improve HfO x -based device performance, providing a constructive approach for the practical application of RRAM.

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Chen, B. J., Y. C. Chang, J. C. Jian, and H. J. Liu. "Flexible Solution-Processed Agar Material for Resistive Switching Memory." IOP Conference Series: Materials Science and Engineering 1250, no. 1 (July 1, 2022): 012006. http://dx.doi.org/10.1088/1757-899x/1250/1/012006.

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Abstract Pure agar (PA)-based resistive random access memory (RRAM) devices using simple solution process method were demonstrated. The memory properties of the investigated PA-based resistive layers are determined by the relationship between the physical properties of the PA thin films and the RRAM performance. The memory properties of PA films with 2 different bottom substrates (glass and PET) and ITO as bottom electrodes were also investigated to explore the differences between rigid and flexible substrates. The RRAM fabricated from PA film and PET substrates exhibit good uniformity acceptable retention over 104 s, and high ON/OFF ratio (>104) at room temperature. According to the fitting results, the RRAM made of PA thin film conforms to the Space-charge-limited current model. This work helps to understand the resistive switching and maintain stable operations of Agar-based RRAM, which means a lot for increasing the application of agar in flexible devices.

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Kuan, Min Chang, Fann Wei Yang, Chien Min Cheng, and Kai Huang Chen. "Fabrication and Switching Characterizations of Copper Oxide Thin Films for Applications in Resistive Random Access Memory Devices." Key Engineering Materials 602-603 (March 2014): 1052–55. http://dx.doi.org/10.4028/www.scientific.net/kem.602-603.1052.

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Many nonvolatile memory devices such as, ferroelectric random access memory (FeRAM), magnetic random access memory (MRAM), ovonic universal memory (OUM), and resistive random access memory (RRAM) were considerable discussed and investigated. For these nonvolatile memory devices, the RRAM devices will play an important role because of its non-destructive readout, low operation voltage, high operation speed, long retention time, and simple structure. The RRAM devices were only consist of one resistor and one corresponding transistor. In this study, the CuO thin films deposited on ITO/glass and Pt/Ti/SiO2/Si substrates for applications in RRAM devices were produced and investigated. The optimal sputtering conditions of as-deposited CuO thin films were the rf power of 80 W, chamber pressure of 20 mTorr, substrate temperature of 580°C, and an oxygen concentration of 40%. The basic mechanisms for the bistable resistance switching were observed. The electrical and physics properties of CuO thin films for applications in RRAM devices were discussed.

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Chen, Kai-Huang, Chien-Min Cheng, Mei-Li Chen, and Yi-Yun Pan. "Bipolar Switching Properties of the Transparent Indium Tin Oxide Thin Film Resistance Random Access Memories." Nanomaterials 13, no. 4 (February 10, 2023): 688. http://dx.doi.org/10.3390/nano13040688.

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In this study, the bipolar switching properties and electrical conduction behaviors of the ITO thin films RRAM devices were investigated. For the transparent RRAM devices structure, indium tin oxide thin films were deposited by using the RF magnetron sputtering method on the ITO/glass substrate. For the ITO/ITOX/ITO/glass (MIM) structure, an indium tin oxide thin film top electrode was prepared to form the transparent RRAM devices. From the experimental results, the 102 On/Off memory ratio and bipolar switching cycling properties for set/reset stable states were found and discussed. All transparent RRAM devices exhibited the obvious memory window and low set voltage for the switching times of 120 cycles. The electrical transport mechanisms were dominated by the ohmic contact and space charge limit conduction (SCLC) models for set and reset states. Finally, the transmittances properties of the transparent ITO/ITOX/ITO RRAM devices for the different oxygen growth procedures were about 90% according to the UV–Vis spectrophotometer for the visible wavelength range.

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34

H. M., Vijay, and V. N. Ramakrishnan. "Geometrical Variation of a Conductive Filament in RRAM and Its Impact on a Single-Event Upset." ECTI Transactions on Electrical Engineering, Electronics, and Communications 20, no. 1 (February 18, 2022): 32–38. http://dx.doi.org/10.37936/ecti-eec.2022201.246101.

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Resistive random access memory (RRAM) is a promising candidate for industry and academia from the research and development perspective. The resistance of RRAM depends on the geometrical dimensions, growth, and rupture of the conductive filament. In this work, the geometrical dimensions such as the length and width of the filament are varied to analyze the resistance. Moreover, the RRAM can be used in aerospace applications. Therefore, the impact of a single-event upset on resistance of RRAM is investigated by means of a double exponential current pulse. The performance of the device is compared in terms of resistance before and after irradiation. A decrease in its original resistance has been observed after radiation.

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Yang, Yintang, Yiwei Duan, Haixia Gao, Mengyi Qian, Jingshu Guo, Mei Yang, and Xiaohua Ma. "Improved switching stability in SiN_x-based RRAM by introducing nitride insertion layer with high conductivity." Applied Physics Letters 122, no. 11 (March 13, 2023): 113504. http://dx.doi.org/10.1063/5.0142897.

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In this Letter, a Pt/SiNx/TiN/Ta resistive random access memory (RRAM) is proposed, which has low switching voltage, uniform resistance distribution, excellent cycle-to-cycle stability, and excellent nonvolatile performance. As an insertion layer, TiN prevents excessive absorption of nitrogen ions by a Ta electrode and avoids the formation of the unstable metal–semiconductor interface, which significantly reduces cycle-to-cycle variability of SiNx-based RRAM. Due to high conductivity, the TiN layer has a small voltage divider effect when voltage was applied, which helps to achieve low power consumption characteristics. This paper provides a direction for improving performance of nitride-based RRAM, which is useful for further development of highly reliable RRAM.

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Bera, Jayanta, Atanu Betal, Ashish Sharma, Arup Kumar Rath, and Satyajit Sahu. "Colloidal MoS₂ quantum dots for high-performance low power resistive memory devices with excellent temperature stability." Applied Physics Letters 120, no. 25 (June 20, 2022): 253502. http://dx.doi.org/10.1063/5.0094892.

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Conventional memory technologies are facing enormous problems with downscaling, and are hence unable to fulfill the requirement of big data storage generated by a huge explosion of digital information. A resistive random access memory device (RRAM) is one of the most emerging technologies for next-generation computing data storage owing to its high-density stacking, ultrafast switching speed, high non-volatility, multilevel data storage, low power consumption, and simple device structure. In this work, colloidal MoS2 quantum dots (QDs) embedded in an insulating matrix of poly-(4vinylpyridine) (PVP) were used as an active layer to fabricate a RRAM device. The MoS2 QDs-PVP based RRAM device reveals an excellent nonvolatile resistive switching (RS) behavior with a maximum current on-off ratio (ION/IOFF) of 105. High endurance, long retention time, and successive “write-read-erase-read” cycles indicate high-performance RRAM characteristics. The ultimate power consumption by this RRAM device is considerably low for energy saving. In addition, the MoS2 QDs-PVP based device shows RS behavior even at 130 °C. High ION/IOFF, low operating power, high endurance, long retention time, and excellent stability with temperatures reveal that the MoS2 QDs-PVP based device can be a promising candidate for high-performance low power RRAM devices that can be operated at relatively higher temperatures.

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Shen, Zongjie, Chun Zhao, Yanfei Qi, Wangying Xu, Yina Liu, Ivona Z. Mitrovic, Li Yang, and Cezhou Zhao. "Advances of RRAM Devices: Resistive Switching Mechanisms, Materials and Bionic Synaptic Application." Nanomaterials 10, no. 8 (July 23, 2020): 1437. http://dx.doi.org/10.3390/nano10081437.

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Resistive random access memory (RRAM) devices are receiving increasing extensive attention due to their enhanced properties such as fast operation speed, simple device structure, low power consumption, good scalability potential and so on, and are currently considered to be one of the next-generation alternatives to traditional memory. In this review, an overview of RRAM devices is demonstrated in terms of thin film materials investigation on electrode and function layer, switching mechanisms and artificial intelligence applications. Compared with the well-developed application of inorganic thin film materials (oxides, solid electrolyte and two-dimensional (2D) materials) in RRAM devices, organic thin film materials (biological and polymer materials) application is considered to be the candidate with significant potential. The performance of RRAM devices is closely related to the investigation of switching mechanisms in this review, including thermal-chemical mechanism (TCM), valance change mechanism (VCM) and electrochemical metallization (ECM). Finally, the bionic synaptic application of RRAM devices is under intensive consideration, its main characteristics such as potentiation/depression response, short-/long-term plasticity (STP/LTP), transition from short-term memory to long-term memory (STM to LTM) and spike-time-dependent plasticity (STDP) reveal the great potential of RRAM devices in the field of neuromorphic application.

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Wan, Weier, Rajkumar Kubendran, Clemens Schaefer, Sukru Burc Eryilmaz, Wenqiang Zhang, Dabin Wu, Stephen Deiss, et al. "A compute-in-memory chip based on resistive random-access memory." Nature 608, no. 7923 (August 17, 2022): 504–12. http://dx.doi.org/10.1038/s41586-022-04992-8.

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AbstractRealizing increasingly complex artificial intelligence (AI) functionalities directly on edge devices calls for unprecedented energy efficiency of edge hardware. Compute-in-memory (CIM) based on resistive random-access memory (RRAM)1 promises to meet such demand by storing AI model weights in dense, analogue and non-volatile RRAM devices, and by performing AI computation directly within RRAM, thus eliminating power-hungry data movement between separate compute and memory2–5. Although recent studies have demonstrated in-memory matrix-vector multiplication on fully integrated RRAM-CIM hardware6–17, it remains a goal for a RRAM-CIM chip to simultaneously deliver high energy efficiency, versatility to support diverse models and software-comparable accuracy. Although efficiency, versatility and accuracy are all indispensable for broad adoption of the technology, the inter-related trade-offs among them cannot be addressed by isolated improvements on any single abstraction level of the design. Here, by co-optimizing across all hierarchies of the design from algorithms and architecture to circuits and devices, we present NeuRRAM—a RRAM-based CIM chip that simultaneously delivers versatility in reconfiguring CIM cores for diverse model architectures, energy efficiency that is two-times better than previous state-of-the-art RRAM-CIM chips across various computational bit-precisions, and inference accuracy comparable to software models quantized to four-bit weights across various AI tasks, including accuracy of 99.0 percent on MNIST18 and 85.7 percent on CIFAR-1019 image classification, 84.7-percent accuracy on Google speech command recognition20, and a 70-percent reduction in image-reconstruction error on a Bayesian image-recovery task.

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Jones, Alexander, Aaron Ruen, and Rashmi Jha. "A Spiking Neuromorphic Architecture Using Gated-RRAM for Associative Memory." ACM Journal on Emerging Technologies in Computing Systems 18, no. 2 (April 30, 2022): 1–22. http://dx.doi.org/10.1145/3461667.

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This work reports a spiking neuromorphic architecture for associative memory simulated in a SPICE environment using recently reported gated-RRAM (resistive random-access memory) devices as synapses alongside neurons based on complementary metal-oxide semiconductors (CMOSs). The network utilizes a Verilog A model to capture the behavior of the gated-RRAM devices within the architecture. The model uses parameters obtained from experimental gated-RRAM devices that were fabricated and tested in this work. Using these devices in tandem with CMOS neuron circuitry, our results indicate that the proposed architecture can learn an association in real time and retrieve the learned association when incomplete information is provided. These results show the promise for gated-RRAM devices for associative memory tasks within a spiking neuromorphic architecture framework.

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Machado, Pau, Salvador Manich, Álvaro Gómez-Pau, Rosa Rodríguez-Montañés, Mireia Bargalló González, Francesca Campabadal, and Daniel Arumí. "Programming Techniques of Resistive Random-Access Memory Devices for Neuromorphic Computing." Electronics 12, no. 23 (November 27, 2023): 4803. http://dx.doi.org/10.3390/electronics12234803.

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Neuromorphic computing offers a promising solution to overcome the von Neumann bottleneck, where the separation between the memory and the processor poses increasing limitations of latency and power consumption. For this purpose, a device with analog switching for weight update is necessary to implement neuromorphic applications. In the diversity of emerging devices postulated as synaptic elements in neural networks, RRAM emerges as a standout candidate for its ability to tune its resistance. The learning accuracy of a neural network is directly related to the linearity and symmetry of the weight update behavior of the synaptic element. However, it is challenging to obtain such a linear and symmetrical behavior with RRAM devices. Thus, extensive research is currently devoted at different levels, from material to device engineering, to improve the linearity and symmetry of the conductance update of RRAM devices. In this work, the experimental results based on different programming pulse conditions of RRAM devices are presented, considering both voltage and current pulses. Their suitability for application as analog RRAM-based synaptic devices for neuromorphic computing is analyzed by computing an asymmetric nonlinearity factor.

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Pedretti, Giacomo, and Daniele Ielmini. "In-Memory Computing with Resistive Memory Circuits: Status and Outlook." Electronics 10, no. 9 (April 30, 2021): 1063. http://dx.doi.org/10.3390/electronics10091063.

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In-memory computing (IMC) refers to non-von Neumann architectures where data are processed in situ within the memory by taking advantage of physical laws. Among the memory devices that have been considered for IMC, the resistive switching memory (RRAM), also known as memristor, is one of the most promising technologies due to its relatively easy integration and scaling. RRAM devices have been explored for both memory and IMC applications, such as neural network accelerators and neuromorphic processors. This work presents the status and outlook on the RRAM for analog computing, where the precision of the encoded coefficients, such as the synaptic weights of a neural network, is one of the key requirements. We show the experimental study of the cycle-to-cycle variation of set and reset processes for HfO2-based RRAM, which indicate that gate-controlled pulses present the least variation in conductance. Assuming a constant variation of conductance σG, we then evaluate and compare various mapping schemes, including multilevel, binary, unary, redundant and slicing techniques. We present analytical formulas for the standard deviation of the conductance and the maximum number of bits that still satisfies a given maximum error. Finally, we discuss RRAM performance for various analog computing tasks compared to other computational memory devices. RRAM appears as one of the most promising devices in terms of scaling, accuracy and low-current operation.

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Prabhu, Nagaraj, Desmond Loy Jia Jun, Putu Dananjaya, Wen Lew, Eng Toh, and Nagarajan Raghavan. "Exploring the Impact of Variability in Resistance Distributions of RRAM on the Prediction Accuracy of Deep Learning Neural Networks." Electronics 9, no. 3 (February 29, 2020): 414. http://dx.doi.org/10.3390/electronics9030414.

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In this work, we explore the use of the resistive random access memory (RRAM) device as a synapse for mimicking the trained weights linking neurons in a deep learning neural network (DNN) (AlexNet). The RRAM devices were fabricated in-house and subjected to 1000 bipolar read-write cycles to measure the resistances recorded for Logic-0 and Logic-1 (we demonstrate the feasibility of achieving eight discrete resistance states in the same device depending on the RESET stop voltage). DNN simulations have been performed to compare the relative error between the output of AlexNet Layer 1 (Convolution) implemented with the standard backpropagation (BP) algorithm trained weights versus the weights that are encoded using the measured resistance distributions from RRAM. The IMAGENET dataset is used for classification purpose here. We focus only on the Layer 1 weights in the AlexNet framework with 11 × 11 × 96 filters values coded into a binary floating point and substituted with the RRAM resistance values corresponding to Logic-0 and Logic-1. The impact of variability in the resistance states of RRAM for the low and high resistance states on the accuracy of image classification is studied by formulating a look-up table (LUT) for the RRAM (from measured I-V data) and comparing the convolution computation output of AlexNet Layer 1 with the standard outputs from the BP-based pre-trained weights. This is one of the first studies dedicated to exploring the impact of RRAM device resistance variability on the prediction accuracy of a convolutional neural network (CNN) on an AlexNet platform through a framework that requires limited actual device switching test data.

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Beckmann, Karsten, Josh Holt, Harika Manem, Joseph Van Nostrand, and Nathaniel C. Cady. "Nanoscale Hafnium Oxide RRAM Devices Exhibit Pulse Dependent Behavior and Multi-level Resistance Capability." MRS Advances 1, no. 49 (2016): 3355–60. http://dx.doi.org/10.1557/adv.2016.377.

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ABSTRACTResistive Random Access Memory (RRAM) is a novel form of non-volatile memory that is expected to play a major role in future computing and memory solutions. It has been shown that the resistance of RRAM devices can be precisely tuned by modulating switching voltages, by limiting peak current, and by adjusting the switching pulse duration. This enables the realization of novel applications such as memristive neuromorphic computing and neural network computing. The RRAM devices described in this work utilize an inert tungsten bottom electrode, hafnium oxide based active switching layer, a titanium oxygen exchange layer, and an inert titanium nitride top electrode. Linear sweep and controlled pulse (down to 10 ns) based electrical characterization of RRAM devices was performed in a 1 transistor 1 RRAM (1T1R) configuration to determine endurance, reliability, retention and threshold voltage parameters. We demonstrated endurance values above 108cycles with an average on/off ratio of 15 and pulse voltages for set/reset operation of ±1.5V. The on-chip 1T1R structures show an excellent controllability with respect to the low and high resistive state by manipulating the peak current from 75 up to 350µA we were able to achieve 10 discrete resistive states. Our results demonstrate that the set operation (which shifts the RRAM device from the high to the low resistance state) is only dependent on the voltage of the switching pulse and the peak current limit. The reset operation, however, occurs in an analog fashion and appears to be dependent on the total energy of the applied switching pulse. Pulse energy was modulated by varying the peak voltage which resulted in a larger relative change of the RRAM device resistance.

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Chen, Ying-Chen, Szu-Tung Hu, Chih-Yang Lin, Burt Fowler, Hui-Chun Huang, Chao-Cheng Lin, Sungjun Kim, Yao-Feng Chang, and Jack C. Lee. "Graphite-based selectorless RRAM: improvable intrinsic nonlinearity for array applications." Nanoscale 10, no. 33 (2018): 15608–14. http://dx.doi.org/10.1039/c8nr04766a.

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Selectorless graphite-based resistive random-access memory (RRAM) has been demonstrated by utilizing the intrinsic nonlinear resistive switching (RS) characteristics, without an additional selector or transistor for low-power RRAM array application.

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Han, Guodu, Yanning Chen, Hongxia Liu, Dong Wang, and Rundi Qiao. "Impacts of LaOx Doping on the Performance of ITO/Al2O3/ITO Transparent RRAM Devices." Electronics 10, no. 3 (January 23, 2021): 272. http://dx.doi.org/10.3390/electronics10030272.

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Fully transparent ITO/LaAlO3/ITO structure RRAM (resistive random access memory) devices were fabricated on glass substrate, and ITO/Al2O3/ITO structure devices were set for comparison. The electrical characteristics of the devices were analyzed by Agilent B1500A semiconductor analyzer. Compared with the ITO/Al2O3/ITO RRAM devices, the current stability, SET/RESET voltage distribution, and retention characteristic of the ITO/LaAlO3/ITO RRAM devices have been greatly improved. In the visible light range, the light transmittance of the device is about 80%, that of the LaAlO3 layer is about 95%, the on-off ratio of the device is greater than 40, and the data retention time is longer than 10,000 s. The devices have great optical and electrical properties and have huge application potential as fully transparent RRAM devices.

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Li, Yingtao, Rongrong Li, Peng Yuan, Xiaoping Gao, and Enzi Chen. "Low-cost bidirectional selector based on Ti/TiO2/HfO2/TiO2/Ti stack for bipolar RRAM arrays." Modern Physics Letters B 29, no. 35n36 (December 30, 2015): 1550244. http://dx.doi.org/10.1142/s0217984915502449.

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In this paper, a low-cost Ti/TiO2/HfO2/TiO2/Ti stack structure is proposed as a selector for bipolar resistive random access memory (RRAM) cross-bar array applications. We demonstrate reproducible resistive switching characteristics with significant nonlinearity and good uniformity in the one selector and one resistor (1S1R) structure device that integrate the bidirectional selector with a bipolar Pt/Ti/HfO2/Pt RRAM device. These results provide a good point of reference for evaluating the potential low-cost applications in bipolar RRAM cross-bar array.

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Shen, Zongjie, Chun Zhao, Yanfei Qi, Ivona Z. Mitrovic, Li Yang, Jiacheng Wen, Yanbo Huang, Puzhuo Li, and Cezhou Zhao. "Memristive Non-Volatile Memory Based on Graphene Materials." Micromachines 11, no. 4 (March 25, 2020): 341. http://dx.doi.org/10.3390/mi11040341.

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Resistive random access memory (RRAM), which is considered as one of the most promising next-generation non-volatile memory (NVM) devices and a representative of memristor technologies, demonstrated great potential in acting as an artificial synapse in the industry of neuromorphic systems and artificial intelligence (AI), due its advantages such as fast operation speed, low power consumption, and high device density. Graphene and related materials (GRMs), especially graphene oxide (GO), acting as active materials for RRAM devices, are considered as a promising alternative to other materials including metal oxides and perovskite materials. Herein, an overview of GRM-based RRAM devices is provided, with discussion about the properties of GRMs, main operation mechanisms for resistive switching (RS) behavior, figure of merit (FoM) summary, and prospect extension of GRM-based RRAM devices. With excellent physical and chemical advantages like intrinsic Young’s modulus (1.0 TPa), good tensile strength (130 GPa), excellent carrier mobility (2.0 × 105 cm2∙V−1∙s−1), and high thermal (5000 Wm−1∙K−1) and superior electrical conductivity (1.0 × 106 S∙m−1), GRMs can act as electrodes and resistive switching media in RRAM devices. In addition, the GRM-based interface between electrode and dielectric can have an effect on atomic diffusion limitation in dielectric and surface effect suppression. Immense amounts of concrete research indicate that GRMs might play a significant role in promoting the large-scale commercialization possibility of RRAM devices.

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48

Udaya Mohanan, Kannan. "Resistive Switching Devices for Neuromorphic Computing: From Foundations to Chip Level Innovations." Nanomaterials 14, no. 6 (March 15, 2024): 527. http://dx.doi.org/10.3390/nano14060527.

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Neuromorphic computing has emerged as an alternative computing paradigm to address the increasing computing needs for data-intensive applications. In this context, resistive random access memory (RRAM) devices have garnered immense interest among the neuromorphic research community due to their capability to emulate intricate neuronal behaviors. RRAM devices excel in terms of their compact size, fast switching capabilities, high ON/OFF ratio, and low energy consumption, among other advantages. This review focuses on the multifaceted aspects of RRAM devices and their application to brain-inspired computing. The review begins with a brief overview of the essential biological concepts that inspire the development of bio-mimetic computing architectures. It then discusses the various types of resistive switching behaviors observed in RRAM devices and the detailed physical mechanisms underlying their operation. Next, a comprehensive discussion on the diverse material choices adapted in recent literature has been carried out, with special emphasis on the benchmark results from recent research literature. Further, the review provides a holistic analysis of the emerging trends in neuromorphic applications, highlighting the state-of-the-art results utilizing RRAM devices. Commercial chip-level applications are given special emphasis in identifying some of the salient research results. Finally, the current challenges and future outlook of RRAM-based devices for neuromorphic research have been summarized. Thus, this review provides valuable understanding along with critical insights and up-to-date information on the latest findings from the field of resistive switching devices towards brain-inspired computing.

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Wu, Chien-Hung, Song-Nian Kuo, Kow-Ming Chang, Yi-Ming Chen, Yu-Xin Zhang, Ni Xu, Wu-Yang Liu, and Albert Chin. "Investigation of Microwave Annealing on Resistive Random Access Memory Device with Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition Deposited IGZO Layer." Journal of Nanoscience and Nanotechnology 20, no. 7 (July 1, 2020): 4244–47. http://dx.doi.org/10.1166/jnn.2020.17561.

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Non-volatile memory (NVM) is essential in almost every consumer electronic products. The most prevalent NVM used nowadays is flash memory (Meena, J.S., et al., 2014. Overview of emerging nonvolatile memory technologies. Nanoscale Res. Letters, 9(1), p.526). However, some bottlenecks of flash memory have been identified, such as high operation voltage, low operation speed, and poor retention time. Resistive random access memory (RRAM) is considered to be the most promising one to become the next generation NVM device since its simple structure, fast program/erase speed, and low power consumption. In this experiment, the RRAM device is fabricated, and its IGZO (memory) layer is deposited with AP-PECVD technique which can reduce cost of the process. Microwave annealing (MWA) is used to enhance electrical characteristics of the RRAM device (Fuh, C.S., et al., 2011. Role of environmental and annealing conditions on the passivation-free In–Ga– Zn–O TFT. Thin Solid Films, 520, pp.1489–1494). Experiment results show that with appropriate MWA treatment, the IGZO RRAM device exhibits better electrical characteristics under bipolar operation, all forming/set/reset voltage for RRAM device is simultaneously lowered.

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WANG, SHENG-YU, and TSEUNG-YUEN TSENG. "INTERFACE ENGINEERING IN RESISTIVE SWITCHING MEMORIES." Journal of Advanced Dielectrics 01, no. 02 (April 2011): 141–62. http://dx.doi.org/10.1142/s2010135x11000306.

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Electric-induced resistive switching effects have attracted wide attention for future nonvolatile memory applications known as resistive random access memory (RRAM). RRAM is one of the promising candidates because of its excellent properties including simple device structure, high operation speed, low power consumption and high density integration. The RRAM devices primarily utilize different resistance values to store the digital data and can keep the resistance state without any power. Recent advances in the understanding of the resistive switching mechanism are described by a thermal or electrochemical redox reaction near the interface between the oxide and the active metal electrode. This paper reviews the ongoing research and development activities on the interface engineering of the RRAM devices. The possible switching mechanisms for the bistable resistive switching are described. The effects of formation, composition and thickness of the interface layer on the resistive switching characteristics and consequently the memory performance are also discussed.

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Journal articles on the topic 'RRAM'

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