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Resistive random access memory (RRAM) with resistive switching devices arranged in crossbar architecture.
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Resistive switching effect in transition metal oxide (TMO) based material is often associated with the valence change mechanism (VCM). Typical modeling of valence change resistive switching memory consists of three closely related phenomena, i.e., conductive filament (CF) geometry evolution, conduction mechanism and temperature dynamic evolution. I...
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Context 1
... high density implementation, resistive switching devices can be arranged in crossbar architecture which has minimum memory cell area of 4F 2 [68,69]. Figure 3 shows three-dimensional modeling of a 2-by-2 resistive random access memory (ReRAM or RRAM) implemented in crossbar structure. ...
Context 2
... et al. [46] reported that the SCLC is the dominant conduction mechanism in HRS and negative-based LRS of the Ti/CuxO/Pt device. However, there is no I-V 2 region observed in positive-biased LRS as shown in Figure 13, which could be capped by the current compliance imposed on the device. Generally, observation of three apparent regions where (i) I ∝ V, (ii) I ∝ V 2 and (iii) steep increase of I, signifies the dominant of SCLC mechanism. ...
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Digital computing is nearing its physical limits as computing needs and energy consumption rapidly increase. Analogue-memory-based neuromorphic computing can be orders of magnitude more energy efficient at data-intensive tasks like deep neural networks, but has been limited by the inaccurate and unpredictable switching of analogue resistive memory....
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Citations
... To strengthen the argument for the proposed switching mechanism, a conduction mechanism analysis was performed and the obtained results are summarized in Figure 2. [45][46][47]. Analyzing the plots of the HRS and LRS for both the PB (b,c) and CB (e,f) samples, as shown in Figure 2, the Schottky emission is revealed as the dominant conduction mechanism. The Schottky emission is a thermionic process in which electrons are injected into the conduction band of the oxide by overcoming an energy barrier through thermal activation [46]. ...
... Analyzing the plots of the HRS and LRS for both the PB (b,c) and CB (e,f) samples, as shown in Figure 2, the Schottky emission is revealed as the dominant conduction mechanism. The Schottky emission is a thermionic process in which electrons are injected into the conduction band of the oxide by overcoming an energy barrier through thermal activation [46]. The Schottky or thermionic emission is often observed as the dominant conduction mechanism in metal oxides and it was already reported for similar memristors [46,48,49] including Ti/TiO 2 [38]. ...
... The Schottky emission is a thermionic process in which electrons are injected into the conduction band of the oxide by overcoming an energy barrier through thermal activation [46]. The Schottky or thermionic emission is often observed as the dominant conduction mechanism in metal oxides and it was already reported for similar memristors [46,48,49] including Ti/TiO 2 [38]. Hence, in the present study, the Schottky emission is safely concluded to be the dominant conduction mechanism, confirming the suggested memristive switching mechanism. ...
Titanium anodic memristors were prepared in phosphate buffer (PB) and citrate buffer (CB) electrolytes. Studying their I-U sweeps, the memristors presented self-rectifying and volatile behaviors. Transmission electron microscopic analysis revealed crystalline protrusions inside a semi-crystalline Ti oxide. Grounded in this, a hybrid interfacial memristive switching mechanism relaying on partial filaments was proposed. Moreover, both analyzed memristor types demonstrated multilevel switching capabilities. The memristors anodized in the PB and CB showed high-to-low resistance ratios of 4 × 104 and 1.6 × 102, respectively. The observed (more than two order of magnitude) ratio improvement of the PB memristors suggests their better performance, in spite of their modestly high resistive state instabilities, attributed to the thermal stress caused by consecutive switching. The endurance and retention of both the PB and CB memristors was measured over up to 106 cycles, indicating very good lifetimes. Phosphate incorporation into the anodic oxide was confirmed by photoelectron spectroscopy analysis and was related to the improved memristive behavior of the PB sample. The presence of phosphate inside the memristively active layer modifies the availability of free O species (vacancies and ions) in the oxide. Taking all this into consideration, Ti anodic memristors anodized in PB are emphasized as candidates for neuromorphic computing.
... The emerging memristor technology has been considered one of the promising candidates for neuromorphic computing and next-generation high-density information storage technology because of its simple device structure, high storage density, high energy efficiency, good scalability, reliability, fast switching response, high endurance, and complementary metal-oxide-semiconductor (CMOS) compatibility [1][2][3][4][5]. In comparison with traditional, memory technologies like flash memory, DRAM, and static random-access memory (SRAM), memristor are considered excellent alternatives. ...
... To date different types of conduction mechanisms have been proposed, to explain memristive behavior i.e. Trapcontrolled space charge limited conduction (SCLC), conduction filament formation, Poole-Frenkel (P-F) emission, ion migration, etc [4,58]. In order to explain the carrier transport mechanism responsible for resistive switching in this novel QDs-based memristor, the I-V curve is plotted in a double logarithmic scale, and then model fitting studies are performed. ...
In recent years Quantum dot (QDs) based resistive switching devices(memristors) have gained a lot of attention. Here we report the resistive switching behavior of nitrogen-doped graphene quantum dots/Polyvinyl alcohol (N-GQDs/PVA) degradable nanocomposite thin film with different weight percentages (wt. %) of N-GQDs. The memristor device was fabricated by a simple spin coating technique. It was found that 1wt% N-GQDs/PVA device shows a prominent resistive switching phenomenon with good cyclic stability and a high on/off ratio of ~10 ² . From a detailed experimental study of band structure, we conclude that memristive behavior originates from the Space Charge Controlled Conduction (SCLC) mechanism. Further transient property of built memristive device was studied. Within three minutes of being submerged in distilled water, the fabricated memory device was destroyed. This phenomenon facilitates the usage of fabricated memristor devices to develop memory devices for military and security purposes.
... Typical GaN micro-wires have distinct bamboo-shaped knots, which are formed by nucleation and radial growth of GaN in the form of seed crystals during the growth process. The memory switching characteristics of piezotronic memory resistors are mainly attributed to nitrogen-deficient defects in the GaN knot region [72,73]. By applying compressive strain to the device using a 3D mechanical stage, they explore the influence of the piezoelectric effect on the performance of GaN memristors. ...
Highlights
The operating mechanism of piezotronic neuromorphic devices and related manufacturing techniques are presented.
Recent research advances in piezotronic neuromorphic devices including multifunctional applications are summarized.
Challenges and prospects for modulating novel neuromorphic devices with piezotronic effects are discussed.
... 39 Equation (1), when m = 0, indicates the Ohmic law, meaning that the conduction mechanism is free electron-controlled. At m = 1, Eq. (1) becomes Child's square formula, which shows the density of electrons controls the conductivity, which the equations can describe [40][41][42] ...
Two-terminal structure memristors are the most promising electronic devices that could play a significant role in artificial intelligence applications of the next generation and the post-Moore era. In this work, we fabricated the memristive device by depositing a heterojunction WO x /TiO y functional layer onto an indium tin oxide substrate using magnetron sputtering. The Ag/WO x /TiO y /ITO device exhibits improved memory behavior of bipolar resistive switching (RS) nonvolatile compared to TiO y-based single-layer memristors, enabling it to meet high-density information storage requirements. Moreover, our device exhibited the coexistence of the negative differential resistance effect and the behavior of the RS memory. Through a comprehensive analysis of conductivity on the curve of current-voltage (I-V), a physical model based on the mechanism of space charge-limited current, ohmic conduction, and Schottky emission was suggested to explain the behavior device RS memory. This study's findings demonstrate that including a heterojunction bilayer WO x /TiO y as a functional layer can significantly improve the performance of memristive devices. This advancement expands the potential application of ferroelectric metallic oxide heterojunctions within the field of memristors.
... In equation (1), when m = 0, it indicates Ohmic law, which means the conduction mechanism is free electron-controlled. At m = 1, equation (1) becomes Child's square formula, which shows the density of electrons controls the conductivity, which the equation can describe [41][42][43]: ...
Memristors represent a cutting-edge technology poised for extensive applications in integrated electronic devices, high-performance computing, digital and analog circuitry, and artificial intelligence. In this study, we fabricated a memristor device using a thin titanium oxide (TiOx) film as a functional layer by magnetron sputtering. We proposed a physical model to explain the device's resistive switching (RS) behavior based on a comprehensive analysis of conductance derived from current-voltage (I-V) curves. We found that the device exhibited improved resistance switching ratio, durability, and low operating voltage, which are desirable for high-density memory applications. We also revealed the roles of the space charge limited current (SCLC) mechanism, Ohmic conduction in the RS process, and the formation and rupture of conductive filaments of silver and oxygen vacancies. Our findings demonstrate the effectiveness of TiOx as a functional layer and the importance of magnetron sputtering as a fabrication method for enhancing the performance of memristive devices. Our study also advances the mechanistic understanding of RS and highlights the potential of metal oxides in memristor technology. This research propels the ongoing exploration of innovative materials to enhance memristive devices' functionality and application scope in various technological domains.
... Among them, transition metal oxides (TMOs) are considered the most promising. Additionally, there are three types of resistive switching mechanisms: electrochemical metallization mechanisms (ECMs), thermochemical mechanisms (TCMs), and valence change mechanisms (VCMs) [11]. Previous studies have shown that resistance switching occurs in VCMs through the migration of oxygen ions, forming conductive filaments as a result of voltage sweeps and switching the device between high and low resistance states [12][13][14]. ...
Sol–gel thin films of amorphous LaNbOx (LNO) were prepared to study the bipolar resistive switching (BRS) properties of Metal/LNO/ITO devices. We investigated the influences of film thickness, top electrode, annealing temperature, post-metal annealing (PMA), and bilayer structure on the resistive switching (RS) characteristics. In comparison to the as-deposited LNO thin film devices, the PMA-treated devices demonstrated better RS characteristics, with lower set/reset voltages (VSet/VReset = − 2.26V/0.9V), longer switching cycles (2466 cycles), and a > 10¹ Ron/Roff ratio. Furthermore, at 85 °C, the retention time exceeded 10⁴ s, similar to the retention time at room temperature, indicating that random access memory (RRAM) may effectively function over 10 years. The improvement in RS characteristics can be attributed to the formation of an AlOx layer between the upper electrode and the insulating layer after PMA treatment, which increases the oxygen vacancy content and facilitates Al ion diffusion. The addition of a bilayer of Al was implemented to increase the thickness of AlOx, thereby improving the Ron/Roff ratio. However, this addition also degrades the RS properties of the device. Furthermore, the space charge-limited current (SCLC) conduction mechanism dominates in the high resistance state (HRS), while ohmic conduction prevails in the low resistance state (LRS) of the devices.
... Figure 3b,d show the best current-voltage and current-temperature fittings for LRS. LRS charge transport is assumed to be controlled by variable range hopping (i.e., temperature dependency of 1/T 4 ) which is usually reported for strongly disorder systems 50,51 . It is bulk-limited model indicating that defects in IGZO have important roles. ...
Solution-based memristors deposited by inkjet printing technique have a strong technological potential based on their scalability, low cost, environmentally friendlier processing by being an efficient technique with minimal material waste. Indium-gallium-zinc oxide (IGZO), an oxide semiconductor material, shows promising resistive switching properties. In this work, a printed Ag/IGZO/ITO memristor has been fabricated. The IGZO thickness influences both memory window and switching voltage of the devices. The devices show both volatile counter8wise (c8w) and non-volatile 8wise (8w) switching at low operating voltage. The 8w switching has a SET and RESET voltage lower than 2 V and − 5 V, respectively, a retention up to 10⁵ s and a memory window up to 100, whereas the c8w switching shows volatile characteristics with a low threshold voltage (Vth < − 0.65 V) and a characteristic time (τ) of 0.75 ± 0.12 ms when a single pulse of − 0.65 V with width of 0.1 ms is applied. The characteristic time alters depending on the number of pulses. These volatile characteristics allowed them to be tested on different 4-bit pulse sequences, as an initial proof of concept for temporal signal processing applications.
... where A is a constant, φ T represents the trap energy level, which refers to the energy of the electron traps in relation to the conduction edge of the oxide. E denotes the applied electric field, m * stands for the electron effective mass in the active layer, and h represents the Plank's constant [43]. ...
Biodegradable electronic devices play a crucial role in addressing the escalating issue of electronic waste accumulation, which poses significant environmental threats. In this investigation, we explored the utilization of a methanol-based extract of the Elaeodendron buchananii plant blended with carboxymethyl cellulose, a biopolymer, to produce a biodegradable and environmentally friendly functional material for a resistive switching memory system using silver and tungsten electrodes. Our analyses revealed that these two materials chemically interacted to generate a perfect composite with near semiconducting optical bandgap (4.01 eV ), surpassing than that of individual materials. The resultant device exhibited O-type memory behavior, with a low ON/OFF ratio, strong endurance (≥ 10 ³ write/erase cycles), and satisfactory (≥ 10 ³ ) data retention. Furthermore through a comprehensive transport mechanism analysis , we observed the formation of traps in the composite significantly improved conduction in the device. In addition, we established that altering the voltage amplitude modifies the concentration of traps, leading in voltage amplitude driven multiple resistance states. Overall, our findings underscore the potential of functionalizing polymers can be functionalized by incorporating plant extracts, thereby resulting in biodegradable nonvolatile memory devices with promising performance metrics
... To study the transport mechanisms responsible for the switching process, SET I-V sweep was plotted on a log-log scale ( Fig. 2d). Device transitioning to LRS during SET traverses through conductance regions with varying slopes, indicating that the dominant charge transport mechanism varies: ohmic conduction with slope~1, space-charge limited conduction (SCLC) in regions with slope~2 and trap-fill limited SCLC in regions with slope >2 56,57 . ...
The ability to scale two-dimensional (2D) material thickness down to a single monolayer presents a promising opportunity to realize high-speed energy-efficient memristors. Here, we report an ultra-fast memristor fabricated using atomically thin sheets of 2D hexagonal Boron Nitride, exhibiting the shortest observed switching speed (120 ps) among 2D memristors and low switching energy (2pJ). Furthermore, we study the switching dynamics of these memristors using ultra-short (120ps-3ns) voltage pulses, a frequency range that is highly relevant in the context of modern complementary metal oxide semiconductor (CMOS) circuits. We employ statistical analysis of transient characteristics to gain insights into the memristor switching mechanism. Cycling endurance data confirms the ultra-fast switching capability of these memristors, making them attractive for next generation computing, storage, and Radio-Frequency (RF) circuit applications.
... The ohmic behavior in the LRS attributes the formation of CF's in switching oxide layers during the SET process. However, in HRS the set cycle of the fitted I-V comprises of an Ohmic region (I V) and Child's law region (I V 2 ).This can be described as trap-controlled space charge limited conduction (SCLC) [23], [24] where V0's present in the switching oxide act as traps for the electrons. ...
We have reported resistive switching characteristics of Au/ZnO/Indium Tin oxide (ITO)/Polyethylene terephthalate (PET) flexible resistive memory device. The device was fabricated at room temperature which is compatible for flexible substrate. The presence of interfacial and filamentary switching operation depending on the operation cycles has been observed in the devices. The interfacial operation occurs at lower current as compared to the filamentary operation.
