Resistive Switching Characteristics Research Articles

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

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

A novel nonvolatile memory device based on oxidized Ti3C2Tx MXene for neurocomputing application

MXenes have shown great potential application in new electronic devices owing to the unique surface properties and 2D structure, especially in the popular memory storage. In this work, Ti3C2Tx, one of the MXenes, is partially oxidized and used as the resistance layer to fabricate memristors with resistance switching characteristics and synapse characteristics. The device exhibits excellent bipolar resistance switching property based on the gradual formation and annihilation of the conductive filaments of oxygen vacancy cation, including enough on/off ratio (≈102), long cyclic endurance (>103 cycles) and retention time (>104 s). Furthermore, since oxygen vacancy cation migration is similar to the Ca2+ ion dynamics of biological synapses, the device successfully mimics biological synaptic functions such as paired-pulse facilitation (PPF), long-term potentiation (LTP) and long-term depression (LTD). This work provides the experimental and theoretical foundation for MXenes in memristor and artificial synapse filed, pushes the development of MXenes in neurocomputing application.

Resistive switching characteristics of interfacial device based on Bi2Ti2O7 film

To solve the problem of information storage and explore a new generation of memory, Au/Bi2Ti2O7/NiO/ITO (Indium tin oxide semiconductor) resistive variable memory is fabricated and its resistive switching characteristics are studied. The device has diode-like rectifier characteristics and shows good durability and stability under 100 cycles of read−and−write tests. At the reading voltage of 0.44 V, the resistive switching ratio of the device reaches 102. Combining the O 1 s spectrum of XPS and further analyzing the I − V double logarithmic curve, it is found that the conduction mechanism of the device is mainly related to the ohmic conduction mechanism and the space charge limiting current mechanism, and its resistive switching behavior is related to the migration of oxygen vacancies to change the interface barrier.

Investigation of Different Oxygen Partial Pressures on MgGa2O4-Resistive Random-Access Memory.

Different oxygen partial-pressure MgGa2O4-resistive RAMs (RRAMs) are fabricated to investigate the resistive switching behaviors. The X-ray photoelectron spectroscopy results, set voltage, reset voltage, cycling endurance, and retention time are drawn for comparison. With the increasing oxygen ratio gas flow, the resistive switching characteristics of MgGa2O4 RRAM are drastically elevated by changing the fabrication conditions of the RS layer. Moreover, we portray a filament model to explain the most likely mechanism associated with the generation and rupture of conductive filaments composed of oxygen vacancies. The formation of the interfacial layer (AlO x ) and the participation of the Joule heating effect are included to explain the highly distributed high-resistance state (HRS). The high randomness among switching cycles for memory application should be prevented, but it is suitable for the physical unclonable function. The relationship between HRS and the next time set voltage shows a strong correlation, and the conduction mechanisms of the low-resistance state (LRS) and HRS correspond to ohmic conduction and space charge-limited conduction, respectively. Meanwhile, the RRAM undergoes 10,000 s retention tests, and the two resistance states can be distinguished without obvious alternation or degradation. A favorable cycling endurance and retention time achieved by optimizing the fabrication parameters of Al/MgGa2O4/Pt RRAM have the potential for nonvolatile memristors and information security applications.

Oxide thickness-dependent resistive switching characteristics of Cu/HfO2/Pt ECM devices

HfO2-based resistive random-access memory devices are promising candidates for new memory and computing applications. Hereby, scaling of the devices is a key issue, where overall fundamental switching and conduction mechanisms can be easily influenced by changes in the oxide layer thickness. This work addresses the oxide thickness-dependent resistive switching characteristics in Cu/HfO2/Pt memory devices through bipolar DC switching characterization. Forming, reset, and set characteristics are investigated depending on the oxide layer thickness, revealing a significant difference for thicker compared to thinner films. Thicker samples tend to show a more abrupt reset behavior and a larger set voltage variance, while for thinner samples, a more gradual reset behavior and a low set variance is found. These phenomena can be explained by a model based on thermally assisted electrochemical metallization. Furthermore, to understand the conduction mechanism of the devices, current–voltage curves of the set process were investigated. The devices are found to have an Ohmic conduction mechanism in the lower voltage region generally, while thinner samples tend to show an additional space-charge-limited current conduction mechanism in a higher voltage region.

Dual Resistive Switching Performance Derived from Ionic Migration in Halide Perovskite Based Memory

Herein, we report an environmentally stable and friendly halide perovskite based resistive random access memory device with an Ag/PMMA/(PMA)2CuBr4/FTO (PMMA = poly(methyl methacrylate); PMA = C6H5CH2NH3) architecture. The device exhibits the coexistence of two bipolar resistive switching modes, including counterclockwise and clockwise switching characteristics. The devices with both switching modes show stable endurance (>100 cycles) and long retention performance (>104 s). By applying a suitable electrical stimulation, the counterclockwise and clockwise switching behaviors are interconvertible. Furthermore, the Au/PMMA/(PMA)2CuBr4/FTO and Ag/(PMA)2CuBr4/FTO devices were fabricated to verify the origin of dual resistive switching behaviors. The similar dual resistive switching behaviors after electroforming processes of three types of memory devices suggest that the interconvertible dual resistive switching characteristics could be attributed to the ionic migration in the (PMA)2CuBr4 perovskite layer.

Tri-level resistive switching characteristics and conductive mechanism of HfO<sub>2</sub>/NiO<sub><i>x</i></sub>/HfO<sub>2</sub> stacks

<sec>With the extensive integration of portable computers and smartphones with “Internet of Things” technology, further miniaturization, high reading/writing speed and big storage capacity are required for the new-generation non-volatile memory devices. Compared with traditional charge memory and magnetoresistive memory, resistive random access memory (RRAM) based on transition metal oxides is one of the promising candidates due to its low power consumption, small footprint, high stack ability, fast switching speed and multi-level storage capacity.</sec><sec>Inspired by the excellent resistive switching characteristics of NiO and HfO<sub>2</sub>, NiO<sub><i>x</i></sub> films are deposited by magnetron sputtering on the Pt<inline-formula><tex-math id="Z-20230629144836">\begin{document}$\langle111\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144836.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144836.png"/></alternatives></inline-formula> layer and the polycrystalline HfO<sub>2</sub> film, respectively. Their microstructures, resistive switching characteristics and conductive mechanisms are studied. X-ray diffractometer data show the <inline-formula><tex-math id="Z-20230629144852">\begin{document}$\langle111\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144852.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144852.png"/></alternatives></inline-formula> preferred orientation for the NiO<sub><i>x</i></sub> film deposited on the Pt<inline-formula><tex-math id="Z-20230629144904">\begin{document}$\langle111\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144904.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144904.png"/></alternatives></inline-formula> layer but the <inline-formula><tex-math id="Z-20230629144913">\begin{document}$\langle100\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144913.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230629144913.png"/></alternatives></inline-formula> preferred one for the film deposited on the polycrystalline HfO<sub>2</sub> layer. X-ray photoelectron depth profile of Ni 2p core level reveals that the NiO<sub><i>x</i></sub> film is the mixture of oxygen-deficient NiO and Ni<sub>2</sub>O<sub>3</sub>. NiO<sub><i>x</i></sub>(111) films show bipolar resistive switching (RS) characteristics with a clockwise current-voltage (<i>I-V</i>) loop, but its ratio of the high resistance to the low resistance (<i>R</i><sub>H</sub>/<i>R</i><sub>L</sub>) is only ~10, and its endurance is also poor. The NiO<sub><i>x</i></sub>(200)/HfO<sub>2</sub> stack exhibits bipolar RS characteristics with a counterclockwise <i>I-V</i> loop. The <i>R</i><sub>H</sub>/<i>R</i><sub>L</sub> is greater than 10<sup>4</sup>, the endurance is about 10<sup>4</sup> cycles, and the retention time exceeds 10<sup>4</sup> s. In the initial stage, the HfO<sub>2</sub>/NiO<sub><i>x</i></sub>(200)/HfO<sub>2</sub> stack shows similar bi-level RS characteristics to the NiO<sub><i>x</i></sub>(200)/HfO<sub>2</sub> stack. However, in the middle and the last stages, its <i>I-V</i> curves gradually evolve into tri-level RS characteristics with a “two-step Setting process” in the positive voltage region, showing potential applications in multilevel nonvolatile memory devices and brain-like neural synapses. Its <i>I-V</i> curves in the high and the low resistance state follow the relationship of ohmic conduction (<inline-formula><tex-math id="Z-20230714031758-1">\begin{document}$ I \propto V $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230714031758-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230714031758-1.png"/></alternatives></inline-formula>), while the <i>I-V</i> curves in the intermediate resistance state are dominated by the space-charge-limited-current mechanism (<inline-formula><tex-math id="Z-20230714031758-2">\begin{document}$ I \propto V^2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230714031758-2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230331_Z-20230714031758-2.png"/></alternatives></inline-formula>). The tri-level RS phenomena are attributed to the coexistence of the oxygen-vacancy conductive filaments in the NiO<sub><i>x</i></sub>(200) film and the space charge limited current in the upper HfO<sub>2</sub> film.</sec>

Resistive switching characteristics of HfO<sub><i>x</i></sub>-based resistance random access memory under photoelectric synergistic regulation

Cu/HfO<sub><i>x</i></sub>/Pt and Cu/HfO<sub><i>x</i></sub>-ZnO/Pt resistance random access memory (RRAM) devices are prepared by magnetron sputtering. The results show that the Cu/HfO<sub><i>x</i></sub>/Pt device has the stable bipolar resistive switching characteristics, good retention (as long as 10<sup>4</sup> s), and a switching ratio greater than 10<sup>3</sup>. The current conduction mechanism of HfO<sub><i>x</i></sub> device is ohmic conduction at low resistance, while space charge limited current (SCLC) mechanism dominates at high resistance, and the conductive filament is composed of oxygen vacancies. Owing to the low content and random distribution of oxygen defects in the HfO<sub><i>x</i></sub> film, the endurance and uniformity of the device are poor. Compared with HfO<sub><i>x</i></sub> device, HfO<sub><i>x</i></sub>-ZnO device exhibits lower operating voltage and better uniformity and stability. The main reason is that ZnO material has smaller formation energy of oxygen vacancy, which can produce more oxygen defects under electric field to participate in the resistive switching behavior of the device, thereby reducing the operating voltage and improving the uniformity of the device. In addition, owing to the existence of the interface between HfO<sub><i>x</i></sub> and ZnO film, the random distribution of oxygen defects is inhibited, that is, the random fracture and formation of conductive filament are inhibited, which is beneficial to improving the uniformity of the device. In addition, the resistive switching behaviors of Cu/HfO<sub><i>x</i></sub>/Pt and Cu/HfO<sub><i>x</i></sub>-ZnO/Pt RRAM devices under different intensities of 255 nm ultraviolet illumination are studied. For Cu/HfO<sub><i>x</i></sub>/Pt device, the light of 255 nm wavelength shows little effect on its resistive switching characteristics. For the Cu/HfO<sub><i>x</i></sub>-ZnO/Pt RRAM device, the operating voltage and stability of the device can be improved by increasing the light intensity. Although the switching ratio of the device decreases with the increase of light intensity, the device can exhibit multiple resistance states by adjusting different light intensities to achieve multi-level storage. Finally, the analysis of the <i>I</i>-<i>V</i> curves of the devices indicates that the two types of devices show similar resistive switching mechanisms under the illumination of light or no light, which can be explained by the resistive switching mechanism of oxygen vacancy conductive filament. Therefore, a physical model based on the oxygen vacancy conductive filament is established to explain the resistive switching behavior of the device in this paper.

Resistive Switching Characteristics of HfO x -Based Memristor by Inserting GeTe Layer

In this study, by inserting a GeTe layer as the current suppression layer and the heating layer, we improved the forming yield (~91%), memory window (> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{3}}$ </tex-math></inline-formula> ), and resistive switching uniformity of HfOx-based memristor. Two forming polarities including positive forming (PF) bias and negative forming (NF) bias were applied to study resistive switching characteristics. After the PF process, the device shows unstable and volatile behavior that is related to ovonic threshold switching (OTS) characteristic. Negative differential resistance (NDR) phenomenon was observed during the NF process. In addition, the device exhibits nonvolatile characteristic, multilevel resistive switching, and good endurance (> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{5}}$ </tex-math></inline-formula> ) after the NF process. We also proposed a corresponding physical model to explain two resistive switching characteristics of the NF and PF processes.

Intensive harmonized synapses with amorphous Cu2O-based memristive using ultrafine Cu nanoparticle sublayers formed via atomically controlled electrochemical pulse deposition.

Resistive random-access memory (RRAM) devices have significant advantages for neuromorphic computing but have fatal problems of uncontrollability and abrupt resistive switching behaviors degrading their synaptic performance. In this paper, we propose the electrochemical design of an active Cu2O layer containing a strategic sublayer of ultrafine Cu nanoparticles (U-Cu NPs) to form uniformly dispersed conducting filaments, which can effectively improve the reliability for analog switching of RRAM-based neuromorphic computing. The electrochemical pulse deposited (EPD) U-Cu NPs are linked to the bottom electrode through a semi-conductive path within the bottom Cu2O layer, since the EPD is preferentially carried out on the conductive sites. All Cu2O films with U-Cu NPs are developed in situ in the single electrolyte bath without any pause. The proposed U-Cu NPs can concentrate the external electric field and can generate conductive filament paths for analog resistive switching. The applied electric field was uniformly spread to U-Cu NPs at the center of the active layer and displays resistive switching behavior via multiple conductive filaments. This shows a strong harmony between the resistance-switching characteristics and the analog operation of the active layer. This RRAM device shows outstanding gradual analog switching, great linearity, dynamic range, endurance, precision, speed, and retention characteristics simultaneously and adequately for neuromorphic computing by realizing multiple weak filament-type operation.

Complementary Resistive Switching in ZnO/Al2O3 Bi-Layer Devices

This paper reports the complementary resistive switching (CRS) characteristics exhibited by Au/ZnO/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /Fluorine doped tin oxide (FTO) bilayer device for the first time, where both ZnO and Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> are active switching layers exhibiting resistive switching properties. The I-V characteristics of the device initially show bipolar resistive switching (BRS) for a few cycles (∼12) before permanently switching to CRS with the extension of SET voltage. The stable CRS state of the device exhibits a high current of ∼500 μA during the ON-state and low current of 3x10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> A during OFF-state at low input voltages (-0.5 V to 0.5V) enables the proposed device suitable to use in crossbar array to mitigate the sneak path current. The device performance to write and read processes is evaluated with pulses of magnitudes ∼|2.5| V and 1.3 V, respectively, and showed a ∼ 60μA difference in read-out current between data bits 0 and 1. Similarly, the device's power consumption is also measured to elucidate that the device is suitable to use as a memory unit with power consumption in the order of microwatts (μW). Further, the possible switching mechanism is demonstrated based on oxygen vacancies migration.

Contrasting analog and digital resistive switching memory characteristics in solution-processed copper(i) thiocyanate and its polymer electrolyte-based memristive devices

Analog and digital resistive switching characteristics of ITO/CuSCN/Cu and ITO/Cu-SPE/Cu memristive devices.

Effect of stoichiometry on the resistive switching characteristics of STO resistive memory

Herein, we modify the stoichiometry of an SrTiOx resistive switching layer to fabricate a memristor with a high ON/OFF current ratio and high data retention capability.

Solution-based in situ deposition of Sb2S3 from a single source precursor for resistive random-access memory devices

A one-step, scalable, reproducible, low-temperature, and in situ solvothermal deposition method has been established for the growth of Sb2S3 on FTO using [Sb{S2P{O(Pr)2}3] precursor. The Ag/Sb2S3/FTO device demonstrated low operating voltage and excellent resistive switching characteristics.

Resistive switching characteristics of W/TiO2/ITO devices

Materials with resistance-switching properties are proving to be promising for the novel non-volatile memories-resistive random-access memory (ReRAM). Despite extensive research on electric field-induced resistance switching, there are diverse opinions about its reliability and working mechanism. In this work, we analysed the impact of SET and RESET voltages on the switching characteristics and the possible current conduction mechanism of W/TiO2/ITO devices. By simple solution processing and spin coating, titanium dioxide thin films were grown on ITO, glass, silicon, and quartz substrates. The precursor and solvent used for the synthesis of the active layer were titanium isopropoxide and ethanol, respectively. Polycrystalline films with an anatase structure were formed after annealing at 400 °C with a 20 nm average crystallite size, as evidenced by X-ray diffraction patterns. The crystalline nature of the fabricated film has been found to improve on annealing. Using Raman spectroscopy, the chemical bonding states of the film were studied. A UV–visible spectrometer study confirms that anatase TiO2 possesses an indirect band gap transition with a 3.42 eV band gap. The device shows reversible, reproducible, stable, and bipolar resistance-switching behaviour as indicated by current–voltage (I-V) measurements, and it was found that there exists a minimum voltage (∼-4 V) to set the device into an ON state. Compared to crystalline TiO2, theamorphous active layer offers much better switching characteristics, such as good cyclic endurance with a Roff-Ronratio ∼ 10.The current–voltage characteristics were fitted to various carrier transport mechanismssuch as Ohmic conduction, Schottky emission (SE), Space-charge-limited conduction (SCLC), and Poole-Frenkel emission (PF). Among these, the ohmic and SE mechanisms were detected at low and high fields, respectively. Schottky barrier modulation at the metal-oxide interface has been identified as the motive for switching.

Low power highly flexible BiFeO3-based resistive random access memory (RRAM) with the coexistence of negative differential resistance (NDR).

We demonstrated the resistive random access memory characteristics for Cu (top contact)/BFO/PMMA (active layer)/ITO (bottom electrode)/PET sheet as a flexible substrate device configuration. The device showed non-volatile bipolar resistive switching characteristics with good repeatability and the coexistence of NDR for 100 cycles or more with 0.28/3.43 mW power consumption for 1st/100th cycles. The device retains its read state for 104 s or more and switches from LRS to HRS or vice versa for 103 cycles with a pulse width of 100 ms for a write-read-erase-read pulse without affecting the memory characteristics. The Weibull distribution suggests that a set state is more stable than the reset state with shape factor β = 25.20. The device follows Ohmic behavior for the lower applied external field and Child square and Schottky emission for the higher external fields. The Joule heating, Sorets, and Fick's forces are responsible for the formation and rupturing of ionic filament. The coexistence of resistive switching and flexible strength of the device sustains the bending curvature of infinity, 0.2 cm, 1 cm, 1.7 cm, and 2.2 cm. The memory characteristics are retained under tensile conditions for 100 cycles or more. More interestingly, the power consumption for sustaining the NDR region with bending (19 μW) is much lower than without bending (0.19 mW). Thus, this study provides the possibility of integrating BFO with flexible substrates suitable for hybrid organic/inorganic memory structures.

Low-voltage resistive switching characteristics of nano-bowl-like NiO arrays

我们利用单层胶体球自组装模板结合电化学沉积和磁控溅射方法在覆盖Pt导电层的白云母衬底上制备了NiO纳米碗状阵列(nano-bowl-like NiO array, 简称nb-NiO). 每个NiO纳米碗高约450 nm, 碗口直径约450 nm, 碗底厚约150 nm, 在Pt导电层上密排形成二维阵列. 在nb-NiO上覆盖厚约20 nm的HfO2薄膜层, 然后制备Ag或Pt点电极形成Ag(Pt)/HfO2/nb-NiO/Pt堆栈结构器件. 器件在小于± 0.4 V的翻转电压下即在高低电阻态之间周期性可逆跳变, 表现出良好的电阻开关特性: 器件在高低电阻态之间翻转的时间< 8.7 μs; 初始高/低电阻比值约为10^4, 连续测试1500个周期后, 高/低电阻值比依然>10^3. 断电后, 器件稳定在高(低)电阻态的时间均>10^4 s. 纳米碗状阵列结构使得NiO厚度在150 ~ 450 nm内周期性连续变化; 由于氧空位导电细丝更易在厚度较小的纳米碗底部导通, 因此碗状阵列结构使得原本随机分布的氧空位导电细丝通道具有了局域有序性, 进而提高了器件电阻开关性能的稳定性. HfO2薄膜层降低了器件漏电流, 提高了器件的高/低电阻值比. Ag电极与氧离子的氧化还原反应加速了氧空位导电细丝通道的导通和断裂, 从而降低了翻转电压.

Forming-free plant resistive random access memory based on the Coulomb blockade effect produced by gold nanoparticles.

Resistive random access memory has been widely studied as a powerful candidate for building future memories and realizing high-efficiency artificial neuromorphic systems. In this paper, gold nanoparticles (Au NPs) are doped in a leaf solution of Scindapsus aureus (SA) as the active layer to fabricate Al/SA:Au NPs/ITO/glass resistive random access memory. The device exhibits stable bipolar resistance switching characteristics. More importantly, the device's multilevel storage capabilities and synaptic potentiation and depression behaviour have been proven. Compared with the device without doped Au NPs in the active layer, the device has a higher ON/OFF current ratio, which is attributed to the Coulomb blockade effect caused by the Au NPs. The device plays an important role in realizing high-density memory and efficient artificial neuromorphic systems.

Resistive switching behaviors of cobalt oxide films with structural change by post-thermal annealing

We have studied the resistive switching behaviors of cobalt oxide films with structural changes by a post-thermal annealing process. During post-annealing at temperatures of 500–700 °C for the CoOx films deposited by ultra-high-vacuum RF magnetron sputtering, two structural phases of CoO and Co3O4 were modulated by selection of ambient N2 or O2 gases. As a device application of these films, the resistive random-access memory (ReRAM) structures of p+-Si/CoOx/Ti/Au were fabricated with CoO or Co3O4 films by post-annealing at 700 °C under N2 and O2 atmosphere, respectively. The resistive switching characteristics of the CoO device appeared much better than that of the Co3O4 device, also showing good uniformity from a cumulative probability distribution, long non-volatile retention characteristics of 104 s, good endurance of ∼100 cycles, and an excellent current ratio of 104. These results demonstrate the method to provide stable and good resistive switching properties of sputtered CoO films using the phase selection during post-thermal annealing.

Improved resistive switching characteristics in the p+-Si/ZnO:Al/Ni heterojunction device

Improved resistive switching characteristics in the p+-Si/ZnO:Al/Ni heterojunction device