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Proceedings ArticleDOI

Resistive Switching Behaviour of $\mathrm{PVP}/\mathrm{HfO}_{\mathrm{x}}$ Hybrid RRAM on Flexible Substrate

01 Apr 2020-
Abstract: Flexible devices have been in focus for their applications in wearable electronics, displays, sensors, and memory. $\mathrm{PVP}/\mathrm{HfO}_{\mathrm{x}}$ based hybrid resistive random access memory devices were demonstrated on flexible PET substrates to study their resistive switching characteristics and memory application. These RRAM devices exhibited decent repeatability of more than 100 cycles with excellent $I_{\mathrm{o}\mathrm{n}}/I_{\mathrm{off}}$ of ~106 at 0.2 V as read voltage. With retention time of more than 6000 s and reliable switching operation, the fabricated devices have potential to be embedded in flexible electronic applications. Moreover, conduction mechanism in devices was found to be ohmic at lower voltage levels in high resistance state (HRS) and space charge limited conduction at higher voltage levels, occurring mainly due to traps sites available in PVP and $\mathrm{HfO}_{\mathrm{x}}$ . The AFM image confirms the presence of pinholes at PVP surface which will eventually assist in filament formation.
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Journal ArticleDOI
TL;DR: This work provides an overview of the current understanding of bipolar-switching RRAM operation, reliability and scaling, and the stability of the low- and high-resistance states will be discussed in terms of conductance fluctuations and evolution in 1D filaments containing only a few atoms.
Abstract: With the explosive growth of digital data in the era of the Internet of Things (IoT), fast and scalable memory technologies are being researched for data storage and data-driven computation. Among the emerging memories, resistive switching memory (RRAM) raises strong interest due to its high speed, high density as a result of its simple two-terminal structure, and low cost of fabrication. The scaling projection of RRAM, however, requires a detailed understanding of switching mechanisms and there are potential reliability concerns regarding small device sizes. This work provides an overview of the current understanding of bipolar-switching RRAM operation, reliability and scaling. After reviewing the phenomenological and microscopic descriptions of the switching processes, the stability of the low- and high-resistance states will be discussed in terms of conductance fluctuations and evolution in 1D filaments containing only a few atoms. The scaling potential of RRAM will finally be addressed by reviewing the recent breakthroughs in multilevel operation and 3D architecture, making RRAM a strong competitor among future high-density memory solutions.

490 citations


Journal ArticleDOI
TL;DR: This manuscript describes the most recommendable methodologies for the fabrication, characterization, and simulation of RS devices, as well as the proper methods to display the data obtained.
Abstract: Resistive switching (RS) is an interesting property shown by some materials systems that, especially during the last decade, has gained a lot of interest for the fabrication of electronic devices, with electronic nonvolatile memories being those that have received the most attention. The presence and quality of the RS phenomenon in a materials system can be studied using different prototype cells, performing different experiments, displaying different figures of merit, and developing different computational analyses. Therefore, the real usefulness and impact of the findings presented in each study for the RS technology will be also different. This manuscript describes the most recommendable methodologies for the fabrication, characterization, and simulation of RS devices, as well as the proper methods to display the data obtained. The idea is to help the scientific community to evaluate the real usefulness and impact of an RS study for the development of RS technology. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

267 citations


Journal ArticleDOI
Abstract: The mechanisms of space-charge-limited (SCL) current in solids are discussed. The practical case is taken of a wide band-gap, high-resistivity material containing empty shallow trapping states but in which empty deep trapping states are eliminated by the mechanism of defect compensation described by L ongini and G reen (1956). One-dimensional and one-carrier (electron) current through a plane parallel crystal is considered for the case when one contact is ohmic and one contact is blocking. At small forward voltage, current occurs by the predominant mechanism of carrier diffusion and increases approximately as the exponential of applied voltage; in this range, current is very sensitive to temperature changes. At large forward voltage, current occurs by the predominant mechanism of carrier drift and, after a voltage threshold due to the work-function difference between anode and cathode metals, increases very nearly as the square of applied voltage; this result confirms the simplified analysis of M ott and G urney (1940) and is the solid-state analogue of the three-halves power law for space-charge-limited current in vacuum. In this range current varies as the inverse cube of crystal thickness and is relatively insensitive to temperature changes. Between these two current ranges a smooth transition occurs from a diffusion to a drift mechanism of current and a “virtual cathode” is established in the crystal; there is no evidence for the existence of a negative-resistance region during the transition as predicted by S kinner (1955). Simple and accurate analytic expressions are derived describing forward current-voltage characteristics in the exponential and square-law ranges; they show that, depending mainly on crystal thicknesses, high forward conductance or high forward resistance can be achieved. With a strongly blocking anode, reverse current is always very small and very high rectification ratios can be achieved. For current in the square-law range the Fermi-level is nearly constant through the crystal, except near the cathode and anode contacts. This justifies the distinction made by R ose (1955) between shallow traps, which lie above the Fermi-level and do not affect the form of the current-voltage characteristics, and deep traps, which lie below the Fermi-level and profoundly modify the current-voltage characteristics. The discussion is illustrated with numerical results calculated on the basis of an electron mobility of 1000 cm2/V-sec which is intermediate between the value of 200 cm2/V-sec for cadmium sulphide and 9300 cm2/V-sec for gallium arsenide. In conclusion, some possible applications are considered for space-charge-limited current in fundamental solid-state research.

133 citations


Journal ArticleDOI
24 Feb 2017-Small
TL;DR: Results directly confirm that CF formation is confined through the nanohole of graphene due to the localized cation injection, and the novel Cu/nanohole-graphene/HfO2 /Pt CBRAM device shows improvement of uniformity, endurance, and retention characteristics, because the cation injections is limited by the nanhole graphene.
Abstract: Conductive-bridge random access memory (CBRAM) is considered a strong contender of the next-generation nonvolatile memory technology. Resistive switching (RS) behavior in CBRAM is decided by the formation/dissolution of nanoscale conductive filament (CF) inside RS layer based on the cation injection from active electrode and their electrochemical reactions. Remarkably, RS is actually a localized behavior, however, cation injects from the whole area of active electrode into RS layer supplying excessive cation beyond the requirement of CF formation, leading to deterioration of device uniformity and reliability. Here, an effective method is proposed to localize cation injection into RS layer through the nanohole of inserted ion barrier between active electrode and RS layer. Taking an impermeable monolayer graphene as ion barrier, conductive atomic force microscopy results directly confirm that CF formation is confined through the nanohole of graphene due to the localized cation injection. Compared with the typical Cu/HfO2 /Pt CBRAM device, the novel Cu/nanohole-graphene/HfO2 /Pt device shows improvement of uniformity, endurance, and retention characteristics, because the cation injection is limited by the nanohole graphene. Scaling the nanohole of ion barrier down to several nanometers, the single-CF-based CBRAM device with high performance is expected to achieve by confining the cation injection at the atomic scale.

108 citations


Journal ArticleDOI
Abstract: Halide perovskite based resistive random-access memory (ReRAM) devices are emerging as a new class of revolutionary data storage devices because their switching material—halide perovskite—has received considerable attention in recent years. Among the electrical characteristics of the material, its current–voltage (I–V) hysteresis, which may occur due to defect formation and migration, means that ReRAM can employ halide perovskites as a resistive switching material. Many studies have been conducted on resistive switching materials; however, the investigation of halide perovskites for ReRAM devices is still in the early research stages; therefore, the application of halide perovskites in ReRAM devices is a topic worth studying. Herein, we introduce halide perovskites and their operating mechanism within a ReRAM device. Moreover, recent notable achievements along with future challenges have been reviewed.

52 citations