Resistive Switching Memory Research Articles

The light-modified resistance switching of BaTiO3/ZnO films

A light-modified resistance switching (RS) memory device with BaTiO3 / ZnO structure is fabricated by radio frequency magnetron sputtering technology. The device exhibits stable resistive switching behavior in the dark and under illumination, respectively. In the dark, the device’s high/low resistance ratio ([Formula: see text] / [Formula: see text] is more than 104 at 0.1 V read voltage, and the set/reset voltage ([Formula: see text] < 0.4 V, [Formula: see text] > −0.2 V) is low. The RS of the device can be modulated by white light. When the device is irradiated by white light with intensity of 250 uw/cm2, the high/low resistance ratio is modulated from 104 to 102, and the set/reset voltage ([Formula: see text] < 0.3 V, [Formula: see text] > −0.2 V) is still low.

Oxygen vacancy engineering of TaO x -based resistive memories by Zr doping for improved variability and synaptic behavior

Resistive switching (RS) devices are promising forms of non-volatile memory. However, one of the biggest challenges for RS memory applications is the device-to-device (D2D) variability, which is related to the intrinsic stochastic formation and configuration of oxygen vacancy (VO) conductive filaments (CFs). In order to reduce the D2D variability, control over the formation and configuration of oxygen vacancies is paramount. In this study, we report on the Zr doping of TaO x -based RS devices prepared by pulsed-laser deposition as an efficient means of reducing the VO formation energy and increasing the confinement of CFs, thus reducing D2D variability. Our findings were supported by XPS, spectroscopic ellipsometry and electronic transport analysis. Zr-doped films showed increased VO concentration and more localized VOs, due to the interaction with Zr. DC and pulse mode electrical characterization showed that the D2D variability was decreased by a factor of seven, the resistance window was doubled, and a more gradual and monotonic long-term potentiation/depression in pulse switching was achieved in forming-free Zr:TaO x devices, thus displaying promising performance for artificial synapse applications.

Organic Memory and Memristors: From Mechanisms, Materials to Devices

AbstractFacing the exponential growth of data digital communications and the advent of artificial intelligence, there is an urgent need for information technologies with huge storage capacity and efficient computing processing. However, the traditional von Neumann architecture and silicon‐based storage and computing technology will reach their limits and cannot meet the storage requirements of ultrasmall size, ultrahigh density, and memory computing. Considering these issues, organic material resistance switching memory and memristor devices have become promising candidates for high‐density storage, logic computing, and neuromorphic computing because of their advantages of fast speed, high energy efficiency, nonvolatile storage, and low cost. In this article, the working mechanism, material design strategy, and device performance of organic memory and memristors are reviewed.

Modeling electrical conduction in resistive-switching memory through machine learning

Traditional physical-based models have generally been used to model the resistive-switching behavior of resistive-switching memory (RSM). Recently, vacancy-based conduction-filament (CF) growth models have been used to model device characteristics of a wide range of RSM devices. However, few have focused on learning the other-device-parameter values (e.g., low-resistance state, high-resistance state, set voltage, and reset voltage) to compute the compliance-current (CC) value that controls the size of CF, which can influence the behavior of RSM devices. Additionally, traditional CF growth models are typically physical-based models, which can show accuracy limitations. Machine learning holds the promise of modeling vacancy-based CF growth by learning other-device-parameter values to compute the CC value with excellent accuracy via examples, bypassing the need to solve traditional physical-based equations. Here, we sidestep the accuracy issues by directly learning the relationship between other-device-parameter values to compute the CC values via a data-driven approach with high accuracy for test devices and various device types using machine learning. We perform the first modeling with machine-learned device parameters on aluminum-nitride-based RSM devices and are able to compute the CC values for nitrogen-vacancy-based CF growth using only a few RSM device parameters. This model may now allow the computation of accurate RSM device parameters for realistic device modeling.

Polymer/TiO2 Nanorod Nanocomposite Optical Memristor Device

Modulation of resistive switching memory by light opens the route to new optoelectronic devices that can be controlled both optically and electronically. Applications include integrated circuits with memory elements switchable by light and neuromorphic computing with optically reconfigurable and tunable synaptic circuits. We report on a unique nanocomposite resistive switching material and device made from a low concentration (∼0.1% by mass) of titanium dioxide nanorods (TiO2-NRs) embedded within the azobenzene polymer, poly(disperse red 1 acrylate, PDR1A). The device exhibits both reversible electronic memristor switching and reversible polarization-dependent optical switching. Optical irradiation by circularly polarized light causes a trans-cis photochemical isomerization that modifies the conformation and orientation of the photoactive azo-unit within the polymer. The resulting expansion of the composite (PDR1A/TiO2-NR) polymer film modifies the conduction pathway, facilitated by the presence of the TiO2-NRs, as a semiconductor material, through the (PDR1A/TiO2-NR) polymer film, which provides a sensitive means to control resistive switching in the device. The effect is reversible by changing the polarization state of the incident light. A charge-flux memristor model successfully reproduces the current-voltage hysteresis loops and threshold switching properties of the device, as well as the effect of the illumination on the electrical characteristics.

Fully Transparent and Sensitivity-Programmable Amorphous Indium-Gallium-Zinc-Oxide Thin-Film Transistor-Based Biosensor Platforms with Resistive Switching Memories

This paper presents a fully transparent and sensitivity-programmable biosensor based on an amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) with embedded resistive switching memories (ReRAMs). The sensor comprises a control gate (CG) and a sensing gate (SG), each with a resistive switching (RS) memory connected, and a floating gate (FG) that modulates the channel conductance of the a-IGZO TFT. The resistive coupling between the RS memories connected to the CG and SG produces sensitivity properties that considerably exceed the limit of conventional ion-sensitive field-effect transistor (ISFET)-based sensors. The resistances of the embedded RS memories were determined by applying a voltage to the CG–FG and SG–FG structures independently and adjusting the compliance current. Sensors constructed using RS memories with different resistance ratios yielded a pH sensitivity of 50.5 mV/pH (RCG:RSG = 1:1), 105.2 mV/pH (RCG:RSG = 2:1), and 161.9 mV/pH (RCG:RSG = 3:1). Moreover, when the RCG:RSG = 3:1, the hysteresis voltage width (VH) and drift rate were 54.4 mV and 32.9 mV/h, respectively. As the increases in VH and drift rate are lower than the amplified sensitivity, the sensor performs capably. The proposed device is viable as a versatile sensing device capable of detecting various substances, such as cells, antigens, DNA, and gases.

Role and optimization of thermal rapid annealing in Ta/TaOx/Ru based resistive switching memory

The performance of resistive switching (RS) device based on sandwich structure is greatly affected by the characteristics of the RS layer, electrode, and interface. In this work, the effect of rapid thermal annealing (RTA) (300 °C for 120 s) on the RS performance of Ta/TaOx/Ru device was investigated. The discrete distribution in high resistance state (HRS) and low resistance state (LRS) was suppressed after RTA. Meanwhile, the endurance in oxygen RTA is higher 104 times than that of vacuum RTA. The optimized oxygen RTA is contributed to change the microstructure of TaOx (amorphous to nanocrystal), providing the local conductive path, and implant oxygens in top electrode (TE) Ta, acting as an oxygen source (reservoir). It is shown that the nanocrystal TaOx and the oxygen content in TE are intrinsically crucial to the RS behavior and the simple low temperature oxygen RTA is a powerful technique to optimize the RS performance.

Designing zero-dimensional dimer-type all-inorganic perovskites for ultra-fast switching memory

Resistive switching memory that uses halide perovskites (HP) has been considered as next-generation storage devices due to low operation voltage and high on/off ratio. However, the memory still faces challenges for stable operation with fast switching speed, which hinders the practical application. Thus, it should be considered from the stage of designing the HP for memory applications. Here, we design the perovskite memory using a high-throughput screening based on first-principles calculations. Total 696 compositions in four different crystal structures are investigated and essential parameters including stability, vacancy formation, and migration are considered as the descriptor. We select dimer-Cs3Sb2I9 as an optimal HP for memory; the device that uses dimer-Cs3Sb2I9 has ultra-fast switching speed (~20 ns) compared to the device that uses layer-Cs3Sb2I9 (>100 ns). The use of lead-free perovskite avoids environmental problems caused by lead in perovskite. These results demonstrate the feasibility to design the memory with ultra-fast switching speed.

Voltage-Tunable Ultra-Steep Slope Atomic Switch with Selectivity over 1010.

Atomic switch-based selectors, which utilize the formation of conductive filaments by the migration of ions, are researched for cross-point array architecture due to their simple structure and high selectivity. However, the difficulty in controlling the formation of filaments causes uniformity and reliability issues. Here, a multilayer selector with Pt/Ag-doped ZnO/ZnO/Ag-doped ZnO/Pt structure by the sputtering process is presented. A multilayer structure enables control of the filament formation by preventing excessive influx of Ag ions. The multilayer selector device exhibits a high on-current density of 2 MA cm-2 , which can provide sufficient current for the operation with the memory device. Also, the device exhibits high selectivity of 1010 and a low off-current of 10-13 A. The threshold voltage of selector devices can be controlled by modulating the thickness of the ZnO layer. By connecting a multilayer selector device to a resistive switching memory, the leakage current of the memory device can be reduced. These results demonstrate that a multilayer structure can be used in a selector device to improve selectivity and reliability for use in high-density memory devices.

Antireflective Self-Cleaning TiO2 Coatings for Solar Energy Harvesting Applications

Titanium(IV) oxide (TiO2, titania) is well-known for its excellent photocatalytic properties, wide bandgap, chemical resistance, and photostability. Nanostructured TiO2 is extensively utilized in various electronic and energy-related applications such as resistive switching memory devices, flat panel displays, photodiodes, solar water-splitting, photocatalysis, and solar cells. This article presents recent advances in the design and nanostructuring of TiO2-containing antireflective self-cleaning coatings for solar cells. In particular, the energy harvesting efficiency of a solar cell is greatly diminished by the surface reflections and deposition of environmental contaminants over time. Nanostructured TiO2 coatings not only minimize reflection through the graded transition of the refractive index but simultaneously improve the device’s ability to self-clean and photocatalytically degrade the pollutants. Thus, novel approaches to achieve higher solar cell efficiency and stability with pristine TiO2 and TiO2-containing nanocomposite coatings are highlighted herein. The results are compared and discussed to emphasize the key research and development shortfalls and a commercialization perspective is considered to guide future research.

Refining the Negative Differential Resistance Effect in a TiOx-Based Memristor.

The N-type negative difference resistance (NDR) is characterized by the peak/valley voltage (Vp/Vv) and the corresponding current (Ip/Iv). The N-type NDR is observed in the resistive switching (RS) memory device of Ag|TiO2|F-doped SnO2 at room temperature. After the TiO2 film is equipped with a nanoporous array, the ∼1.2 V gap voltage between Vp and Vv is effectively downscaled to ∼0.5 V, and the gap current of ∼7.23 mA between Ip and Iv is improved to ∼30 mA. It demonstrates that a lower power consumption and faster switching time of the NDR can be obtained in the memristor. Compensations and synergies among the nanoscale conduction filaments (OH-, Ag+, and Vo) are responsible for the refining NDR behavior in our devices. This work provides an efficient method to construct a high-performance N-type NDR effect at room temperature and gives a new horizon on the coexistence of this type of NDR effect and RS memory behaviors.

Coexistence of memory and threshold switching behaviors in natural milk-based organic memristor

Natural biomaterials have attracted great interest for the fabrication of biocompatible memristors. Here, dense and smooth milk films were deposited on the Pt/SiO2/Si substrate by spin-coating method and resistive switching (RS) devices based milk films with the configuration of Ag/milk/Pt/SiO2/Si are fabricated for the first time. Furthermore, memory RS (MRS) and threshold RS (TRS) effects coexist in the devices, which can be controlled by appropriately setting the compliance current (I cc). The current conduction mechanisms of the devices with MRS and TRS effects are controlled by typical trap-controlled space charge limited current (SCLC) conduction and filamentary conduction mechanism. The good RS performances of the milk-based devices make them promising for sustainable bioelectronics and novel logic device applications.

Computational Study of the Curviness Percolation Threshold in Nanotube/Nanowire Networks for Flexible and Transparent Conductors

Two-dimensional (2D) or quasi-2D networks of one-dimensional (1D) nanoelements, such as carbon nanotubes, metal nanowires, and graphene nanoribbons, have attracted significant research interest recently for next-generation flexible and transparent conductors, as a replacement for indium tin oxide (ITO), which suffers from brittleness, scarcity, high cost, and slow deposition. These nanotube/nanowire networks can be used in many device applications, such as touch screens, flat panel displays, solar cells, light-emitting diodes (LEDs), and wearable flexible electronics. They also have applications in thin film transistors and resistive switching memory.At the high optical transmittance values required for flexible and transparent conductors, the electrical properties of nanotube/nanowire networks are governed by percolation transport, which deals with the formation of long-range connectivity in random networks. As a result, Monte Carlo simulations need to be employed to theoretically calculate, predict, and optimize the electrical properties of 1D nanoelement networks [1,2]. In most computational work, nanotubes/nanowires in such networks have been modeled as straight sticks. However, experimentally deposited nanotubes/nanowires exhibit some degree of curviness.There has been some computational work on the density percolation threshold of carbon nanotube/nanofiber networks and nanocomposites at fixed curviness, where the network undergoes an insulator-to-conductor phase transition [3-7]. These studies have shown that curviness increases the density percolation threshold of random networks. However, the curviness percolation threshold at fixed density has not been investigated.In this work, we employ Monte Carlo simulations to compute the curviness percolation threshold in 2D networks consisting of curvy nanotubes or nanowires. We generate curvy nanotubes/nanowires using third order Bezier curves, which are parametric functions specified by the values of four control points. We introduce the concept of the curviness angle, which puts a geometrical constraint on the locations of the two intermediate control points of the Bezier curve, and hence on the statistical distribution of nanotube/nanowire curviness in the network. For a more universal definition of the degree of curviness, we define the curl ratio as the ratio of the actual length of the nanotube/nanowire to the effective straight length between its two ends. Using simulation data, we establish an empirical relationship between curviness angle and curl ratio.We first study the percolation probability as a function of curviness angle at fixed density for randomly distributed nanotube/nanowire networks. We extract the curviness percolation threshold at fixed density characterized by the critical curviness angle and the critical curl ratio using finite size scaling analysis. We find that the critical curviness angle and curl ratio increase with increasing density. We also find that there is a minimum (maximum) density below (above) which the percolation probability is 0 (1) regardless of the curviness angle. Second, we find that nanotube/nanowire alignment significantly changes the curviness percolation threshold, resulting in a reversal of the percolation probability versus curviness angle curve.These results show that nanotube/nanowire curviness plays a significant role in determining the percolation threshold in 2D or quasi-2D networks, films, or nanocomposites consisting of 1D nanoelements. These results further show that computational studies are an essential tool for providing insights into the insulator-to-conductor transition in nanotube/nanowire networks, which are promising candidates for a wide range of applications such as flexible transparent conductors, thin film transistors, and resistive switching memory.[1] N. Fata, S. Mishra, Y. Xue, Y. Wang, J. Hicks, and A. Ural, J. Appl. Phys. 128, 124301 (2020).[2] J. Hicks, J. Li, C. Ying, and A. Ural, J. Appl. Phys. 123, 204309 (2018).[3] Y. B. Yi, L. Berhan, and A. M. Sastry, J. Appl. Phys. 96, 1318 (2004).[4] L. Berhan and A. M. Sastry, Phys. Rev. E 75, 041121 (2007).[5] C. Li and T.-W. Chou, Appl. Phys. Lett. 90, 174108 (2007).[6] Y. Yu, S. Song, Z. Bu, X. Gu, G. Song, and L. Sun, J. Mater. Sci. 48, 5727 (2013).[7] H. M. Ma, X.-L. Gao, and T. B. Tolle, Appl. Phys. Lett. 96, 061910 (2010). Figure 1

Electrolyte Incorporation in Anodic Memristors

In the field of semiconductor electronics, the metal-oxide- semiconductor technology (CMOS) has attracted a lot of scientific attention as one of the main representatives for non-volatile memories. The development of memory systems is crucial for a fast data processing for which purpose namely microprocessors are used, following the miniaturization trends at the same time. However, the limits of CMOS technology are already exhausted in terms of power consumptions, leakage current and processing speed. Surely, novel non-volatile elements and materials are necessary to fulfill such demands and memristors are in the front as the most promising candidates.Valve metals and their oxides are frequently used as the main constitutes of metal-insulator-metal (MIM) memristive structures. Recently, Hf and Ta became the most studied valve metals playing an important role in the next-generation of thin film micro- and nano-electronic devices primarily due to applications in redox-based resistive switching memories (ReRAMs), logic circuits, sensors and artificial neural networks. The operating mechanism of memristors is based on the electric field assisted conductive filaments (CFs) formation due to the ionic drift inside the insulating oxide layer. The understanding of CFs formation is a key point to ensure excellent switching and memory characteristics of memristive devices. In accordance with the reported studies, the regulated movement of oxygen vacancies or other mobile species through the CFs can allow their pining at the constant positions and consequently high switching reproducibility of a device. Therefore, the immediate findings on the oxygen enriched media that will ensure the controlled CFs formation is of high importance. With this regard, the selection of a proper electrolyte for the fabrication of the oxide layer sandwiched between two metallic electrodes may play a significant role. It can be assumed that incorporation of electrolyte species can increase the amount of oxygen vacancies leading to a possible manipulation with their movement.Tantalum and Hf were sputtered onto Si wafers to produce thin films. Both metals were electrochemically anodized to produce oxides responsible for the memristive properties. The aim was to replace expensive fabrication methods for oxides such as sputtering or laser deposition with cost-efficient, simple and rapid anodization. The bottom electrode was either Ta or Hf thin films, Ta2O5 or HfO2 were anodic oxide layers and Pt was patterned as the top electrode, that can be seen in the inserted Figure. Two groups of these samples were anodized in the same conditions, in three electrolytes (phosphate buffer (PB), borate buffer (BB), citrate buffer (CB)) to produce three different anodic oxide layers with the thickness in the range of 20 nm. For all cases, memristive switching between high and low resistance states was demonstrated and the corresponding I-U switching curves were compared. Additionally, writing (switching) and reading tests were done for high numbers of cycles and the endurance and retention of devices were analyzed. The same tests were performed when samples were thermally treated resulting in improved or worsened switching properties, depending on the solid electrolyte placed between the metallic electrodes. Unquestionably, the use of PB, CB and BB for anodization has differently influenced the electrical properties of the memristors likely due to the trapped electrolyte species inside the oxide layer. The incorporation was confirmed by the X-ray photoelectron spectroscopy (XPS) and the presence of CFs by transmission electron microscopy (TEM). Interestingly, Ta memristors formed in PB showed the presence of Ta oxyphosphate which has induced the increase of O vacancies and thus improved switching features. However, the presence of Hf-O-P bonds found in Hf memristors that was anodized in PB did not show any improvement of electrical properties.In summary, the current study offers a reliable, controllable and cost-efficient approach for the production of ReRAMs based on Hf and Ta anodic memristors as potential candidates for the future industrial implementation. Figure 1

Light‐Assisted Resistive Switching Memory Device with Reduced SET/RESET Voltage Using Sol–Gel TiO2 on Al‐Doped ZnO Electrode

Herein, light‐assisted resistive switching (RS) characteristic of low‐cost sol–gel TiO2 film‐based metal–insulator–metal (MIM) configuration using Al‐doped ZnO (AZO) as the bottom electrode is demonstrated. Unprecedentedly, instead of the costly transparent conducting electrode such as tin‐doped indium oxide, AZO electrode is exploited in this study due to its dual role as a transparent and an additional oxygen vacancy (VO)‐rich electrode. The Al/TiO2/AZO device shows electroforming free bipolar RS characteristics, which can be explained by the formation (rupture) of conducting filaments composed of VO. The memory window is increased three times under the blue light illumination compared to dark conditions. Interestingly, the SET and RESET voltages are decreased from 5.2 to 4.5 V and −3.9 to −3.3 V, respectively, under the blue light illumination with respect to the dark condition. The enhancement in the RS effect under the blue light illumination is explained in terms of the photoresponsive properties of TiO2. The MIM device exhibits good switching repeatability with stable retention characteristics, making them attractive for next‐generation nonvolatile resistive random access memory devices.

The transformation of digital to analog resistance switching behavior in Bi2FeCrO6 thin films

ABSTRACT Bi2FeCrO6 (BFCO) thin films were fabricated by sol-gel method. Digital and analog resistive switching behaviors were sequentially observed in Au/BFCO/FTO/Glass structure by applying a continuous cyclic voltage. By analyzing formation mechanism of the two types of the resistive switching behaviors, it is found that the digital resistive behavior conductance mechanism is a bulk-limited conduction, and the analog resistive switching behavior is accompanied with rectification effects and negative differential resistance behaviors, which are considered as interface-limited conductivity behaviors. So the change of digital and analog resistive switching behaviors may be result of the transformation of conductive mechanism. These research results will help us to design and manufacture digital and analog multifunctional resistive switching memory devices.

System-Theoretic Methods for Designing Bio-Inspired Mem-Computing Memristor Cellular Nonlinear Networks

The introduction of nano-memristors in electronics may allow to boost the performance of integrated circuits beyond the Moore era, especially in view of their extraordinary capability to process and store data in the very same physical volume. However, recurring to nonlinear system theory is absolutely necessary for the development of a systematic approach to memristive circuit design. In fact, the application of linear system-theoretic techniques is not suitable to explore thoroughly the rich dynamics of resistance switching memories, and designing circuits without a comprehensive picture of the nonlinear behaviour of these devices may lead to the realization of technical systems failing to operate as desired. Converting traditional circuits to memristive equivalents may require the adaptation of classical methods from nonlinear system theory. This paper extends the theory of time- and space-invariant standard cellular nonlinear networks with first-order processing elements for the case where a single non-volatile memristor is inserted in parallel to the capacitor in each cell. A novel nonlinear system-theoretic method allows to draw a comprehensive picture of the dynamical phenomena emerging in the memristive mem-computing array, beautifully illustrated in the so-called Primary Mosaic for the class of uncoupled memristor cellular nonlinear networks. Employing this new analysis tool it is possible to elucidate, with the support of illustrative examples, how to design variability-tolerant bio-inspired cellular nonlinear networks with second-order memristive cells for the execution of computing tasks or of memory operations. The capability of the class of memristor cellular nonlinear networks under focus to store and process information locally, without the need to insert additional memory units in each cell, may allow to increase considerably the spatial resolution of state-of-the-art purely CMOS sensor-processor arrays. This is of great appeal for edge computing applications, especially since the Internet-of-Things industry is currently calling for the realization of miniaturized, lightweight, low-power, and high-speed mem-computers with sensing capability on board.

Negative Photoconductance Effect: An Extension Function of the TiOx‐Based Memristor

AbstractThe negative photoconductance (NPC) effect, defined as an increase in resistance upon exposure to illumination, holds great potential for application in photoelectric devices. A prepared memristor with the structure of Ag|graphene quantum dots (GQDs)|TiOx|F‐doped SnO2 exhibits typical bipolar resistive switching (RS) memory behavior. The NPC effect is impressively observed in the high resistance state branch of the RS memory, enabling the memristor function to be extended to both memory logic display and multistate data storage. The observed NPC effect is attributed to the excitation, migration, and compensation of oxygen vacancy at the GQDs/TiOx interface, at which the electron transportation is efficiently restricted because of the variation in the charge distribution and electrostatic potential under illumination. Experiments, theoretical calculations, and physical models are used to provide engineer the interface with the aim of building the NPC effect in the memristive device. These results unveil a new horizon on extending the functionality of the memristor.

Recent, Bioelectricity-Related Articles Selected by Ann M. Rajnicek, Media Editor of Bioelectricity.

Recent, Bioelectricity-Related Articles Selected by Ann M. Rajnicek, Media Editor of Bioelectricity.

Resistive switching characteristics and theoretical simulation of a Pt/a-Ta2O5/TiN synaptic device for neuromorphic applications

Internet of things and big data demand the development of new techniques for memory devices going beyond conventional ways of memorizing and computing. In this work, we fabricated a Pt/a-Ta2O5/TiN resistive switching memory device and demonstrated its resistive and synaptic characteristics. Firstly, X-ray photoelectron spectroscopy (XPS) of a-Ta2O5/TiN analysis was conducted to determine elemental compositions of a-Ta2O5/TiN and TiON interfacial layer between a-Ta2O5 and TiN layer. Repetitive bipolar resistive switching was achieved by a set at a negative bias and a reset at a positive bias. Moreover, its biological potentiation and depression behaviors were well emulated by applying a repetitive pulse on the device. For deep understanding of this device’s properties based on materials, oxygen vacancies, and stack engineering, theoretical calculations were performed employing Vienna ab-initio simulation Package (VASP) code. All calculations were carried out using PBE and GGA+U method to obtain accurate results. Work function difference between electrodes provided a localized path for forming a Vo based conducting filament in a-Ta2O5. Iso-surface charge density plots confirmed the formation of intrinsic Vo based conducting filaments in a-Ta2O5. These conducting filaments became stronger with increasing concentration of Vos in a-Ta2O5. Integrated charge density, density of states (DOS), and potential line ups also confirmed that Vo was responsible for charge transportation in a-Ta2O5 based RRAM devices. Experimental and theoretical results confirmed the formation of TiON layer between a-Ta2O5 and active electrode (TiN), suggesting that the bipolar resistive switching phenomenon of the proposed device was based on oxygen vacancy (Vo).