共查询到20条相似文献,搜索用时 15 毫秒
1.
Yi Wei Perner Frederick Qureshi Muhammad Shakeel Abdalla Hisham Pickett Matthew D. Yang J. Joshua Zhang Min-Xian Max Medeiros-Ribeiro Gilberto Williams R. Stanley 《Applied Physics A: Materials Science & Processing》2011,102(4):973-982
In nanoscale memristive switching devices, the statistical distribution of resistance values and other relevant parameters
for device operation often exhibits a lognormal distribution, causing large fluctuations of memristive analog state variables
after each switching event, which may be problematic for digital nonvolatile memory applications. The state variable w in such devices has been proposed to be the length of an undoped semiconductor region along the thickness of the thin film
that acts as a tunnel barrier for electronic transport across it. The dynamical behavior of w is governed by the drift diffusion of ionized dopants such as oxygen vacancies. Making an analogy to scanning tunneling microscopes
(STM), a closed-loop write scheme using current feedback is proposed to switch the memristive devices in a controlled manner.
An integrated closed-loop current driver circuit for switching a bipolar memristive device is designed and simulated. The
estimated upper limit of the feedback loop bandwidth is in the order of 100 MHz. We applied a SPICE model built upon the TiO2 memristive switching dynamics to simulate the single-device write operation and found the closed-loop write scheme caused
a narrowing of the statistical distribution of the state variable w. 相似文献
2.
Martin Ziegler Karlheinz Ochs Mirko Hansen Hermann Kohlstedt 《Applied Physics A: Materials Science & Processing》2014,114(2):565-570
In nature, the capability of memorizing environmental changes and recalling past events can be observed in unicellular organisms like amoebas. Pershin and Di Ventra have shown that such learning behavior can be mimicked in a simple memristive circuit model consisting of an LC (inductance capacitance) contour and a memristive device. Here, we implement this model experimentally by using an Ag/TiO2?x /Al memristive device. A theoretical analysis of the circuit is used to gain insight into the functionality of this model and to give advice for the circuit implementation. In this respect, the transfer function, resonant frequency, and damping behavior for a varying resistance of the memristive device are discussed in detail. 相似文献
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Unipolar memristive devices are an important kind of resistive switching devices. However, few circuit models of them have been proposed. In this paper, we propose the SPICE modeling of flux-controlled unipolar memristive devices based on the memristance versus state map. Using our model, the flux thresholds, ON and OFF resistance, and compliance current can easily be set as model parameters. We simulate the model in HSPICE using model parameters abstracted from real devices, and the simulation results show that the proposed model caters to the real device data very well, thus demonstrating that the model is correct. Using the same modeling methodology, the SPICE model of charge-controlled unipolar memristive devices could also be developed. The proposed model could be used to model resistive memory cells, logical gates as well as synapses in artificial neural networks. 相似文献
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J. Joshua Yang John Paul Strachan Feng Miao Min-Xian Zhang Matthew D. Pickett Wei Yi Douglas A. A. Ohlberg G. Medeiros-Ribeiro R. Stanley Williams 《Applied Physics A: Materials Science & Processing》2011,102(4):785-789
The interfaces between metal electrodes and the oxide in TiO2-based memristive switches play a key role in the switching as well as in the I–V characteristics of the devices in different resistance states. We demonstrate here that the work function of the metal electrode
has a surprisingly minor effect in determining the electronic barrier at the interface. In contrast, Ti oxides can be readily
reduced by most electrode metals. The amount of oxygen vacancies created by these chemical reactions essentially determines
the electronic barrier at the device interfaces. 相似文献
8.
Ch. Sargentis K. Giannakopoulos A. Travlos D. Tsamakis 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):85
Floating gate devices with nanoparticles embedded in dielectrics have recently attracted much attention due to the fact that these devices operate as non-volatile memories with high speed, high density and low power consumption. In this paper, memory devices containing gold (Au) nanoparticles have been fabricated using e-gun evaporation. The Au nanoparticles are deposited on a very thin SiO2 layer and are then fully covered by a HfO2 layer. The HfO2 is a high-k dielectric and gives good scalability to the fabricated devices. We studied the effect of the deposition parameters to the size and the shape of the Au nanoparticles using capacitance–voltage and conductance–voltage measurements, we demonstrated that the fabricated device can indeed operate as a low-voltage memory device. 相似文献
9.
Fabrication and investigation of ferroelectric memristors with various synaptic plasticities
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In the post-Moore era, neuromorphic computing has been mainly focused on breaking the von Neumann bottlenecks. Memristors have been proposed as a key part of neuromorphic computing architectures, and can be used to emulate the synaptic plasticities of the human brain. Ferroelectric memristors represent a breakthrough for memristive devices on account of their reliable nonvolatile storage, low write/read latency and tunable conductive states. However, among the reported ferroelectric memristors, the mechanisms of resistive switching are still under debate. In addition, there needs to be more research on emulation of the brain synapses using ferroelectric memristors. Herein, Cu/PbZr0.52Ti0.48O3 (PZT)/Pt ferroelectric memristors have been fabricated. The devices are able to realize the transformation from threshold switching behavior to resistive switching behavior. The synaptic plasticities, including excitatory post-synaptic current, paired-pulse facilitation, paired-pulse depression and spike time-dependent plasticity, have been mimicked by the PZT devices. Furthermore, the mechanisms of PZT devices have been investigated by first-principles calculations based on the interface barrier and conductive filament models. This work may contribute to the application of ferroelectric memristors in neuromorphic computing systems. 相似文献
10.
忆阻器是一种具有记忆功能和纳米级尺寸的非线性元件,作为混沌系统的非线性部分,能够提高混沌系统的信号随机性和复杂度.本文基于增广Lü系统设计了一个三维忆阻混沌系统.仅仅通过改变系统的一个参数,该系统能产生单涡巻、双涡卷和四涡巻的混沌吸引子,说明该系统具有丰富的混沌特性.首先对该忆阻混沌系统的基本动力学行为进行了理论分析和数值仿真,如平衡点稳定性、对称性,Lyapunov指数和维数,分岔图和Poincare截面等.同时,建立了模拟该忆阻混沌系统的SPICE(simulation program with integrated circuit emphasis)电路,给出了不同参数下的电路实验相图,其仿真结果与数值分析相符,从而验证了该忆阻混沌系统的混沌产生能力.由于脉冲同步只在离散时刻传递信息,能量消耗小,同步速度快,易于实现单信道传输,因而在混沌保密通信中更具有实用性.因此,本文从最大Lyapunov指数的角度实现了该忆阻混沌系统的脉冲混沌同步,数值仿真证实了忆阻混沌系统的存在性以及脉冲同步控制的可行性,为进一步研究该忆阻混沌系统在语音保密通信和信息处理中的应用提供了实验基础. 相似文献
11.
采用常见元器件等效实现一个广义忆阻器, 进而制作出一个电路特性可靠的非线性电路, 有助于忆阻混沌电路的非线性现象的实验展示及其所产生的混沌信号的实际工程应用. 基于忆阻二极管桥电路, 构建了一种无接地限制的、易物理实现的一阶有源广义忆阻模拟器; 由该模拟器并联电容后与RC桥式振荡器线性耦合, 实现了一种无电感元件的忆阻混沌电路; 建立了无感忆阻混沌电路的动力学模型, 开展了相应的耗散性、平衡点、稳定性和动力学行为等分析. 结果表明, 无感忆阻混沌电路在相空间中存在分布2个不稳定非零鞍焦的耗散区和包含1个不稳定原点鞍点的非耗散区; 当元件参数改变时, 无感忆阻混沌电路有着共存分岔模式和共存吸引子等非线性行为. 研制了实验电路, 该电路结构简单、易实际制作, 实验测量和数值仿真两者结果一致, 验证了理论分析的有效性. 相似文献
12.
Shu-Chao Qin Rui-Xin Dong Xun-Ling Yan 《Applied Physics A: Materials Science & Processing》2014,116(1):1-7
The excellent memristive behavior of ZnO-based devices with embedded Ti nano-layers is obtained. The results show that inserting Ti layers can effectively reduce the switching voltages and increase the R off/R on ratio (more than 103). In particular, the stable switching properties is obtained by introducing 2.5 nm Ti layer, and the devices show good sweep endurance (about 320 cycles) and a long retention time of more than 106 s as compared with the devices without Ti layer. A model combining the redox reaction and the oxygen vacancy-based conducting filament is proposed to explain the memory effect. The conducting filament will be formed and ruptured along fixed paths at a certain region due to the non-uniform distribution of oxygen vacancies, which is responsible for the improvement of device performance. 相似文献
13.
Memristors, as memristive devices, have received a great deal of interest since being fabricated by HP labs. The forgetting effect that has significant influences on memristors' performance has to be taken into account when they are employed. It is significant to build a good model that can express the forgetting effect well for application researches due to its promising prospects in brain-inspired computing. Some models are proposed to represent the forgetting effect but do not work well. In this paper, we present a novel window function, which has good performance in a drift model. We analyze the deficiencies of the previous drift diffusion models for the forgetting effect and propose an improved model. Moreover,the improved model is exploited as a synapse model in spiking neural networks to recognize digit images. Simulation results show that the improved model overcomes the defects of the previous models and can be used as a synapse model in brain-inspired computing due to its synaptic characteristics. The results also indicate that the improved model can express the forgetting effect better when it is employed in spiking neural networks, which means that more appropriate evaluations can be obtained in applications. 相似文献
14.
Fabien Alibart Dmitri B. Strukov 《Applied Physics A: Materials Science & Processing》2013,111(1):199-202
Variations in the switching threshold voltage of memristive devices present significant challenges for their integration into large-scale circuits. In this paper, we propose to address this problem by adding a device exhibiting S-type (N-type) negative differential resistance (NDR) in series (parallel) with memristive devices. The main effect comes from the transition between low- and high-conductivity branches of the NDR device, which leads to a redistribution of the voltage drop inside the device stack, and, as a result, the effective lowering of variations in the switching threshold. The idea is checked experimentally using a TiO2?x memristive device connected in parallel with a tunnel GaAs diode. 相似文献
15.
S. A. Gerasimova A. N. Mikhaylov A. I. Belov D. S. Korolev O. N. Gorshkov V. B. Kazantsev 《Technical Physics》2017,62(8):1259-1265
A physical model of synaptically coupled neuron-like generators interacting via a memristive device has been presented. The model simulates the synaptic transmission of pulsed signals between brain neurons. The action on the receiving generator has been performed via a memristive device that demonstrates adaptive behavior. It has been established that the proposed coupling channel provides the forced synchronization with the parameters depending on the memristive device sensitivity. Synchronization modes 1: 1 and 2: 1 have been experimentally observed. 相似文献
16.
Liu Lifeng Chen Bing Gao Bin Zhang Feifei Chen Yuansha Liu Xiaoyan Wang Yi Han Ruqi Kang Jinfeng 《Applied Physics A: Materials Science & Processing》2011,102(4):991-996
Based on a unified physical model and first-principle calculations, a material-oriented methodology has been proposed to control
the bipolar switching behavior of an oxide-based resistive random access memory (RRAM) cell. According to the material-oriented
methodology, the oxide-based RRAM cell can be designed by material engineering to achieve the required device performance.
In this article, a Gd-doped HfO2 RRAM cell with excellent bipolar switching characteristics is developed to meet the requirements of memristive device application.
The typical memristive characteristics of the Gd-doped HfO2 RRAM cell are presented, and the mechanism is discussed. 相似文献
17.
I. P. Nevirkovets 《Czechoslovak Journal of Physics》1996,46(Z2):647-648
Modified geometry (MG) devices, Nb/Al/Nb/Al−AlOx−Al−AlOx−Al/Nb/Al/Nb, have been fabricated and investigated in comparison with the basic geometry (BG) double-barrier Nb/Al−AlOx−Al−AlOx−Al/Nb devices. The enhancement of the critical temperature in the Al film is found to be weaker for the MG devices as compared
with the BG devices at temperatures nearT=4.2 K but stronger at lowT. Indication of an enhancement of dc Josephson critical current density,j
c
, at bias voltageV≠0 as compared withj
c
(V=0) has been observed in the MG devices for the first time. 相似文献
18.
Solar cells based on the poly(N-vinylcarbazole):porphyrin: tris(8-hydroxyquinolinato) aluminium blend system
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Organic solar cells based on poly(N-vinylcarbazole)(PVK):porphyrin:tris(8-hydroxyquinolinato) aluminium(Alq3) blend p-n junction systems have been fabricated in this work.The roles of the different components in the blend system and of the amount of porphyrin have been investigated.The 5,10,15,20-tetraphenylporphyrin(TPP) and 5,10,15,20-tetra(o-chloro)phenylporphyrinato-copper(CuTClPP) are used in the solar cells.The results show that TPP is better than CuTClPP in enhancing the performance of PVK:Alq3 solar cells.When the weight ratio of PVK:TPP:Alq3 is 1:1.5:1,the best performance of solar cell is obtained.The open circuit voltage(V oc) is 0.87 V,and the short circuit current(J sc) is 17.5 μA·cm 2.In the ternary bulk hereojunction system,the device may be regarded as a cascade of three devices of PVK:TPP,TPP:Alq3 and PVK:Alq3.PVK,TPP and Alq3 can improve the hole mobility,light absorption intensity and electron mobility of the ternary bulk hereojunction system,respectively. 相似文献
19.
Zinc Oxide (ZnO) thin films have been addressed as promising candidates for the fabrication of Resistive Random Access Memory devices, which are alternative to conventional charge-based flash memories. According to the filamentary conducting model and charge trapping/detrapping theory developed in the last decade, the memristive behavior of ZnO thin films is explained in terms of conducting filaments formed by metallic ions and/or oxygen vacancies, and their breaking through electrochemical redox reactions and/or recombination of oxygen vacancies/ions. A comparative review of the memristive properties of ZnO thin films grown by sputtering, atomic layer deposition (ALD), pulsed laser deposition (PLD), and sol-gel methods is here proposed. Sputtered ZnO thin films show promising resistive switching behaviors, showing high on/off ratios (10–104), good endurance, and low operating voltages. ALD is also indicated to be useful for growing conformal ZnO layers with atomic thickness control, resulting in important resistive switching characteristics, such as relatively high on/off ratios and low operating voltages. High insulating epitaxial ZnO thin films can be obtained by PLD, showing reliable switching properties at low voltages and with good retention. On the contrary, the sol-gel approach generally results in ZnO thin films with poor resistive switching behaviors. Nevertheless, thin films derived from ZnO NPs show improved switching performances, with higher on/off ratios and lower operating voltages. Independently of the synthetic approach, doped ZnO thin films exhibit better resistive switching behaviors than pristine ones, coupling a strong increase of the on/off ratio with a more stable switching response. 相似文献
20.
Changming Chen Xiaoqiang Sun Dan Zhang Zhibo Shan Sang-Yung Shin Daming Zhang 《Optics & Laser Technology》2009,41(4):495-498
A new type of single-mode embedded dye-doped polymeric planar waveguide device based on cross-linkable negative photoresist has been successfully designed and fabricated using a UV-bleaching technique. A notable difference in the refractive index of the resist between exposed and un-exposed regions was observed, which was found to be dependent on the curing temperature. The new fabrication technique is a simple, rapid, and controllable process. The easy-to-fabricate waveguide structure is suitable for planar light-wave circuit applications. By optimizing the poling temperature and the dopant levels of Disperse Red 1, the material showed excellent photostability and exhibited a electro-optic coefficient, γ33, of 25 pm/V. The dye-doped polymeric planar waveguide devices will be useful in realizing electro-optic (EO) modulators and switches. 相似文献