Resistive switching characteristics and conducting nanobits of polycrystalline NiO thin films

Thin films of NiO were deposited on Pt/Ta/glass sub-strates using a radio frequency (RF) sputtering method. The NiO thin films showed polycrystalline nature, indicating preferentially (111)-oriented structure. The resistive random access memory (RRAM) capacitor of a Pt/NiO/Pt structure exhibited unipolar switching characteristics and bistable resistivities for 200 repeated switching cycles. Furthermore, RRAM nanobits array was formed on the NiO thin films by applying a bias. The RRAM nanobits had a diameter of approximately 8 nm and were observed via a conducting atomic force microscope (CAFM). The density of the RRAM nanobits array was estimated to be approximately 0.64 Tbit/cm².     

Building structured biomaterials using AC electrokinetics

In this article, the application of alternating current (ac) electrokinetics in the formation of multicellular structured biomaterials from cells is reviewed. The formation of bacterial biofilms with defined internal architectures is investigated. Investigating such interactions could not only help in understanding how biofilms operate, but biofilms could also be used as a primitive model for cell interactions and development in higher organisms such as animals and plants. A discussion on how the same techniques can be used to create multicellular systems from animal and plant cells is presented.     

HVDC tapping using soft switching techniques

Contents  Soft switching techniques have been applied to develop a novel dc/dc power converter for feeding small loads (under 5 MW) with low cost and high reliability, from HVDC transmission lines. This dc/dc converter is connected in series with a pole of the HVDC transmission line. It drains energy to a dc capacitor through an air-core transformer. From this dc capacitor, a voltage-source converter may be directly connected to supply ac loads. This HVDC tap can supply high quality ac power to isolated areas, with or without ac power generation. The controller of the HVDC tap is independent from the master control of the HVDC link. It does not need any communication channel to the control of the main HVDC converter stations. Simulation results have revealed that the proposed HVDC tap can be a very good option for feeding small loads along the HVDC transmission line. It generates high quality ac voltage and is extremely robust. Received: 26 July 2000     

Ceramic Based Resistive Sensors

This paper reviews the current status and research trends of two types of ceramic based resistive sensors, thermistors and gas sensors. The issues and challenges associated with their development for high temperature applications are examined and discussed. Worldwide research efforts in ceramic based resistive sensors, devoted mostly to resolve the issues of selectivity and stability, are also reviewed. These efforts tend to integrate the results obtained from both empirical and basic science approaches, and focus on various stages of sensor development, including development of new material systems, sensor fabrication and manufacturing techniques, and smart sensor arrays.     

静止同步补偿器的开关函数建模与仿真

针对目前静止同步补偿器(Static Synchronous Compensator,STATCOM)输出建模和拓扑建模等方法的不足,通过引入单极性二值逻辑开关函数,建立了基于变换器物理特性和拓扑结构的开关函数模型.该模型的参数都是装置实际的物理参数,易于确定,更具一般性.对380V两机系统进行的仿真计算证明了所提模型和方法的正确性和有效性,并验证了STATCOM对系统无功补偿和电压稳定具有重要作用.     

Physics-based modeling approaches of resistive switching devices for memory and in-memory computing applications

The semiconductor industry is currently challenged by the emergence of Internet of Things, Big data, and deep-learning techniques to enable object recognition and inference in portable computers. These revolutions demand new technologies for memory and computation going beyond the standard CMOS-based platform. In this scenario, resistive switching memory (RRAM) is extremely promising in the frame of storage technology, memory devices, and in-memory computing circuits, such as memristive logic or neuromorphic machines. To serve as enabling technology for these new fields, however, there is still a lack of industrial tools to predict the device behavior under certain operation schemes and to allow for optimization of the device properties based on materials and stack engineering. This work provides an overview of modeling approaches for RRAM simulation, at the level of technology computer aided design and high-level compact models for circuit simulations. Finite element method modeling, kinetic Monte Carlo models, and physics-based analytical models will be reviewed. The adaptation of modeling schemes to various RRAM concepts, such as filamentary switching and interface switching, will be discussed. Finally, application cases of compact modeling to simulate simple RRAM circuits for computing will be shown.     

Ignition Criteria for Resistive Circuits

The criterion of no ignition is stated in general. The relation between the electrical power output and the discharge voltage, and the power output and time are discussed for resistive circuits with source voltages ranging from 24-60 V, tested by the German breakflash. Shadow photographs of the electrode area with the incipient kernel and the relevant oscillograms of the discharge voltage are recorded. From the oscillograms a general discharge voltage pattern emerges. The theoretical considerations as well as the experimental results suggest that the critical section when ignition is likely to occur under minimum igniting conditions coincides with the peak of the power transfer function. Suggestions are made about the practical application of these results to monitor the sensitivity of the breakflash or forecast the probable value of minimum igniting current or power for a given circuit.     

Stochastic modeling of bipolar resistive switching in metal-oxide based memory by Monte Carlo technique

A stochastic model of the resistive switching mechanism in bipolar metal-oxide based resistive random access memory (RRAM) is presented. The distribution of electron occupation probabilities obtained is in agreement with previous work. In particular, a low occupation region is formed near the cathode. Our simulations of the temperature dependence of the electron occupation probability near the anode and the cathode demonstrate a high robustness of the low occupation region. This result indicates that a decrease of the switching time with increasing temperature cannot be explained only by reduced occupations of the vacancies in the low occupation region, but is related to an increase of the mobility of the oxide ions. A hysteresis cycle of RRAM switching simulated with the stochastic model including the ion dynamics is in good agreement with experimental results.     

电阻式电压互感器的研究

介绍了电阻分压器传感电压的电阻式电压互感器;它在整个测量范围内无饱和畸变、线性好而且体积小、结构紧凑,便于测量和控制系统小型化。分析表明分布电容和温度变化是它最主要的误差源。通过分压电阻的选择及结构设计研制成10 kV电阻式电压互感器,型式试验验证达到0.2级准确度。     

Impedance Measurement by a Resistive Bridge

The possibility of measuring an unknown impedance Z=R+jX by including it in one arm of a Wheatstone bridge, whose other arms are purely resistive, is examined. It is shown that by adjusting the variable resistance for minimum bridge output and measuring this output, one can calculate the magnitude ?Z?, the resistive part R, and the magnitude of the reactive part ?X? of the unknown impedance. Using a fixed auxiliary capacitor whose reactance is less than 2?X?, the sign of the reactive part can also be determined. The sensitivity of the bridge decreases as the ratio ?X?/R increases; this can be remedied by adding a suitable series resistance to Z and/or by measuring the bridge output when its rate of variation with the adjustable resistance is maximum. An alternative method not involving voltage measurements, but requiring a suitable fixed, standard inductor or capacitor, has also been discussed. The theory involved in these measurements is pretty well within the reach of a sophomore student of electrical engineering and as such, this may constitute a simple, but interesting, laboratory exercise at that level.     

Resistive circuit topologies that admit several solutions

Necessary and sufficient conditions are given that a resistive circuit may have several but finitely many solutions. Whether it actually has several solutions depends on the values of the sources and linear resistors as well as on the characteristics of the non-linear resistors. Such circuits are required for static memory applications of all kinds, including associative memories realized by neural networks. These criteria are given both in terms of linear circuits and circuit topology. In the same way the minimal memory circuits are characterized. They constitute the building blocks for more complicated memory circuits.     

氧化锌避雷器阻性电流的在线监测

介绍了避雷器在线监测的几种常用方法,对阻性电流在线监测的原理和具体操作方法进行了详细的阐述,对可能出现的误差和干扰进行了解释并提出了解决的办法。     

TCSC allocation in power systems considering switching loss using MOABC algorithm

This paper is dedicated to investigate the influence of switching losses on Thyristor Controlled Series Compensator (TCSC) optimum allocation in power systems by using a Multi-Objective optimization technique. This allocation is performed with respect to minimization in system cost and voltage deviation as the objectives. For this purpose, cost of active power losses, investment cost of devices and active power generation cost in the peak load are considered to constitute the cost function as the economical objective. In addition, the paper considers interest rate in cost calculations to avoid impractical allocation results and imprecise solutions. The operational, technical and controlling constraints as well as load constraints are regarded in the allocation procedure. Also, the simulations are utilizing three unequal annual load levels to find optimum location and size of TCSC. The IEEE-14 Bus test system is used to validate the proposed method and show the importance of TCSC switching loss. Here, a novel optimization algorithm, Multi-Objective Artificial Bee Colony, is presented to provide Pareto optimal solutions. Also, an approach based on the goal attainment method combined with Genetic Algorithm is used to compromise between contradictory objectives and approach to the global optimum.     

Novel polyphosphazene-hydroxyapatite composites as biomaterials

Evaluating a polymer-ceramic biomaterial as a candidate for bone tissue engineering. The objective of the present work was to develop novel composites of biodegradable polyphosphazenes and HA as candidate materials for bone tissue engineering. The mechanical and degradation properties of novel PPHOS/HA composites were compared to PLAGA/HA composites as PLAGA being the most extensively investigated polymer for bone tissue engineering application.     

Resistive random access memory (RRAM) technology: From material,device, selector, 3D integration to bottom-up fabrication

Emerging non-volatile memory technologies are promising due to their anticipated capacity benefits, non-volatility, and zero idle energy. One of the most promising candidates is resistive random access memory (RRAM) based on resistive switching (RS). This paper reviews the development of RS device technology including the fundamental physics, material engineering, three-dimension (3D) integration, and bottom-up fabrication. The device operation, physical mechanisms for resistive switching, reliability metrics, and memory cell selector candidates are summarized from the recent advancement in both industry and academia. Options for 3D memory array architectures are presented for the mass storage application. Finally, the potential application of bottom-up fabrication approaches for effective manufacturing is introduced.     

Impedance Magnitude Measurement from a Resistive Bridge

It is shown that the familiar resistive bridge can be used to measure the magnitude of an unknown impedance. In order for this conclusion to hold, the bridge must have equal ratio arms. The measured voltage is then a minimum when the variable resistance in the bridge is equal to the magnitude of the unknown resistance. The sensitivity, however, decreases as the reactive component of the unknown impedance increases. The analytical tools used are well within the reach of the sophomore student in electrical engineering.     

Capacitor placement for switching noise reduction using genetic algorithms and distributed computing

This work investigates capacitor placement on a printed circuit board (PCB) to reduce the effect of simultaneous switching noise as a genetic algorithm (GA) search problem. The solution process makes use of distributed computing resources available on a local area network in order to solve larger problems more efficiently. The objective is to determine the number of added capacitors with minimum cost, and their position on the PCB, while keeping the maximum voltage deviation within some specified noise margin. The presence of capacitors at the selected positions is represented by a stream of zeros and ones, which is interpreted as a genotype. At each generation, the GA assesses the fitness function of a population of genotypes using linear transient circuit analysis, which involves a single matrix inversion, by determining the maximum voltage dip given the capacitor locations. For large systems, the fitness calculations are divided among several processors according to a simple distributed computing algorithm.     

氧化锌避雷器阻性电流的准确测量

用阻性电流仪测量氧化锌避雷器的阻性电流和全电流,其准确度与取样参考电压有关.通过实测和现场试验结果比较,证明从变压器测量线圈取参考电压测量阻性电流,其测量结果误差比电容分压器二次侧取参考电压的大很多.这将会导致对避雷器性能的误判断.     

Investigation on Resistive Memory Switching Mechanism of NiO

ABSTRACT

Experimental investigations on the resistive memory switching in sub-micron sized NiO memory cell are presented to elucidate the resistive memory switching mechanism. The voltage or current-biased I-V measurements show that the resistive switching transitions can be regarded as the combination of a voltage-controlled negative differential resistance phenomenon and a current-controlled negative differential resistance phenomenon. Along with experimental observations of multiple resistance states, these indicate that the memory switching in NiO would come from the percolative formation and rupture of filamentary conducting paths. Pulse experiments further suggest that the memory switching would come from local domains inside filaments.     

一种电阻脉冲分压器的研制

陡前沿高压脉冲测量对分压器的响应性能提出了非常苛刻的要求。电阻分压器对地分布电容是影响其性能的关键因素。采取在高压臂的低压端加入套筒电极的补偿措施,部分地收集原本由高压臂电阻体流向地的杂散电容电流,并调节各相关参数的匹配以减小分压器高压臂对地分布电容的影响,研制出了一种新型的电阻分压器。PSpice性能仿真分析表明:该设计可以减少响应时间和上升时间3 ns以上,改变电极的长度即可在一定的范围内调节其响应性能;适当的电感将有助于降低上升时间。仿真分析还证实了阶跃响应上升时间能够实现<1 ns。对准阶跃波、静电放电枪校准波及纳秒双指数脉冲的实验测量表明该分压器性能优越。