Microscopic noise simulation of long- and short-channel nMOSFETs by a deterministic approach

We compute small-signal and noise quantities of nMOSFETs with different channel lengths with a fully self-consistent and deterministic Poisson, Schrödinger, and Boltzmann equation solver. We show how noise qualitatively changes due to short-channel effects and how noise is generated in the domain of ballistic transport. Furthermore, we inspect the suppression of noise due to the Pauli principle and due to the coupling to the fluctuations of the potential.     

A comparative study of characterization techniques for oxide reliability in flash memories

We compare two different methods for extracting the leakage distribution from accelerated data-retention experiments. It is shown that the equivalent-cell (EC) scheme, which provides a fast estimation of leakage distribution in the array, is totally accurate as compared to a more detailed analysis of single memory cells within the array. The fair agreement between the results of the two characterization schemes is explained, and advantages of the EC technique for fast reliability monitoring in Flash memories are discussed.     

Stress-induced leakage current (SILC) and oxide breakdown: are theyfrom the same oxide traps?

Many research groups have used stress-induced leakage current SILC as a mean to measure the oxide traps (defects) buildup in the oxide film during electrical stress. It is commonly believed that these very same traps will lead to oxide breakdown when their density reaches a critical value. We studied the annealing kinetic of SILC as well as, the oxide breakdown distribution and found that they are quite different. Our result casts serious doubt on the validity of the popular assumption     

Dielectric relaxation and breakdown detection of doped tantalum oxide high-k thin films

While TaO/sub x/, HfO/sub x/, ZrO/sub x/, Hf-doped TaO/sub x/, and Zr-doped TaO/sub x/ thin films are promising high-k gate dielectric candidates, their intrinsic reliability has not yet been investigated. In this paper, the authors examine some fundamental reliability aspects of these high-k films through ramp voltage stress testing. By studying dielectric relaxation and analyzing the transient conductivity, the breakdown mode of the tested high-k film is identified; a sensitive method of breakdown detection in ramped voltage tests is proposed and investigated.     

A comparative study of single-switch three-phase high-power-factorrectifiers

Three three-phase single-switch high-power-factor rectifier implementations were evaluated on a comparative basis. Specifically, the discontinuous-conduction-mode (DCM) boost rectifier with a 5th-harmonic-trap filter, the DCM boost rectifier with a harmonic-injection circuit, and the multiresonant, zero-current-switching buck rectifier were compared with respect to their efficiencies, compliance with the IEC555-2 specifications, volumes, weights and costs. The comparisons were done for the three-phase line-to-line input voltage of 380 V_rms±20% and for 0-6 kW output power range     

铅酸蓄电池板栅用铅合金中锑与锡

研究了锑和锡加入铅合金后对铅基合金的影响,并对腐蚀钝化阻挡层形成过程的工作原理进行对比分析,讨论了锑和锡在钝化层中的存在形式和位置.铅锑和铅锡合金板栅表面钝化层由Pb、铅氧化物、PbSO4、锑氧化物或锡氧化物构成.锑在腐蚀钝化层中以复杂氧化物PbSb2O6的形式存在;锡在钝化层中的存在形式有Sn(Ⅱ)氧化物SnO和Sn(Ⅳ)氧化物SnO2;此外,Sn还可以Sn(Ⅲ)、Sn(Ⅳ)形式嵌入到PbO/PbOx和PbOx晶格中.Sn在钝化层中既可以沉积在氧化物晶界位置,同时又能渗入到晶格内部.     

变压器信任度与安全指数的对比研究

为准确掌握变压器的真实运行工况,对变压器的状态评估方法进行对比研究,找出不同评估方法的优缺点和共同规律。首先对变压器风险评估和信任度评估的基本原理进行分析,找到各自算法本身的优缺点。在此基础上对云南电网的50台变压器分别进行状态评估,得到其信任度和安全指数。最后进行对比研究,确定了状态检修策略中与评估结果相对应的阀值。该研究为变压器的状态检修提供更全面有效的评估依据,对电网的经济安全运行有着重要的指导意义。     

Quantifying the nature of hot carrier degradation in the spacerregion of LDD nMOSFETs

A detailed quantitative analysis of the hot carrier degradation in the spacer region of LDD nMOSFETs using stress conditions for maximum hole (V_g ~ V_t), substrate (I_submax) and electron (V_g = V_d) current from microseconds is presented. Damage in the spacer region reveals a two-stage drain series resistance degradation with an early stage lasting about 100 ms. The nature of damage is investigated by alternate electron, hole injection, and charge pumping measurements. It is seen that the hot carrier damage in the spacer oxide in the early stage is dominated by interface state creation with no evidence of significant damage by trapping mechanism either by electrons or holes. These results are in contrast to degradation behavior in the channel region where damage by trapping is a well-established mechanism of degradation under electron or hole injection     

电子式互感器积分方案的比较研究

基于罗科夫斯基线圈原理的电子式电流互感器得到了广泛的认可和应用,但是罗氏线圈输出需经积分处理,方能获得被测信号.针对积分还原过程进行了深入的研究,提出了硬件积分、软件积分两种方案.从原理上给出了各自的传递函数,并对幅频特性、相频特性分别进行了分析;结合具体实现形式,对两种方案的优、缺点分别加以阐述;结合实际的工程应用波形,提出了软件积分方案更适合工程化应用的观点.     

An analytical model for a TFET with an n-doped channel operating in accumulation and inversion modes

The tunnel field-effect transistor (TFET) is an ambipolar device that conducts current with the channel in both accumulation and inversion modes. Analytical expressions for the channel potential and current in a TFET with an n-doped channel when operating in the accumulation and inversion modes are proposed herein. The potential model is derived by solving the two-dimensional (2D) Poisson equation using the superposition principle while considering the charges present in the channel due to electron or hole accumulation along with the depletion charges. An expression for the tunneling current corresponding to the maximum tunneling probability is also derived. The tunneling current is obtained by analytically calculating the minimum tunneling length in a TFET when operating in the accumulation or inversion mode. The results of the proposed potential model is compared with technology computer-aided design (TCAD) simulations for TFET with various dimensions, revealing good agreement. The potential and current in an n-type TFET (nTFET) obtained using the proposed models are also analyzed.

     

A comparative study for current transformer dimensioning in overcurrent relay

Dimensioning a current transformer (CT) is one of the most important tasks during the substation planning process. The installation of a correctly specified CT will ensure the integrity of the protection scheme. However, some parameters required for dimensioning a CT can be obtained only after the CT is installed in the substation. Because of the conflicting requirements, utility companies commonly adopt a simplified approach in compensating for the missing parameters. Two other methods for dimensioning CT under the given constraint during the planning stage have also been proposed by several authors. In view of the availability of the three methods of approximating CT specifications, this paper will conduct a comparative study to evaluate their accuracies. The approximated specifications of the CT during the planning stage are compared against those measured from a practical substation. Based on the findings from the comparative studies, the most reliable approach for CT dimensioning during the planning stage is proposed. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Adaptive control in a heating vessel: A comparative study

This paper presents experimental results obtained in temperature adaptive control of a heating vessel. A non-linear model of the process showed that the feed flow rate causes severe variations in time constant and process gain. An extended horizon self-tuning controller and two different model reference adaptive controllers were tested. The influence of design parameters on control performance for each algorithm was assessed. The control system was disturbed with load and setpoint changes.     

A comparative study of normalized and unnormalized tuning errors in parameter adaptive control

In the past year several advances in the development of adaptive control for non-linear systems have made it clear that algorithms not using error normalization have several significant advantages over algorithms which do, in spite of their much greater complexity. In this paper simple examples are used to give a detailed account of the essential differences in structure between adaptive algorithms of the normalized and unnormalized types. It is explained why only the latter readily generalize to non-linear process models with non-global Lipschitz non-linearities. It is shown that one of these algorithms is capable of stabilizing linear process models with different relative degrees.     

A comparative study of voltage stability indices in a power system

The paper compares the effectiveness of voltage stability indices in providing information about the proximity of voltage instability of a power system. Three simple voltage stability indices are proposed and their effectiveness is compared with some of the recently proposed indices. The comparison is carried out over a wide range of system operating conditions by changing the load power factor and feeder X/R ratios. Test results for the IEEE 57 bus and IEEE 118 bus system are presented.     

A comparative study of damping schemes on damping generatoroscillations

Results of a comparative study of the application of three different compensators, the power system stabilizer (PSS), the static VAR compensator (SVC), and the rectifier current regulator (RCR), for the damping enhancement of generator oscillations in a power system are presented. In order to enhance the dampings of both the mechanical mode and the exciter mode in the system, a unified approach based on modal control theory is proposed for the design of the PSS, the SVC, and the RCR. A proportional-integral-derivative (PID) type controller using generator speed deviation as a modulated signal to generate the desired damping is proposed, and it is shown that both affected system modes can be exactly located at the prespecified positions on the complex plane by the proposed damping schemes. To demonstrate the effectiveness of the proposed PID controllers and their relative merits, a frequency-domain study based on eigenvalue analysis under different operating conditions and a time-domain study based on nonlinear model simulations under disturbance conditions are performed     

Impacts of SiN-Capping Layer on the Device Characteristics and Hot-Carrier Degradation of nMOSFETs

Impacts of silicon nitride (SiN)-capping layer and the associated deposition process on the device characteristics and hot-electron degradation of nMOSFETs are investigated in this paper. The SiN layer used to induce channel strain for mobility enhancement was deposited by a low-pressure chemical vapor deposition. The deposition of the SiN aggravates threshold-voltage roll-off due to additional thermal budget and the strain effect. It is also found that the device hot-electron degradation is worse with the addition of the SiN capping. Furthermore, our results indicate that both the bandgap narrowing caused by the channel strain and the abundant hydrogen species from the precursors of SiN deposition contribute to the aggravated hot-electron effect.     

A comparative study of short-term forecasting of energy and peak power demand

The general requirements in the construction of demand forecasting schemes are discussed, followed by a comparative study, based on seven year data, of conventional extrapolative techniques and univariate stochastic time series modelling methods in forecasting monthly energy and peak power demands. The performance of each forecasting approach is evaluated in terms of adequate data characterization and ability to project data behaviour into the future, and a method for selecting a preferred forecasting model is explained.     

A comparative study of high temperature properties of cobalt-free perovskites

Co-free perovskites with chemical composition Ba_0.5Sr_0.5Fe_0.8M_0.2O_3-δ (M = Ni, Cu, Zn) were synthesized by the modified Pechini method, and their structure and microstructure were characterized by XRD and SEM. Oxygen content, electrical resistivity and Thermal Expansion Coefficient (TEC) were evaluated in air between room temperature and 900 °C. The high-temperature properties of these perovskites were compared with those of Co containing Ba_0.5Sr_0.5Fe_0.8Co_0.2O_3-δ perovskite. The highest electrical conductivity was obtained for Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3-δ, with values of 47.6 Scm^?1 at 544 °C. This same composition also exhibits the highest oxygen vacancies concentration: 3-δ = 2.61 at room temperature. In contrast, the Ba_0.5Sr_0.5Fe_0.8Zn_0.2O_3-δ, showed lower electrical conductivity suggesting that the Zn⁺² ions block electron transport. Co-free perovskites seem to be stable at high temperatures for long term periods. However, these compounds suffered degradation at room temperature in samples stored in air.