Nonlinear magnetoelastic interactions

The physical basis for magnetoelastic coupling is presented in terms of simple models. These models are used to illustrate the magnetoelastic nonlinearities present in real crystals, and an enumeration is made of the instabilities which can be excited by means of these nonlinearities. Published material on instability theory and experiments is reviewed, and current possibilities for device applications are briefly evaluated.     

Slow-Scale and Fast-Scale Instabilities in Voltage-Mode Controlled Full-Bridge Inverter

This paper discusses the slow-scale and fast-scale instabilities of a voltage-mode controlled full-bridge inverter which is widely used in AC power supply applications. The main results are illustrated by exact cycle-by-cycle simulations. It is shown that the slow-scale instability is a type of low-frequency instability which manifests itself as a Hopf-type low-frequency oscillation in the whole line cycle, whereas the fast-scale instability is a type of local instability which manifests itself as a period-doubling bifurcation in some intervals of a line cycle. An averaged model and an improved discrete-time model are used to theoretically analyze the slow-scale and fast-scale instabilities, respectively. Finally, experimental results are presented to verify the results from simulations and analysis. Our work has revealed more instabilities which are likely to occur in the inverter, and has provided a convenient means of predicting stability boundaries to facilitate the design of the inverter.     

Small-signal operation of semiconductor devices includingself-heating, with application to thermal characterization andinstability analysis

A rigorous mathematical treatment of dynamic self-heating in semiconductor devices is presented. Two formulations for the admittance parameters are given. The thermal behavior of the device is referred to device temperature in the first formulation, and to ambient temperature in the second. Contrary to previous work, nonlinear thermal effects are included. An analytical model for the thermal resistance is derived which confirms the relevance of these effects. Applications of the above results to device modeling and thermal characterization are studied in detail by means of numerical simulations. Possible sources of inaccuracies are evidenced. Finally, it is shown that the differential analysis of thermal feedback provides a general and rigorous means to determine the conditions for the onset of thermally-induced instabilities     

Bifurcations in electrooptic bistable devices with short delay times in the feedback

We have investigated experimentally the behavior of a hybrid bistable electrooptic device with a delayed feedback when the delay time is comparable to the time constant of the device. The behavior is governed by a nonlinear difference-differential equation. The threshold of instability and the period of the oscillations observed close to threshold agree relatively well with the predictions obtained from a linear stability analysis of this equation. For larger input signals or feedback, bifurcations take place. We then observe period-2, period-4, and chaotic behavior following the period-doubling scheme of Feigenbaum. For delay times shorter than the time constant this bifurcation behavior can still be observed for large input signals. Furthermore, for such short delay times the threshold for onset of instabilities was observed to exhibit hysteresis, so different thresholds were observed when the input signal was increasing and decreasing.     

Semiconductor Instability Failure Mechanisms Review

This paper reviews the mechanisms of semiconductor instabilities for the purpose of better understanding this very complex phenomenon. As a result of this understanding, the semiconductor instabilities can be kept to a minimum in design and production. The basic ideas, diagrams, and references are presented for: instabilities due to surface charge on the silicon dioxide (SiO2), conduction on oxide surfaces/lateral charge spreading, instabilities caused by charges within the SiO2, instabilities in double-layer insulator structures, hFF degradation by avalanched emitter-base junction, and instabilities due to parasitic actions. A case study in reducing manufacturing assembly fallout is presented. Its electrical manifestations, as hFF degradation, the causes and corrective action are described. This study shows the importance of vendor-user cooperation to find the proper corrective action. Electrical diagnostic techniques such as the current-voltage curve trace characteristics of a junction are reviewed. The threshold test used in detecting parasitic MOS action caused by improper layout and/or ionic contamination is presented. They are used to pinpoint the area of instability on the semiconductor. High temperature bake and biased operating life procedures and their use in identifying and pinpointing causes of instabilities are discussed. Finally a method for removing various materials and/or layers of a semiconductor device is presented. This method is used in pinpointing the manufacturing step which might have caused the observed abnormal electrical characteristics.     

Instabilities of inertial transport in semiconductors

A derivation of the potential and the current-voltage relation is given for collisionless (inertial) transport of electron carriers in high-mobility low effective-mass one-dimensional short space-charge limited semiconductor diodes. No instability for longitudinal fluctuations is found, but transverse spatial instabilities or current filament formation is predicted by minimum entropy production. The negative differential resistance that gives rise to the transverse spatial instabilities restricts the range of stable device operation where a minimum current density is found.     

Interaction between electromigration and mechanical-stress-inducedmigration; New insights by a simple, wafer-level resistometric technique

A wafer-level resistometric technique was used as an indirect way to detect the combined effect of mechanical stress migration and electromigration (EM). A technique was developed to perform reliable high-resolution resistance measurements. In this technique, the compensation of small thermal instabilities is achieved by means of an additional measurement on a reference device. EM tests performed at constant temperature and current on Al-1%Si stripes exhibit an initial nonlinear resistance vs. time behavior, probably due to the simultaneous action of the accumulated mechanical stress and the high current density, followed by linear behavior. An activation energy is extracted by means of an original statistical analysis of the experimental data, and its meaning is discussed, taking into account the influence of temperature- and time-dependent mechanical stress. It is concluded that kinetics of stress relaxation should be known more deeply in order to perform reliable operating temperature extrapolations from the calculated activation energies     

Linear analysis of cyclotron-cherenkov and cherenkov instabilities in dielectric-loaded coaxial waveguides

We present, based on the cold fluid theory, linear analysis of the Cherenkov and cyclotron-Cherenkov instabilities which are driven when a linear electron beam is injected into a dielectric-loaded waveguide immersed in an axial magnetic field. In the analysis we consider azimuthally symmetric TM_0n modes. We derive dispersion relations for three types of waveguide, and compare computationally obtained linear growth rates of both instabilities. For the type A, which consists of a metallic cylinder with dielectric liner on its inner surface, the growth rate of the Cherenkov instability is larger than that of the cyclotron-Cherenkov instability. For the type B, which consists of a dielectric core and an outer metallic cylinder, both growth rates are comparable. And for the type C, which consists of a metallic core with dielectric liner on its surface and an outer metallic cylinder, the growth rate of the latter instability is higher than that of the former instability. Finally, for the type C, obtained are dependences of the oscillation frequency and the growth rates of both instabilities on the following parameters: the beam energy, the beam current, the axial magnetic field, the dielectric constant, and the thickness of the dielectric.     

Deep level defects involved in MOS device instabilities

The physical and chemical nature of several defects involved in metal–oxide–silicon (MOS) device instabilities have become fairly well understood through studies involving electron paramagnetic resonance (EPR). Recent EPR studies suggest that some of these defects play important roles in the negative bias temperature instability (NBTI). This paper reviews recent NBTI EPR studies as well as earlier EPR studies dealing with other MOS instability problems.     

T型微通道内液滴流型分布及不稳定性分析

以辛烷为分散相、水为连续相,对宽度为200μm、深度为40μm的T型交错微通道内水包油型液液相微反应器的形成进行了实验研究。通过改变分散相和连续相流量比例,在T型节点的下游发现射流状液滴和滴状液滴两种液滴形成方式。比较了两种液滴形成过程中界面张力、黏性剪切力和惯性力的关系,分析了形成两种液滴的界面不稳定性,得到界面不稳定是微尺度下液滴形成的主要原因,而较大的黏性剪切力可以提前激发界面失稳。最后,分析了由表面活性剂的质量分数引起的Marangoni效应对液滴形成的影响。     

Advanced RBSOA analysis for advanced power BJTs

Performances of some modern power BJT's in inductive turn-off are experimentally evaluated, by means of an unclamped non-destructive method. The different instabilities exhibited are classified and their influence on device performances is discussed both in clamped and unclamped applicationsAn “Instability Map” is proposed both as a synthetic picture which eases comparison of reverse-bias performances of devices having different ratings, and as an investigation tool for linking device behaviour to its physical features.It results that RBSOA performances are not just related to lateral dimensions of the emitter, but also to metallization lay-out of the chip, which evidently influences current distribution among cells.Finally, stray elements of testing circuit which affect results of RBSOA measurements are investigated, and some suggestions are proposed in order to let measurement results become independent of testing circuit.     

Spontaneous spatiotemporal instabilities in current modulatedmaster oscillator power amplifier lasers

We provide the first comprehensive theoretical evidence for nonlinear space-time dynamical behavior which seriously degrades the performance of a monolithically integrated master oscillator power amplifier laser under direct current modulation of the master oscillator. A host of instabilities, reflecting dynamical behavior of different sections of the device, are possible. These instabilities are due to the combination of weak feedback from the power amplifier section of the device causing leakage into the master oscillator section, from the buildup of unsaturated carriers along the narrow edges of the expanding flare and differential saturation of the passive regions under the distributed Bragg reflector grating sections     

Design and development of an integrated device consisting of an independent solar cell with electrical storage capacity

A thin film‐integrated device was constructed consisting of photovoltaic layers combined with additional layers to store charge in real time within the same device. In our design, a dye‐sensitized solar cell and capacitor layers are integrated by a double‐anodized titanium plate, which consists of TiO₂ nanotubes grown on either side by electrochemical anodization. The combination device can act either as an independent solar cell, a capacitor, or as a solar cell/capacitor device. The results presented here illustrate the capacitive behavior of high surface area nanotubular metal oxide films, with an achieved capacitance of 140 μF cm⁻². Copyright © 2012 John Wiley & Sons, Ltd.     

Characteristics of radio-frequency-generated plasmas in static magnetic fields

When plasmas are immersed in static magnetic fields a number of plasma instabilities are likely to develop. In turns out that in many cases the type of instability which occurs is in some way related to the method used to generate the plasma. One of the easiest and most common ways of generating a plasma is to pass a radio-frequency current through it. On the other hand, very little is known about the behavior of such RF-generated plasmas when immersed it static magnetic fields. In this paper experiments dealing with the behavior of RF magnetoplasmas are reviewed. It is observed in many different RF experiments that once the static magnetic field exceeds a critical value, the rate at which plasma is transported across the magnetic field is enhanced. This phenomenon, which is known as anomalous diffusion, is accompanied by an onset of fluctuations it plasma density and potential. The characteristics of the experimental onset data are reviewed and compared with the onset conditions of a number of particularly applicable theories. On the basis of this comparison, it is concluded that the ion-acoustic instability comes closest to explaining the experimental behavior of high-frequency discharges in static magnetic fields.     

Stability and spectral behavior of grating-controlled activelymode-locked lasers

Amplitude, timing, and wavelength instabilities in a semiconductor mode-locked laser are studied experimentally and by using an accurate numerical model. It is shown that these instabilities can occur when the RF drive frequency is tuned to give a minimum average pulsewidth. It is shown that experimental measurement techniques, such as sampling and averaging, can mask these instabilities. Using this numerical model, it is shown that the wavelength instability is associated with the amplitude and timing instabilities and that the large broadening of the optical spectrum observed experimentally is caused by a cyclic wavelength instability     

Simulation of arc-circuit instability in a low current DCautomotive switching application

The dynamic arc produced in a switch breaking an inductive load sometimes interacts with the rest of the circuit to produce a highly nonlinear response characterized by growing, high frequency oscillations, current chopping and transient overvoltages. System simulation, therefore, requires an approach that includes switch arc behavior. A technique for employing a well-known equation from power circuit breaker design to analyze such arc-circuit interaction for switch arcs of less than 2 mm in length is described. The so-called Mayr arc equation provides a basis for accurate modeling of arc-circuit instability after one recognizes that the drawn switch arc exists in two distinct phases, for which the mechanisms of arc erosion and instability are effectively decoupled. This approach provides a technique for predicting instabilities in switched automotive electrical systems that could result in either radiofrequency interference to vehicle electronics, or potentially damaging high voltage transients     

Comprehensive Analysis of Random Telegraph Noise Instability and Its Scaling in Deca–Nanometer Flash Memories

This paper presents a comprehensive investigation of random telegraph noise (RTN) in deca–nanometer Flash memories, considering both the nor and the nand architecture. The statistical distribution of the threshold voltage instability is analyzed in detail, evidencing that the slope of its exponential tails is the critical parameter determining the scaling trend for RTN. By means of 3-D TCAD simulations, the slope is shown to be the result of cell geometry, atomistic substrate doping, and random placement of traps over the cell active area. Finally, the slope dependence on cell geometry (width, length, and oxide thickness), doping, and bias conditions is summarized in a powerful formula that is able to predict the RTN instabilities in deca–nanometer Flash memories.      

On Common–Base Avalanche Instabilities in SiGe HBTs

This paper presents a detailed investigation of the key device-level factors that contribute to the bias-dependent features observed in common-base (CB) dc instability characteristics of advanced SiGe HBTs. Parameters that are relevant to CB avalanche instabilities are identified, extracted from measured data, and carefully analyzed to yield improved physical insight, a straightforward estimation methodology, and a practical approach to quantify and compare CB avalanche instabilities. The results presented support our simple theory and show that CB-instability characteristics are strongly correlated with the parasitic base and emitter resistances. The influence of weak quasi-pinch-in effects are shown to contribute additional complexity to the bias dependence of the CB-instability threshold. Measured data from several technology nodes, including next-generation (300-GHz) SiGe HBTs, are presented and compared. Experimental analysis comparing different device geometries and layouts shows that while device size plays an important role in CB avalanche instabilities across bias, these parameters are not sensitive to standard transistor layout variations. However, novel measurements on emitter-ring tetrode transistor structures demonstrate the influence of perimeter-to-area ratio on CB stability and highlight opportunities for novel transistor layouts to increase .     

Processing effects on the morphological stability at epitaxial interfaces

A phenomenological framework has been developed to account for interfacial instabilities during epitaxial growth. It is proposed that these instabilities are influenced by surface phenomena, through modification of surface free energy of the substrate by the first monolayers of the depositing element. Instabilities occuring in the CoSi₂/Si system are considered as an example. Specifically, Gjostein’s (1963) treatment of surface instabilities caused by an adsorbing gas is applied here, and instability criteria are derived in terms of the Herring construction (Herring, 1951).     

Theory of electrothermal behavior of bipolar transistors: part II-two-finger devices

A thorough theoretical and numerical analysis of the electrothermal behavior of two-finger bipolar transistors is presented. It is shown that thermal feedback and coupling effects introduce an additional singularity in the output I-V characteristics, namely a current bifurcation, which manifests itself as multiple solution branches emanating from a branching point. As a result, when the bifurcation condition is reached, the device is triggered in an asymmetrical operation mode in which one device carries most of the current. A unified formulation for the electrothermal behavior of a two-finger device is derived for different bias conditions at the input port: constant voltage, constant base current and constant emitter current. The analysis proofs that the critical condition defining the onset of current bifurcation is the same for all kinds of bias conditions. While operation under a constant base-emitter voltage is limited by the flyback condition, the current bifurcation condition defines the boundary of the normal operation region for the constant base current and constant emitter current cases. Finally, a rigorous method for identifying the conditions of thermal instability for an arbitrary number of emitter fingers is outlined. As an example, the method is used to derive the thermal instability conditions for the general case of temperature dependent thermal conductivity in a two-finger device.