On Rank Driven Dynamical Systems

We investigate a class of models related to the Bak–Sneppen (BS) model, initially proposed to study evolution. The BS model is extremely simple and yet captures some forms of “complex behavior” such as self-organized criticality that is often observed in physical and biological systems. In this model, random fitnesses in \([0,1]\) are associated to agents located at the vertices of a graph \(G\) . Their fitnesses are ranked from worst (0) to best (1). At every time-step the agent with the worst fitness and some others with a priori given rank probabilities are replaced by new agents with random fitnesses. We consider two cases: The exogenous case where the new fitnesses are taken from an a priori fixed distribution, and the endogenous case where the new fitnesses are taken from the current distribution as it evolves. We approximate the dynamics by making a simplifying independence assumption. We use Order Statistics and Dynamical Systems to define a rank-driven dynamical system that approximates the evolution of the distribution of the fitnesses in these rank-driven models, as well as in the BS model. For this simplified model we can find the limiting marginal distribution as a function of the initial conditions. Agreement with experimental results of the BS model is excellent.     

Accurate extraction of trap depth responsible for RTS noise in nano-MOSFETs

This paper presents an accurate analytical model of the random telegraph signal(RTS) noise time-constant ratio(τc/τe) for RTS noise in nano-MOSFETs,in which the Coulomb-blockade effect on trapping and detrapping processes was taken into account.Based on this new model,the depth of the trap responsible for RTS noise in a sample n-type nano-MOSFET is extracted.The results show that large errors will be introduced to the calculated trap depth when the Coulomb-blockade effect is neglected.     

Probing the spin state of a single electron trap by random telegraph signal

We have studied the random telegraph signal (RTS) generated by a single paramagnetic spin center adjacent to a submicrometer silicon metal-oxide-semiconductor field-effect transistor. An in-plane magnetic field induces a substantial change in the statistics of the RTS. We show that a model using the grand partition theorem can qualitatively explain the change in statistics of the RTS as a function of the applied magnetic field. While the data at high temperatures can be well described by this simple model, quantitative discrepancy increases as the temperature is lowered.     

Argon-ion laser direct-write Al deposition from trialkylamine alane precursors

This paper studies the Hot-Carrier (HC) degradation of submicrometer Si MOSTs by the changes in the Random Telegraph Signal (RTS) parameters. It is demonstrated that the amplitude of a pre-existing RTS is markedly changed after stress. In linear operation, a reduction is generally observed for n-MOSTs, while an increase is found for p-MOSTs. For larger drain voltages, the changes are most pronounced in reverse operation, i.e. with source and drain switched, for a forward stress. Hence, the trap-amplitude asymmetry increases after stress. As is demonstrated, there exists a close correlation between the observed changes in the RTS amplitude and in the static device parameters. A simple, first-order model is derived, showing that the HC stress-induced reduction (n-channel), or increase (p-channel) is proportional to the variation of the oxide/interface charge density near the drain. Alternatively, it is demonstrated that the normalized change in the RTS amplitude is equal to the normalized conductance change of the narrow hot-carrier damaged region.     

Pressure effect study on the I－V property of the GaAs-based resonant tunnelling structure by photoluminescence measurement

This paper discusses the I-V property of the GaAs-based resonant tunnelling structure （RTS） under external uniaxial pressure by photoluminescence studies. Compressive pressure parallel to the [110] direction, whose value is determined by Hooke＇s law, is imposed on the sample by a helix micrometer. With the increase of the applied external uniaxial compressive pressure, the blue shift and splitting of the luminescence peaks were observed, which have some influence on the I-V curve of RTS from the point of view of the energy gap, and the splitting became more apparent with applied pressure. Full width at half maximum broadening could also be observed.     

Random telegraph signal noise simulation of decanano MOSFETs subject to atomic scale structure variation

As MOSFETs shrink into the decanano regime it is predicted that random telegraph signals (RTS), resulting from trapping events in defect states near the Si/SiO₂ interface, will significantly affect analogue and digital circuit performance. At these same scales, intrinsic parameter fluctuations introduced by atomic differences between devices will also be significant. In this work, a methodology based on 3D simulation is developed which can correctly model RTS noise in the time and frequency domain in the presence of random discrete dopants. The approach is illustrated with results obtained for 30×30  nm devices. We find that atomicity can significantly increase RTS magnitude in devices with particular doping configurations, and ensemble average RTS effects vary markedly from those predicted on an assumption of continuous doping.     

Non-Triviality of a Discrete Bak–Sneppen Evolution Model

Consider the following evolution model, proposed in ref. 1 by Bak and Sneppen. Put N vertices on a circle, spaced evenly. Each vertex represents a certain species. We associate with each vertex a random variable, representing the state or fitness of the species, with values in [0,1]. The dynamics proceeds as follows. Every discrete time step, we choose the vertex with minimal fitness, and assign to this vertex, and to its two neighbours, three new independent fitnesses with a uniform distribution on [0,1]. A conjecture of physicists, based on simulations, is that in the stationary regime, the one-dimensional marginal distributions of the fitnesses converges, when N, to a uniform distribution on (f,1), for some threshold f<1. In this paper we consider a discrete version of this model, proposed in ref. 2. In this discrete version, the fitness of a vertex can be either 0 or 1. The system evolves according to the following rules. Each discrete time step, we choose an arbitrary vertex with fitness 0. If all the vertices have fitness 1, then we choose an arbitrary vertex with fitness 1. Then we update the fitnesses of this vertex and of its two neighbours by three new independent fitnesses, taking value 0 with probability 0<q<1, and 1 with probability p=1–q. We show that if q is close enough to one, then the mean average fitness in the stationary regime is bounded away from 1, uniformly in the number of vertices. This is a small step in the direction of the conjecture mentioned above, and also settles a conjecture mentioned in ref. 2. Our proof is based on a reduction to a continuous time particle system.     

Microwave irradiation effects on random telegraph signal in a MOSFET

We report on the change of the characteristic times of the random telegraph signal (RTS) in a MOSFET operated under microwave irradiation up to 40 GHz as the microwave field power is raised. The effect is explained by considering the time dependency of the transition probabilities due to a harmonic voltage generated by the microwave field that couples with the wires connecting the MOSFET. The RTS experimental data are in agreement with the prediction obtained with our model.     

A percolation study of RTS noise in deep sub-micron MOSFET by Monte Carlo simulation

Based on percolation theory and random telegraph signal (RTS) noise generation mechanism, a numerical model for RTS in deep submicron metal-oxide-semiconductor field-effect transistor (MOSFET) was presented, with which the dependence of Tc/Te (where Tc=capture time, Te=emission period ) on energy levels and trap depth with respect to the interface of traps can be simulated. Compared with experimental results, the simulated ones showed a good qualitative agreement.     

Scale-free networks from varying vertex intrinsic fitness

A new mechanism leading to scale-free networks is proposed in this Letter. It is shown that, in many cases of interest, the connectivity power-law behavior is neither related to dynamical properties nor to preferential attachment. Assigning a quenched fitness value x(i) to every vertex, and drawing links among vertices with a probability depending on the fitnesses of the two involved sites, gives rise to what we call a good-get-richer mechanism, in which sites with larger fitness are more likely to become hubs (i.e., to be highly connected).     

On the gate- and drain-voltage dependence of the RTS amplitude in submicron MOSTs

The experimental gate- (V _GS) and drain-voltage (V _DS) dependence of the fractional Random Telegraph Signal (RTS) amplitude I _D/I _D, obtained on a large series of submicron Metal-Oxide Semiconductor Transistors (MOSTs), is reported. The observed variation of the RTS amplitude in linear operation is discussed in view of recently published models. As will be shown, the large spread in weak-inversion amplitudes can only be explained by taking into account the microscopic nature of the oxide trap and its environment. The position of a trap along the channel can in principle be retrieved from studying the so-called RTS amplitude asymmetry, defined as the V _DS dependence of the amplitude in both normal and reverse operation of the transistor. Widely different asymmetry behaviour is observed in this work. Here, a qualitative model will be derived which gives a more refined analysis and offers some deeper insight than existing theories. However, to fully understand the RTS amplitude in weak inversion, more microscopic detail is needed.     

Statistical fluctuations for the noise current from random telegraph signals in semiconductor devices: Monte Carlo computer simulations and best fits

Random Telegraph Signals (RTS) has become a major source of variability in the electrical behavior of modern transistors. The major contribution of this work is a new model based on a Monte Carlo algorithm for the mechanisms leading to RTS noise in semiconductor devices. To describe the statistical sample noise current produced by Monte Carlo simulations we experiment with many possible fits using different functions. In order to perform this fitting we follow two distinct approaches: (a) by calculating the sampling moments and by direct substitution in assumed distributions and (b) by performing a non-linear fit using the Levenberg Marquardt algorithm. Our results show a breaking of gaussianity for the nanometer dimensions of deeply scaled technologies, and we show that the ECS peak function is the most appropriate distribution to fit suitably the data for these dimensions. Another relevant contribution is the study of how ballistic effects can change the current distribution. The results indicate an enlargement of the average and variance of the total current when ballistic effects are considered, which are analytically expressed as a function of relevant physical parameters of the semiconductor device.     

Electroreflectance and photoluminescence measurement of passivation by hydrogenation in GaAs/AlGaAs structures

We have studied by electrolyte electroreflectance and photoluminescence a GaAs/AlGaAs resonant tunneling structure (RTS) with a highly n-doped GaAs cap, before and after hydrogenation. We measured the amount of passivation of shallow donor states and of deep traps in the cap and found the approximate pinning levels and interace charges of the RTS.     

Measurement of the moments of the relaxation time spectrum of a liquid by pulsed acoustic spectroscopy

On the basis of theoretical results describing the propagation of short acoustic pulses in relaxation media, the temporal characteristics of a signal that carry the information on the first five moments of the relaxation time spectrum (RTS) are determined. The measurement of these characteristics forms the basis of the proposed variant of pulsed acoustic spectroscopy of relaxation media. An experimental setup was developed in which short acoustic pulses were excited by a neodymium glass laser. Test measurements of RTS moments for an acetic acid, the liquid with a single relaxation time, are carried out.     

The combination of QoS,aggregation and RTS/CTS in Very High Throughput IEEE 802.11ac networks

We consider a single WiFi cell in which multiple mobile stations transmit multiple QoS constrained Application flows to the Access Point. We investigate the efficiency of using RTS/CTS in the face of the QoS constraints, in various Access Categories that are defined in the WiFi standard, in a number of transmitting stations and in various amounts of aggregation. We show that using RTS/CTS is efficient in terms of Throughput, when there are collisions and the time to recover these collisions is within the Delay/Loss constraints of the Application flows. It turns out that RTS/CTS is most efficient in the Video and Voice Access Categories and Delay constrains in the order of several tens of milli-seconds. For smaller Delay constraints it is more efficient without RTS/CTS. Thus, we show the existence of cross-points: In Delay constraints smaller than the cross points it is more efficient without RTS/CTS and beyond the cross-points the opposite is true.     

Identification of inherent noise components of semiconductor devices on an example of optocouplers

In the paper, a method of estimation of parameters of Gaussian and non-Gaussian components in the noise signal of semiconductor devices in a frequency domain is proposed. The method is based on composing estimators of two spectra, corresponding to 1/f^α noise (Gaussian component) and two-level RTS noise (non-Gaussian component). The proposed method can be applied for precise evaluation of the corner RTS frequency fRTS in the noise spectrum.     

Burst and 1/f noise in light-emitting diodes with quantum dots

We study the low-frequency electric noise characteristics of light-emitting diodes with InAs quantum dots in a GaInAs layer. Burst noise having the character of random telegraph signal (RTS) is found against the 1/f noise background in the noise voltage of some specimens. A procedure based on the standard theory of signal detection against the noise background is proposed for a separate study of these noise components. It is found that Hooge’s empirical relation applied to p-n diodes for the first time by Kleinpenning is also applicable to 1/f noise in quantum-dot diodes. The current dependences of statistical characteristics of the 1/f and RTS noise components are compared to show that the physical origins of RTS noise and 1/f noise in the studied specimens are different. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 5, pp. 437–447, May 2006.     

Gore-Tex Medialization Thyroplasty: Objective and Subjective Evaluation

Management of vocal fold paralysis and paresis continues to give rise to controversy and the use of numerous surgical techniques. The senior authors' (RTS, JRS) initial experience with fourteen patients using Gore-Tex Medialization Thyroplasty suggests that this technique has value. Evaluation included pre- and postoperative videostroboscopic assessment, aerodynamic measures, acoustic analysis, phonatory analysis, psychoacoustic evaluation, and patient self-evaluation. Stroboscopic and perceptual assessments were blinded. Statistical analysis supports the efficacy of this technique.     

Analysis of the uncertainties in the physical calculations of water-moderated power reactors of the VVER type by the parameters of models of preparing few-group constants

The article covers the uncertainty analysis of the physical calculations of the VVER reactor core for different meshes of the reference values of the feedback parameters (FBP). Various numbers of nodes of the parametric axes of FBPs and different ranges between them are investigated. The uncertainties of the dynamic calculations are analyzed using RTS RCCA ejection as an example within the framework of the model with the boundary conditions at the core inlet and outlet.     

Analysis of noise properties of an optocoupler device

In the paper, localization of a source of random telegraph signal noise (RTS noise) in optocoupler devices of CNY 17 type was defined. The equivalent noise circuit in low frequency noise for these types of optocouplers was proposed.