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Noise and Fluctuations (ICNF), 2013 22nd International Conference on

Date 24-28 June 2013

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Displaying Results 1 - 25 of 142
  • All the colors of noise

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3707 KB) |  | HTML iconHTML  

    In the frequency domain electrical noise of a two terminal device under steady state is characterized by its spectrum, Sx(f), with X indicating voltage or current fluctuations depending upon the boundary conditions of the experimental/theoretical set-up. The measured spectrum covers the typical range from micro to Tera Hz, corresponding to colors in the dark region for human eyes but clearly detectable by experimental apparata and/or predictable by theoretical modeling. Overall, essential information on the microscopic time scale of charge transport is available from the knowledge of this “dark” noise-spectroscopy. This paper reviews some interesting features of noise spectra that have been challenged during my research activity and which I believe can still be sources of discussion and open problems, as remarked in the text. View full abstract»

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  • How useful is Hooge's empirical relation

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (814 KB) |  | HTML iconHTML  

    Merits of Hooge's empirical relation for 1/f noise are investigated: SR/R2= α/Nf with N the number of free charge carriers and α a parameter with a range: 10-8 <; α <; 10-2, depending on temperature, lattice quality and mobility μ. Parameters affecting the α-value are discussed. We propose a model explaining: α ~ μ-m with m ≈ 3 as observed in undoped quantum wells (QW) and m ≈ 1 attributed to screening as observed in 2DEG's of gated QW. Hooge's relation implies that 1/f noise is a bulk effect. The normalized noise in films for bias, frequency and unit area as Cus [cm2] is proportional to the sheet resistance Rsh[Ω]. The proportionality factor K [cm2/Ω] = Cus/Rsh is also a figure of merit, applicable for materials even if N is unknown. The K- and α-values are a useful metrics. View full abstract»

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  • Low frequency noise in silicon-based devices, circuits and systems

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    Silicon-based devices, circuits and systems are expected to continue to dominate the semiconductor and electronics industries in the near to medium-term. However, to maintain this dominance, several innovations have been made in fabrication technologies, material systems, device architecture, and circuit and system designs. While these innovations have helped to improve their large-signal properties and maintain reliability, often, the result in worse low-frequency noise properties. In this paper, we examine the impact of scaling, material systems used in device manufacture, new device architectures, sensors and sensor systems on the noise characteristics. Finally, from the applications perspective, the push to lower voltages for portable/mobile applications leads to the signal-to-noise dilemma which becomes more challenging with each new generation of scaled technologies. View full abstract»

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  • Low frequency noise characterization in n-channel UTBOX devices with 6 nm Si film

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (590 KB) |  | HTML iconHTML  

    The noise spectra of the studied n-channel UTBOX devices contain flicker noise and Lorentzian components. At room temperature it was found that the flicker noise is explained by the carrier number fluctuation model for both front and back interfaces. Due to the thin silicon film thickness a strong electrostatic coupling between front and back interface was evidenced. The evolution of the low frequency noise versus the temperature allows to identify traps in the silicon film and to make a correlation between the observed traps and some technological steps. View full abstract»

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  • Impact of oxide trap passivation by fluorine on the low-frequency noise behavior of gate-last pMOSFETs

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (645 KB) |  | HTML iconHTML  

    The low-frequency noise of gate-last pMOSFETs is studied, with particular attention to the passivation of oxide traps by fluorine. It is shown that the lowest flicker noise power spectral density is obtained after 6 min of exposure to an SF6 plasma. At the same time, the dominant 1/f-noise mechanism changes from carrier number fluctuations to mobility fluctuations, indicating the de-activation of the gate oxide traps by the plasma treatment. View full abstract»

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  • 1/f Noise of accumulation mode p- and n-MOSFETs

    Page(s): 1 - 4
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    The noise of inversion and accumulation mode MOSFETs has been compared and analysed in terms of doping concentration. For low doping concentration, both devices have similar noise levels. The increase of the doping concentration results in a degradation of the noise to the disadvantage of the accumulation mode n-MOSFETs while its level remains unchanged for the p-MOSFETs. A further increase leads to a drastic reduction of the noise in favour of both accumulation mode n- an p-MOSFETs on account of a change in the nature of the noise source. View full abstract»

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  • Random telegraph noise induced drain-current fluctuation during dynamic gate bias in Si MOSFETs

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    The influence of random telegraph noise (RTN) in MOSFETs on drain current (Id) during transition edge of pulse gate voltage (Vg) was investigated. The Id fluctuation under dynamic Vg was larger than that under de bias by a factor of 2.2. We have revealed that the initial trap occupation states before varying Vg significantly affect the Id values during the transition edge of dynamic Vg. The trap occupation states were governed by the initial time and the profiles of RTN, e.g., the distribution of time constant (τc and τe). The Id fluctuation under dynamic Vg can be controlled according to the profiles of RTN. These results provide useful information for designing an ultra-high speed circuit. View full abstract»

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  • Electron waiting times in mesoscopic transport

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB) |  | HTML iconHTML  

    Investigations of electrical noise and fluctuations in mesoscopic conductors have traditionally involved measurements of the shot noise and the full counting statistics of transferred charges. Recently, the distribution of waiting times between consecutive electrons has been suggested as another useful and complementary characterization of stochastic quantum transport. In this contribution, we provide a brief overview of our recent Geneva efforts to describe and evaluate the electronic waiting time distributions for several types of quantum conductors. For driven single-electron emitters described by quasi-classical master equations, the electronic waiting time distribution provides us with a simple and intuitive picture of the charge transport. For fully phase-coherent conductors, we have formulated a compact determinant formula based on scattering theory that for instance predicts a crossover in the waiting time distribution for a quantum point contact from Wigner-Dyson statistics at full transmission to Poisson statistics close to pinch-off. Finally, to describe the influence of dephasing as well as non-Markovian dynamics, we have employed an open-quantum-systems approach and evaluated the waiting times between electrons propagating through a dissipative double quantum dot. We conclude by providing an outlook on future work and identify possible avenues for further developments. View full abstract»

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  • Dynamic behaviors of the charge carriers investigated by means of noise spectroscopy

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (369 KB) |  | HTML iconHTML  

    Fluctuation Spectroscopy is a very informative method to study the dynamic behavior of the charge carriers and the kinetic processes in condensed matter. Investigation of noise properties is a powerful technique, especially when complemented with standard transport measurements based on average quantities. Various materials have been tested, ranging from Mn oxides, to novel superconductors, to carbon nanotube composites. In all cases, the 1/f noise dependence on external parameters, such as temperature, bias current, and/or electric field, is usually characterized by non-standard properties. View full abstract»

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  • Highly sensitive nanohall sensors on GaAlAs/GaAs heterojunctions

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    We present an experimental study on the performance of nano-Hall sensors made on the two dimensional electron gaz of a pseudo morphic GaAlAs/GaInAs heterostructures. The active area of the sensor is from sub-micronic scale (down to 500 nm) to 5 microns. Ohmic contacts have micronic size, and a reference sample of 80 micron width has been caracterized as well, as a reference. In our process, we have improved the contacts technology to limit the thermal Shottky noise. Thus although ohmic contacts have small dimensions they have low resistance and do not limit the sensitivity of our nano-sensors. Extensive caracterization of those devices demonstrate a diffusive transport at 300 K, and a magnetic field sensitivity up to 1000 V/T/A. We have focused our attention on the smallest detectable magnetic field in the smallest sensor, and performed a systematic study of the noise measurements. We have measured the excess noise in both the longitudinal configuration and the Hall configuration, as a function of the current. Our noise measurements performed at room temperature in the range [1 Hz-100 kHz] show, at low frequency, an 1/f noise spectrum whose intensity is proportional to the square of the current. We understand our data by the conductivity fluctuations model and we obtain the Hooge parameter for this technology. We demonstrate that the noise intensity is inversely proportional to area of the sensor. Of course reducing the dimensions induces physical limitations but we demonstrate that a magnetic field of few μT can be measured with a micron scale sensor at low frequencies; at higher frequencies, when the thermal noise limits the resolution, the measurement of 300 nT is achievable. View full abstract»

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  • Energy and particle number fluctuations in superconducting heterostructures

    Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (290 KB) |  | HTML iconHTML  

    We consider fluctuations of the energy on a mesoscopic island coupled to two leads. We use the Keldysh effective action formalism to derive the Langevin equation for the energy of the island in a very general setting and show how the Langevin equation for the case of uncorrelated tunneling events is derived from a more general one. As an application of the theory, we consider a superconducting island coupled to two normal metal leads and calculate the statistics of the temperature (in the quasiequilibrium case) and the number of quasiparticle excitations on the island. View full abstract»

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  • Noise in terahertz detectors based on semiconductor nanochannels

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    By means of Monte Carlo simulations, we calculate (and compare with experimental results) the Noise Equivalent Power (NEP) in AlGaN/GaN-based submicron self-switching diodes at zero bias and provide guides for detection optimization in terms of number of devices and geometry (width and length of the channel). We also calculate the NEP under biased conditions. View full abstract»

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  • Accurate predictions of terahertz noise in ultra-small devices: A limiting factor for their practical application?

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    With the aim of manufacturing faster devices, the electronic industry scales down device's dimensions and is today entering into a nanoscale and Terahertz frequency regimes. In this work, we show how the reduction of the length L of the active region of two terminal devices implies (apart from the expected improvement of their dynamic behavior) a typically disregarded increment on the fluctuations of the current. In particular, the high-frequency current fluctuations are proportional to 1/L so that the noise grows unlimitedly when the device's dimensions are reduced. This important drawback, common to classical and quantum regimes, remains mainly unnoticed by the scientific community. View full abstract»

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  • Modeling of the emission/noise temperature in MOSFET/HEMT structures

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (206 KB) |  | HTML iconHTML  

    A generalization of the approach which describes the emission capabilities of micron and submicron semiconductor structures in terms of the spectrum of thermally non-equilibrium noise/emission temperature is considered for the case of three-terminals FET/HEMT structures. By using, in the framework of hydrodynamic approach, a direct numerical modeling of the frequency dependence of the components of the small-signal impedance/admittance and spectral densities of voltage/current fluctuations at FET/HEMT terminals, it is shown that: (i) in contrast with two-terminal devices (diodes) the emission capabilities of FET/HEMT cannot be characterized by a single spectrum of the noise/emission temperature, and (ii) the character of the noise/emission temperature spectrum depends on both the choice of the FET/HEMT loading circuit which contains the emitting antenna (source-to-drain or source-to-gate) and the operation mode (constant current or constant voltage) of the accompanying non-emitting external circuit. View full abstract»

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  • Numerical simulation of non-homogeneous 2D-CNT structures

    Page(s): 1 - 4
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    A numerical model for inhomogeneous devices simulation as 2D-carbon nanotubes thin films is presented. This model takes into account nonlinear effects, in this work the proposed approach is based on tube-tube junctions which are presented as nonlinear dipoles depending on the nature of each junction (M/M), (SC/SC) and (M SC). Modified Nodal Analysis “MNA” and the adjoint network method are respectively used to simulate the current and the 1/f noise. This type of simulation allows understanding and analyzing of unexpected experimental results. In this paper simulation point-out the impact of nanotubes' clusters on the 1/f noise behavior of the NT films. View full abstract»

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  • Numerical simulation of shot noise in disordered graphene

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (263 KB) |  | HTML iconHTML  

    Following the intriguing results analytically obtained for the shot noise suppression in wide and short graphene samples with doped contacts, efforts were made to achieve an experimental verification, and, while one experiment yielded a clear confirmation of the theory, another one provided data with no clear dependence of the Fano factor on gate voltage. This was attributed to the presence of a disordered potential. Here we perform a numerical study, based on an envelope function analysis, of disordered graphene samples with different aspect ratios, focusing in particular on the dependence of shot noise suppression on gate voltage. We conclude that such a dependence should survive, unless disorder with an unrealistically large amplitude is considered. View full abstract»

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  • Applications of integrated solar cells in low noise instrumentation

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    Small sized solar cells in compact SOIC packages are investigated as candidates for the design of floating low noise voltage reference to be used in low noise applications. The noise introduced by the solar cell as a function of the incident light is investigated and a simplified model is extracted that can be used, together with a proper filtering stage and a closed loop control system, for the implementation of very low noise, high accuracy programmable voltage and current sources. In proper conditions and down to a few hundreds mHz, the residual low frequency noise of such sources can be reduced down to the noise introduced by the very low noise JFET devices employed for the realization of the output buffer (voltage sources) or of the voltage to current converter (current sources). View full abstract»

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  • Thermal noise measurements on micro-cantilevers coated with dielectric materials

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (702 KB) |  | HTML iconHTML  

    In recent years an increasing number of devices and experiments are shown to be limited by mechanical thermal noise. In particular sub-Hertz laser frequency stabilization and gravitational wave detectors, that are able to measure fluctuations of 10-18 m/√(Hz) or less, are being limited by thermal noise in the dielectric coatings deposited on mirrors. We present a novel technique of structural relaxation analysis based on the direct thermal noise measurements on micro-cantilevers and we compare it with the results obtained from the mechanical loss measurements. The dielectric coatings are deposited by ion beam sputtering. The results presented here give a loss angle of annealed tantala and as-deposited silica coatings of (3.9 ± 0.4)·10-4 and (5.8 ± 1.0)·10-4 respectively, from 10 Hz to 20 kHz. View full abstract»

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  • Noise partition in S-parameter measurement

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    The noise in vector network analyzer (VNA) and time domain reflectometer (TDR) is analyzed from perspective principle of operation and instrument hardware, complementing the metrological and black-box modeling, which use phenomenological input for the noise. The analyses and experiments confirm a noise partition in the S-parameter measurement. The partition is between noise from signal generator and measurement, and between low-frequency plateau and quadratic elevation in the noise spectra at high frequency. The noise scales with the thermal noise in an effective noise bandwidth, signal power and power loss. The noise partition is an input for other models, providing for scaling of the random error with measurement settings, frequency and S-parameter values. View full abstract»

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  • Stochastic dynamics of remote knock-on permeation in biological ion channels

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (158 KB) |  | HTML iconHTML  

    Brownian dynamics simulations provide evidence for a remote knock-on mechanism facilitating the permeation of a biological ion channel by an ion that is initially trapped at the selectivity filter (SF). Unlike the case of conventional direct knock-on, the second ion that instigates permeation does not need to enter the channel. Nor does it necessarily take the place of the permeating ion at the SF, and it can even be of a different ionic species. The study is based on the simultaneous, self-consistent, solution of the coupled Poisson and Langevin equations for a simple generic model, taking account of all the charges present. The new permeation mechanism involves electrostatic amplification attributable to the permittivity mismatch between water and protein: the arrival of the instigating ion at the channel entrance reduces the exit barrier for the ion trapped at the SF, facilitating escape. View full abstract»

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  • Non-Gaussian fluctuations in opsins

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB) |  | HTML iconHTML  

    We investigate conductance fluctuations of two transmembrane proteins, bacteriorhodopsin and proteorhodopsin, belonging to the family of opsins. These proteins are sensitive to visible light and are promising biomaterials for the realization of novel photodevices. The conductance exhibits, over a threshold bias value, a rapid increase which is well described by a power-law behaviour. In the same way, over the threshold value the variance fast decreases following a power-law. Furthermore, the conductance fluctuations evidence a non-Gaussian behaviour with a probability density function (PDF) which follows a generalized Gumbel distribution, typical of extreme-value statistics. The theoretical model is validated on existing current-voltage measurements and the interpretation of the PDF of conductance fluctuations is proven to be in line with the microscopic mechanisms responsible of charge transport. View full abstract»

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  • Signals of critical transitions in ecosystems associated with fluctuations of spatial patterns

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    The identification of early-warning signals of critical transitions represents a crucial issue for semi-arid ecosystems which are strongly exposed to desertification risks. Previous studies in this field suggested that the observation of vegetation patchiness and, in particular, changes in the patch size distributions, could provide early indicators of desertification transitions. Through numerical simulations based on a cellular automaton model, we have investigated the time fluctuation properties of several quantities characterizing the vegetation patterns of semiarid ecosystems under different conditions. At increasing value of a mortality parameter measuring the strength of external stresses, we have found different and earlier transition indicators, related to the time fluctuations of the biggest cluster size. View full abstract»

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  • Fluctuation analysis of the three agent groups herding model

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (313 KB) |  | HTML iconHTML  

    We derive a system of stochastic differential equations simulating the dynamics of the three agent groups with herding interaction. Proposed approach can be valuable in the modeling of the complex socio-economic systems with similar composition of the agents. We demonstrate how the sophisticated statistical features of the absolute return in the financial markets can be reproduced by extending the herding interaction of the agents and introducing the third agent state. As well we consider possible extension of proposed herding model introducing additional exogenous noise. Such consistent microscopic and macroscopic model precisely reproduces empirical power law statistics of the return in the financial markets. View full abstract»

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  • Microwave noise in InP and SiGe HBTs: Modeling and challenges

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    DC, RF and noise characteristics of advanced InP/InGaAs DHBTs and Si/SiGe HBTs were measured and modeled in a broad frequency and temperature range. A systematic model for correlated noise in bipolar transistors and its implementation in HICUM/LO v.1.31 and L2 v.2.31 is presented. The models were verified on SiGe HBTs up to 500 GHz with device simulation results from hydrodynamic and Boltzmann transport equation. HICUM with its implemented noise model also shows very good agreement with measured data in a broad frequency range. The verified model was used for noise analysis of advanced InP/InGaAs DHBTs and Si/SiGe HBTs. It was shown that shot noise correlation for high/speed InP/InGaAs DHBTs is not significant. Compared to Si/SiGe HBTs a higher noise at lower microwave frequencies was observed in InP/InGaAs DHBTs due to their high base recombination current. Nevertheless InP DHBTs show a good noise performance beyond 100 GHz and, due to better fT BVCEO, can compete with advanced Si/SiGe HBTs for LNA design. View full abstract»

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  • A study on scaling behavior of responsivity and low frequency noise of Si MOSFET-based terahertz detectors

    Page(s): 1 - 4
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    We study scaling behaviour of terahertz responsivity and low-frequency noise of silicon MOSFET-based detectors. A set of 550-GHz resonant patch-antenna-coupled transistors with different channel widths varying from 320 nm to 1920 nm have been fabricated and investigated in temperature range from 77 K to 360 K. We find that the best sensitivities are achieved for narrowest devices without applied bias. When biased, all samples exhibit strong contributions random-telegraph switching noise. Characteristic time constants of the generation and recombination processes in investigated transistors vary from millisecond to microseconds. View full abstract»

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