I/f noise in systems showing stochastic resonance

Stochastic resonator systems with input and/or output 1/f noise have been studied. Disordered magnets/dielectrics serve as examples for the case of output 1/f noise with white noise (thermal excitation) at the input of the resonators. Due to the fluctuation-dissipation theorem, the output noise is related to the out-of-phase component of the periodic peak of the output spectrum. Spin glasses and ferromagnets serve as interesting examples of coupled stochastic resonators. A proper coupling can lead to an extremely large signal-to-noise ratio. As a model system, a l/f-noise-driven Schmitt trigger has been investigated experimentally to study stochastic resonance with input 1/f noise. Under proper conditions, we have found several new nonlinearity effects, such as peaks at even harmonics, holes at even harmonics, and 1/f noise also in the output spectrum.     

A theory of 1/f noise

Letu() be an absolutely integrable function and define the random process where thet _i are Poisson arrivals and thes _i, are identically distributed nonnegative random variables. Under routine independence assumptions, one may then calculate a formula for the spectrum ofn(t), S _n(), in terms of the probability density ofs, p_s(). If any probability density p_s() having the property p_s() I for small is substituted into this formula, the calculated S_n() is such that S_n() 1 for small . However, this is not a spectrum of a well-defined random process; here, it is termed alimit spectrum. If a probability density having the property p_s() for small , where > 0, is substituted into the formula instead, a spectrum is calculated which is indeed the spectrum of a well-defined random process. Also, if the latter p_s is suitably close to the former p_s, then the spectrum in the second case approximates, to an arbitrary, degree of accuracy, the limit spectrum. It is shown how one may thereby have 1/f noise with low-frequency turnover, and also strict 1/f ^1– noise (the latter spectrum being integrable for > 0). Suitable examples are given. Actually, u() may be itself a random process, and the theory is developed on this basis.     

PbS红外探测器低频噪声物理模型及缺陷表征研究

为了表征PbS薄膜光导红外探测器的材料缺陷,详细推导了1/f和产生-复合(g-r)噪声物理模型,并由实验数据验证了模型的准确性. 利用1/f噪声与表面缺陷关系,计算了不同偏压下表面陷阱密度. 得到该值随偏压升高而增加,由此得出1/f噪声与所加偏压成正比变化,与实验测试结果相一致. 在此模型基础上,研究了g-r噪声与深能级缺陷特征参量的关系,提出由低频噪声表征缺陷激活能、简并因子、俘获截面等缺陷参数的方法. 关键词： 红外探测器 1/f噪声')" href="#">1/f噪声 噪声')" href="#">g-r噪声 缺陷     

Studies of metal-insulator transition in TiSxSe2-x single crystals

A temperature induced metal-insulator transition has been found in TiS_xSe_2-x single crystals. The M-I transition is found to occur over the temperature range 250° to 300°C for 1.0 ≤ x ≤ 1.7. The present observation of the M-I transition has been compared and contrasted with the earlier reported M-I transition in TiS_1.7 single crystals. Evidence is presented and arguments are put forward in support of the occurrence of the M-I transition in terms of the variation in disorder of the extra Ti atoms in the van der Waals gap. The possible reason for the suppression of the M-I transition in TiS_xSe_2-x for x ≤ 1 is outlined.     

一种估计半导体激光器1/f噪声参数的新方法

对含白噪声的1/f分形信号小波变换系数的方差随尺度变化的关系进行适当的变换,提出了一种基于最小二乘法的估计半导体激光器1/f噪声参数的新方法.实验表明,该方法可以有效地提取出淹没在白噪声中的激光器1/f噪声,而且估计出的噪声信号的功率谱与对比仪器的测量结果有较好的一致性. 关键词： 半导体激光器 f噪声')" href="#">1/f噪声 参数估计 小波分析     

The phase transition in the discrete Gaussian chain with 1/r 2 interaction energy

We exhibit a phase transition from a rough high-temperature phase to a rigid (localized) low-temperature phase in the discrete Gaussian chain with 1/r ² interaction energy. This transition is related to a localization transition in the ground state for a quantum mechanical particle in a one-dimensional periodic potential, coupled to quantum 1/f noise.This paper is dedicated to J. L. Lebowitz on the occasion of his 60th birthday     

Electronic properties and superconductivity of amorphous Si1-xAux alloys near the metal-insulator transition

We report on specific-heat and resistivity measurements on quench-condensed Si_1-xAu_x films for 0.11 ⩽ x 0.36 in the temperature range 0.35 K ⩽ T ⩽ 6 K. A distinct increase of the specificheat derived electronic density of states at the Fermi level is observed at x_b ≈ 0.2, i.e., in the vicinity of the metal-insulator transition occurring for our samples at x_c = 0.16. This suggests a different type of bonding between Au and Si for x < x_b and x > x_b. While resistive transitions to superconductivity are observed for x⩾0.21, the absence of a specific-heat anomaly at the transition points to filamentary superconductivity except for × = 0.35 where a sizable anomaly is seen. The difference in various electronic properties between differently prepared samples of these metastable alloys, in particular the influence of different preparation and annealing temperatures is emphasized. It is suggested that these differences are caused by incipient phase separation in the room-temperature prepared samples.     

Current noise and long time tails in biased disordered random walks

We calculate the mean velocity and the velocity correlation function for a random walk with a uniform bias on a disordered chain. We find a new long time tail in the velocity correlation function due to the combined effects of the bias and of the disorder in the site variables. This long time tail persists to a low-frequency cutoff inversely proportional to the square of the bias. By associating the velocity correlation function with the spectrum of current fluctuations, we calculate the excess low-frequency current noise associated with this long time tail. The spectrum of current fluctuations goes as(I ²/N)f ^–1/2, whereI is the DC current,N is the number of charge carriers, andf is the frequency. The possible connection to 1/f noise is discussed. The calculation is done by a perturbation expansion in the strength of the disorder, but is shown to be exact to all orders for weak enough bias.Supported by a fellowship of the German Academic Exchange Service (DAAD).Supported by the National Science Foundation through Grant No. DMR-8108328 and through the Cornell Materials Science Center.     

基于小波变换和维纳滤波的半导体器件1/f噪声滤波

针对半导体器件中普遍存在的1/f噪声提出了一种结合了提升小波变换和维纳滤波器的处理方法.首先利用重新加权迭代最小二乘法拟合1/f噪声的功率谱曲线得到噪声参数的估计,从而选择恰当的小波.其次,对包含了1/f噪声的信号进行提升小波变换.考虑到小波变换对1/f噪声的白化作用,利用维纳滤波器对每一层小波系数进行处理.设计了最优全通滤波器以校正维纳滤波器的相频特性,使得小波系数经滤波后相位不变.最后利用提升小波逆变换获得被1/f噪声淹没的信号.利用实验检验了提出方法的有效性,实验数据采自用于微创外科手术机器人的力传感器.结果表明提出的方法能够有效抑制1/f噪声,并使传感器的分辨力提高了25%. 关键词： 半导体器件 f噪声')" href="#">1/f噪声 提升小波变换 维纳滤波     

基于辐照前1/f噪声的金属-氧化物-半导体场效应晶体管辐照退化模型

基于金属-氧化物-半导体场效应晶体管(MOSFET)噪声的载流子数涨落和迁移率涨落理论,建立了MOSFET辐照前1/f噪声参量与辐照后分别由氧化层陷阱和界面陷阱诱使阈值电压漂移之间的定量数学模型,并通过实验予以验证.研究结果表明,辐照诱生的氧化层陷阱通过俘获和发射过程与沟道交换载流子,在引起载流子数涨落的同时也通过库仑散射导致沟道迁移率的涨落,因此辐照前的1/f噪声幅值正比于辐照诱生的氧化层陷阱数.利用该模型对MOSFET辐照前1/f噪声与辐照退化的相关性从理论上 关键词： f噪声')" href="#">1/f噪声 辐照 金属-氧化物-半导体场效应晶体管 陷阱     

Optical properties of pure and doped Y3Fe5O12 single crystals

Institute of Physics of Solids and Semiconductors, Academy of Sciences of Belarus, 17, P. Brovka Str., GSP, Minsk, 220072. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 63, No. 4, pp. 667–675, July–August, 1996.     

A unified drain current 1/f noise model for GaN-based high electron mobility transistors

In this work, we present a theoretical and experimental study on the drain current 1/f noise in the AIGaN/GaN high electron mobility transistor （HEMT）. Based on both mobility fluctuation and carrier number fluctuation in a two- dimensional electron gas （2DEG） channel of AlGaN/GaN HEMT, a unified drain current 1/f noise model containing a piezoelectric polarization effect and hot carrier effect is built. The drain current 1/f noise induced by the piezoelectric polarization effect is distinguished from that induced by the hot carrier effect through experiments and simulations. The simulation results are in good agreement with the experimental results. Experiments show that after hot carrier injection, the drain current 1/f noise increases four orders of magnitude and the electrical parameter degradation Agm/gm reaches 54.9%. The drain current 1/f noise degradation induced by the piezoelectric effect reaches one order of magnitude; the electrical parameter degradation Agm/gm is 11.8%. This indicates that drain current 1/f noise of the GaN-based HEMT device is sensitive to the hot carrier effect and piezoelectric effect. This study provides a useful reliability characterization tool for the A1GaN/GaN HEMTs.     

二维约瑟夫森结阵列中的相变及噪声频谱研究

采用电阻分路(RSJ)模型，运用数值计算方法研究二维约瑟夫森结阵列的涡旋度,涡旋密度涨落随温度的变化，表明了超导阵列中存在KTB型相变.还研究了相变点附近的涡旋噪声频谱随温度、驱动电流变化的特性.计算结果与最近实验报导定性一致，并能用涡旋的运动图像来解释噪声频谱的变化规律. 关键词： 高温超导 噪声频谱 约瑟夫森结阵列 KTB相变     

Quality assessments of electrochromic devices: the possible use of 1/<Emphasis Type="Italic">f</Emphasis> current noise

Electrochromic (EC) devices, capable of modulating their optical transmittance by charge insertion/extraction, were produced by laminating films comprised of nanoporous W oxide and Ni–V oxide by a polymer electrolyte and having this three-layer stack between transparent conducting In₂O₃:Sn films backed by polyester foils. 1/f noise in the current (I) was observed when the charged (colored) EC device was discharged via a resistor. The power spectral density S _i at fixed frequency scaled as S _i  ∼ I ². Extended color/bleach cycling degraded the optical quality and homogeneity of the device and concomitantly increased the 1/f noise intensity. These initial data indicate that 1/f noise has a potential to serve as a quality measure for EC devices.     

基于稀疏分解的大功率半导体激光器1/f噪声参数估计的新方法

本文结合1/f噪声信号功率谱随频率成反比变化的关系, 以及稀疏分解可以根据信号灵活构造原子库的特点, 提出一种基于稀疏分解估计大功率半导体激光器1/f噪声的新方法, 构造了具备1/f噪声特点的过完备库. 在该过完备库中通过Matching Pursuit(MP)算法完成了白噪声与1/f噪声混叠信号的稀疏分解. 实验结果显示:该方法估计出淹没在白噪声环境中1/f噪声的γ 参数, 与频谱分析仪的测量结果有较好的一致性, 通过对比不同的过完备库证明了所构造的过完备库的优越性.     

Investigation of nonlinear absorption in YAP and YAG single crystals doped with Co and co-doped with Si

Since our attempts to grow YAP:Co,Si non-linear absorbers have failed, we switched to Czochralski grown YAGs doped with the same ions. This time, however, the new material was found to exhibit excellent, non-linear absorption, which can be used directly in Q-switching elements in laser systems. In this work we report on technology of YAG single crystals doped with Co and Si, their optical properties, and, finally, on their non-linear absorption. An explanation on why the YAPs were found to be inefficient in non-linear absorption was also provided.     

光电耦合器电离辐射损伤电流传输比1/f噪声表征

在研究光电耦合器电离辐射损伤机理基础上,分别建立光电耦合器电离辐射损伤电流传输比(CTR)表征模型和1/f噪声表征模型.结果表明CTR退化和噪声增加都归因于辐射后光敏三极管集电结和发射结处SiO₂/Si界面缺陷增多.根据CTR退化和噪声变化分别与辐射剂量的关系,建立起噪声变化与CTR退化之间的关系,辐照实验对表征模型正确性进行了验证.运用噪声变化与辐射剂量的关系,通过低剂量辐照实验可以预测高剂量辐射后光电耦合器退化程度,故可用于评价光电耦合器抗辐射能力. 关键词： f噪声')" href="#">1/f噪声 光电耦合器 缺陷 模型