Simulation of a microprofile and electric field distribution in MIM structures

Simulation of etching of a microtip’s lower electrode and deposition of a dielectric film has shown that the film undergoes a strong thinning at lateral surfaces and at the microtip’s bases. It is demonstrated that, at a microtip density of 5 × 10⁸ cm⁻², the electric field’s strength at the base of the tip is 3.5 times that at its apex, which gives rise to additional emission centers.     

单周期超短脉冲光束的时空传输

当电偶极子以高斯脉冲形式随时间振荡时，辐射出的电磁场可以用来描写非缓变包格近似条件下单周期超短脉冲光束在自由空间中的传输特性。利用复点源模型，通过分析和计算，我们得出它的传输特性。第一，在空间传输过程中，单周期超短脉冲高期光束能流密度基本保持高斯函数不变，振幅大小随不同的z平面振荡。第二，单周期超短脉冲光束在真空中主要以光速c沿z方向传输。在传输过程中，脉冲宽度保持不变，脉冲形状演变成不对称。能流密度不再随时间作简谐振荡，它的振幅构成一个高斯形状的包络。     

Computation of Dyadic Green’s functions for generalized cylinders in free space

Dyadic Green’s functions are powerful and efficient for solving the boundary problems in electromagnetic theory. The key problem involved is how to deal with the additional term in the electric dyadic Green’s function at the source region. In this paper, the dyadic Green’s functions for generalized cylinders in free space are derived with the technique in another paper of author (1984). The dyadic Green’s functions for conducting wedges, half-plates and elliptic cylinders, whose integral of continuous spectrumh has been eliminated, are given particularly.     

The near-field thermal microwave radiation response of a biological object to the local change of the lateral temperature distribution

A layer-by-layer method is theoretically developed for reconstructing the temperature distribution inside a biological object from the measured outgoing thermal microwave radiation energy flux. The measurement is carried out along the plane parallel to the heated object surface in the surface’s near-field area. The equation of the inverse problem is obtained. The equation couples the 2D spatial Fourier-component of Poynting’s outgoing radiation vector with the similar Fourier-component of the lateral temperature distribution along elementary inner layers parallel to the object surface. The obtained equation is solved for the case of a 1D periodic or local depth-uniform lateral temperature distribution inside an object. The effective half-width of the spatial-harmonic spectrum for the outgoing thermal radiation energy flux is shown to be estimated by the double wave number inside the object. At the same time, the spatial half-width of a biological object’s thermal-radiation response to a local change in the lateral temperature distribution is estimated as a half of the wavelength inside the object. This result justifies the antenna size conventionally applied in biomedical research.     

Effect of surface conduction in the semiconductor electrode on the distribution of the gas-discharge current

A planar gas-discharge structure, in which one of the electrodes is a high-resistivity semiconductor capable of providing stable uniform distribution of the current and the gas-discharge’s light emission within the entire volume of the gas-discharge gap, is studied. It is established that the effect of the semiconductor electrode on the distribution of the steady-state current in the gas-discharge gap is associated with the conductivity of the electrode’s surface layer, whereas the resistance of the semiconductor bulk defines only the load resistance. It is experimentally shown that local metallization of the semiconductor surface results in current pinching in the metallized areas. It is concluded that the basic physical effect that limits the probability of current pinching and provides stable discharge is associated with the electric field orthogonal to the current pinch at the point of its contact with the semiconductor. A qualitative analysis of this effect is presented. The obvious condition of smallness of this field compared to the longitudinal field in the pinch allows two types of pinching: one corresponds to the formation of a solitary pinch at a fairly high conductivity of the semiconductor’s surface layer, whereas the other corresponds to the formation of a large number of pinches, almost totally covering the surface of the electrode, at a low surface conductivity.     

Effect of avalanche-type barrier discharge on a silver halide photographic material in the case of blocked ionic conductivity

Imaging of avalanche-type barrier gas discharge excited by single videopulses ∼7 μs long is studied via chemical activation of an ion subsystem of microcrystals of silver halide photographic emulsions by 1-phenyl-5-mercaptotetrazole. Using “Retina” commercial X-ray film and specially fabricated photoemulsion microcrystals with effective surface and deep electron traps as an example, the selective gas-discharge sensitivity of photographic layers to applied-voltage polarity is detected. It is shown that their sensitivity to barrier discharge ignited by negative-polarity pulses (on the electrode with a photographic material) is higher than in the case of positive pulses, irrespective of the photographic material’s position in the capacitor system.     

多脉冲飞秒激光烧蚀铝靶动态特性研究

利用时间分辨阴影图研究了脉冲能量在200微焦的多脉冲飞 秒激光烧蚀铝靶的动态过程、并使用 扫描电镜研究了靶材表面烧蚀区域的形貌特征。时间分辨阴影图的记录结果表明,在不同时 间延迟条件 下,飞秒激光烧蚀铝靶形成的冲击波体积和喷射物的空间分布均随着脉冲个数的增加而发生 不同程度的变 化,尤其是单脉冲烧蚀情况下在1ns延时阴影图中观察到的近同心圆条纹会随着脉冲数目增 加逐渐变得模 糊乃至消失。烧蚀区的电子扫描显微镜图像清楚地揭示出烧蚀过程中伴随有液态铝的产生, 其溅射凝固后 在靶材表面形成小球和细丝状微纳结构。实验结果进一步证实了由前序脉冲烧蚀导致的铝靶 表面结构的改 变会对后继脉冲的烧蚀产生显著影响,从而使多脉冲烧蚀表现出明显不同于单脉冲烧蚀的特 性。这些结果 对飞秒激光脉冲沉积薄膜、直写生成表面微结构等应用的工艺参数优化具有很好的指导意义 。     

Analysis of rectangular microstrip patch antenna covered with N-dielectric layers

A generalized spectral Green’s function formulation of N-layer substrate structure is given with three dimension sources, which is a set of closed form formulas. A full-wave analysis model for rectangular microstrip antennas covered with N-dielectric layers has been established by using the above spectral Green’s function. The unknown surface current density on the microstrip patch for such structure is found as a solution of an integral equation. The input VSWR and radiation patterns of the antenna are also obtained. The numerical results have been verified by the experimental results. Partly supported by the Research Item B96(56) of the Ministry of Railways of China     

Hole trapping in E-beam irradiated SiO2 films

Low energy (25 kV) electron beam irradiation of MOS capacitors is shown to produce neutral hole traps in thin ‘radiation hardened’ SiO₂ films. These traps are found in an uncharged state after irradiation and are populated by passing a small hole current, generated by avalanche breakdown of then-type silicon substrate, through the oxide. From the time dependence of the observed trapping, a capture cross-section between 1 × 10∼⁻¹³ and 1 × 10⁻¹⁴ cm² is deduced. The trap density is found to depend on the annealing conditions and incident electron beam dosage. The density of traps increases with incident electron beam exposure. Once introduced into the oxide by the radiation the traps can be removed by thermal anneals at temperatures above 500° C. Parallels between electron and hole trapping on these neutral centers are strong evidence for an amphoteric uncharged trap generated by ionizing radiation.     

超短脉冲强激光大气传输的非线性效应

超短脉冲强激光大气传输在光学遥感、电子对抗、以及人工放电等方面具有重要的应用．例如,利用超短脉冲强激光使得远距离处的大气局域电离,其所产生的紫外辐射可以为大气组分主动荧光光谱学研究提供光源。对短脉冲强激光在大气中的传输进行了理论分析,对超短脉冲强激光大气传输中的各种线性效应及非线性效应,诸如色散效应、非线性自聚焦效应、受激拉曼散射效应、多光子电离及隧道电离效应、电离引起的能量损耗效应、相对论聚焦、有质动力激发的等离子体尾波场等效应进行了讨论,给出了一组描述超短脉冲强激光大气传输的三维非线性传输方程,为此类问题的进一步研究提供了理论基础。     

FORWARD GATED-DIODE R-G CURRENT METHOD:A SIMPLE NOVEL TECHNIQUE FOR CHARACTERIZING LATERAL LIGHTLY DOPING REGION OF LDD MOSFET’s

 This paper presents a simple novel technique-forward gated-diode R-G current method-to determine the lateral lightly-doped source/drain (S/D) region interface state density and effective surface doping concentration of the lightly-doped drain (LDD) N- MOSFET’s simultaneously. One interesting result of the numerical analysis is the direct characterization of the interface state density and characteristic gate voltage values corresponding to LDD effective surface doping concentration. It is observed that the S/D N- surface doping concentration and corresponding region’s interface state density are R-G current peak position and amplitude dependent, respectively. It is convincible that the proposed method is well suitable for the characterization of deep sub-micron MOSFET’s in the current ULSI technology.     

Malfunctioning of Microcontroller Irradiated with Ultrashort Ultrabroadband Pulse Trains

Effect of the number of ultrashort ultrabroadband pulses with a repetition rate of 1 kHz on malfunctioning of microcontroller in radio transparent housing is studied when the device is irradiated using pulse trains at a pulse duration of about 10^–10 s and radiation frequencies ranging from 1 to 30 GHz. The radiation is received by internal conducting stripes that connect the electronic circuit and external outputs. The malfunction probability is determined by the number of pulses in the pulse train, pulse number, and electric field strength. It is shown that malfunctioning is predominantly caused by the leading pulses in the pulse train.     

The nature of electrical interaction of Schottky contacts

Electrical interaction between metal-semiconductor contacts combined in a diode matrix with a Schottky barrier manifests itself in an appreciable variation in their surface potentials and static current-volt-characteristics. The necessary condition for appearance of electrical interaction between such contacts consists in the presence of a peripheral electric field (a halo) around them; this field propagates to a fairly large distances (<30 μm). The sufficient condition is the presence of regions where the above halos overlap. It has been shown that variation in the surface potential and the current-voltage characteristics of contacts occurs under the effect of the intrinsic electric field of the contact’s periphery and also under the effect of an electric field at matrix periphery; the latter field is formed as a result of superposition of electric fields of halos which form its contacts. The degree of the corresponding effect is governed by the distance between contacts and by the total charge of the space charge regions for all contacts of the matrix: their number, sizes (diameter D _{i, j} ), concentration of doping impurities in the semiconductor N _D , and physical nature of a metal-semiconductor system with a Schottky barrier (with the barrier height φ _b ). It is established that bringing the contacts closer leads to a relative decrease in the threshold value of the “dead” zone in the forward current-voltage characteristics, an increase in the effective height of the barrier, and an insignificant increase in the nonideality factor. An increase in the total area of contacts (a total electric charge in the space charge region) in the matrix brings about an increase in the threshold value of the “dead” zone, a relative decrease in the effective barrier height, and an insignificant increase in the ideality factor.     

Calculation of the radiation of a waveguide-horn antenna excited by short electromagnetic pulses

A method for the numerical calculation of the electromagnetic field radiated into free space by a waveguide-horn antenna excited by short ultra-wideband electromagnetic pulses (UWB EMPs) is described. Calculations are based on the method of nonstationary waveguide equations, which was proposed earlier, and the concept of a virtual electromagnetic waveguide. It is shown that the proposed approach allows calculation of the “forward radiation field” with control of the error in the obtained results and ensures a high accuracy of calculations.     

Experimental tests of the cortical imaging technique-applicationsto the response to median nerve stimulation and the localization ofepileptiform discharges

In a previous paper a method for simulating the electric potentials on the surface of the brain was introduced. This method consisted of the construction of a layer of radially oriented current dipoles in a conducting sphere that simulated the head so that the voltages generated by the layer would take the values measured on the surface of the medium (the scalp). The harmonic potential function for this layer was then evaluated in the interior of the medium in an attempt to approximate the potentials that would be generated by the actual neural sources but which could not be observed without recourse to invasive recording techniques. This method, the cortical imaging technique (CIT), has been previously tested by applying it to artificially generated data where the "cortical surface" potentials were known and could be compared with CIT-generated potentials. In this paper the method is tested by applying it to the scalp-recorded potentials evoked by right median nerve stimulation, where direct cortical recordings are available for comparison, and to the scalp-recorded epileptiform discharges from two patients where the spike foci were well defined. The effects of varying the "noise ratio," an input parameter in CIT which allows one to account for noise in scalp-recorded data, is discussed.     

Time-domain near-field analysis of short-pulse antennas .II.Reactive energy and the antenna Q

For pt. I see ibid., vol.47, no.2, p.271-79 (1999). The time-domain (TD) multipole expansion, developed in the first part of this two-part sequence, is extended here to analyze the power-flow and energy balance in the vicinity of a pulsed antenna. Using the spherical transmission line formulation, we derive expressions for the pulsed power-flow and energy and identify the radiative and the reactive constituents. For time-harmonic fields, the reactive concepts are well understood in terms of the stored energy, but this interpretation is not applicable for short-pulse fields where there is no stored energy. By considering the TD energy balance, we clarify the transition of the near-zone pulsed reactive energy to the radiation power and show that the pulsed reactive energy discharges back to the source once the pulse has been radiated. We thus introduce a TD Q factor that quantifies the radiation efficiency. In particular, we show that super resolution using short-pulse fields involves large TD reactive energies and Q and is, therefore, not feasible. The general TD concepts discussed are demonstrated through a numerical example of radiation from a circular disk carrying a pulsed current distribution     

An effective method of numerical solution of a boundary electrodynamics problem for arbitrary conducting surfaces

An alternative to Packlington’s and Harrington’s integral equations method of numerically solving a boundary electrodynamics problem for curvilinear perfectly conducing surfaces is suggested. The essence of this method consists in a joint solution of integral equations system with respect to the unknown complex vectors of current and charge density, the use of parametric mapping technique to represent the curvilinear surface, Galerkin’s method with boundary elements, “points sewing” method for Lorentz calibration. On an example of calculating the current distribution on a bicubic surface the advantages of the suggested method are demonstrated in comparison to Packlington’s and Harrington’s integral equations.     

Plasma travelling wave antenna

The possibility of using plasma column as linear travelling wave antenna is studied. It is shown that surface current waves propagating in plasma column of finite length are a source of paraxial electromagnetic radiation of decimeter band. Influence of dielectric waveguide, which surrounds cold isotropic plasma, on dispersion properties of plasma column is investigated. The corresponding dispersion equation for eigenwaves of circular dielectric waveguide filled with plasma is derived and solved numerically. Plasma and waveguide parameters are determined under which the surface wave slowing-down is close to unity leading to antenna’s radiation primarily in axial direction. It is shown that in case of plasma density around 10¹²−10¹³ cm⁻³ dispersion of the considered wave is close to dispersion of waves propagating in metal travelling wave antenna.     

Application of optics-geometrical method in short-range optical radar

The paper describes application of optics-geometrical method in short-range optical radar for measuring reflection characteristics of target and radiator’s angular energy distribution. The possibility of signal sampling in a base-type optical radar device using multi-element photoreceiver is studied as well as ways of improving precision of measurements with respect to linear coordinate up to ∼1 mm. A ratio between reflection coefficient of target’s surface and image coordinate in photoreceiver’s plane is determined. A working equation for calculating radiation pattern of radiator using the method of self-scanning of photoreceiver’s field of view with respect to its flare with precision ±0.5° with respect to angle coordinate is obtained.     

A method for determining the absolute total electron content in the ionosphere on the basis of the analysis of the characteristics of unmodulated coherent multifrequency signals

A theoretical method for determining the absolute total electron content (TEC) on the basis of processing the phase of unmodulated coherent multifrequency signals is considered. Calculation of the values of the phase ambiguity and resolution in terms of TEC values is presented. A combination of the frequencies of coherent signals that enables reconstruction of the absolute TEC of the Earth’s ionosphere with the use of simple receiving facilities is substantiated.