Independent control of ion density and ion bombardment energy in adual RF excitation plasma

A dual RF excited discharge is described. The dual RF excitation system provides a method to control the substrate self-bias without affecting the state of the discharge. The substrate can be RF-biased utilizing an appropriate excitation frequency and power significantly less than the plasma generating RF power. The substrate self-bias dependence on various system parameters, including substrate excitation frequency, pressure, plasma generating upper electrode RF power, substrate material, and process gas compositions, is described. For a simplified model, a linear relationship between self-bias and RF power is derived using the space-charge limited assumption. The effect of substrate bias on the thermal-oxide etch rate has been studied. The results show good correlation between the ion bombardment energy, i.e., the potential difference across the substrate dark space, and the SiO ₂ etch rate. The SiO₂ etch rate in a CF₄ plasma increases linearly with the ion bombardment energy, having a threshold etch energy of ~19 V     

Measurements of electron density and plasma current distributions in Tokamak plasma

A submillimeter-wave, phase-modulated polarimeter/interferometer is used for simultaneous time-dependent measurement of line-averaged electron density and poloidal field-induced Faraday rotation along chords of the plasma column in ISX-B tokamak. Heterodyne detection and hollow dielectric waveguide are utilized to achieve the high sensitivity required for the multichord experiment. A data analysis code has been developed to reconstruct the asymmetric distributions of plasma density. The validity of the code is examined, and the result shows good agreement with density profiles measured by Thomson scattering.     

Saturation energy density and line profile of the atomic iodine laser transition at high pressure

The saturation energy density of an iodine laser amplifier is proportional to the homogeneous medium linewidth and inversely proportional to the Einstein coefficient. For good energy extraction high values of the saturation energy density are needed, thus also requiring large values of the medium linewidth, especially when the Einstein coefficient increases with pressure, as inferred from fluorescence measurements recently reported in the literature. In order to check this conclusion, we measured the saturation energy density in the pressure range between 0.5 and 4 bar for the buffer gases Ar, SF6, and Xe and also the medium linewidth at a pressure of 2 bar for Ar, SF6, and Xe. It is found that, at least in this pressure range, the Einstein coefficient is constant and does not change with pressure. This is in contrast to the results published in the paper mentioned earlier. From our experimental data an optimum pressure range for high-power iodine laser amplifiers of large extraction efficiency is also inferred.     

蜂窝系统中用户能效值的分析与计算

目前随着信息技术的快速发展,蜂窝系统中的移动用户数迅速增长,如此巨大的用户数量将会造成通信能耗的快速增加。而如何降低能耗、提升能效是目前通信领域的重中之重。因此将基于哈塔模型的COST231扩展模型对用户能效进行分析,并通过MATLAB对其进行仿真与计算,最终根据实验结果提出提高能效的方法。     

Spatial-correlation functions of fields and energy density in areverberation chamber

A plane-wave integral representation is used to derive spatial-correlation functions for the complex electric and magnetic field components, and the results agree with previously published results derived by volume averaging of a mode sum. Results are also presented for the correlation functions of squared electric and magnetic field components and electric, magnetic, and total energy densities. The theory for the spatial correlation function of the squared transverse electric field is shown to agree well with published measurements of the power received by transverse monopole antennas     

The effect of multiple time scales and subexponentiality in MPEGvideo streams on queueing behavior

Guided by the empirical observation that real-time MPEG video streams exhibit both multiple time scale and subexponential characteristics, we construct a video model that captures both of these characteristics and is amenable to queueing analysis. We investigate two fundamental approaches for extracting the model parameters: using sample path and second-order statistics-based methods. The model exhibits the following two canonical queueing behaviors. When strict stability conditions are satisfied, i.e., the conditional mean of each scene is smaller than the capacity of the server, precise modeling of the interscene dynamics (long-term dependency) is not essential for the accurate prediction of small to moderately large queue sizes. In this case, the queue length distribution is determined using quasistationary (perturbation theory) analysis. When weak stability conditions are satisfied, i.e., the conditional mean of at least one scene type is greater than the capacity of the server, the dominant effect for building a large queue size is the subexponential (long-tailed) scene length distribution. In this case, precise modeling of intrascene statistics is of secondary importance for predicting the large queueing behavior. A fluid model, whose arrival process is obtained from the video data by replacing scene statistics with their means, is shown to asymptotically converge to the exact queue distribution. Using the transition scenario of moving from one stability region to the other by a change in the value of the server capacity, we synthesize recent queueing theoretic advances and ad hoc results in video modeling, and unify a broad range of seemingly contradictory experimental observations found in the literature. As a word of caution for the widespread usage of second-order statistics modeling methods, we construct two processes with the same second-order statistics that produce distinctly different queueing behaviors     

Operation of a semiconductor opening switch at the pumping time of a microsecond and low current density

Semiconductors - The mechanism of operation of a semiconductor opening switch (a SOS diode) at the forward-pumping time of a microsecond and low current density was studied. The current’s...     

Laser-induced anisotropic absorbtion, reflection, and scattering of light in chalcogenide glassy semiconductors

Anisotropy induced in thin-film and bulk samples of chalcogenide glassy semiconductors by the linearly polarized light of different spectral ranges is studied. Three different ranges of exciting photon energy can be distinguished. 1) Above-band-gap light excitation is studied in film samples, two distinct processes are identified in this range: creation of photoinduced defects and their photostimulated orientation and reorientation; a “defect-based” model of photoinduced anisotropy is further developed. 2) Subband-gap light excitation is studied in bulk samples; creation of anisotropically scattered centers is assumed to be the basis of all photoinduced vector phenomena in that spectral range. 3) Superband-gap light excitation is studied in film and bulk samples because the application of differential reflectance spectroscopy; it was shown that not only defects but also main covalent bonds of the glass can be oriented and reoriented by the linearly polarized light that generates the photoinduced dichroism in this spectral interval. Fiz. Tekh. Poluprovodn. 32, 915–922 (August 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

激光等离子体中密度孤波和自生磁场的数值模拟

为了深入理解激光与等离子体相互作用时产生的密度孤波和自生磁场的形成机制,从动力论出发,数值模拟了从波-波、波-粒相互作用出发的轴对称柱坐标下的密度扰动非线性控制方程,得到了密度孤波和自生磁场的形成和演化过程。数值结果表明,强度为4×1014W/cm2的激光打靶时形成的孤波最大密度扰动率达到82%,并产生30T的自生磁场,与实验测量结果相符合,为密度孤波和自生磁场的形成提供了理论依据。     

激光等离子体镁光谱线Stark展宽的测量与计算

本文用光学多道分析仪测量了用Ｎｄ：ＹＡＧ激光烧蚀固体等离子体的发射光谱，得到了延时Ｔｄ＝１至１０μｓ时Ｍｇ的５５２．８４，５１６．７４，４７０．３０，３８３．８３ｎｍ等谱线的Ｓｔａｒｋ展宽，采用半经典理论和电偶极近似，对Ｔｄ＝１μｓ和２μｓ时上述的谱线的Ｓｔａｒｋ展宽从理论上进行了计算，理论结果与实验符合得很好。     

Area,energy, and time assessment for a distributed TPM for distributed trust in IoT clusters

IoT clusters arise from natural human societal clusters such as a house, an airport, and a highway. IoT clusters are heterogeneous with a need for device to device as well as device to user trust. The IoT devices are likely to be thin computing clients. Due to low cost, an individual IoT device is not built to be fault tolerant through redundancy. Hence the trust protocols cannot take the liveness of a device for granted. In fact, the differentiation between a failing device and a malicious device is difficult from the trust protocol perspective. We present a minimal distributed trust layer based on distributed consensus like operations. These distributed primitives are cast in the context of the APIs supported by a trusted platform module (TPM). TPM with its 1024 bit RSA is a significant burden on a thin IoT design. We use RNS based slicing of a TPM where in each slice resides within a single IoT device. The overall TPM functionality is distributed among several IoT devices within a cluster. The VLSI area, energy, and time savings of such a distributed TMP implementation is assessed. A sliced/distributed TPM is better suited for an IoT environment based on its resource needs. We demonstrate over 90% time reduction, over 3% area reduction, and over 90% energy reduction per IoT node in order to support TPM protocols.     

Numerical calculation of electromagnetic energy and temperature distribution in a microwave irradiated breast carcinoma: preliminary results.

In this study an attempt was made to calculate temperature distribution in a breast tumor irradiated by microwaves. An ellipsoidal model of absorbing dielectric surrounded by a nonabsorbing medium irradiated by a plane wave was considered. The energy was calculated inside and outside the ellipsoid by an analytical method. Three-dimensional and densitographic patterns were calculated for different frequencies, conductivities and shapes of the model. Assuming experimental (in vivo) thermal properties of breast tissue thermal patterns were calculated.     

类氟CoⅪⅩ,NiⅩⅩ,CuⅩⅪ,ZnⅩⅫ,GaⅩⅩⅢ和GeⅩⅪⅤ精细结构能级和跃迁波长的相对论多组态Dirac-Fock计算

本文用相对论多组态Dirac-Fock广义平均能级模型(MCDF-EAL)计算了可能成为激光工作物质的类氟CoⅪⅩ、NiⅩⅩ、CuⅩⅪ、ZnⅩⅫ、GaⅩⅩⅢ和GeⅩⅩⅣ的2s~22p~5、2s2p~6、2s~22p~43s、2s~22p~43p组态的精细结构能级和若干3s-3p组态跃迁波长值。大部份计算值都是本文预言值。     

Plasma ion implantation hydrogenation of poly-Si CMOS thin-filmtransistors at low energy and high dose rate using aninductively-coupled plasma source

Defect passivation in polycrystalline silicon (poly-Si) CMOS thin-film transistors (TFT's) has been performed by plasma ion implantation (PII) hydrogenation process. Implantation at low energy (2 keV) and high dose rate(~10¹⁶/cm² S) was achieved by an inductively-coupled plasma source. The device parameter improvements are saturated in 3-4 min, which is much shorter than other hydrogenation methods reported in the literature. The stress measurements indicate that the devices hydrogenated by this new technique have much better long-term reliability than that hydrogenated by other techniques     

Noise reduction, smoothing and time interval segmentation of noisy signals using an energy optimisation method

Noise reduction and time interval segmentation of a noise-contaminated piecewise continuous signal is considered by the authors as a non-linear optimisation problem. The mathematical framework of this method is presented both in continuous-time and discrete-time domains. The smoothed signal and segmented time intervals of the original noisy signal are calculated as an optimised solution for an energy functional. An algorithm similar to the level set method is developed to find the optimised solution. In this algorithm, the discontinuity points separating consecutive continuous signals are preserved while the noise is reduced. Therefore this method fundamentally exhibits a better performance compared with a traditional low-pass filter suppressing high frequency components, including discontinuity points. The results also demonstrate a better quality in noise reduction in comparison to the median and Gaussian filters.     

Small-signal power flow and energy density for streaming carriers in the presence of collisions

The Poynting theorem, or equation of continuity relating energy density and power flow, is extended to include the effects of diffusion and collisions. It is shown that the presence of the thermal power due to diffusion is accompanied by an increase in electrokinetic power. The effects of collisions on the electrokinetic power and energy density are examined in detail in the absence of diffusion. It is found that the kinetic power is zero in isolated streams when collisions are frequent (nu > 2omega_{p}). However, when such streams couple to "circuit-like" positive-energy waves (as in the acoustic amplifier) the stream's kinetic power becomes finite; in particular, it becomes negative if the stream drifts faster than the wave. Thus the usual picture, used in collision-free theory, in which the active wave must carry negative power, is preserved. It is also shown that, on the other hand, if the stream is lossless but interacts with a lossy and nonpropagating medium (as in a stationary collisional plasma), then the stream's finite-energy waves are coupled by the lossy medium. In contrast to the previous case where both systems propagate, it is now the negative-energy wave that grows. It is found that the electrokinetic energy density in a collision-dominant stream is negative for both modes due to collisional losses.     

Dynamic power density, wavelength, and switching time modulation of optically triggered power transistor (OTPT) performance parameters

Optical modulation by varying the intensity, wavelength, or switching time can dynamically alter the performance parameters of direct optically controlled power semiconductor device. Understanding the effect of optical parameters on these parameters from a first principle approach is necessary for making optimal design choices and gaining design insights. We focus on performance parameters whose variations with direct optical modulation have not been reported previously for a power semiconductor such as switching times and on-state resistance. We carry out analytical modeling and two-dimensional (2D) finite-element simulations for a GaAs/AlGaAs based superjunction lateral optically controlled power transistor that has been fabricated and successfully tested for high-voltage capability. It is shown that optical power density can modulate on-state resistance and more importantly the trade-off curve between breakdown voltage and on-state resistance. A closed-form analytical equation relating switching times with optical parameters via logarithmic function is derived and the nonlinear variation of on-state resistance and switching time with optical wavelength is illustrated. We also derive the analytical expression for power device rise time as a function of optical signal rise time and show that they are related by Lambert's W-function with exponential coefficients.     

Electron density and temperature measurements of the ignited mode plasma in a thermionic converter

Spectroscopic measurements of the electron density and temperature have been made on a planar thermionic converter operated in the quasi-saturation region of the ignited mode. The effects of several independent converter variables on the electron density were investigated quantitatively. From this investigation it was found that the emitter temperature and current density were the most significant parameters affecting the electron density. Collector temperature, cesium vapor pressure, and interelectrode spacing were less important. Complete electron density profiles and electron temperature profiles were obtained and compared to conditions characteristic of local thermodynamic equilibrium (LTE). A representative case indicated the measured temperature, 2600°K, was only 200°K higher than required for complete LTE in the region of the peak electron density. This corresponds to an electron density approximately 45 percent below the equilibrium value.     

Density of displacement cascades for cluster ions: An algorithm of calculation and the influence on damage formation in ZnO and GaN

A method of statistical calculation of parameters of averaged individual collision cascades formed by cluster ions composed of a small number of atoms is suggested. The results of calculations are compared with experimental data on the accumulation of structural damage in ZnO and GaN irradiated with PF _n ions (n = 0, 2, 4) with the specific energy of 1.3 keV/amu at room temperature. It is shown that, for ZnO, the density of the displacement cascade does not affect the concentration of stable postimplantation defects in the region of the bulk peak, but significantly affects this concentration in the near-surface region. For GaN, as the displacement-cascade density increases, both an increase in the concentration of stable defects in the region of the bulk maximum of the defect concentration and an increase in the thickness of the surface’s amorphous layer are observed.