The oxidation of GaAs(1 0 0) surfaces under atmospheric pressure conditions studied in real time using dynamic reflectance anisotropy spectroscopy at 2.6 and 4 eV

Using real-time, dynamic reflectance anisotropy spectroscopy (RAS) at both 2.6 eV and 4.0 eV, we demonstrate that an anisotropic oxide will form on As rich c(4 × 4)/d(4 × 4) GaAs surfaces when exposed to moisture- free air diluted in inert gases in a metal organic chemical vapour deposition (MOCVD) reactor, and that the initial c(4 × 4)/d(4 × 4) structure effects the resulting optical anisotropy of the oxide. This was achieved by investigating how the RA signals at 2.6 eV and 4 eV of annealed GaAs (1 0 0) surfaces evolve relative to the as-etched and as-annealed signals when exposed to oxygen. It is found that while the 2.6 eV response, which is known to be associated with the As dimers, degrades to pre-process levels indicating their destruction, the 4 eV signal, stabilizes at an intermediate, permanent level, suggesting the formation of an anisotropic oxide film whose structure is determined at least in part, by the initial c(4 × 4)/d(4 × 4) surface.     

塑封硅器件中介电薄膜的温湿效应分析(英文)

随着铜互连以及low-k电介质在超大规模集成电路中地广泛使用,low-k电介质的机械完整性及其对互连可靠性变得更加重要。影响介电膜的机械完整性和互连可靠性的因素包括介电膜的工艺制程,芯片与封装材料的相互影响,以及环境温度和湿度的影响。本文研究集中于了解环境温度和湿度对塑封硅器件中介电薄膜的可靠性影响。采用快速温度和湿度实验条件,对塑封硅器件中介电薄膜受水分和温度损伤的敏感性进行了分析。运用商业有限元(FEA)分析软件,对水分在塑封材料和硅器件中的扩散过程进行了建模及仔细分析。并对硅器件周边密封圈的防水分扩散效力进行了研究。通过这一系列实验与分析,对塑封硅器件中介电薄膜的温湿效应有了完整地了解,并提出和建立了相关的物理模型和经验公式。运用这物理模型和经验公式可对在各种使用环境温度和湿度条件下,塑封硅器件中介电薄膜的可靠性进行评估及分析。     

A heuristic approach for airport gate assignments for stochastic flight delays

To make good flight to gate assignments, not only do all the relevant constraints have to be considered, but stochastic flight delays that occur in actual operations also have to be taken into account. In past research, airport gate assignments and stochastic disturbances have often been handled in the planning and the real-time stages separately, meaning that the interrelationship between these stages, as affected by such delays, has been neglected. In this research, we develop a heuristic approach embedded in a framework designed to help the airport authorities make airport gate assignments that are sensitive to stochastic flight delays. The framework includes three components, a stochastic gate assignment model, a real-time assignment rule, and two penalty adjustment methods. The test results are based on data supplied by a Taiwan international airport, and show that the proposed framework performs better than the current manual assignment process and the traditional deterministic model.     

内增强变象管相机中的干扰研究

本文讨论了带快门的内增强变象管相机的快门电路及其对扫描电路的干扰,干扰信号对相机性能指标的影响及解决方法。     

Influence of postdeposition annealing on structural properties and electrical characteristics of thin Tm2O3 and Tm2Ti2O7 dielectrics

We describe the structural properties and electrical characteristics of thin thulium oxide (Tm₂O₃) and thulium titanium oxide (Tm₂Ti₂O₇) as gate dielectrics deposited on silicon substrates through reactive sputtering. The structural and morphological features of these films were explored by X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy, measurements. It is found that the Tm₂Ti₂O₇ film annealed at 800 °C exhibited a thinner capacitance equivalent thickness of 19.8 Å, a lower interface trap density of 8.37 × 10¹¹ eV⁻¹ cm⁻², and a smaller hysteresis voltage of ∼4 mV than the other conditions. We attribute this behavior to the Ti incorporated into the Tm₂O₃ film improving the interfacial layer and the surface roughness. This film also shows negligible degrees of charge trapping at high electric field stress.     

场发射栅孔阵列的制备

 采用硅的局部氧化技术以及湿法刻蚀技术,利用2.6 μm的光刻掩模板在n型硅片上形成了栅极孔径为1 μm的场发射阴极的栅极空腔阵列,实现了用大阵点尺寸的栅极掩模板制备较小尺寸栅孔阵列。硅的湿法刻蚀溶液采用各向同性的硝酸和氢氟酸混合溶液,刻蚀后空腔的深度和宽度均随刻蚀时间线性增加。同时,由于刻蚀溶液具有较高的Si/SiO₂ 刻蚀选择比,栅极孔径随刻蚀时间增大的速度远低于深度和宽度增大的速度,栅极孔径主要取决于掩模的尺寸和氧化层的厚度。通过选择掩模板的尺寸以及氧化层的厚度,采用局部氧化技术和湿法刻蚀技术能够制备出微米或亚微米的场发射阴极的栅极空腔阵列。     

采集强干扰下微弱信号的APD电路系统研究

基于雪崩光电二极管反向偏压及其电容特性,利用时间同步原理,构建了一个用于回避强烈反射光信号,探测微弱回波信号的雪崩光电二极管探测系统.对雪崩光电二极管电容效应作出了分析,得出交流高压供电会使雪崩光电二极管产生干扰尖峰脉冲的结论.为了消除这个电容效应产生的尖峰干扰,提出了施加直流反向低压的方案,以达到减少雪崩光电二极管电容变化量的目的.通过实验数据验证了方法可行性.     

迭代正则化方法求解电介质中空间电荷分布

首先介绍了迭代正则化方法的理论基础,建立了含有空间电荷密度分布的Fredholm第一类积分方程的反卷积算法,利用数值实验研究了加性高斯白噪声对迭代反卷积算法的影响,以及迭代停止标准对非适定问题的数值解的影响,最后使用该方法求解电介质样品中的空间电荷分布.结果表明,在无噪或者低噪环境下,反卷积算法能够非常好地计算出非适定问题的解.当噪声影响增大,信噪比降低时,反卷积的计算结果受到明显的影响.迭代停止标准对数值解的计算精度起着明显的作用.对实际测量数据进行处理表明,迭代正则化反卷积算法能够计算出固体电介质中的空间电荷分布.     

Dielectric spectroscopy and calorimetry during postcuring of a linear chain polymer thermoset formed from a diepoxide and cyclohexylamine,and the nature of the products

The dielectric permittivity and loss spectra of an equimolar liquid mixture of diglycidyl ether of bisphenol-A and cyclohexylamine have been studied during the liquid's isothermal polymerization or curing in separate experiments at different temperatures and thereafter during the postcuring, both on rate-heating and isothermally. The spectra obtained during the growth of the linear chain polymer during the curing and postcuring show the evolution of an intermediate relaxation process whose position in the frequency plane remains relatively insensitive to the decrease in the configurational entropy during the postcuring, but whose strength increases. Postcuring ceases to occur once the calorimetric glass-liquid transition temperature of 345 K, corresponding to the ultimately formed polymeric state, has been reached. The increase in the number of covalent bonds, n, formed during curing and postcuring decreased the equilibrium dielectric permittivity, ε_s, and increased the characteristic relaxation time, τ₀, for all curing and postcuring conditions. For a fixed temperature and n, (dε_s/dT) and (dτ₀/dT), as well as the values ε_s and τ₀ of the ultimately formed state of the polymers differ significantly when the thermal history of polymerization differs. The slow dynamics in the glass-liquid transition region were analyzed in terms of the enthalpy relaxation and fictive temperature concepts. The distribution of relaxation times for these dynamics correspond to the stretched exponential parameter of 0.6, which is significantly greater than 0.39 determined for the dielectric α-relaxation spectra measured at a temperature 30 K higher. The enthalpy relaxation involves a narrower distribution of intermolecular barriers than dielectric relaxation. The results also show that the recently proposed method for determining the gelation time from the plots of the imaginary component of electrical impedance lacks scientific merit. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 303–318, 1998     

Calorimetric and dielectric effects during polymerization of an elastomer‐containing mixture and liquid‐liquid phase separation

Calorimetry and dielectric spectroscopy of an elastomer, amine terminated butadiene acrylonitrile (ATBN), dissolved in a stoichiometric mixture of ethylene diamine and diglycidyl ether of bisphenol‐A, were studied in real time during the polymerization and phase separation of the mixture. In the two polymer compositions containing 8 w/w % ATBN and 20 w/w % ATBN, the total enthalpy released per mole of DGEBA's reaction was the same, indicating indetectably small changes in molecular interactions before and after the phase separation. The dielectric relaxation spectra showed no evidence for phase separation, which indicated a gradual phase separation with time and the extent of polymerization, and relatively small differences in the permittivity and conductivity between the ATBN particles and the network matrix at the time of phase separation. The equilibrium permittivity and dc conductivity showed a nonideal mixing of ATBN. The stretched exponential relaxation parameter remained at 0.36, but the characteristic dielectric relaxation time and the dc conductivity increased on addition of ATBN. An increase in the temperature had a greater effect on the relaxation time than the increase in the extent of polymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1911–1919, 1999