脉冲激光辐照光学薄膜的缺陷损伤模型

建立了缺陷吸收升温致薄膜激光损伤模型,该模型从热传导方程出发,考虑了缺陷内部的温度分布以及向薄膜的传导过程,通过引入散射系数简化了Mie散射理论得出的吸收截面.对电子束蒸发沉积的ZrO₂:Y₂O₃单层膜进行了激光破坏实验,薄膜样品的损伤是缺陷引起的,通过辉光放电质谱法对薄膜制备材料的纯度分析发现材料中的主要杂质元素为铂,其含量为0.9％.利用缺陷损伤模型对损伤过程进行了模拟,理论模型和实验结果取得了较好的一致性.     

Growth behavior of high k LaAlO3 films on Si by metalorganic chemical vapor deposition for alternative gate dielectric application

LaAlO₃ (LAO) is explored in this work to replace SiO₂ as the gate dielectric material in metal–oxide–semiconductor field effect transistor. Amorphous LAO gate dielectric films were deposited on Si (0 0 1) substrates by low pressure metalorganic chemical vapor deposition using La(dpm)₃ and Al(acac)₃ sources. The effect of processing parameters such as deposition temperature and precursor vapor flux on growth, structure, morphology, and composition of LAO films has been investigated by various analytical methods deeply. The film growth mechanism on Si is reaction limiting instead of mass transport control. The reaction is thermally activated with activation energy of 37 kJ/mol. In the initial growth stage, Al element is deficient due to higher nucleation barrier on Si. The LAO films show a smooth surface and good thermal stability and remain amorphous up to a high temperature of 850 °C. The electrical properties of amorphous LAO ultrathin films on Si have also been evaluated, indicating LAO is suitable for high k gate dielectric applications.     

Interfacial structure and electrical properties of LaAlO3 gate dielectric films on Si by metalorganic chemical vapor deposition

LaAlO₃ (LAO) gate dielectric films were deposited on Si substrates by low-pressure metalorganic chemical vapor deposition. The interfacial structure and composition distribution were investigated by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectroscopy (SIMS), and Auger-electron spectroscopy (AES). HRTEM confirms that there exists an interfacial layer between LAO and Si in most samples. AES, SIMS, and XPS analyses indicate that the interfacial layer is compositionally graded La–Al silicate and the Al element is severely deficient close to the Si surface. Electrical properties of LAO films were evaluated. No evident difference in electrical properties between samples with and without native SiO₂ layers was observed. The electrical properties are discussed in terms of LAO growth mechanisms, in relation to the interfacial structure. PACS 73.40.Qv; 81.15.Gh; 77.55.+f; 68.35.-p     

磁控反应溅射法制备渐变折射率薄膜的模型分析

阐述了磁控反应溅射法制备渐变折射率薄膜的机理;探讨了磁控反应溅射法制备渐变折射率薄膜的理论模型,给出了渐变折射率薄膜的折射率与反应气体分压的关系,在一定的沉积参数下,由要得到的膜层折射率随膜层几何厚度的变化规律可推导出反应气体分压比随时间的变化规律;最后以制备折射率线性变化的薄膜为例说明了如何推导得到反应气体分压比随时间的变化规律. 关键词： 渐变折射率 磁控反应溅射 模型     

TiN/TiB2异结构纳米多层膜的共格生长与力学性能

采用多靶磁控溅射法制备了一系列具有不同TiB₂调制层厚度的TiN/TiB_{2纳米多层膜.利用x射线衍射仪、高分辨电子显微镜和微力学探针研究了TiB2层厚变化对多层膜生长结构和力学性能的影响.结果表明，在fcc-TiN层(111)生长面的模板 作用下，原为非晶态的TiB2层在厚度小于2.9nm时形成hcp晶体态，并与fcc-TiN 形成共格外延生长；其界面共格关系为{111}TiN//{0001}TiB2，〈110〉TiN//〈1120〉TiB2.由于共格界面存在晶格失配 度，多层膜中形成拉、压交变的应力场，导致多层膜产生硬度和弹性模量升高的超硬效应， 最高硬度和弹性模量分别达到46.9GPa和465GPa.继续增加TiB2层的厚度，TiB2形成非晶态并破坏了与TiN层的共格外延生长，多层膜形成非晶TiN层和非晶TiB< sub>2层交替的调制结构，其硬度和弹性模量相应降低. 关键词： 2}纳米多层膜')" href="#">TiN/TiB₂纳米多层膜 共格生长 晶体化 力学性能     

90Mo电磁跃迁几率的测量

利用束流能量为116MeV的⁵⁹Co(³⁵Cl,2p2n)⁹⁰Mo反应布居⁹⁰Mo的高自旋态.用10台反康普顿HPGe探测器组成的探测阵列进行γγ符合测量.通过多普勒展宽峰的形状分析测定⁹⁰Mo高自旋态的寿命.在正宇称衰变系观察到增强的M1跃迁,推断I=13以上是扁椭形变.负宇称高自旋态具有大的B(E2)值,并随自旋增大而起伏变化.正、负宇称态之间的跃迁显示增大的E1跃迁,似有八极关联的可能.但是,⁹⁰Mo并不处在理论预言的存在八极形变的核区内.     

Crossover from high-temperature vortex-liquid to low-temperature vortex-glass behavior in single phase HgBa2Ca2Cu3O8+δ superconductor

The ρ-T curves in our single phase HgBa₂Ca₂Cu₃O_8+δ superconductor were measured as a function of temperature and magnetic field, ρ=ρ₀exp(−U_eff/κ_BT). It can be transformed to another form d(lnρ)/d(1/T)=−U_eff+TdU_eff/dT, then this becomes a plot of the activation energy U_eff as a function of temperature. Our data plotted in these ways show a clear crossover from high-temperature two-dimensional vortex-liquid to a critical region associated with the low-temperature three-dimensional vortex-glass phase transition. The critical exponents v(z−1)=3.9±1.9 in this system are little different with previous measurements in BSCCO and YBCO systems.     

Experimental study of polarity dependence in repetitive nanosecond-pulse breakdown

Pulsed breakdown of dry air at ambient pressure has been investigated in the point-plane geometry, using repetitive nanosecond pulses with 10 ns risetime, 20--30 ns duration, and up to 100 kV amplitude. A major concern in this paper is to study the dependence of breakdown strength on the point-electrode polarity. Applied voltage, breakdown current and repetitive stressing time are measured under the experimental conditions of some variables including pulse voltage peak, gap spacing and repetition rate. The results show that increasing the E-field strength can decrease breakdown time lag, repetitive stressing time and the number of applied pulses as expected. However, compared with the traditional polarity dependence it is weakened and not significant in the repetitive nanosecond-pulse breakdown. The ambiguous polarity dependence in the experimental study is involved with an accumulation effect of residual charges and metastable states. Moreover, it is suggested that the reactions associated with the detachment of negative ions and impact deactivation of metastable species could provide a source of primary initiating electrons for breakdown.     

Impulsive control of chaotic systems with exogenous perturbations

The impulsive control of chaotic systems, which are subjected to unbounded exogenous perturbations, is considered. By using the theory of impulsive differential equation together with the fuzzy control technique, the authors propose an impulsive robust chaos controlling criterion expressed as linear matrix inequalities (LMIs). Based on the proposed control criterion, the procedure for designing impulsive controllers of common (perturbed) chaotic systems is provided. Finally, a numerical example is given to demonstrate the obtained theoretical result.     

纳米氧化锌的过饱和控制生长与大小分布控制.

"在非水介质中合成了纳米氧化锌,测定了纳米氧化锌的紫外吸收光谱,并用有效质量模型计算了粒子大小,开发并命名了一种称之为纳米粒子过饱和控制生长的技术,该技术涉及将小的纳米粒子悬浊液加入到大的粒子悬浊液中,结果因为不同大小粒子间的溶解度差异小的粒子将全部溶解,大的粒子将整体长大,大粒子悬浊液的粒子数将保持不变,大粒子的生长速度显著比Ostwald老化的高．该技术最显著的特征是只要最初两悬浊液粒子大小的差异足够大,分布不是太宽,则粒子大小的分布将会因为粒子如此长大而变窄．"