可信计算(1)

随着信息技术的发展和网络应用拓展,可信计算已经成为当前学术界和工业界的研究热点。本讲座将分3期对可信计算的内涵、关键技术和未来进行讨论:第1讲从可信计算的演进过程简单叙述可信计算技术发展历程、可信计算的定义和范畴、相关研究领域;第2讲从技术的角度探讨可信计算研究的系统架构、主要关键技术及其当前研究的热点问题;第3讲介绍可信计算的应用模式和未来。     

无线市话(1)

无线市话被视为中国电信、中国网通新的经济增长点。目前已在中国得到广泛的应用。本讲座将分3讲对其加以介绍．第一讲主要介绍无线市话的基本概念及各种实用系统,第二讲和第三讲分别介绍无线市话的应用和未来发展。     

综合信息(1)

日立制作所在德国批量生产16MbDRAM日立制作所在德国新建半导体生产线，投资额为300亿日元。从1998年下半年起，16MbDRAM生产能力提高3倍，月产约300万块，微计算机提高5倍，月产50万个。这主要是欧洲个人计算机和工作站等用的存储器需要增长和通信设备用的微计算机的需要增长所致。一凡译自《日经工》No．652，1996，P．24Philips和Motorola等公司相继在中国建设LSI工厂综合信息据报道，中国正在建设LSI工厂。荷兰PhilpsElectronicsNV与台湾省AdvancedSemiconduetorManufacturingCorp（ASMC）共同投资10亿美元，采用0．5～0．…     

基带调制解调器(1)

介绍了基带调制解调器与频带调制解调器的特点和区别，常用基带调制解调器的编码方式及基本原理，以及调制解调器今后的发展     

硅谷采访(1)

2002年11月，笔者再次来到美国硅谷，参加亚洲记者团的采访活动。由于全球经济的影响，这里失去了二、三年前的繁华与躁动，而更多了几分平和与理性。公司的讲演很切实际，亚洲乃至中国对他们越来越重要了。Linear的模拟战略及产品LTC(Linear Technology Corporation)公司董事长兼首席执行官(CEO)Robert H. Swanson, Jr.首先介绍了公司的基本情况。2002财年是各公司最为艰苦的一年，但优秀的公司在这个阶段反而加强了他们的竞争地位。因此，为未来适量的投资与在艰苦年代保持相当利润同样重要，公司削减了16%的雇员，但却增加了16%的…     

卫星电视基础知识(1)

应广大读者的要求,本刊特约有关作者撰写卫星电视及节目接收初步知识的系列文章,该系列文章包括卫星电视基础知识与卫星电视节目接收两部分,分若干篇,于今年后几期刊载。要提醒读者注意的是:在进行接收卫星电视节目的实践时,应遵守国家有关法规。     

印制电路历史(1)

我们即将跨入充满难以预料的,令人激动的技术发展新的千年纪元。我们将同样进入第二个电子世纪。不错,我们伟大的信息时代开始于十八世纪末,那时,数字系统和无线通讯的应用还十分有限。二十世纪的突破,包括持续飞行,大量运输,电影,原子能,计算机,太空旅行,固态电路等确实令人吃惊,但如果没有电子线路,这些都无法实现。这样,我们感到是应该将印制电路的发明和发     

低温固相反应合成纳米Ba1-ySryTi1-xSnxO3

以TiCl4,SnCl4·5H2O,Sr(OH)2·8H2O和Ba(OH)2.8H2O为原料,采用低温固相反应合成了一系列纳米Ba1–yZnyTi1–xSnxO3(0≤x≤0.30,0≤y≤1.00)固溶体。XRD物相分析证明产品为立方晶系的完全互溶取代固溶体。TEM形貌观察,粒子为均匀球形,平均粒径50 nm。制陶实验发现,在BaTiO3纯相中掺入适量的Sn 4+和Sr2+,当(x=0.1,y=0.1)时,经1 150℃烧结的陶瓷片室温相对介电常数达到13 000,介质损失仅为0.008,烧结温度较之微米级粉体降低200～250℃。     

用拉曼散射谱与远红外反射谱研究Ga_xIn_(1-x)As_ySb_(1-y)四元混晶的长波光学声子

报道了 MBE外延生长的 Gax In1 - x Asy Sb1 - y四元混晶的拉曼散射谱与远红外反射谱 ,并从拉曼散射谱中观察到了 Gax In1 - x Asy Sb1 - y四元混晶的晶格振动四模行为 ;从实验中还观察到低于 180 cm- 1的若干散射峰 ,提出它们可能是与次近邻原子间相互作用的晶格振动模式有关 ;从拉曼散射谱和红外反射谱中观察到了与 Gax In1 - xAsy Sb1 - y四元混晶多声子吸收过程的有关的现象     

稀土锰氧化物Sm1-xBaxMnO3的结构、红外及电性能研究

采用传统固相反应法,制备了一系列钙钛矿结构的稀土锰氧化物Sm<,1-x>Ba<,x>MnO<,3>(x=0～0.5)样品,借助XRD和FTIR对样品的相结构和组成进行了研究,用四端子法测量了样品在室温下的电导率.结果表明,当x<0.4时,样品为单一的钙钛矿结构;当0.4≤x≤0.5时,样品为Sm<,1-x>Ba<,x....     

MBEGaAs1—xSbx的喇曼光谱

在比较宽的组份范围内首次报道了MBE GaAs_(1-x)Sb_x混晶的喇曼光谱。发现声子频移强烈地依赖于Sb的组份x,而光学声子的双模行为仅仅在x>0.15时才发现,用远红外傅里叶光谱已证实这一结果。类GaAs LO模的线形分析表明本文的GaAs_(1-x)Sb_x质量较好。用质量缺陷模型和渗流理论讨论实验结果,用团聚效应解释x>0.15时声子的双模行为并估算了平均团聚尺寸。理论与实验结果符合得很好。     

低暗计数率InGaAsP/InP单光子雪崩二极管

通过对InGaAsP/InP单光子雪崩二极管（SPAD）的探测效率、暗计数率等基本特性与该器件的禁带宽度、电场分布、雪崩长度、工作温度等参数之间关系的分析,采用比通常的InxGaAs （x=0.53）材料具有更宽带隙的InxGa1-xAsyP1-y（x=0.78,y=0.47）材料作为光吸收层,并且精确控制InP倍增层的雪崩长度,有效地降低了SPAD的暗计数率。其中InGaAsP材料与InP材料晶格匹配良好,可在InP衬底上外延生长高质量的InGaAsP/InP异质结,InGaAsP材料的带隙为Eg=1.03 eV,截止波长为1.2 m,可满足1.06 m单光子探测需要。同时,通过设计并研制出1.06 m InGaAsP/InP SPAD,对其特性参数进行测试,结果表明,当工作温度为270 K时,探测效率20%下的暗计数率约20 kHz。因此基于时间相关单光子计数技术的该器件可在主动淬灭模式下用于随机到达的光子探测。     

Raman Scattering in GaxIn1-xP and (AlxGa1-x)0.51In0.49P Alloys

Raman scattering spectroscopy is applied to investigate the phonon modes in GaxIn1-xP (x=0.52) and (AlxGa1-x)0.51In0.49P (x=0.29) alloys. Two-mode behavior in GaxIn1-xP and three-mode behavior in (AlxGa1-x)0.51In0.49P are observed. In ordered GaxIn1-xP, we clearly distinguish the TO1(GaP-like) mode and the splitting of LO1(GaP-like) and LO2 (InP-like) modes, which is believed to be the result of superlattice effect of ordering, and the LO1 LO2 mode, which is observed for the first time. In addition to the b/a ratio, it‘s found that the relative intensity of the FLA and the LO1 LO2 modes also corresponds to the degree of order. The TO1 and the splitting of LO1 and LO2 devote together to the reduction of the “valley depth“. In (AlxGa1-x)0.51In0.49P, the doubling of FLA is observed. Due to the influence of Al composition, the GaP-like LO mode becomes a shoulder of the InP-like LO mode. The unresolved Raman spectra indicate the existence of ordered structure in (AlxGa1-x)0.51In0.49P alloys.     

Cathodoluminescence and Raman scattering in Ga1−x AlxP epitaxial films

Low-temperature cathodoluminescence and Raman scattering of Ga_1?x Al_xP epitaxial layers (0≤x≤0.8) grown by liquid phase epitaxy on the GaP(100) substrate are studied. The obtained cathodoluminescence spectra indicate that the dependence of the indirect energy gap on the composition parameter x is nonlinear. This nonlinearity can be described by the parabolic function with the inflection parameter b=0.13. Raman scattering studies show that the phonon spectrum of Ga_1?x Al_xP consists of one (Al-P)-like vibrational mode and three (Ga-P)-like modes.     

Structural characterization of AlxGa1−xSb grown by LPE

Al_xGa_1−xSb ternary solid solutions lattice-matched to the GaSb (001) substrate with composition in the range 0.05≤x≤0.2 were grown by liquid phase epitaxy. High resolution X-ray diffraction and Raman scattering techniques were applied to characterize Al_xGa_1−xSb alloys. The out of plane lattice parameter was estimated directly from the asymmetrical diffractions of planes (115) and (−1−15). The out of plane lattice parameter as a function of Aluminium content is higher than the corresponding bulk lattice parameter of Al_xGa_1−xSb layers obtained with Vegard's law. These results show that some of the layers are more strained than others. Two peaks are observed in their Raman spectra over this composition range. The assignment of the observed modes to GaSb-like modes is discussed. The studies of the chemical composition of the layers by SIMS exhibit the presence of tellurium, carbon and oxygen like the main residual impurities.     

Studies of the Ga1-xI^As1-ySby quaternary alloy system:-II characterisation by far-infrared reflectance spectroscopy

Reflectivity spectra have been measured on LPE Ga_1-xIn_xAs_1-ySb_y, quaternary alloy layers, lattice-matched to InAs and GaSb substrates. The compositions studied were limited by a miscibility gap to the regionsx = 0,y - 1 (GaSb) tox ~ 0.2,y ~ 0.8 andx = 1,y = 0 (InAs) tox ~ 0.9,y ~ 0.1. The spectra were analysed to give values of carrier density and mobility to investigate Te doping. Fory ~ 0.8 layers werep-type as-grown,n-type conduction being obtained for Te concentrations in the melt above about 10^-6 at.%. Electron mobility for low carrier densities was found to increase sharply with decreasingy. The lattice vibrational properties of the system were also investigated. Three phonon modes were observed in the composition range studied, with GaAs, InSb and mixed InAs/GaSb characteristics. Thus the behaviour of the system may be termed “three-mode” due to the degeneracy of the GaSb and InAs modes. The oscillator strengths of the observed modes are qualitatively as expected from a comparison with appropriate binary systems.     

退火对CNx薄膜光学性质的影响

报道了退火对电子回旋共振(ECR)辅助脉)中激光溅射方法制备的CNx薄膜样品光学性质的影响，X射线衍射(XRD)结果显示CNx薄膜基本为无定形结构，但存在微量的多晶结构，拉曼散射谱显示所制备的CNx薄膜样品主要由C≡N、少量的C—C和微量的C≡N组成，随着退火温度的升高，拉曼散射谱不但在1357cm^-1附近出现了一个新峰(新峰对应无序的CN键)，而且C≡N和CN的相对含量比随着退火温度的提高大致呈先减小后增大再减小的趋势，从而证实在退火过程中部分N原子发生了迁移，椭偏仪所测量的CNx薄膜的光学常数表明退火温度对ε1、ε2、n、κ的大小和谱线的形状均产生了显著影响，结合拉曼散射谱可断定其原因为退火改变了CNx薄膜样品的内部结构和键结构，实验中得到的ε1、ε2、n、κ随光子能量的变化关系可用洛伦兹色散理论得到很好解释。