碳化硼五次孪晶纳米线的结构弛豫现象研究

通过透射电子显微学方法研究纳米材料内部结构有助于理解界面与缺陷对纳米材料性能的影响.在碳化硼五次孪晶纳米线体系中,为了缓解5°角度过剩引起的五次孪晶轴心区域的弹性应变能,在纳米线内部会产生一些结构缺陷.本文通过系列电子衍射分析结合暗场成像技术揭示了碳化硼五次循环孪晶纳米线中的一种结构弛豫模式.孪晶轴向纳米线边缘偏移从而...     

低维纳米材料中五次孪晶结构的透射电镜研究

本文对Ag纳米线中的五次孪晶结构进行了深入系统的透射电镜研究。首次获得了Ag纳米线截面的五次孪晶结构的高分辨图像和电子衍射花样;研究了单根孪晶Ag纳米线中五次孪晶的结构特性。结果表明:Ag纳米线沿着[110]方向生长,具有显著的五次孪晶结构特点,其中五次孪晶是由五个{111}晶体旋转组成。并针对五重旋转孪晶产生7°20′本征间隙的这一典型结构问题,进行了统计实验分析,提出了纳米线中五次孪晶的新的结构模型。电子能量损失谱(EELS)研究表明:五次孪晶的中心部位相对于Ag单晶,其Ag M4,5峰向低能量方向有轻微漂移。单根纳米线的选区电子衍射或者是由[112]和[110]方向,或者是由[110]和[111]方向叠加产生的。对五次孪晶纳米线高温动态行为的透射电镜原位观察将有利于了解纳米线的生长机理。     

银纳米线中五次孪晶结构的透射电镜研究

五次孪晶结构是一个典型的结构问题。过去人们深入研究了纳米团簇(颗粒)中的多重孪晶现象。但关于金属纳米线中的五次孪晶结构，特别是孪晶晶界和孪晶关系的问题尚有待深入研究。本文对Ag纳米线中的五次孪晶结构进行了透射电镜研究。     

纳米氧化钴电极材料的制备与电子显微学表征

通过模板水热法合成了氧化钴（ CoO）纳米材料。用透射电子显微镜观察发现样品中CoO为岩盐立方结构,以纳米线的形态存在,每根纳米线均由尺寸在30～100 nm的纳米颗粒附着而成。同时,实验产物中也存在一些Co单质。 Co单质以纳米手指的形态存在,且多数具有孪晶结构,孪晶面为｛111｝。 Co孪晶的生成归因于高温高压的反应条件,同时Co单质的存在增强了CoO作为电极材料的导电性能。     

LEC-InP晶体中孪晶现象的研究

在LEC-InP晶体生长过程中,孪晶的产生是一个影响InP单晶率的突出问题.生长高质量、大直径的单晶是当前InP晶体生长的发展方向,减少孪晶一直是InP单晶生长技术的研究重点.国内外学者研究了影响孪晶产生的相关因素,但具体产生机制仍未确定.大量的实验研究表明InP晶体中的孪晶通常出现在三相界面处的边缘小平面上,且不论内砍还是外切孪晶均产生在{111}面上.晶体生长转肩过程中改变提拉速度会导致边缘过冷度增加,很容易产生孪晶.研究表明可以调整降温速率来实现对晶体直径的控制,减少拉速改变的频率避免造成边缘处过冷度增大,使得晶体生长实现平滑转肩,减小转肩时孪晶的产生概率.     

KxWO3有序孪晶纳米线的合成和TEM表征

通过简单的实验方法在玻璃衬底上得到了钾钨青铜(KxWO3)纳米线。利用透射电镜选区电子衍射方法结合明场像及高分辨电子显微像分析确定了KxWO3纳米线的结构及生长方向,发现KxWO3纳米线具有有序的单斜超结构,该单斜KxWO3相以[001]m为孪晶轴的120°三次旋转孪晶的形式存在,纳米线的生长方向为[001]m。通过暗场像分析,确定了纳米线是由更小尺度的纳米单元构成的。根据透射电子显微分析结果并结合实验过程,对KxWO3纳米线可能的形成机制进行了讨论。     

VGF法中降温速率对InP单晶生长的影响

垂直梯度凝固(VGF)法生长磷化铟(InP)单晶时产生的缺陷主要有孪晶、位错、多晶等，这些缺陷严重影响了InP单晶的产量与品质。首先简述了VGF法生长InP单晶过程中容易产生的主要缺陷，然后通过实验对各生长阶段的降温速率进行调整，成功改善了孪晶、位错重复出现的情况。实验结果表明，增大放肩过程的降温速率有利于抑制放肩过程产生的内切孪晶，但容易增加晶体肩部的位错密度，至等径部位发生位错增殖。为解决此问题，实验在增加放肩降温速率的同时，适当减小了等径降温速率，从而有效抑制了等径部位的位错增殖。最终，实验中生长出了平均位错密度低于50 cm^-2的高质量掺S InP单晶。     

纳米Ir薄膜中缺陷结构的原子尺度研究

金属铱(Ir)因具有高密度,高熔点,高硬度等特点而被广泛应用于航空航天、军工等高新科技领域。但Ir的塑性差,严重影响其进一步广泛应用。金属自身的结构及缺陷对其力学性能具有重要影响,研究Ir的原子尺度微观结构可为其力学性能优化提供重要参考。本文主要利用透射电子显微镜(TEM)对纳米Ir薄膜中的缺陷类型和缺陷密度进行了研究。发现薄膜中存在高密度的孪晶以及位错。其中,薄膜中的孪晶密度为1.6×10³(1/μm²)。此外,研究还发现薄膜中有两大类缺陷的相互作用:位错与孪晶相互作用以及孪晶与孪晶相互作用。前者包括层错与孪晶相互作用以及全位错对孪晶的钉扎作用;孪晶之间的相互作用形态包括头对头对接式,三重孪晶和五重孪晶等多种形态。     

ZnSe纳米材料及界面的制备与表征

利用热蒸发法对ZnSe纳米材料的相控合成进行了研究,制备了多种具有稳定闪锌矿和亚稳纤锌矿结构的ZnSe纳米材料,如ZnSe纳米线、纳米圈、纳米轮及三晶纳米带。同时,在相控合成基础上,通过改变管式炉内反应压强获得了几种同质与异质界面。利用多种透射电子显微学手段对合成的ZnSe纳米材料及相关同质与异质界面进行了深入表征,并对ZnSe纳米材料的生长机理进行了探讨。     

Al-7Si合金在热处理过程中的显微结构演变

本文利用扫描电子显微镜(SEM)和高分辨透射电子显微镜(HRTEM)研究了固溶处理和时效处理过程中铝硅二元合金中硅颗粒、析出相及硅颗粒与铝基体界面处的微观结构变化特征。研究结果表明:随着固溶时间的延长,硅颗粒的形态由树枝状逐渐变成椭球状和球状;时效过程中,溶入α-Al基体中的硅原子会在铝基体中聚集,形核并形成沿铝基体{111}面生长的硅析出相,同时还会在硅颗粒上析出一层硅的纳米孪晶,这些纳米孪晶会随着时效时间的延长不断长大。硅的孪晶壳层中存在大量孪晶和其他缺陷,除了常见的SiΣ3(111)孪晶外,观察到的孪晶类型还包括多重孪晶,如五重孪晶。     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-