Si/SiGe/Si-SOI异质结构的同步辐射双晶貌相术和高分辨三轴晶X射线衍射

运用同步辐射双晶貌相术结合高分辨三轴晶X射线衍射对经原位低温热处理的Si/SiGe/Si-SOI异质结构进行研究,发现Si层(004)衍射峰两侧半高宽(FWHMs)处同步辐射双晶形貌像特征存在明显差异.对同步辐射双晶摇摆曲线中Si层(004)衍射峰的不对称性给予了解释,同时阐明了高分辨三轴晶X射线衍射2θ-ω扫描曲线中Si层(004)衍射双峰与Si层衍射结构的对应关系.     

X射线在超晶格材料衍射中的相干性分析

X射线双晶衍射仪系统中受参考晶体分辨率等因素的影响,X射线的相干长度不超过1 μm.X射线在异质外延晶体材料内衍射时,不超过相干长度范围内厚度外延层中的衍射波会产生相干叠加,否则,产生非相干叠加.分子束外延(MBE)生长了短周期InGaAs/GaAs超晶格,在其摇摆曲线中观察到显示X射线在超晶格结构中衍射相干特征的多级卫星峰及Pendell(o)song干涉条纹,并利用相干光理论对超晶格结构信息诸如周期及"0"级峰位置等进行了分析.     

应变量子阱结构材料X射线双晶衍射摇摆曲线的测试与分析

报告了多薄层质结构材料Ｘ射线衍射模拟摇摆曲线和压应变，张应变量子阱材料的实测摇摆曲线，指出了计算机模拟分析实测摇摆曲线是精确求得失配率，量子阱周期的科学方法，分析和讨论了与失配率，量子阱周期有关的简单计算公式的适用性。     

In Situ Data Analysis on High Altitude Balloons Using Microprocessors

The use of a microprocessor to reduce scientific data on high altitude balloons is described. The transmitted data rate is reduced by two orders of magnitude.     

ZnO/Si (111）界面结构的同步辐射掠入射X射线衍射研究

在不同的衬底温度下,用脉冲激光沉积(PLD)方法制备了c轴高度取向的ZnO薄膜.采用同步辐射掠入射X射线衍射(GID)技术研究了ZnO薄膜与Si(111)衬底的界面结构.GID结果表明:不管衬底温度是500℃还是300℃,在无氧气氛下用PLD方法制备的ZnO外延膜均处于压应力状态,且随着X射线探测深度的增加,应力增大.结合常规X射线衍射技术,计算了薄膜内的双轴应力;给出了样品的泊松比和c/a值,得出两样品均接近理想的六方密堆积结构,偏离标准的ZnO值.综合各方面实验结果,说明衬底温度控制在500℃时生长的ZnO薄膜具有较好的晶体质量.     

双晶x射线衍射法测量超薄层外延材料厚度

介绍了通过双晶ｘ射线衍射测量超薄外延层厚度的一种方法。利用回摆曲线中的干涉条纹测量了通过ＭＢＥ生长的Ｇａ０．７Ａｌ０．３Ａｓ／Ｇａ０．９Ａｌ０．１Ａｓ／Ｇａ０．７Ａｌ０．３Ａｓ结构的各层层厚。     

线形拟合在X射线衍射研究GaN薄膜材料结构时的必要性

利用高分辨X射线衍射仪(XRD)分析了长时间退火前后的GaN样品.通过对各个样品的(0002)面摇摆曲线进行线形拟合及分析,发现虽然退火后摇摆曲线的半峰宽变大,但面外倾斜角(tilt)的值却变小,从而螺型穿透位错(TD)密度变小,这与化学腐蚀实验的结果一致.我们的结果表明,线形拟合在利用XRD研究GaN薄膜材料结构的过程中是十分必要的,而不能用摇摆曲线的展宽直接表征TD密度.     

线形拟合在X射线衍射研究GaN薄膜材料结构时的必要性

利用高分辨X射线衍射仪(XRD)分析了长时间退火前后的GaN样品.通过对各个样品的(0002)面摇摆曲线进行线形拟合及分析,发现虽然退火后摇摆曲线的半峰宽变大,但面外倾斜角(tilt)的值却变小,从而螺型穿透位错(TD)密度变小,这与化学腐蚀实验的结果一致.我们的结果表明,线形拟合在利用XRD研究GaN薄膜材料结构的过程中是十分必要的,而不能用摇摆曲线的展宽直接表征TD密度.     

In Situ Observation of Strain Development and Porosity Evolution in Nanoporous Gold Foils

The formation of nanoporous gold by open circuit dealloying of 100 nm AgAu foils in nitric acid is investigated in situ and in real time by combining synchrotron small angle X‐ray scattering (SAXS) and X‐ray diffraction (XRD). The time dependence of the dealloying is followed as a function of acid concentration. For all concentrations, several characteristic dealloying stages are observed. Firstly, there is a fast initial dissolution stage with an increase in surface area due to pore and mound formation; this leads to strain in the nanoporous gold that results from an increase in capillary pressure. After dissolution is complete, there is rapid coarsening of the quasi‐periodic, pore–ligament morphology. During this later stage, we deduce strong strain anisotropies that can be explained by preferred crystallographic orientation of ligaments. This rapid coarsening stage is followed by a slow coarsening stage where the SAXS patterns, and hence the quasi‐periodic morphology, is self‐similar in time. There is a strong correlation between the morphology evolution and strain development, which can be explained by capillary forces.     

Error Modeling of Seebeck Coefficient Measurements Using Finite-Element Analysis

Using finite-element analysis, we have developed a metrology simulation to model errors in the measurement of the Seebeck coefficient. This physical parameter is the constant of proportionality relating the electric potential generated across a conductor to the applied thermal gradient. Its measurement requires careful attention to the electrical and thermal contact interfaces. Furthermore, it is essential that the electric potential and temperature difference be acquired at the same time and at the same location. We have performed Seebeck coefficient measurement simulations to quantitatively explore the effect of temporal perturbation to the voltage and temperature correspondence, by comparing simultaneous and staggered data acquisition techniques under the quasi-steady-state condition. Using a similar method, we have developed an error model to explore the effect of misalignment between the voltage and temperature probes on the measurement of the Seebeck coefficient. This approach enables the exploration of experimentally inaccessible data spaces under ideal conditions.     

Strain Analysis of CdTe on InSb Epitaxial Structures Using X-ray-Based Reciprocal Space Measurements and Dynamical Diffraction Simulations

The structural properties of CdTe layers grown by molecular beam epitaxy on (001) InSb substrates were assessed using high-resolution x-ray scattering methods. Triple-axis diffraction measurements and dynamical diffraction theory were employed to determine the strain in the epitaxial layer and at the interface for CdTe layer thicknesses of 1.0 μm and 1.8 μm. Reciprocal space maps were generated around the 004, 115, 224 and 335 reciprocal lattice points (RLP). An alignment procedure is described which ensured all reflections were aligned to the same zone axes. (335) reflections exhibited greater sensitivity to strain relaxation than (115) reflections due to a larger in-plane component; so these were used to better determine the strain state of the layers. Both of our 1.0-μm and 1.8-μm thick samples exhibited no relaxation, showing that pseudomorphic layers formed. Additionally, interference oscillations in the (004) ω:2θ scan of the 1.0-μm CdTe sample were observed. These oscillations were replicated through dynamical diffraction simulations by including a ～1-nm highly strained interfacial layer. These results are consistent with an earlier electron microscopy study that detected a similar strained layer at a defect-free CdTe/InSb interface. The CdTe lattice parameter and Poisson ratio are determined to be 0.648201?±?0.000002 nm and 0.408, respectively.     

一种同时测量温度和应变的光纤光栅传感器

报道了一种新型实用的用单根光纤布拉格光栅(FBG)实现温度和应变分离传感的技术。当光纤光栅一部分包层直径变小时，整个光栅可以看成由两个周期相同但直径不同的子光栅连接而成。理沦分析和实验都证实了这两个子光栅具有相同的温度敏感性和不同的应变敏感性．由此实现光纤光栅传感器中温度和应变两参数的分离测量，而且这两个子光栅的中心波长间距可以直接测量应变大小．温度变化不影响所测量的应变值。实验中光栅的一部分包层直径被HF酸腐蚀到82μm．获得了两子光栅应变响应系数分别为0．00201nm/με．0．000858nm/με，二峰间距的应变响应系数为0．00116nm／με．二峰的温度响应系数均为0．01nm/℃的测量结果．依据这些结果可以对温度和应变进行同时分离测量。     

Analysis of Open Waveguides Using the Finite-Element Method and Boundary Integral Equations

To analyze dielectric waveguides, an iterative procedure coupling the finite-element method in the interior to an integral equation of the exterior domain is developed. The robustness of this method is confirmed by the numerical results presented in this paper and corresponding the computation of the propagation constant.     

应变测量系统误差分析

电阻应变式传感器在实际工程中应用较广。介绍影响电阻应变式传感器精度的一些因素,并对其在实际应用中可能出现的问题进行全面细致的分析。分析电测试验中应变片粘贴质量、非线性及导线长度、温度、不同组桥方式对测试结果所产生的影响,修正了导线电阻引起的误差,大大提高了测量精度,得出了应变电测试试验中减小误差的方法。     

GaN外延结构中微区应变场的测量和评价

 采用电子背散射衍射(EBSD)技术,测量GaN/蓝宝石结构中的弹性应变场.将EBSD菊池衍射花样的图像质量IQ值及小角度错配作为应力敏感参数,表征GaN-Buffer层-蓝宝石结构中的晶格畸变和转动,显示微区弹性应变场.在GaN/蓝宝石系统中,弹性应变的影响范围大约200×700nm.采用快速傅立叶变换(FFT)提取菊池花样的衍射强度,识别GaN外延结构中的应变/无应变区域.     

Simultaneous Measurement of PWB and Chip Package Warpage Using Automatic Image Segmentation

The shadow moire and projection moire techniques are widely used methods for measuring printed wiring board (PWB) and PWB assembly (PWBA) warpage. Both methods have high resolution, high accuracy and are suitable for use in an online environment. When measuring the warpage of a bare PWB, maximum warpage across the PWB is calculated by subtracting the minimum out-of-plane displacement on the PWB from the maximum out-of-plane displacement on the PWB. However, when the PWB is populated with electronic components (chip packages); the difference between the maximum and minimum out-of-plane displacements on the PWBA is not the warpage of the PWB or the warpage of the chip packages. In order to use warpage measurement methods such as the shadow and projection moire techniques to accurately and separately determine the warpage of a PWB and chip packages in a PWBA, an automated chip package segmentation algorithm is developed and will be presented in this paper. The automated algorithm is based on active contour models (snakes) and can be used to detect chip package locations on an out-of-plane displacement image of a PWBA. This paper will discuss the characteristics of the automated algorithm, which is applicable to all warpage measurement methods, not just the out-of-plane moire methods. Warpage case studies of PWBs populated with plastic ball grid array chip packages measured using the projection moire technique will also be presented and will show that the developed algorithm along with a warpage measurement method is a powerful tool for measuring the warpage of populated PWBs.     

Recapitulation of In Situ Endochondral Ossification Using an Injectable Hypoxia-Mimetic Hydrogel

Due to the limited ability for perfusion, traditional intramembranous ossification (IMO) often fails to recapitulate the natural regeneration process of most long bones and craniofacial bones. Alternatively, endochondral ossification (ECO) strategy has emerged and has been evidenced to circumvent the drawbacks in the routine application of IMO. Here, an injectable, poly(glycerol sebacate)-co-poly (ethylene glycol)/polyacrylic acid (PEGS/PAA) hydrogels are successfully developed to induce a hypoxia-mimicking environment and subsequently recapitulate ECO via in situ iron chelation. With the incorporation of PAA, these hydrogels present remarkable viscoelasticity and high efficacy of iron ion-chelating after injection, giving rise to the activation of HIF-1α signaling pathway and suppression of inflammatory responses, and thereby improving chondrogenic differentiation in the early stage and facilitating vascularization in the later stage, which consequently trigger typical ECO. More importantly, through sustained and stable expression of HIF-1α regulated by PEGS/PAA hydrogels throughout the regeneration, a harmonious chondrogenic/osteogenic balance can be struck and thereby accelerating the progress of ECO compared to the PEGS. The findings provide an efficient strategy to achieve in situ ECO via biomaterial-based iron ion-chelating and ensuing hypoxia-mimicking, representing a novel and promising concept for future application in bone regeneration.     

Finite-Element Analysis of Overmoded Waveguide Using Silvester's Algorithm (Short Paper)

A general, high-order finite-element waveguide analysis program originated by Silvester [1], [2] has been used to analyze overmoded waveguides. The algorithm approximates arbitrarily shaped waveguides by triangular subsections and solves the Hehnholtz equation subject to homogeneous Dirichlet or Neumann boundary conditions to obtain the eigenvalues (cutoff wavelengths) and the eigenvectors (scalar potentials). During these investigations of arbitrarily shaped overmoded waveguides, a computer program error was identified. This error resulted in incorrect higher-order mode potential functions. As this algorithms has been rather widely disseminated, it is the purpose of this communication to inform users of a correction which yields the correct higher-order-mode potential functions.     

Synchrotron X-Ray Topography Study of Structural Defects and Strain in Epitaxial Structures of Yb- and Tm-Doped Potassium Rare-Earth Double Tungstates and Their Influence on Laser Performance

Monoclinic potassium rare-earth double tungstates [KRE(WO₄)₂, RE = Y, Lu, Yb; KREW] are well suited as hosts for active lanthanide ion (Ln³⁺) dopants for diode-pumped solid-state lasers, with particular interest in thin-disk laser configurations when they are grown as thin films. Using synchrotron white-beam x-ray topography, we have imaged defects and strain in top-seeded solution-grown (TSSG) bulk substrates of different rare-earth tungstates as well as within Yb³⁺- and Tm³⁺-doped epitaxies for thin-disk laser applications grown on these substrates by liquid-phase epitaxy. Higher structural stress in Yb:KYW/KYW epitaxies compared with Yb:KLuW/KLuW epitaxies is found to lower efficiency in laser operation. The quality of Tm:KLuW/KLuW epitaxial films is sensitive to doping level, film thickness, and growth rate. Inhomogeneous stresses within the layers are dominated by lattice-mismatch effects rather than by crystallographic anisotropy.     

Visualizing Strain Evolution and Coordinated Buckling within CNT Arrays by In Situ Digital Image Correlation

Spatial mapping of strain fields within compressed carbon nanotube (CNT) array columns is achieved using digital image correlation (DIC) analysis of in situ scanning electron microscopy (SEM) image sequences. Full‐field displacement and strain maps are generated based upon the motion of the constituent CNTs, which serve as a traceable high‐contrast speckle pattern for DIC analysis. The deformation modes and CNT array buckling characteristics vary systematically as a function of column aspect ratio, including bending, crushing, and bottom‐up buckle accumulation behaviors. In spite of disparate appearing deformation modes, strain maps indicate that CNT array buckling consistently initiates at 5% local principal strain (?₂) for all columns. The ability to quantitatively assess the deformation modes and buckling behavior of CNT arrays at the nanoscale will enable their improved design for high‐strain electrical contacts, compliant thermal interfaces, force sensors, energy‐absorbing foams, or other applications.