集中力作用下硅中位错结构

本文用化学侵蚀法研究了硅单晶样品在800—1000℃印压得到的位错“花结”。实验结果说明:印压产生的位错分布在{111}滑移面上;位错线的取向大部分是<110>或<112>方向。分析并观察到在压印下有两种位错环,一种是柏格斯矢量沿<110>方向并平行于(111)印压面;一种是柏格斯矢量沿<110>方向并与印压面相交。对位错环的结构进行了分析。     

聚变材料钨辐照后退火形成的位错环特性及inside-outside衬度分析

对纯钨透射电镜薄膜样品在400℃进行了58 keV、1×10¹⁷ cm^-2(约0.1 dpa)的氘离子辐照,辐照后进行了900℃/1 h的退火处理.离子辐照产生了平均尺寸为(11.10±5.41)nm,体密度约为2.40×10²² m^-3的细小位错环组织,未观察到明显的空洞组织.辐照后退火造成了位错环尺寸的长大和体密度的下降,分别为(18.25±16.92) nm和1.19×10²² m^-3.通过透射电镜的衍射衬度分析,判断辐照后退火样品中的位错环主要为a/2<111>类型位错环.通过“一步法” inside-outside衬度分析判断位错环为间隙型位错环.辐照后退火还造成了较大位错环之间接触融合,形成不规则形状的大型位错环.此外,退火后样品中还观察到了尺寸为1—2 nm的细小空洞组织.     

氮气喷射成形FGH4095的组织特征

以氮气为雾化气体采用喷射成形工艺制备了FGH4095高温合金沉积坯, 记录了沉积过程坯体表面温度曲线, 并采用定量金相法、排水法测试了坯体致密度, 观察了坯体晶粒及γ'相的形貌. 结果表明采用氮气作为雾化介质进行喷射成型喷射沉积坯基体致密度可达99%以上, 但也存在着较大的(1—2μm)的气孔, 经热等静压和近等温锻后宏观气孔闭合, 氮以尺寸不超过1 μm的碳氮化物形式存在. 喷射沉积坯以等轴晶组织为主, 坯体内部平均晶粒尺寸约为20—40 μm, 近表面区域晶粒较细, 约为13 μm; 一次γ' 相多数呈尺寸约0.3—0.5 μm不规则块状形貌. 喷射成形坯组织结构的形成与喷射成形过程的降温过程有密切关系.     

强流脉冲电子束诱发纯镍表层纳米结构的形成机制

利用强流脉冲电子束（HCPEB）技术对多晶纯镍进行了表面处理,并采用扫描电镜和透射电镜对强流脉冲电子束诱发的表面及亚表面的微观组织结构进行了分析.实验结果表明,HCPEB辐照后表面熔化,形成了深度约为2 μm的重熔层,快速的凝固使重熔层中形成晶粒尺寸约为80 nm的纳米结构.位于轰击表面下方5—15 μm深度范围内强烈塑性变形引起的位错墙和其内部的亚位错墙结构是该区域的主要结构特征.这些缺陷结构通过互相交割细化晶粒,最终导致尺寸约为10 nm的纳米晶粒的形成. 关键词： 强流脉冲电子束 纳米结构 多晶纯镍 位错墙     

硅中位错运动速度

本文用化学侵蚀法显示了硅晶体印压产生的位错。测量了在不同温度、不同切应力下“花结”上刃型(或60°)位错的运动速度。设位错运动是热激活的,激活能为～2.94eV.比较了900℃下刃型(或60°)位错及螺型位错的速度,后者较小。在不同样品上进行速度的测定,说明原生位错对形变位错运动有阻碍作用。观察到原生位错和晶界位错在外加力作用下的增殖,对位错在增殖中的速度进行了测量。讨论了本工作所用的实验方法,并分析了影响速度测量值的某些因素。     

基于两种辐射传输模型的雪粒径与反照率反演

提出一种渐近辐射传输(ART)理论与离散纵标辐射传输法(DISORT)相结合的方法,用于反演雪光谱反照率。基于雪粒形状的二级科赫分形假设,利用不同卫星数据与ART理论的三种粒径反演方法反演研究区域的雪粒径,反演的雪粒径大小不同,但平均值均在50μm左右。基于雪粒球形假设,根据反演的雪粒径,基于DISORT模型计算波段为0.3～5.0μm的雪光谱反照率,同时基于ART理论计算波段为0.3～1.5μm的雪的黑空与白空光谱反照率。由两种辐射传输模型计算的0.3～1.5μm的雪光谱反照率差异较小,表明雪粒形状假设合理,利用两种辐射传输模型相结合的方法能够计算太阳光谱的雪反照率。考虑到研究区域内黑碳等吸光性杂质的影响,修正了DISORT模型计算的雪光谱反照率。研究区域靠近国境边缘的西伯利亚地区时,吸光性杂质对于雪光谱反照率影响很小;研究区域为东北工业地区时,吸光性杂质会明显降低可见光波段的雪光谱反照率。     

用声学方法遥测地下空穴的形体

1概况在工程地质勘探中遥测地下空洞的形状和体积，常用的探测方法有：浅层地震勘探法、电磁波透视法和井中电视法等，在这里我们介绍一个用非常规物探方法——声学方法探测地下空洞的形状和体积的实例．十三陵蓄能电站高压管道倾角50o，全长400多米，文要坐落于安山岩和砾岩中．该区地质情况极为复杂，要穿过几十条断层，其中一条最大的断层破碎带宽度20－40m，开工前对此断层的条件不甚清楚．当压力管道导井上掘时，通该断层，发生大塌方，距地表约180m．当时，估算塌方量约为4000m’，并且对损穴体的形状看法不一．为及时充填断层塌穴，…     

聚合物微环谐振器电光开关阵列的优化与模拟

利用耦合模理论、电光调制理论和微环谐振理论,提出了一个聚合物微环谐振器电光开关阵列的模型.该器件由N-1个微环和N条平行信道构成,在微环上施加不同方式的驱动电压,可以实现N条信道的开关功能.以7微环8信道结构为例,在1550 nm谐振波长下对该器件进行了优化和模拟.结果表明,微环波导芯的截面尺寸为1.7μm×1.7μm,波导芯与电极间的缓冲层厚度为2.5 μm,电极厚度为0.2μm,微环半径为13.76 μm,微环与信道间的耦合间距为0.14μm,输出光谱的3 dB带宽约为0.05 nm,开关电压约为8.1 V左右,插入损耗约为0.23～4.6 dB,串扰小于-20 dB.     

多孔气液分离强化传热结构单相流中传热性能

本文对金属多孔气液分离强化传热结构单相流中传热性能进行了分析。分别研究了粉末颗粒形状、粉末颗粒大小对传热性能的影响。测试样品分别为采用五组不同参数粉末颗粒进行烧制,其中2组为球状粉末样品(颗粒大小为75~100μm,100~125μm),3组枝状粉末样品(颗粒大小为25μm,100~125μm,150μm)。水作为工作介质。样品雷诺数测试范围为3654~14617。研究结果表明,粉末颗粒大小对传热性能有重要影响,对于枝状粉末颗粒样品,粉末颗粒尺寸为100~125μm样品换热性能最好;粉末颗粒形状对传热也有较大影响,同枝状粉末颗粒样品相比,球形粉末颗粒样品传热系更高,但产生的流动阻力也高,综合换热性能,球形粉末不如枝状粉末。     

Lateral Epitaxy Overgrown (LEO) GaN 导热系数的数值研究

利用修正的Callaway模型对含杂质、位错、以及同位素的LEO GaN的导热系数进行了研究,计算表明同位素对LEO GaN的导热系数影响较大,而位错和杂质大于一定值时其值才对导热系数产生影响.     

Formation and nature of swirl defects in silicon

Point defect agglomerates in dislocation-free silicon crystals, usually called “swirls”, have been investigated by means of high-voltage electron microscopy. It was found that a single swirl defect consists of a dislocation loop or a cluster of dislocation loops. By contrast experiments it could be shown that these loops are formed by agglomeration of self-interstitial atoms. Generally the loops have a/2〈110〉 Burgers vectors, but in specimens with high concentrations of carbon (～10¹⁷ cm^?3) and oxygen (～10¹⁶ cm^?3) also dislocation loops including a stacking fault were observed. In crystals grown at growth rates higher thanv=4 mm/min no swirls are observed; lower growth rates do not markedly affect the size and shape of the dislocation loops. With decreasing impurity content (particulary of oxygen and carbon) the swirl density decreases, whereas the dislocation loop clusters become larger and more complex. A model is presented which describes the formation of swirls in terms of agglomeration of silicon self-interstitials and impurity atoms.     

应力预释放对单晶硅片的压痕位错滑移的影响

单晶硅片的压痕位错在一定温度下的滑移距离反映了硅片的机械强度. 压痕位错的滑移是受压痕的残余应力驱动的, 因此研究残余应力与位错滑移之间的关系具有重要的意义. 本文首先采用共聚焦显微拉曼术研究了单晶硅片压痕的残余应力经过300或500 ℃ 热处理后的预释放, 然后研究了上述应力预释放对压痕位错在后续较高温度(700–900 ℃)热处理过程中滑移的影响. 在未经应力预释放的情况下, 压痕位错在700–900 ℃热处理2 h后即可滑移至最大距离. 当经过上述预应力释放后, 位错在900 ℃热处理2 h后仍能达到上述最大距离, 但位错滑移速度明显降低; 而在700和800 ℃时热处理2 h后的滑移距离变小, 其减小幅度在预热处理温度为500 ℃时更为显著. 然而, 进一步的研究表明: 即使经过预应力释放, 只要足够地延长700和800 ℃ 的热处理时间, 位错滑移的最大距离几乎与未经预应力释放情形时的一样. 根据以上结果, 可以认为在压痕的残余应力大于位错在某一温度滑移所需临界应力的前提下, 压痕位错在某一温度滑移的最大距离与应力大小无关, 不过达到最大距离所需的时间随应力的减小而显著增长.     

Role of the rate factor in the hardness testing of β-irradiated silicon single crystals

The effect of the indenter penetration rate on the magnitude of changes in the hardness and length of radial cracks in silicon, induced by low-intensity β radiation has been studied using the dynamic microindentation method. The elementary volume taking part in plastic deformation of the initial and irradiated silicon during indentation have been calculated using load versus penetration depth curves.     

Mechanical properties and photomechanical effect in GaP single crystals

Mechanical properdes of GaP single crystals have been investigated from 100° to 300°C by observing dislocation rosette patterns on indented specimen surfaces. It has been found that GaP has mechanical properties which are common to those of other III–V compounds or elemental semiconductors in several points: the {111} surface polarity dependence of microhardness, the mobility difference between α- and β-dislocations, and the conduction type dependence of dislocation mobility. The growth of dislocation rosettes is suppressed by baking specimens in air. Contrary to the case of II–VI compounds, illumination of visible light during indentation enhances the mobility of dislocations. These experimental results are discussed in terms of an effect of electronic charge of dislocation on its mobility.     

Confinement scaling laws for the conventional reversed-field pinch

Mechanical behavior of the Si(111)/Si(3)N4(0001) interface is studied using million atom molecular dynamics simulations. At a critical value of applied strain parallel to the interface, a crack forms on the silicon nitride surface and moves toward the interface. The crack does not propagate into the silicon substrate; instead, dislocations are emitted when the crack reaches the interface. The dislocation loop propagates in the (1; 1;1) plane of the silicon substrate with a speed of 500 (+/-100) m/s. Time evolution of the dislocation emission and nature of defects is studied.     

Redistribution of dislocations in silicon near stress concentrators

The distribution of defects in dislocation tracks in silicon plates was studied for various indentation angles. The regularities of variations in the linear density and maximum path of dislocations in slip bands are established. A model is proposed to describe the distribution of dislocations in the dislocation tracks. By fitting the theory to the experimental data, the dependence of this distribution on the energy relaxation time is determined.     

Formation of ordered arrays of gold particles by nanoindentation templating

Ordered arrays of gold‐rich particles, with diameters ranging from 50 nm to 180 nm, have been formed on a silicon (100) surface through pre‐patterning by nanoindentation. Indentation and gold deposition of the sample is followed by thermal processing, causing the gold to become trapped at the indentation sites. We suggest that gold trapping is via an alloying process with the underlying Si substrate where the native oxide is structurally compromised by the indentation process. The final size for a given particle is directly dependent on the size of the indentation site. It has also been demonstrated that excess gold found on the surface outside of these indentation sites can be readily removed via simple mechanical abrasion without affecting the particles within the indent. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)