Structural evaluation of polycrystalline silicon thin films by hot-wire-assisted PECVD

Tungsten wires were introduced into a plasma-enhanced chemical vapor deposition (PECVD) system as a catalyzer: we name this technique 'hot-wire-assisted PECVD' (HW-PECVD). Under constant deposition pressure (p(g)), gas flow ratio and catalyzer position, the effects of the hot wire temperature (T-f) on the structural properties of the poly-Si films have been characterized by X-ray diffraction (XRD), Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. Compared with conventional PECVD, the grain size, crystalline volume fraction (X-e) and deposition rate were all enhanced when a high T-f was used. The best poly-Si film exhibits a preferential (220) orientation, with a full width at half-maximum (FWHM) of 0.2 degrees. The Si-Si TO peak of the Raman scattering spectrum is located at 519.8 cm(-1) with a FWHM of 7.1 cm(-1). The X-c is 0.93. These improvements are mainly the result of promotion of the dissociation of SiH4 and an increase in the atomic H concentration in the gas phase. (C) 2001 Elsevier Science B.V. All rights reserved.

两种聚砜预聚物和多嵌段聚合物的合成及形态结构

以双酚A、酚酞和4，4'-二氯二茉砜为单体，合成了双酚A型聚砜和酚酞型聚砜两系列不同分子量的预聚物。将这两系列预聚物作为硬段，以不同分子量的聚氧化丙烯或聚氧化丙烯-聚二甲基硅氧烷作为软段，以二异氰酸酯二苯甲烷作为硬段和软段间的连接桥，合成了硬、软段分子量不同的双酚A型聚砜-聚氧化丙烯多嵌段聚合物、双酚A型聚砜-（聚氧化丙烯-聚二甲基硅氧烷）多嵌段聚合物的酚酞型聚砜-聚氧化丙烯多嵌段聚合物。经红外光谱分析、分子量测定和粘度测定等表征，确认产物与预想结果相符。用示差扫描量热仪、扭辨分析仪和电子显微镜研究了硬段预聚物和多嵌段聚合物的形态结构及性能。硬段预聚物在实验温度范围（-30到250 ℃）内，具有三种转变，分别为局部短程有序（60到70 ℃）的破坏，玻璃化转变，玻璃化温度与分子量的关系如下式所示：双酚A型聚砜 T_g = 462 - 8.07 * 10~4/M-bar 酚酞型聚砜 Tg = 519 - 8.33 * 10~4/M-bar和较大范围的长程有序性的解离。在双酚A型聚砜-聚氧化丙烯多嵌段聚合物体系中，当硬段分子量固定在1500时，多嵌段聚合物的形态结构随软段的分子量降低由两相结构（软段分子量≥1000）变成为单相结构（软段分子量为450）。当软段分子量固定为2000时，多嵌段聚合物的形态结构随硬段的分子量增加由单相结构（硬段分子量为700）变为两相结构（硬段分子量≥1500）。双酚A型聚砜-（聚氧化丙烯-聚二甲基硅氧烷）多嵌段聚合物均显示两相结构（软段分子量2400，硬段分子量≥700）。在硬段分子量增加到3900就发生相倒转，软段变为分散相，硬段成为连续相。酚酞型聚砜-聚氧化丙烯多嵌段聚合物，当固定分子量为2000时，硬段分子量在本工作的变化范围内，850至1900，所得产物均为两相结构。

Structural evaluation of polycrystalline silicon thin films by hot-wire-assisted PECVD

Tungsten wires were introduced into a plasma-enhanced chemical vapor deposition (PECVD) system as a catalyzer: we name this technique 'hot-wire-assisted PECVD' (HW-PECVD). Under constant deposition pressure (p(g)), gas flow ratio and catalyzer position, the effects of the hot wire temperature (T-f) on the structural properties of the poly-Si films have been characterized by X-ray diffraction (XRD), Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. Compared with conventional PECVD, the grain size, crystalline volume fraction (X-e) and deposition rate were all enhanced when a high T-f was used. The best poly-Si film exhibits a preferential (220) orientation, with a full width at half-maximum (FWHM) of 0.2 degrees. The Si-Si TO peak of the Raman scattering spectrum is located at 519.8 cm(-1) with a FWHM of 7.1 cm(-1). The X-c is 0.93. These improvements are mainly the result of promotion of the dissociation of SiH4 and an increase in the atomic H concentration in the gas phase. (C) 2001 Elsevier Science B.V. All rights reserved.

8阶群速度控制格式及其应用

构造了8阶精度的群速度控制型差分格式.根据激波捕捉能力及对小尺度分辨能力对格式系数进行了优化.采用该格式对可压缩均匀各向同性湍流进行了直接数值模拟,所计算的最大湍流马赫数达到0.95.相同计算条件下的结果与他人结果吻合较好,说明了格式在捕捉激波的同时对湍流小尺度有较好的分辨能力.

蛋白质吸附和竞争吸附对ROS 17/2.8细胞粘附和生长的影响

细胞在材料表面的粘附是贴壁依赖型细胞生长的前提.本文以胶原和牛血清蛋白(BSA)为模型蛋白,研究了两者的吸附和竞争吸附对细胞粘附和生长的影响.

The Nonlinear Phenomena Of Thin Polydimethylsiloxane (Pdms) Films In Electrowetting

Electrowetting (EW) is an effective way to manipulate small volume liquid in micro- and nano-devices, for it can improve its wettability. Since the late 1990s, electrowetting-on-dielectric (EWOD) has been used widely in bio-MEMS, lab-on-a-chip, etc. Polydimethlsiloxane (PDMS) is extensively utilized as base materials in the fabrication of biomedical micro- and nano-devices. The properties of thin PDMS films used as dielectric layer in EW are studied in this paper. The experimental results show that the thin PDMS films exhibit good properties in EWOD. As to PDMS films with different thicknesses, a threshold voltage and a hysteresis were observed in the EIWOD experiments.

1989年3月和8月太阳大事件的日地系统整体行为研究

<正> 1989年3月日面出现了近四十年来最大的黑子群,发生了剧烈的太阳活动,产生了重大的地球物理效应。对这些事件的联测取得了大量日地物理的资料。为了推动进一步的分析和研究,中国科学院第22周太阳活动峰年日地系统整体行为研究专家组于1990年4月23日至26日在北京召开了“1989年3月和8月重大日地事件观测与分析研

激光毛化技术对18-8不锈钢疲劳性能影响的研究

通过模拟分析 ,对激光毛化 18 8不锈钢的疲劳寿命与毛化覆盖率的关系进行研究 ,预测结果与相关实验结果进行对比。结果显示 ,由于激光毛化处理的影响 ,18 8不锈钢的疲劳寿命得到改善 ,而且在毛化覆盖率为 2 0 %左右时 ,材料疲劳性能最好

脉冲激光辐照ZrO_2涂层的18-8不锈钢快凝组织与精细结构

利用脉冲辐照研究超高温度梯度下表层预轩ZrO_2纳米颗粒涂层的18-8奥氏体不锈钢的快凝组织形态、微结构特征及力学性质，结果表明，在表层约15μm范围内形成Zr的合金化微区，Zr最大含量(原子分数)为43.3%，但Zr成分分布存在不连续特征；预置纳米ZrO_2陶瓷涂层明显提高了激光作用深度。超高温梯度和高冷却速度显著细化了快凝亚组织并得到超细枝晶及胞晶，并观察到位错胞及栅栏孪晶两类亚晶，而激光熔区的外延生长机制未使晶粒细化。激光辐照后，合金化区硬度增加而弹性模量降低，其余部分硬度增加而弹性模量无变化。

滦县M_L=4.8地震的局部多台数字记录

据中国数字地震台网测定,2004年1月20日16时34分11.9秒在滦县发生了ML=4.8的地震,震中位于东经118.77°,北纬39.71°,震源深度H=10km。尽管地震造成的破坏轻微,但有感范围较大,在秦皇岛市、青龙县、北京市、廊坊市、天津市等地均有震感。这次地震使震中及其附近地区的5台数字强震仪触发,记录了5组3分量数字加速度记录。本文对这次地震事件、地震地质概况作了简要介绍,并就台站(阵)基本背景资料、数字强震仪主要技术指标作了详细说明。最后,对获取的15条数字加速度记录作了初步处理分析,如基线校正、加速度峰值计算、傅里叶谱及反应谱计算等。

Effects of Thermocapillary Convection on the Growth Process in Industrial 8-inch Silicon Czochralski Growth

Czochralski (CZ) crystal growth process is a widely used technique in manufacturing of silicon crystals and other semiconductor materials. The ultimate goal of the IC industry is to have the highest quality substrates, which are free of point defect, impurities and micro defect clusters. The scale up of silicon wafer size from 200 mm to 300 mm requires large crucible size and more heat power. Transport phenomena in crystal growth processes are quite complex due to melt and gas flows that may be oscillatory and/or turbulent, coupled convection and radiation, impurities and dopant distributions, unsteady kinetics of the growth process, melt crystal interface dynamics, free surface and meniscus, stoichiometry in the case of compound materials. A global model has been developed to simulate the temperature distribution and melt flow in an 8-inch system. The present program features the fluid convection, magnetohydrodynamics, and radiation models. A multi-zone method is used to divide the Cz system into different zones, e.g., the melt, the crystal and the hot zone. For calculation of temperature distribution, the whole system inside the stainless chamber is considered. For the convective flow, only the melt is considered. The widely used zonal method divides the surface of the radiation enclosure into a number of zones, which has a uniform distribution of temperature, radiative properties and composition. The integro-differential equations for the radiative heat transfer are solved using the matrix inversion technique. The zonal method for radiative heat transfer is used in the growth chamber, which is confined by crystal surface, melt surface, heat shield, and pull chamber. Free surface and crystal/melt interface are tracked using adaptive grid generation. The competition between the thermocapillary convection induced by non-uniform temperature distributions on the free surface and the forced convection by the rotation of the crystal determines the interface shape, dopant distribution, and striation pattern. The temperature gradients on the free surface are influenced by the effects of the thermocapillary force on the free surface and the rotation of the crystal and the crucible.

汶川8级地震前加卸载响应比的大尺度异常

孕震初期加卸载响应比(LURR)通常在1左右涨落,然后逐渐上升至峰值点。但强地震并不在峰值点上发生,而要滞后一段时间(T2)。T2与震级有关,震级越大,T2越长。对于8级地震,T2的计算值为28±8个月,汶川8级地震实际的T2是23个月。对于大地震,T2很长,峰值点后LURR通常迅速下降,在大地震前夕LURR常常降得很低,而预测的地震又迟迟没有发生,这种情况下很容易误导人们怀疑,甚至放弃原来的预测,殊不知,这时大地震正在迫近。这正是汶川8级地震给予人们血的教训。大地震不仅孕育时间长,孕震区面积也很大。大地震的前兆在时空上都是大尺度。基于这种认识,根据LURR的演化,中国大陆西南地区可能正在孕育一个特大地震。

IL-8-induced L-selectin shedding regulates its binding kinetics to PSGL-1

L-selectin plays a crucial role in inflammation cascade by initiating the tethering and rolling of leukocytes on endothelium wall. While many L-selectin molecules are rapidly shed from the cell surface upon activation, the remaining membrane-anchored L-selectin may still play an important role in regulating leukocyte rolling and adhesion with different binding kinetics. Here we developed an in vitro model to activate Jurkat cells via interlukin-8 (IL-8) and quantified the two-dimensional (2D) binding kinetics, using a micropipette aspiration assay, of membrane-anchored L-selectin to P-selectin glycoprotein ligand 1 (PSGL-1) ligand coupled onto human red blood cells (RBCs). The data indicated that L-selectin shedding reduced the amount of membrane-anchored L-selectin and lowered both its reverse and forward rates. These results suggested that the rolling dynamics of activated leukocytes was determined by two opposite impacts: reducing the surface presentation would enhance the rolling but lowering the kinetic rates would decrease the rolling. This finding provides a new insight into understanding how L-selectin shedding regulates leukocyte rolling and adhesion.

IL-8刺激L-选择素水解断裂对细胞膜拓扑结构和刚度的影响

目的 研究IL-8刺激所致的L-选择素水解断裂是否会引起细胞膜结构和刚度的变化,进而影响L广选择素-配体的反应动力学.方法 分别用IL-8、TAPI-0+IL-8和TAPI-0处理本构表达L-选择素的Jurkat细胞,用以构建L-选择素水解断裂、阻断水解断裂和阻断剂对照的细胞-分子模型.采用扫描电镜观察其表面拓扑结构,采用微管吸吮方法测量其刚度.结果 与正常组相比,水解断裂组和阻断水解断裂组细胞微绒毛减少、表面趋于光滑,而阻断剂对照组则无明显变化;无论是水解断裂组,阻断水解断裂组还是阻断剂对照组,细胞膜刚度与正常组相比均无显著性差异.结论 IL-8刺激所致L-选择素水解断裂会引发细胞膜拓扑结构的变化,进而影响L一选择素一配体反应动力学的变化;而细胞膜刚度未见明显变化,表明载体刚度不是水解断裂引发L-选择素-配体反应动力学变化的因索.

Laser action from 1,3,5,7-tetramethyl-2,6-diethyl-8-n-propyl pyrromethene-BF2

We measured spectroscopic and laser action properties of a novel 8-position substituted pyrromethene-BF2, namely 1,3,5,7-tetramethyl-2,6-diethyl-8-n-propyl pyrromethene-BF2 complex. The laser action was performed with the corresponding dye solution in ethanol, which was placed in a Littman-type laser cavity pumped by the second harmonic of a Q-switched Nd:YAG laser. The spectroscopic measurements clearly indicated that the corresponding dye solution in ethanol exhibited intense absorption in the visible spectral region with large fluorescence quantum yield. It possesses rather low triplet-triplet absorption in the spectral region 460-550 nm and almost negligible triplet-triplet absorption in the lasing spectral region. As a consequence, it lases nearly as efficiently as commercially available benchmark laser dyes such as Rhodamine-6G and outperformed them in wavelength tunability in our laser cavity and pump geometry. (C) 2002 Optical Society of America.