Ice crystallization induced by optical breakdown

Ice crystallization in supercooled water has been initiated by focused Nd:YAG laser pulses at 1064 nm wavelength. The pulses of 8 ns duration and up to 2 mJ energy produce a bubble in the supercooled liquid after optical breakdown and plasma formation. The subsequent collapse and disintegration of the bubble into fragments was observed to be followed by ice crystal nucleation in many, but not all cases. Details of the crystallization events have been investigated by high-speed imaging, and nucleation statistics and crystal growth rates are given. It is argued that homogeneous nucleation in the compressed liquid phase is a plausible explanation of the effect.     

Atomic scale conductance induced by single impurity charging

A scanning tunneling microscope was used to probe electron transport through an alkali doped C(60) monolayer crystal on Al(2)O(3) grown by the oxidation of NiAl(110). Each individual alkali atom forms a localized complex with the neighboring C(60) molecules. Charging of the complex induces a substantial rise in the current that persists outside the physical dimensions of the complex. This induction of the current rise is characterized by spatially resolved spectroscopy and mapping of the differential conductance (dI/dV) in the vicinity of the complex.     

Polycrystalline silicon thin films prepared by Ni silicide induced crystallization and the dopant effects on the crystallization

Intrinsic and doped polycrystalline silicon thin films were grown by the Ni silicide seeds induced crystallization. The Ni first reacted to Si forming a silicide seeds, then these seeds act as nuclei, from which the grains start to grow laterally. Compared with traditional Ni induced lateral crystallization, polycrystalline silicon thin film was grown by Ni silicide induced crystallization with low Ni contamination and large grain sizes. It can be found that the Ni silicide induced crystallization rate is accelerated by p-type doping and is decelerated by n-type doping. And the slightly and strongly phosphorous-doped polycrystalline silicon can be obtained with different grain shapes. Also, the sheet resistance of doped polycrystalline silicon decreases with the increasing of the doping atoms. A reasonable explanation is presented for the dopant effects on the growth rate, microstructure and electronic properties of the samples.     

Solution-based metal induced crystallization of a-Si

This paper investigates a simplified metal induced crystallization (MIC) of a-Si, named solution-based MIC (S-MIC). The nickel inducing source was formed on a-Si from salt solution dissolved in de-ionized water or ethanol. a-Si thin film was deposited with low pressure chemical vapour deposition or plasma enhanced chemical vapour deposition as precursor material for MIC. It finds that the content of nickel source formed on a-Si can be controlled by solution concentration and dipping time. The dependence of crystallization rate of a-Si on annealing time illustrated that the linear density of nickel source was another critical factor that affects the crystallization of a-Si, besides the diffusion of nickel disilicide. The highest electron Hall mobility of thus prepared S-MIC poly-Si is 45.6cm²/(V.s). By using this S-MIC poly-Si, thin film transistors and display scan drivers were made, and their characteristics are presented.     

几种铁基非晶合金激波诱导晶化中的若干奇异物理效应研究

应用x射线衍射、透射电子显微镜和差示扫描量热实验技术，研究了FeCuNbBSi，FeBSi，FeMoBSi几种铁基非晶合金的激波诱导晶化.研究结果表明：非晶态合金激波诱导晶化中存在若干应用传统长程扩散相变理论难以解释的奇异物理效应.用非晶态合金激波流化晶化可以很好地解释激波诱导非晶晶化中的各种奇异物理效应. 关键词： 激波晶化 非晶态合金 激波流化 流体扩散     

Partial crystallization in amorphous magnetic film induced by Ru layer interface

Partial crystallization in amorphous magnetic film is observed in this study. The film of Co₄₆Fe₄₆Zr₅B₃/Ru/Co₄₆Fe₄₆Zr₅B₃ (CFZB/Ru/CFZB) was prepared on glass substrate by DC magnetron sputtering. The CFZB underlayer (CFZB‐UL) and the CFZB overlayer (CFZB‐OL) were deposited under nominally same sputtering conditions, i.e. target, working gas, working pressure, input power, and deposition duration. The transmission electron microscopy (TEM) images with fast Fourier transform (FFT) patterns revealed that the CFZB‐UL was amorphous while the CFZB‐OL became unexpectedly partially crystallized. The result of X‐ray diffraction (XRD) spectra verified the TEM observation. The cause of the partial crystallization is attributed to the lower concentration of glass formers and the lattice matching between the overlayer and the Ru layer below.     

航天器内部充电效应及典型事例分析

航天器内部充电效应是由空间高能电子诱发的,通常发生在航天器内部以及表面绝缘材料深层,所产生的放电击穿及静电放电脉冲干扰较表面充电更为严重. 对内部充放电的一般规律进行了总结,并就一次典型的航天器异常事件,从异常的时空表现特征及其与高能电子环境扰动的相关性角度进行了深入分析和定量计算,得出了高能电子产生的内部充电引起的卫星异常的结论,为卫星异常诊断提供了范例.     

航天器内部充电效应及典型事例分析

航天器内部充电效应是由空间高能电子诱发的,通常发生在航天器内部以及表面绝缘材料深层,所产生的放电击穿及静电放电脉冲干扰较表面充电更为严重. 对内部充放电的一般规律进行了总结,并就一次典型的航天器异常事件,从异常的时空表现特征及其与高能电子环境扰动的相关性角度进行了深入分析和定量计算,得出了高能电子产生的内部充电引起的卫星异常的结论,为卫星异常诊断提供了范例. 关键词： 高能电子 内部充电 静电放电 空间环境     

Development of polycrystalline silicon films on flexible metallic substrates by aluminium induced crystallization

Thin film silicon solar cells on low cost foreign substrates could be attractive for highly efficient and low cost production of photovoltaic electricity. An attempt has been made to synthesise high-quality continuous polycrystalline silicon (pc-Si) layers on flexible metallic substrates using aluminium induced crystallization (AIC) for the first time. Amorphous silicon films deposited by ECR-PECVD were crystallized on diffusion barrier coated metallic substrates at lower temperatures (<577°C). The crystallization was studied using Raman as well as UV reflectance spectroscopy. The as-grown AIC pc-Si films were found to be continuous and densely packed without amorphous phase. The migration of impurities from the substrate to the pc-Si films and the conformability of the barrier layer with the substrate and pc-Si films were studied systematically in terms of chemical and stress level analysis, which are the important aspects to be considered when metallic foils are used as substrates. It was observed that the barrier layer also serves as a buffer layer to minimise the stress level enormously in the AIC grown pc-Si layer, though the supporting material has a thermal expansion coefficient of higher order at higher annealing temperatures. The present investigation proves the possibility to grow better-quality polycrystalline silicon films on flexible metallic foils and further demonstrates the steps that need to be considered to improve the quality of AIC pc-Si films as well as the strength of the barrier layer.     

溶液法铝诱导晶化制备多晶硅薄膜

采用铝（Al）盐溶液作为诱导源进行了非晶硅晶化成多晶硅的研究.光学显微镜观测与Raman光谱分析表明,合适配比的铝盐溶液能够将非晶硅予以诱导晶化.采用剥层XPS测试分析,探究了Al盐溶液与硅表面可能的化学反应以及随之发生的硅-铝层交换的过程.最后对溶液法诱导晶化的机理进行了讨论. 关键词： 铝诱导晶化 多晶硅薄膜 溶液法     

Effects of corotron size and parameters on the dielectric substrate surface charge

Effects of variation of parameters of a corona device (corotron) used in electro-photographic machines on the amount of surface charge build-up on the surface of dielectric substrate were studied. Particular attention was given to the effect of corotron dimension including wire–shields and wire–plate distances, substrate thickness, shields insulation and the substrate speed on the amount of substrate surface charge. The computational analyses were performed for a two-dimensional cross-section of the corotron under steady-state condition. The Maxwell equations were solved and the electrical quantities in a rectangular positive single wire corotron were evaluated. The simulation results showed that for a fixed wire voltage, the corotron size, the substrate thickness, insulation of shields and the substrate speed will affect the distributions of electrical quantities in the corotron. The wire–substrate distance and the substrate speed, however, were found to be the main parameters that control the amount of surface charge build-up on the substrate.     

Skeletonization by crystallization

A skeleton of a planar contour is a set of centres of bitangent circles lying inside the contour. If contour of a planar shape was made up of a spatial distribution of sodium acetate crystals the propagating crystallization patterns would implement distance transformation, or thinning, of the contour. In such a case, boundaries between colliding patterns represent skeleton of the planar shape. In laboratory experiments we demonstrate that a supersaturated solution of a sodium acetate is a massively parallel processor. In this sodium-acetate processor data are inputted as spatial distribution of nucleation sites, information is transmitted via propagating patterns of crystallization and results of computation are represented by boundaries between stationary domains of crystals.     

TEM studies on the formation of nano crystallites of Si by metal induced crystallization

In the present investigations, we have grown the nano-crystallites of Si by metal induced crystallization process. Layers of two different metals (Al and Au) were deposited on either side of Si using thermal evaporation technique to study metal induced crystallization. Annealing of such samples was carried out in the hot stage of TEM. We have found that the crystallization of amorphous silicon starts at 150 °C through the formation of metal silicides. Formation of metal silicides was observed through selected area diffraction. Nearly complete formation of nano crystallites of Si throughout the sample was observed at 200 °C. High-resolution TEM studies confirm the formation of nano-crystallites of Si all along the film.     

Nickel induced lateral crystallization behavior of amorphous silicon films

Nickel induced lateral crystallization of amorphous silicon with and without electric field has been studied. Dendritic silicon growth behavior is observed, with crystallites of a few hundred nanometers in width and up to a few microns in length. The behavior can be understood from the preferential epitaxial growth of silicon from the (1 1 1) facets of the NiSi₂ precipitate, which forms during the early stage of the annealing process. The dendritic growth fronts are different with and without electric field in the nickel induced lateral crystallization process. Electric field is found to be beneficial in increasing the lateral crystallization rate and improving the film crystallinity. Joule heating plays an important role as well to enhance the lateral crystallization.     

化学源金属诱导多晶硅研究

以硝酸镍溶液为化学源，对于用不同方法沉积得到的非晶硅膜作晶化前驱物，都能予以不同程度的晶化.用VHF-PECVD方法获得的非晶硅膜作前驱物，易于去氢并更容易晶化.当化学源浓度不同时，晶化效果会存在一定差别，在一定的范围内，溶液浓度越高，晶化后形成的晶粒越大.退火气氛对晶化结果产生某些影响，可以发现，在N₂气氛下退火，比在大气下有更好的晶化效果.最后对物理源与化学源作诱导金属的晶化结果进行了比较，结果表明，对诱导金属源而言，化学源显示出更为有效的晶化趋势. 关键词： 金属诱导晶化 多晶硅薄膜 低温制备 退火处理     

Strain rate induced crystallization in bulk metallic glass-forming liquid

We report on the solidification of Au49, Ag5.5, Pd2.3, Cu26.9, Si16.3 bulk metallic glass under various strain rates. Using a copper mold casting technique with a low strain rate during solidification, this alloy is capable of forming glassy rods of at least 5 mm in diameter. Surprisingly, when the liquid alloy is splat cooled at much higher cooling rates and large strain rates, the solidified alloy is no longer fully amorphous. Our finding suggests that the large strain rate during splat cooling induces crystallization. The pronounced difference in crystallization behavior cannot be explained by the previously observed strain rate effect on viscosity alone. A strain rate induced phase separation process is suggested as one of the explanations for this crystallization behavior. The strain-rate-dependent critical cooling rate must be considered in order to assess the intrinsic glass forming ability of metallic liquid.     

变温退火制备铝诱导大晶粒多晶硅薄膜的机理研究

为了缩短铝诱导法制备大晶粒多晶硅薄膜的退火时间,用射频磁控溅射法在玻璃衬底上沉积了a-Si/SiO2/Al叠层膜,并用两种方法进行变温退火.分析了变温退火工艺对铝诱导晶化过程的影响,着重讨论了退火过程中温度由低温升到高温时不形成小晶粒的机理和条件.研究表明,当退火温度升高时,是否形成小晶粒取决于晶粒半径、耗尽层厚度和相邻晶粒间距三者之间的关系.     

Chiral symmetry breaking during crystallization: complete chiral purity induced by nonlinear autocatalysis and recycling

We report experimental results that show a large and symmetric population of D and L crystals moving into complete chiral purity, with one of the enantiomers completely disappearing. The results indicate (i) a new symmetry breaking process incompatible with the hypothesis of an initial single chiral phase or "mother crystal," (ii) that total symmetry breaking and complete chiral purity can be achieved from a system that initially includes both enantiomers, and (iii) that this is achieved through a nonlinear autocatalytic-recycling process.     

Laser- and gamma-ray induced crystallization of IR-transmitting calcium gallate glass

Ar⁺-laser (=488 nm) irradiation of calcium gallate (CG) glass with the composition of 60CaO·39Ga₂O₃·Fe₂O₃ resulted in a distinct decrease in the IR transmittance (T) due to the formation of crystalline CaGa₂O₄ and CaGa₄O₉ phases. The Mössbauer spectrum of non-irradiated glass comprised a broad doublet due to distorted Fe³⁺(T_d) with, , and of 0.20, 1.33, and 1.00 mm s^–1, respectively. An additional doublet due to Fe³⁺(T_d) was observed in the Ar⁺-irradiated glass and, , and were 0.17, 1.32, and 0.75 mm s^–1, respectively. A decrease inT was also observed after the⁶⁰Co -ray irradiation with doses 10⁵Gy, and the precipitation of CaO, Ga₂O₃, and CaGa₄O₇ phases was confirmed by X-ray diffraction.