Alignment-free optical modules using solder-bump-bonding technique for free-space optical interconnections

We propose alignment-free optical modules using a solder-bump-bonding technique for constructing free-space optical interconnection systems without a special alignment procedure. Bonding pads for mounting an optoelectronic device chip are fabricated by exposing a photosensitive resin film to light traveling through the optical system of the module so that the image positions of the bonding pads on both image planes of the optical interconnection system are aligned with each other. A device chip is mounted by solder-bump bonding and is set at a proper position by the surface tension of molten solder. The effectiveness of the technique is verified by constructing alignment-free optical modules.     

Novel pad structures for the improvement of wire bonding strength in DXD panel

New pad structures are suggested to improve the wire bonding strength in the TFT panels suitable for the flat panel X-ray detector application. Several candidates of bonding pad structure are tested and one of them is chosen which shows the strongest and the most stable bonding with aluminum wire. Some morphological consideration was adopted to the surface of AlNd (Nd 2 at.%) pads whose thickness are 4000 Å. To avoid the defect of signal lines such as hillocks due to increased thickness of AlNd, we selectively increased the thickness of AlNd on the bonding area only.     

Removal of scratch on the surface of MgO single crystal substrate in chemical mechanical polishing process

Etching and chemical mechanical polishing (CMP) experiments of the MgO single crystal substrate with an artificial scratch on its surface are respectively performed with the developed polishing slurry mainly containing 2 vol.% phosphoric acid (H₃PO₄) and 10-20 nm colloidal silica particles, through observing the variations of the scratch topography on the substrate surface in experiments process, the mechanism and effect of removing scratch during etching and polishing are studied, some evaluating indexes for effect of removing scratch are presented. Finally, chemical mechanical polishing experiments of the MgO substrates after lapped are conducted by using different kinds of polishing pads, and influences of the polishing pad hardness on removal of the scratches on the MgO substrate surface are discussed.     

Numerical simulation of water vapor nucleation on electrically neutral nanoparticles

Atomic-level Monte Carlo simulations are performed to calculate the free energy, entropy, and work of nucleation for clusters of more than 6 × 10³ water molecules growing on silver iodide crystalline particles of size up to 4 nm at a temperature of 260 K. The Hamiltonian of the system includes explicit expressions for hydrogen bonding energy and Coulomb, dispersion, exchange, and polarization interactions. The work of nucleation exhibits complex behavior depending on the nucleation-site size. With increasing nanoparticle size, clusters become less stable and the probability of crystallization increases. Mutual polarization enhances the bonding between a cluster and a crystalline particle. Cluster growth on relatively large nanoparticles involves two stages characterized by two critical sizes: monolayer growth on the surface and growth normal to the surface. Spontaneous microdroplet polarization involving domain formation is found to occur at the crystal surface. The dependence of the ice-forming activity of an aerosol on particulate size observed in experiments is explained by combined effects of several competing factors, the dominant ones being the stabilizing and destabilizing effects of the nanoparticle electric field.     

The fluid phenomena in the crystallization of the protein crystal

This paper reports that an optical diagnostic system consisting of Mach-Zehnder interferometer with a phase shift device and image processor has been used for study of the kinetics of protein crystal growing process. The crystallization process of protein crystal by vapour diffusion is investigated. The interference fringes are observed in real time. The present experiment demonstrates that the diffusion and the sedimentation influence the crystallization of protein crystal which grows in solution, and the concentration capillary convection associated with surface tension occurs at the vicinity of free surface of the protein mother liquor, and directly affects on the outcome of protein crystallization. So far the detailed analysis and the important role of the fluid phenomena in protein crystallization have been discussed a little in both space- and ground-based crystal growth experiments. It is also found that these fluid phenomena affect the outcome of protein crystallization, regular growth, and crystal quality. This may explain the fact that many results of space-based investigation do not show overall improvement.     

微粒和析晶混合污垢模型

假设微粒和析晶污垢独立存在,而结晶过程同时发生在换热面和微粒表面,据此建立了一个微粒和析晶混合污垢热阻值的分析模型。并通过MgO微粒污垢和CaCO3析晶污垢实验验证了模型的正确性。     

The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties

The PA66-based nanocomposites containing surface-modified nano-SiO₂ were prepared by melt compounding. The interface structure formed in composite system was investigated by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The influence of interface structure on material's mechanical and thermal properties was also studied. The results indicated that the PA66 chains were attached to the surface of modified-silica nanoparticles by chemical bonding and physical absorption mode, accompanying the formation of the composites network structure. With the addition of modified silica, the strength and stiffness of composites were all reinforced: the observed increase depended on the formation of the interface structure based on hydrogen bonding and covalent bonding. Furthermore, the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that the presence of modified silica could affect the crystallization behavior of the PA66 matrix and lead to glass transition temperature of composites a shift to higher temperature.     

Deposition of ITO Nanopowder Layers on Flexible Substrate by Spin Coating Using Pulsed Nd-YAG Laser for Crystallization and Bonding

A transparent thin layer of indium–tin oxide (ITO) is coated on polyethylene terephthalate (PET) by a spin coating process. The surface is treated by a pulsed Nd-YAG laser. We investigate the effect of laser treatment on crystallization and bonding processes of the thin layer using atomic force microscope (AFM) and scanning electron microscope (SEM). The best results are obtained when the pulse frequency, duration, and energy were 1000 Hz, 0.2 to 20 ms, and 25 to 40 J, respectively. The results show that the ITO layer coated on a flexible PET substrate is conductive and transparent. The sheet resistance obtained is 0.6 kΩ, and the transparency of a 350-nm layer in the visible range is more than 83.6%. Using the Nd-YAG laser treatment, we increase the conductivity by a factor of 100 times, and higher bonding performances are achieved.     

Al2O3陶瓷涂层尖端受载下的声发射信号参量分析

为了考察再制造零件涂层结合强度检测仪评价涂层结合强度的可行性,以Al₂O₃陶瓷涂层为研究对象,在涂层表面进行压入试验,提取并分析了试验过程中声发射信号中的幅度、计数、能量与有效值电压(RMS)特性参数的时间分布曲线,读取了声发射信号突变点的波形,观测了压痕处涂层截面微观形貌。结果表明,声发射信号出现明显突变时,涂层界面确实产生了开裂失效。采用此检测设备可以有效诱导、界定涂层界面的断裂失效,声发射信号可以作为涂层开裂的临界判据,其中幅度的时间分布更能体现出Al₂O₃陶瓷涂层在压入过程中的裂纹萌生至涂层断裂的扩展过程;能量值对涂层的失效更为敏感,最为适合评价涂层的结合强度。      

氢稀释对纳米晶硅薄膜晶化特性的影响及薄膜生长机理

以SiH4与H2作为前驱气体,采用射频等离子增强化学气相沉积技术制备了纳米晶硅薄膜.利用Raman散射和红外吸收光谱等技术,对不同氢稀释比条件下薄膜的微观结构和键合特性进行了研究.结果表明,随着氢稀释比增加,薄膜的晶化率明显提高,而氢稀释比过高时,薄膜晶化率呈现减少趋势.红外吸收光谱分析表明,纳米晶硅薄膜中氢的键合模式与薄膜的晶化特性密切相关.随着氢稀释比增加,薄膜中整体氢含量和SiH2键合密度明显减少,而在高氢稀释比条件下,氢稀释比增加导致薄膜中SiH2键合密度和整体氢含量增加.     

氢稀释对纳米晶硅薄膜晶化特性的影响及薄膜生长机理

以SiH₄与H₂作为前驱气体,采用射频等离子增强化学气相沉积技术制备了纳米晶硅薄膜.利用Raman散射和红外吸收光谱等技术,对不同氢稀释比条件下薄膜的微观结构和键合特性进行了研究.结果表明,随着氢稀释比增加,薄膜的晶化率明显提高,而氢稀释比过高时,薄膜晶化率呈现减少趋势.红外吸收光谱分析表明,纳米晶硅薄膜中氢的键合模式与薄膜的晶化特性密切相关.随着氢稀释比增加,薄膜中整体氢含量和SiH₂键合密度明显减少,而在高氢稀释比条件下,氢稀释比增加导致薄膜中SiH₂键合密度和整体氢含量增加.     

Cu（001）表面CO吸附的电子结构效应

本文应用Ｒｅｃｕｒｓｉｏｎ方法，计算了ＣＯ在Ｃｕ（００１）表面不同位置（顶位、桥位和空位）吸附的电子结构，分析了ＣＯ与Ｃｕ表面原子之间的键作用。分析表明ＣＯ在顶位吸附时，Ｃｐｘ（ｐｙ）－Ｃｕｄｓ（１号）和Ｃｐｘ（ｐｙ）－Ｃｕｄ２（ｄｓ）（２号）之间存在较强的键作用，这有利于ＣＯ在顶位吸附。桥位和空位吸附时，ＣＯ与表面原子形成的键较弱，是不稳定的。计算结果得到了实验的支持。     

Effect of the stabilizing coating and the presence of free polymer on the rate of crystallization of colloidal systems

Visual observations and preliminary light scattering experiments on the crystallization process in various colloidal systems are reported. In the first place we studied the influence of the stabilizing coating of the colloidal particles on the rate of crystallization. The various coatings give rise to different ranges of the repulsive interaction. This is found to have a pronounced effect on the rate of crystallization. Furthermore we investigated the effect of free polymer added to the dispersion. It appears that addition of free polymer has a dramatic effect on the crystallization phenomena.     

微间隙受限液体行为与昆虫爪垫在光滑壁面的粘着机理

自然界中许多昆虫通过分泌一层油性液体薄膜实现其爪垫表皮和光滑壁面之间粘附和解粘附,从而实现在光滑壁布的快速爬行.为了提示昆虫爪垫与光滑壁面间微量液体薄膜对生物粘着的意义,基于自行研制的粘着接触实验仪,采用微量的[emim[Tf2N]离子液体和聚α烯烃油,观测其受限在纳米级光滑钢球表面与玻璃表面之间的接触行为以及法向粘着力.实验发现,临界体积(10^-12—10^-9L)范围内的受限液滴达到临界厚度（小于2μm）后会出现自动铺展和瞬时收缩行为，并同时提供幅值稳定且数值 关键词： 受限液体 粘着力 昆虫爪垫 类固化     

The Mechanisms of Oxygen Accelerated Low-Temperature Bonding by Ag Nanoparticles

Low-temperature bonding (≤300 ^o C) using Ag nanoparticles (Ag NPs) is considered to be the new generation of bonding technology in power electronics. The oxygen-accelerated sintering has been observed by many researchers which is attributed to the decomposition of organics covered on Ag NPs. In this work, organic-free Ag NPs are fabricated to eliminate the influence of organics, and it is found that the accelerated bonding process by oxygen is strongly correlated to the self-confined amorphous Ag-O compound shell on the surface of Ag NPs. In experiments, the sintering process is apparently accelerated by the elevating oxygen content, and the amorphous shell is observed after sintering, which do not grow thicker even in pure oxygen ambient for a long time while performing active chemical evolutions. In simulations, the results match well with the experiments and indicate that the amorphous shell performed the dynamic oxidation and decomposition process. This dynamic equilibrium is caused by the instability of silver oxides, which would enable the amorphous shell to activate the mobility of the surface mass flow and promote the surface diffusion. The shear strength of SiC chip increased by 354% when bonding in pure oxygen, targeting a broad variety of applications in electronic packaging.     

Effect of TiO2 nanoparticle size on the performance of PVDF membrane

The comparison of the performance and morphology was carried out between neat PVDF membrane and PVDF composite membranes with nanosized TiO₂ particles of different size. The results of permeability and instrumental analysis illustrated that nanometer size obviously affected the performance and structure of the PVDF membranes. The smaller nanoparticles could improve the antifouling property of the PVDF membrane more remarkably. The surface and cross-section of the membranes were observed with an atomic force microscopy (AFM), a scanning electron microscope (SEM). The TiO₂/PVDF membrane with smaller nanoparticles had smaller mean pore size on its surface and more apertures inside the membrane. X-ray diffraction (XRD) experiments also suggested that smaller TiO₂ nanoparticles had stronger effect on the crystallization of PVDF molecules.     

Hydrogen-induced surface metallization of beta-SiC(100)-(3x2) revisited by density functional theory calculations

Recent experiments on the silicon terminated (3 x 2)-SiC(100) surface indicated an unexpected metallic character upon hydrogen adsorption. This effect was attributed to the bonding of hydrogen to a row of Si atoms and to the stabilization of a neighboring dangling bond row. Here, on the basis of density-functional calculations, we show that multiple-layer adsorption of H at the reconstructed surface is compatible with a different geometry: in addition to saturating the topmost Si dangling bonds, H atoms are adsorbed at rather unusual sites, i.e., stable bridge positions above third-layer Si dimers. The results thus suggest an alternative interpretation for the electronic structure of the metallic surface.     

Crystallization of poly(ethylene-co-octene): II Melt memory effects on first order kinetics

Dilatometric and X-ray scattering experiments of the crystallization kinetics of a sample of poly(ethylene-co-octene) show pronounced melt memory effects, i.e., the shapes of isotherms and characteristic times vary systematically with the temperature of the melt prior to cooling to the crystallization temperature. The temperature range of the effect is limited; crystallization kinetics remains constant below a melt temperature Tm l and above a melt temperature Tmh and varies only in-between. Analysis shows that the melt memory effect is caused by a variation of the characteristic time of a first order crystallization process. The process can be assigned to the in-filling of crystallites into objects of a previously generated precursor structure.     

氢化非晶硅叠层薄膜对单晶硅表面钝化研究

采用等离子体增强化学气相沉积法生长的单层本征氢化非晶硅薄膜对单晶硅片进行钝化,结果表明增加氢稀释比有利于减少薄膜中的缺陷,增强钝化效果,过量的氢稀释比会导致非晶硅在硅片表面的外延晶化生长,降低钝化效果。退火导致非晶硅晶化程度增加,降低了钝化效果,同时退火提升了薄膜的质量,改变了H键合方式,增强了钝化效果。因此,单层氢化非晶硅只有在合适的氢稀释比和退火温度才可以获得最佳钝化效果。为了提高非晶硅薄膜对硅片的钝化效果,采用具有高低氢稀释比的叠层本征非晶硅薄膜对硅片进行钝化。因此将高氢稀释比沉积的非晶硅薄膜叠层生长于低氢稀释比的薄膜之上,避免非晶硅在硅片表面的外延生长。在退火过程中,高氢稀释比薄膜中的氢扩散到低氢稀释比薄膜中,有效地钝化了非晶硅中和单晶硅表面的悬挂键,改善了非晶硅/硅片的界面质量,叠层钝化后硅片的少子寿命为7.36 ms,隐含开路电压为732 mV。     

Crystallization over the liquid layer

In this article, a new phenomenon of high-speed crystallization of metals in a low-temperature plasma formed as a result of the effect of a short laser pulse is considered. The mechanism of the way the reaction occurs on the surface of the melt formed under the effect of the laser pulse on an amorphous substrate is described. The main factors affecting the crystallization process are described. Primary attention is paid to laminar convection and the latent heat of crystallization.