Surface electromigration of Au-Ag binary film on SiO2

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Synthesis of Au-Ag alloy nanoparticles with Au/Ag compositional control in SiO2 film matrix

Au-Ag alloy nanoparticles with tunable atomic ratios have been generated in SiO2 film matrix using a new two layer (TL) approach. Two successive overlapping coating layers of similar thickness were deposited on silica glass substrates using Au- and Ag-incorporated inorganic-organic hybrid silica sols, respectively. The Au and Ag concentrations in the individual layers were varied to obtain the desired Au-Ag alloys of different compositions. Four sets of such TL coating assemblies were prepared from the following pair of sols: (i) 4 equivalent mol.% Au-96% SiO2 and 2 equivalent mol.% Ag-98% SiO2, (ii) 3 equivalent mol.% Au-97% SiO2 and 2 equivalent mol.% Ag-98% SiO2, (iii) 3 equivalent mol.% Au-97% SiO2 and 3 equivalent mol.% Ag-97% SiO2, and (iv) 2 equivalent mol.% Au-98% SiO2 and 3 equivalent mol.% Ag-97% SiO2 and subjected to UV (2.75 J/cm2) and heat-treatments (450-550 degrees C) in air and H2-N2 atmospheres for the generation of Au-Ag alloy nanoparticles of approximate compositions Au.66Ag0.33, Au0.6Ag0.4, Au0.5Ag0.5, and Au0.4Ag0.6, respectively. After UV-treatment, individual Au and Ag nanoparticles were formed in the respective layers. The heat-treatment (450-550 degrees C) induces interlayer diffusion of Au and Ag to each other with the generation of Au-Ag alloy nanoparticles, and as a result, Au-Ag alloy surface plasmon resonance (SPR) absorptions were observed in between the Ag- and Au-SPR absorption positions in the visible spectra. The expected alloy compositions are formed through several intermediate alloy nanoparticles, which can also be arrested by controlling the annealing parameters. The alloy formations were monitored by UV-VIS, FTIR, XRD, EDAX, and TEM studies.     

Characterization of implantation induced defects in Si-implanted SiO2 film

Si-implanted thermal SiO2 layers and their annealing behaviour were investigated. In the results of variable-energy positron annihilation spectroscopy, the defects caused by ion implantation are manifested as a particularly low S parameter in the Si ion implantation region of the SiO2 layer. Compared with Fourier transform infrared measurements, it suggests that the decrease of the line shape S parameter after implantation is related to the compaction of implanted layers induced by the breaking of the SiO2 network structure. The presence of blue band emission (430-470 nm) in the implanted SiO2 layer is associated with neutral oxygen vacancy. An increase of the S parameter in the implanted layers is observed after annealing at different temperatures, but it is impossible completely recover the pre-implantation condition after a thermal treatment.     

Electric field induced enhancement in the interfacial charge transfer kinetics of a solid polymer electrolyte

A novel electrostatic method for preparing modified solid polymer electrolytes (SPEs) is reported. Application of an electric field on an evaporating mixture of KYNAR, ethylene carbonate (EC), propylene carbonate (PC) and LiPF₆ dissolved in tetra hydro furan (THF) resulted in a solid polymer electrolyte whose charge transfer resistance was at least an order of magnitude lower than that formed without the application of an electric field. We believe that the observed enhancement is probably due to an electric field induced orientation of dipoles in the polymer chain.     

Microstructure analysis of ion beam-induced surface nanostructuring of thin Au film deposited on SiO2 glass

Effects of the irradiation dose on surface nanostructuring accompanied with the dewetting process of Au films deposited on SiO₂ glass were examined using an atomic force microscope and a scanning electron microscope. In addition, the microstructural evolution and the chemical concentration of Au films were investigated using a transmission electron microscope equipped with an energy-dispersive spectrometer. As increasing the Ar ion irradiation dose, the lattice expansion of Au nanoscale islands sustained on the SiO₂ glass was observed and irradiation-induced lattice defects together with irradiation-induced interface ion mixing were accounted for this lattice expansion. Finally a layer of photosensitive Au nanoballs with highly spherical shape embedded in a SiO₂ substrate was obtained after Ar ion irradiation to 10.0 × 10¹⁶/cm² and some of Au nanoballs were found to be single crystals. As the irradiation energy of the Ar ions increased from 100 to 150 keV, the average diameter of the Au nanoballs in the substrate increased and the red shift of the SPR peak was observed. This tendency of the experimental SPR peaks corresponded with that of the theoretically calculated SPR peaks using Mie solution.     

PVA对SiO2减反膜表面结构的影响

以正硅酸乙酯(TEOS)为有机硅源,乙醇为溶剂,NH3.H2O为催化剂,采用溶胶-凝胶技术,加入PVA(聚乙烯醇)添加剂,在玻璃上用旋涂法制备减反膜,并对其进行热处理;分别采用椭偏仪和扫描电镜对所制备减反膜的结构、物性进行研究,研究PVA添加剂对减反膜结构、折射率的影响。结果表明:适量的PVA添加剂可以控制SiO2太阳电池减反膜的开裂。     

The effect of SiO2 on TiO2 up-conversion photoluminescence film

In order to increase the photoelectric conversion efficiency of silicon solar cell, the up-conversion film has been tried to enhance the response of the solar cells to the infrared band. Yb³⁺, Er³⁺ co-doped SiO₂/TiO₂ composite films with different Ti/Si molar ratio were deposited on the glass substrate with sol–gel method and spin-coating technique. The effect of different molar ratio of Ti/Si on the film’s morphology and optical properties was investigated. The morphology, the absorption spectra and photoluminescence (PL) spectra of the film were tested and analyzed. After the film was annealed at 900 °C, the XRD diffraction pattern indicated that rare earths ions have evenly dispersed into the matrix lattice. The FT-IR showed that Si ions entered into the lattice of titanium dioxide, and the Ti–O–Si bonds came into being. When the film pumped with a laser of 980 nm, there were a dominant red emission and several weak green peaks. In addition, with the increase of the mole ratio of Si/Ti, the intensity of the film’s up-conversion luminescence increases at first and then decreases. When the molar ratio of Si/Ti is 1/8, the sample had the highest intensity of up-conversion luminescence.     

SiO2气凝胶柔性保温隔热薄膜

由SiO2气凝胶、聚酰亚胺和镀铝层(SiO2／PI／Al)组成的柔性多层薄膜具有很好的保温隔热特性和广泛的应用前景。采用溶胶-凝胶方法制备的SiO2气凝胶具有很高的气孔率和很低的体积密度，尝试了在溶胶-凝胶过程申先酸性后碱性的二步法催化．使孔洞率提高到97％，体积密度降低为50kg／m^3，成为优秀的保温隔热的主体材料。选择柔性耐温隔热的聚酰亚胺作为骨架材料，并用真空蒸发镀制上金属铝膜与多孔SiO2气凝胶复合成保温隔热薄膜。当薄膜叠加到10层时其保温隔热效果可提高5倍。     

SiO2薄膜制备的现行方法综述

在导电基体上制作薄膜传感器的过程中,需要在基体与薄膜电极之间沉积一层绝缘膜.二氧化硅薄膜具有良好的绝缘性能,并且稳定性好,膜层牢同,长期使用温度可达1000℃以上,应用十分广泛.通常制备SiO2薄膜的现行方法主要有磁控溅射、离子束溅射、化学气相沉积、热氧化法、凝胶-溶胶法等.本文系统阐述了各种方法的基本原理、特点及适用场合,并对这些方法做了比较.     

化学溶液电沉积法制备Li2SiO3薄膜研究

利用化学溶液电沉积方法，在阴极和阳极衬底材料上都成功制备出了单相的含氧酸盐硅酸锂（Li2SiO3）薄膜。探讨了该工艺下的实验反应机理。通过X射线衍射技术（XRD）、扫描电子显微镜（SEM）分别表征研究了不同实验条件下薄膜的晶体结构和表面形貌。研究结果表明，采用化学溶液电沉积法制备的Li2SiO3薄膜具有物相结构单一，表面形貌平整致密的特点。与制备Li2SiO3的传统方法相比，这一技术具有廉价、简单、低温等特点。     

SiO_2表面包覆改性钛酸钡/聚酰亚胺复合薄膜的制备与性能

以聚酰亚胺(PI)为基体,将聚酰亚胺与钛酸钡(BaTiO3)纳米粒子进行复合,采用原位聚合法制备BaTiO3/PI复合薄膜。为提高BaTiO3纳米粒子的分散性和表面性能,采用SiO2对BaTiO3纳米粒子进行表面包覆改性,并制备改性BaTiO3/PI复合薄膜。采用红外光谱、X射线衍射、扫描电镜等对制备得到的改性BaTiO3进行了表征,测试了复合薄膜的介电性能。结果发现,SiO2与BaTiO3粒子间仅是物理包覆,没有新物质形成。测试频率为103 Hz时,质量分数为5%的SiO2包覆改性使复合薄膜的介电常数增大到21.8,介电损耗为0.00521,击穿强度为76 MV/m,储能密度为0.56J/cm3。研究表明,采用SiO2对BaTiO3改性使得复合薄膜的介电性能有所提高。     

Effects of annealing in O2 and N2 on the microstructure of metal organic chemical vapor deposition Ta2O5 film and the interfacial SiO2 layer

Ta₂O₅ films were made by metal organic chemical vapor deposition (MOCVD) and annealed at various temperatures under N₂ and O₂ ambients in a conventional furnace and a rapid thermal reactor (RTR). The microstructure and composition of the Ta₂O₅ film and the interfacial SiO₂ layer before and after various annealing treatments were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). The as-deposited Ta₂O₅ film has an amorphous structure. The surface topology of the as-deposited Ta₂O₅ film is smooth without any apparent features. Annealing of the as-deposited film results in crystallization to an orthorhombic structure with (1 0 0) preferred orientation, and an increase in surface roughness, with the appearance of grain boundaries under AFM. The crystallization temperature varies in the various annealing treatments. An interfacial SiO₂ layer was found between the as-deposited/annealed Ta₂O₅ films and silicon substrate. The annealing treatments result in an increase in thickness of the SiO₂ layer and roughness changes of the Ta₂O₅/SiO₂/Si interfaces, which are discussed in terms of element diffusion and thermodynamic stability.     

Study of ultrafine grains formed on the microsized catalyst surface induced growth of aligned SiO2 nanowires

In this study, beard-like and sea cucumber-like silica structures have been successfully synthesized on the Si substrate by a novel and simple water assisted method. The investigation of SEM and TEM reveals that the as-grown products possess many similar features like that they all have a very big, nearly spherical microsized body and uncountable, high density and highly oriented silica nanowire antennas. It is proved that ultrafine nanosized metal catalysts could be generated on the surface of one microsized catalyst during their growth process due to the indications of surface local softening and different elastic deformation along different crystal plane taking place on the catalyst surface during growth process. Our results could introduce a new way to control the growth of high-density and well-oriented functional nanowire arrays with desired morphologies.     

Electric field singularity on the line of wetting of dielectric surface

The pattern of electric field singularity on the line of wetting of dielectric by conducting liquid is considered. It is known that the modulus of electric field in this case tends to infinity while the distance from the line of wetting tends to zero, i.e., the electric field has a singularity on the line of wetting. In the case of nonzero wetting angle, this singularity is integrable, with the total volume density of electric energy remaining finite. It is demonstrated that, if the surface is wetted by dielectric liquid, a critical wetting angle exists defined by the permittivity ratio of contacting dielectrics. When the wetting angle becomes less than critical, the electric field singularity disappears.     

SiO_2介孔薄膜材料的隔热理论

SiO2介孔薄膜具有优良的绝热性能,在热学、光学、微电子等领域有广阔的应用前景,其介孔结构对降低薄膜的热导率有着十分重要的作用,对介孔薄膜热导率的计算模型及测量方法的研究仍在不断探索中。对SiO2介孔膜的隔热机理进行了概述,从理论方面综述了对热导率研究的一些基本方法,并对薄膜热传导的尺寸效应作了说明。     

溶胶-凝胶SiO2在变色薄膜中的应用

变色薄膜是一种非常有用的光学产品。用溶胶－凝胶SiO2作为变色薄膜中的介质层（Cr/SiO2/Al）能明显提高产品的质量和生产效率。本文介绍了溶胶－凝胶SiO2薄膜的制作方法，提出了用酸性催化控制SiO2溶胶过程；用网线辊涂布的方法形成薄膜，连同烘烧后处理完成SiO2凝胶过程。文章还对SiO2薄膜的光学特性和在制备变色薄膜中相关条件对整个薄膜性能的影响进行了分析。     

Enhanced effect of vacuum-deposited SiO2 overlayer on photo-induced hydrophilicity of TiO2 film

Photo-induced hydrophilicity of SiO₂/TiO₂ multilayer film prepared by using the vacuum deposition method was investigated by means of water contact angle measurement. Using black light irradiation of the films centering at a wavelength of 365 nm, an extreme photo-induced hydrophilicity was achieved when the TiO₂ film was covered by SiO₂ overlayer ranging from 10 to 20 nm in thickness. These multilayer films exhibited much more extreme hydrophilicity than the TiO₂ film without SiO₂ overlayer. The surface analyses revealed that the enhanced photo-induced hydrophilic surface of the multilayer films exhibited an improved photo-catalytic activity towards decomposition of organic substances on their surfaces. It was found that significant growth of the SiOH group occurred in the uppermost surface of the SiO₂ overlayer of the multilayer films through the depth profile measurement of TOF-SIMS. This result suggests that the photo-generated reactive species such as hole created in the TiO₂ film may transmit the SiO₂ layer to reach the surface. The enhanced photo-induced hydrophilicity of the films can be explained by a synergetic effect of the improved photo-catalytic activity of the multilayer film and the stable hydrophilicity of SiO₂ itself.     

化学表面处理对微型化的氮氧化硅驻极体层电荷储存性能的影响

研究了化学表面处理对微型化的氮氧化硅膜电荷稳定性的影响,考察了表面处理对脱阱面电荷横向扩散的抑止作用。借助对微型化前后的样品在高温和高湿环境中的表面电位衰减测量的对比,研究了不同试剂的表面处理对微型化样品的电荷储存及其动态特性的影响。