Ag−Sn Alloys and dental amalgams: A119Sn Mössbauer,x-ray diffraction and scanning electron microscopy study

Examination has been made on aged and fresh Ag?Sn alloys and on commercial Cu?Ag?Sn dental alloys. Although x-ray diffractograms of aged Ag?Sn showed only λ Ag?Sn and free silver,¹¹⁹Sn Mössbauer spectra exhibited Sn(IV) oxide also. A low Debye temperature showed the oxide to be in intimate dynamical contact with the metallic matrix. Upon adding mercury, the phases λ₁ Ag?Hg and η′ Cu?Sn were observed in a commercial specimen. Conversion-electron spectra of a mercury-coated disk showed the presence of λ₂ Sn?Hg and a distribution of line positions smaller than that for particulate amalgams. Internal oxidation was found to prevent amalgamation.     

Three-dimensional macroporous Sn–Ag thin film anode prepared by electro-less reduction method: effect of micro-structure

A three-dimensional Sn–Ag thin film with open interconnected walls consisting of active small grains of Sn and Ag was fabricated by electro-less reduction method as anode for lithium-ion batteries application. The morphologies and electrochemical performance of the macroporous Sn–Ag thin films were investigated by using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and galvanostatical charge–discharge measurement. The results demonstrated that through controlling the plating time, the electrode with optimized microstructure exhibited the largest reversible capacities, maintaining a capacity of 583 mAh g^?1 after 100 cycles, due to the well-preserved micro-porous structure after extended cycling.     

A survey of surface tension,molar volume and density for Sn–Ag–Cu–Bi–Sb quinary alloys as lead-free solders

ABSTRACT

By applying the geometric models and the theoretical equation, the surface tension, the molar volume and the density were studied. The empirical calculations were carried out in temperature range 623?K?≤?T?≤?1123?K. Only few thermophysical properties were estimated for eight quinary alloys: Sn3.55Ag0.5Cu3Bi3Sb, Sn3.48Ag0.5Cu3Bi5Sb, Sn3.48 Ag0.5Cu5Bi3Sb, Sn3.40 Ag0.5Cu5Bi5Sb, Sn3.53Ag1Cu3Bi3Sb, Sn3.46Ag1Cu3Bi5Sb, Sn3.46Ag1Cu5Bi3Sb, Sn3.38Ag1Cu5Bi5Sb. The results show that surface tension and density have a linear appearance for all temperatures. We have also studied the influence of the composition and temperature in the studied alloys. The obtained theoretical results are compared with the experimental ones and with the conventional Pb–Sn welds.     

Influence of Ag and Sn incorporation in In_2S_3 thin films

Ag- and Sn-doped In2S3 thin films were deposited on glass substrates using the thermal evaporation technique. The doping was realized by thermal diffusion. The influences of Ag and Sn impurities on the electrical, structural, morphological, and optical properties of the In2S3 films were investigated. In all deposited samples, the x-ray diffraction spectra revealed the formation of cubic In2S3 phase. A significant increase in the crystallite size was observed after Ag doping,while the doping of Sn slightly decreased the crystallite size. The x-ray photoelectron spectroscopy verified the diffusion of Ag and Sn into the In2S3 films after annealing. The optical study illustrated that Ag doping resulted in a reduction of the optical band gap while Sn doping led to a widening of the gap. Optical properties were investigated to determine the optical constants. Besides, it was found that the resistivity decreases significantly either after Ag or Sn incorporation. The study demonstrates that the Sn-doped In2S3 thin films are more suitable for buffer layer application in solar cells than the Ag-doped In2S3 thin films.     

Metal-ceramic contact angles determined by thin film techniques

A method of estimating contact angles is described in which 1000 A thick layers of metals are condensed from the vapour. If condensation takes place at temperatures greater than about 0.8 T_m the film is observed to break up into drops which are approximately segments of spheres, and the contact angle may be calculated from measurements on the drop size when the average film thickness is known. The experimental method is straightforward and relatively very fast, yet gives results in good agreement with earlier measurements. Results for the following metals on sapphire are presented: Al, Ag, Au, Cu, In, Sn. In addition results for Al on quartz are discussed, and it is suggested that the method may give meaningful results even when, as in this case, chemical reaction takes place.     

In situ measurement of the surface stress evolution during magnetron sputter-deposition of Ag thin film

We measured the evolution of in situ surface stress of Ag thin film during the magnetron sputter deposition. The measurement of force per width of Ag thin film showed that both the surface state and surface stress of Ag layer can be controlled through the variation of the deposition conditions such as the deposition temperature and rate. At room temperature, the force per width curve of Ag film deposited to 1 Å/s showed a typical curve consisting of three stages of surface stress. A brief presence of initial compressive stage and broad tensile maximum resulting in a compressive state had a tendency to disappear with increasing the deposition temperature. Meanwhile, a development of final compressive stage was more at higher temperature. Similar effect was observed but less obvious on increasing the deposition rate.     

Enhanced Raman scattering of graphene on Ag nanoislands

The effect of Ag nanoislands on the Raman of graphene was investigated in this work. Compared with that on the bare silicon wafer, Raman enhancement was observed in the graphene film that covered on Ag/Si surface with nanoscale Ag islands, which would be induced by the localized plasmon resonance in Ag nanostructures. The interaction between the graphene sheet and Ag/Si substrate was further studied. The peak shift and line shape of Raman spectroscopy indicated a nonuniform strain distribution in the Ag/Si supported graphene film.     

Synthesis and characterization of highly conductive Sn–Ag bimetallic nanoparticles for printed electronics

To synthesize low-cost, highly conductive metal nanoparticles for inkjet printing materials, we synthesized Sn–Ag bimetallic nanoparticles using a polyol process with poly(vinyl pyrrolidone). Because a surface oxidation layer forms on Sn nanoparticles, various compositions of Sn–xAg [x = 0, 20, 40, 60, 80, 100 (wt%)] nanoparticles were synthesized and characterized for the purpose of removing the β-Sn phase. The results of XPS, TEM, and XRD analyses confirm that the formation of a bimetallic phase, such as Ag₄Sn or Ag₃Sn, hinders the β-Sn phase and, consequently, leads to the removal of the surface oxidation layer. To measure the sheet resistance of various compositions of Sn–Ag nanoparticles, we made the ink that contains Sn–Ag by dispersing 10 wt% of Sn–Ag nanoparticles in methanol. The sheet resistance is decreased by the conductive Sn–Ag phases, such as the fcc, Ag₄Sn, and Ag₃Sn phases, but sharply increased by the low-conductive Sn nanoparticles and the surface oxidation layer on the Sn nanoparticles. The sheet resistance results confirm that 80Ag20Sn and 60Ag40Sn bimetallic nanoparticles are suitable candidates for inkjet printing materials.     

金属Sn薄膜的高温氧化与表面特征

侧重研究了高温氧化（300－550℃）引起金属Sn薄膜的表面显微形貌和表面氧化状态的变化．利用原子力显微镜（AFM）的测量，观察到金属Sn薄膜表面的金属晶粒呈现近似方形的显微形貌，但是金属Sn氧化薄膜表面的金属氧化物颗粒却具有近似圆形的显微形貌，因此，金属晶粒的高温氧化是一个各向异性的过程．在X射线光电子能谱（XPS）测量的基础上，不仅发现在金属Sn薄膜和金属Sn氧化薄膜的表面都存在大量的吸附氧粒子，而且发现吸附氧粒子的吸附形式与表面的氧化程度有关 关键词：     

Sn-C60薄膜的紫外吸收光谱和X-射线衍射谱分析

对Sn-C60薄膜进行紫外可见光吸收，X-射线衍射和扫描电镜的测定结果显示，薄膜样品紫外可见光吸收的两个短波段吸收峰比纯C60薄膜的吸收峰显著下降，说明Sn-C60薄膜的电子光吸收跃迁为间接跃迁，能带中有杂质能级的存在；样品的X射线衍射峰则对应于面心立方结构；扫描电镜结果显示薄膜为纳米级颗粒组成。     

Der Einfluß der Unterlage auf die Struktur und Leitfähigkeit metallischer Aufdampfschichten

The influence of the substrate on the electrical conductance and on the structure of condensed metal films is investigated. Ag, Cu and Sn films are condensed at different temperatures onto two identical quartz plates. One of them was prenucleated at room temperature. At low condensation temperatures the influence of the metallic prenucleation on the structure of the film is very strong. Surprisingly we find the same influence if the prenucleation and the film are of the same metal. The influence of the nucleation on the electrical conductance of the film is not so strong. Gold films are condensed onto different dielectric substrates at room temperature. From measurements of the electrical conductivity we find that a fraction of the conduction electrons are specularly reflected at the boundaries of the film. This fraction depends on the substrate material and the annealing temperature of the film.     

Electronic properties of the SnSe–metal contacts:First-principles study

The geometries and electronic properties of Sn Se/metal contact have been investigated using first-principles calculation. It is found that the geometries of monolayer Sn Se were affected slightly when Sn Se adsorbs on M(M = Ag, Au, Ta)substrate. Compared with the corresponding free-standing monolayer Sn Se, the adsorbed Sn Se undergoes a semiconductorto-metal transition. The potential difference ?V indicates that Sn Se/Ta contact is the best candidate for the Schottky contact of the three Sn Se/M contacts. Two types of current-in-plane(CIP) structure, where a freestanding monolayer Sn Se is connected to Sn Se/M, are identified as the n-type CIP structure in Sn Se/Ag contact and p-type CIP structure in Sn Se/Au and Sn Se/Ta contact. The results can stimulate further investigation for the multifunctional Sn Se/metal contact.     

Ag纳米颗粒对富Ag二氧化硅薄膜电致发光谱的影响

利用磁控溅射和热退火在硅衬底上制备了Ag纳米颗粒镶嵌的氧化硅薄膜(SiO2∶ Ag),制作了电致发光结构ITO/SiO2∶Ag/p-Si,观测到了可见区的电致发光.发现薄膜中的Ag纳米颗粒不仅成倍地提高器件的发光强度,还明显地移动电致发光的峰位.Ag含量越高,颗粒越大,发光峰位越红移.氧化硅中的发光中心与纳米Ag间的电...     

Search for localized phonon modes inlead-based alloys by superconducting tunneling

To investigate the appearance of localized phonon modes, superconductive tunneling was performed into films of Pb_0·9M_0·1 (M = Ag, Cd, Ga, Ge, In, Mg, Mg, Sb, Sn, Te, Zn) and Pb_0·97Sn_0·03. The films were quench-condensed and later annealed at 30, 100 and 300°K. Structure in tunneling curves resulting from localized phonons was observed only for a well annealed In alloy film. For most of the impurities an absence of observable local phonon modes could be explained as due to a lack of solid solubility or of sufficient structural order in the film. For Na and Sn alloys, however, these arguments cannot be used. No modes could be seen for such alloys even in films condensed at room temperature, heat-treated slightly, and quenched directly into liquid helium.     

Optoelectronics and formaldehyde sensing properties of tin-doped ZnO thin films

Sn-doped ZnO thin films were deposited on clean glass substrates using the chemical spray pyrolysis technique. XRD analyses confirm stable ZnO hexagonal wurtzite structure of the films with crystallite size in the range of 20–28 nm. The surface roughness of the films increases on Sn doping, which favors to higher adsorption of oxygen species on the film surface, resulting in higher gas response. Optical studies reveal that the band gap decreases on Sn doping. All the films show near band edge emission, and on Sn doping the luminescence peak intensity has been found to increase. Photocurrent in the 1.5 at.% doped film enhances about three times to that observed in the undoped ZnO film. Among all the films examined, the 1.5 at.% Sn-doped film exhibits the maximum response (～94.5 %) at the operating temperature of 275?°C for 100 ppm concentration of formaldehyde, which is much higher than the response (～35 %) in the undoped film. The gas response of the film is attributed to the chemisorption of oxygen on the film surface and the subsequent reaction between the adsorbed oxygen species and the formaldehyde molecules.     

Rapid Ag/Sn/Ag transient liquid phase bonding for high-temperature power devices packaging by the assistance of ultrasound

Rapid transient liquid phase (TLP) bonding process on Ag/Sn/Ag system is achieved in air by the assistance of ultrasonic, which has great potential to be applied to high-temperature power devices packaging. In this study, the influence of ultrasonic effect on the morphology and growth kinetics of Ag₃Sn grains, and the joint microstructure, mechanical property and thermal reliability were systematically investigated. Experimental results indicated that the rapid consumption of the “dynamic” transient liquid phase was attributed to the accelerated dissolution of Ag substrate and the extrusion of liquid Sn, which were entirely induced by the complex sonochemical effects on the liquid/solid intermetallic compounds (IMCs) interface. An elongated scallop-like morphology of Ag₃Sn grains was developed during Ag/Sn interfacial reaction with ultrasonic, accompanied by widening of grooves between neighbored grains. This phenomenon is called as a strengthening thermal grooving, in which the grooves at grain boundaries provide stable molten channels for Ag atoms diffusion from the substrate. Consequently, the improved elemental diffusion was evaluated through the growth kinetics of Ag₃Sn IMCs, with conservative estimation of 6–16.5 times faster than the traditional TLP process. In addition, both excellent mechanical property and thermal reliability of the Ag-Sn intermetallic joint were experimentally verified by shear test and high-temperature storage test, respectively.     

不同预淀积层银膜表面等离子激元波的辐射效率

测量了棱镜／ＬＢ膜／银膜／空气，棱镜／银膜／空气，棱镜／银膜／空气三种结构在衰减全反射条件下激发的表面等离子激元波由于银膜－空气界面粗糙度而散射以空气中的辐射效率，同时，由散射光强分布计算出表面度粗糙度参数随横向相关长度σ和表面波纹深度δ，再由σ和δ计算出理论辐射效率，理论与实验结果相符合。     

Electrical resistivity of Sn–3.5Ag–xBi solder melts

This article reported the temperature dependence of the electrical resistivity (ρ) of liquid Sn–3.5Ag lead-free solder alloy in continuous heating and cooling processes with varying Bi content in the range of 0, 2, 3.5, 5, and 7?wt.% Abnormal transitions can be observed on ρ–T curves, which indicate liquid–liquid structure transition (LLST) occurs in Sn–3.5Ag–xBi melts. Interestingly, unlike the pattern at first heating cycle, the LLST is reversible during subsequent cooling and heating cycles. Sn may play an important role on the reversibility, and Bi has a noticeable influence on the turning temperatures and characteristics during first heating cycle. The transition mechanism is analyzed from the viewpoint of short-range orders.     

Structure of Epitaxial Layers of KCl on Ag(100)

We investigated the epitaxial growth of thin KCl films on Ag(100) by spot-profile-analysis low energy electron diffraction (SPA-LEED) and scanning tunnelling microscopy (STM). The structural relation of the (100)-oriented KCl film with respect to the Ag(100) surface is incommensurate, nevertheless the structural quality is very high and terraces with an average diameter of 250 Å are obtained. The unit cells of KCl and Ag(100) are aligned, and there is no rotational mosaicity as present in the case of NaCl on Ag(100). We attribute this to a small interaction between KCl and Ag(100) and growth starting at step edges of the metal substrate. In order to demonstrate the high structural quality of the KCl films, we deposited a monolayer of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) on these films. We obtained the identical monolayer structure that was observed earlier on bulk KCl. We thus suggest that KCl/Ag(100) is ideal for surface experiments on thin dielectric films.     

不同衬底银膜表面等离子激元波的辐射效率

不同衬底银膜表面等离子激元波的辐射效率邓里文王恭明（复旦大学物理系上海２００４３３）ＥｆｉｃｉｅｎｃｙｏｆＥｍｉｓｉｏｎｆｒｏｍＳｕｒｆａｃｅＰｌａｓｍｏｎＷａｖｅｓｆｏｒＤｉｆｅｒｅｎｔＳｔｒｕｃｔｕｒｅｓｏｆＡｇＦｉｌｍｓＤｅｎｇＬｉｗｅｎ，Ｗａ...