High-temperature reliability of sintered microporous Ag on electroplated Ag,Au, and sputtered Ag metallization substrates

Ag sinter joining technology has been used in the advanced power applications to replace conventional soldering technology due to its high temperature stability, along with its excellent electrical and thermal conductivity. In this paper, we report the high-temperature reliability (250 °C for 1000 h) for die-attachment structures using Ag sintering technology on Cu substrates with different top metallization layers (Au and Ag), formed via different deposition processes (electroplating and sputtering). The bonding strength over 40 MPa and high-temperature reliability of sintered Ag on the sputtered Ag surface was the best among the systems studied here. Bonding quality and the bonding fracture behavior of sintered Ag on the different metallization substrates were characterized. Ag–Au solid solution was formed due to metallizaion Au atoms diffused into sintered Ag layer, leading to decreased shear strength under high temperature process. The influence of grain structure on the bonding quality at the interface between sintered Ag and the metallization Ag layers were discussed. It revealed that the grain size and orientation of the top metallization Ag layer influenced the bonding quality. The sintered Ag layer formed by Ag hybrid particles may have a selective orientation of metallization layer on the surface (111) of the Ag crystal. These results will be helpful to understand both technological perspectives for design and the applications of sintered Ag from the viewpoint of high-temperature reliability, as well as the fundamental understanding of its bonding quality mechanism with top metallization layers.     

Ag nanotubes and Ag/AgCl electrodes in nanoporous membranes

Miniaturization of the entire experimental setup is a key requirement for widespread application of nanodevices. For nanopore biosensing, integrating electrodes onto the nanopore membrane and controlling the pore length is important for reducing the complexity and improving the sensitivity of the system. Here we present a method to achieve these goals, which relies on electroless plating to produce Ag nanotubes in track-etched polymer nanopore templates. By plating from one side only, we create a conductive nanotube that does not span the full length of the pore, and thus can act as a nanoelectrode located inside the nanopore. To give optimal electrochemical behavior for sensing, we coat the Ag nanotube with a layer of AgCl. We characterize the behavior of this nanoelectrode by measuring its current-voltage response and find that, in most cases, the response is asymmetric. The plated nanopores have initial diameters between 100 and 300?nm, thus a range suitable for detection of viruses.     

Multiplexed dot immunoassay using Ag nanocubes,Au/Ag alloy nanoparticles,and Au/Ag nanocages

We report the first application of Ag nanocubes, Au/Ag alloy nanoparticles, and Au/Ag nanocages in a multiplexed dot immunoassay. The assay principle is based on the staining of analyte drops on a nitrocellulose membrane strip by using multicolor nanoparticles conjugated with biospecific probing molecules. Nanoparticles were prepared by a galvanic replacement reaction between the Ag atoms of silver nanocubes and Au ions of tetrachloroauric acid. Depending on the Ag/Au conversion ratio, the particle plasmon resonance was tuned from 450 to 700 nm and the suspension color changed from yellow to blue. The particles of yellow, red, and blue suspensions were functionalized with chicken, rat, and mouse immuno gamma globulin (IgG) molecular probes, respectively. The multiplex capability of the assay was illustrated by a proof-of-concept experiment involving simultaneous one-step determination of target molecules (rabbit anti-chicken, anti-rat, and anti-mouse antibodies) with a mixture of fabricated conjugates. Under naked eye examination, no cross-colored spots or nonspecific bioconjugate adsorption were observed, and the low detection limit was about 20 fmol.      

原子氧对金属银和有机防护涂层的侵蚀

用光电子能谱（XPS）和扫描电镜（SEM）观测了在模拟原子氧（AO）环境中Ag及在其表面涂覆的有机防护层的表面，研究了表面的形貌和质量损失。结果表明，AO对Ag有较严重的侵蚀作用，使原来光亮的表面失去光泽，变得粗糙，采用环氧树脂，聚胺酯或醇酸树脂作为防护涂层，AO辐照后其表面形貌也发生了较大变化，表明腐蚀严重，采用有机硅作为涂层，被AO侵蚀后其表面形貌的变化甚小，质量损失较小，表明这种涂层具有较明显的防护效果。经AO辐照后有机硅涂层表面生成致密的氧化硅膜层，对抑制AO的进一步侵蚀具有关键作用。     

Room-temperature synthesis of flowerlike Ag nanostructures consisting of single crystalline Ag nanoplates

We demonstrate a simple wet-chemical route for the high-yield synthesis of flowerlike silver nanostructures consisting of single crystalline Ag nanoplates by mixing AgNO₃ and p-phenylenediamine (PPD) in the presence of polyvinylpyrrolidone (PVP) at room temperature. PPD serves both as a reducing agent, and as an architecture soft template with PVP to the formation of such Ag nanostructures. It is found that the presence of PVP has a significant effect on the formation and growth of these novel nanostructures. The flowerlike silver nanostructures could serve as highly sensitive and reproductive surface-enhanced Raman scattering (SERS) substrates for chemical and biological detection.     

Size-adjusted hollow Ag spheres fabricated through reducing Ag2O in situ

Hollow Ag spheres with tunable sizes in a range of 74–167 nm were fabricated using a two-step synthesis including the creation of solid Ag₂O particles and the reduction of these Ag₂O particles in situ. Ag nanoclusters were generated by the reduction of Ag₂O. Ag₂O particles were as scaffolds to create Ag spheres. Namely, the reduction of Ag₂O occurred firstly on the surface of the Ag₂O particles. The H₂ was generated due to the hydrolysis of borohydride ions. The diffusion of H₂ and the further reduction of Ag₂O particles resulted in the formation of a hollow part within Ag spheres. The average diameter of the hollow Ag spheres can be adjusted by varying the concentration of NaOH and NaBH₄, the kinds of solvent, and reaction temperature.     

纳米Ag颗粒/In-3Ag复合焊料的微观组织演变

通过外向法制备纳米Ag颗粒/In-3Ag复合焊料, 研究在多次回流过程中, 添加不同含量的纳米Ag颗粒对In-3Ag焊料焊点基体组织和界面IMC层(intermetallic compound)的影响规律, 采用SEM、HRTEM、能量色散仪(EDS)和电子探针(EPMA)分别对焊点基体及IMC层的微观结构及成分进行观察和分析。研究结果表明: 纳米Ag颗粒能诱发晶粒成核, 多次回流后, 复合焊料基体中颗粒状二次相AgIn₂没有明显长大现象; 通过塞积扩散通道和表面吸附效应, 纳米Ag颗粒能显著抑制焊料界面IMC层在多次回流过程的生长; 纳米Ag颗粒的合适添加量为0.5%(质量分数,下同), 当添加1%时, 颗粒团聚, 导致界面处出现球形AgIn₂, 降低焊料的力学性能。     

Nano-sized Ag rather than single-atom Ag determines CO oxidation activity and stability

Single-atom catalysis recently attracts great attentions,however,whether single atom or their nanoparticle(NP)has the advantage in its intrinsic activity remains under heated debate.Ag/Al₂O₃ is a widely used catalyst for many catalytic reactions,while the effect of Ag particle size on the actity is seldom investigated due to the great difficulty in synthesizing single atom Ag and Ag clusters/particles with different sizes.Herein,we firstly prepared an atomically dispersed Ag/Al₂O₃ catalyst using a nano-sized y-Al₂O₃ as the support,subsequently obtained a series of Ag/Al₂O₃ catalysts with different Ag particle sizes by H₂ reducing single-atom Ag/Al₂O₃ catalyst at various temperatures.The Ag/Al₂O₃ treated at 600℃demonstrated superior CO oxidation performance over single-atom Ag/Al₂O₃ and the Ag/Al₂O₃ treated at 400 and 800℃.Based on experimental data and dpnsity functional theory(DFT)calculation results,we reveal that the larger Ag°particle is beneficial to oxygen activation and improves the valence stability during oxidation reaction,while the aggregation of Ag°particle also accordingly decreases the concentration of surface active sites,hence,there is an optimum Ag0 particle size.Our findings clearly confirm that Ag0nanoparticle has the advantage over single-atom Ag species in its intrinsic activity for CO oxidation.     

Interfacial reactions between liquid Sn3.5Ag0.5Cu solders and Ag substrates

The morphology and growth kinetics of intermetallic compounds (IMCs) formed during the soldering reactions between Sn3.5Ag0.5Cu and Ag substrates at various temperatures ranging from 250 to 350 °C were investigated. The interfacial microstructure was quantified with scanning electron microscopy (SEM) for each processing condition. Experimental results show that the thickness of the scallop-shaped Ag₃Sn IMCs layer increased with increasing soldering time and temperature. Furthermore, Cu₆Sn₅ particle precipitates were observed in the Ag₃Sn IMCs layer around and thus suppressing the Ag₃Sn IMCs layer growth. Furthermore, the large Cu₆Sn₅ IMCs tend to appear in the vicinity of interfacial wicker-Ag₃Sn IMCs. Kinetics analyses showed that growth of the Ag₃Sn intermetallic compound was diffusion controlled. The activation energies for the growth of Ag₃Sn IMCs are calculated to be 66.7 kJ/mol.     

Induced synthesis and characterisation of Ag and Ag2S assembly nanoparticle chains

A facile and efficient template method was developed for the fabrication of Ag and Ag₂S nanoparticle chains. The morphologies and structures of products were characterised by X-ray powder diffraction and transmission electron microscopy. The result shows that the length of Ag and Ag₂S nanoparticle chains are up to several micrometres. Systematic studies exhibit that the concentration of template (polyacrylamide) reagent, reaction solution and ageing time are important factors on the control synthesis of nanoparticle chains. The possible mechanism for the formation of Ag and Ag₂S nanoparticle chains was also discussed. The physical and chemical properties of the Ag and Ag₂S nanoparticle chains were investigated and their phytotoxicities were also researched for the first time. The phytotoxic result shows that the Ag and Ag₂S nanoparticle chains have obvious inhibition of seed germination.     

团簇大小对Fe－Ag和Co－Ag包埋团簇形貌及结构的影响

利用蒸发－气体－聚集（ＥＧＡ）共沉积方法，在有方华膜的电镜载网上制备了Ｆｅ－Ａｇ及Ｃｏ－Ａｇ系列纳米磁性包埋团簇，通过控制蒸发电流等沉积条件，获得了不同团簇大小的样品。ＴＥＭ／ＥＤ分析表明，当样品中Ｆｅ（Ｃｏ）团簇尺寸较小时（分别为１０ｎｍ和２０ｎｍ），样品形貌表现为Ｆｅ（Ｃｏ）团簇弥散地分布在Ａｇ膜基质中，形成了Ａｇ膜对Ｆｅ（Ｃｏ）团簇的分隔与包埋；其结构分别为Ｆｅ、Ａｇ多晶和Ｃｏ、Ａｇ多晶共存的形态。而当Ｆｅ（Ｃｏ）团簇尺寸较大时（分别为９０ｎｍ和５０ｎｍ），样品中Ａｇ原子也相对聚集，Ａｇ膜没有形成对Ｆｅ（Ｃｏ）团簇的完全包裹，在形貌上Ｆｅ－Ａｇ样品呈现为“串状”，Ｃｏ－Ａｇ样品呈现为“花瓣状”；而在结构上则都表现为非晶形态     

Influence of Ag thickness of aluminum-doped ZnO/Ag/aluminum-doped ZnO thin films

Highly conducting aluminum-doped ZnO (30 nm)/Ag (5-15 nm)/aluminum-doped ZnO (30 nm) multilayer thin films were deposited on glass substrate by rf magnetron sputtering (for top/bottom aluminum-doped ZnO films) and e-beam evaporation (for Ag film). The transmittance is more than 70% for wavelengths above 400 nm with the Ag layer thickness of 10 nm. The resistivity is 3.71 × 10^− 4 Ω-cm, which can be decreased to 3.8 × 10^− 5 Ω-cm with the increase of the Ag layer thickness to 15 nm. The Haacke figure of merit has been calculated for the films with the best value being 8 × 10^− 3 Ω^− 1. It was shown that the multilayer thin films have potential for applications in optoelectronics.     

Density and Thermal Expansion of Liquid Ag–Cu and Ag–Au Alloys

The densities of liquid Cu–Ag and Ag–Au alloys were measured using the technique of electromagnetic levitation. This technique involves producing shadow images of the sample from which the volume is calculated by an image processing algorithm. The density and thermal expansion of several alloys and the pure elements copper, gold, and silver are measured at temperatures above their melting points. In addition, they were investigated as a function of either the copper or gold concentration. It was found from data analysis that the densities can be derived from a linear combination of the molar volumes of the elements and that thermodynamic excess quantities are negligibly small.     

Enhancement of the thermoelectric power factor in Ag/Bi-Te/Ag composite devices

The resultant thermoelectric properties of the p- and n-type Ag/Bi-Te/Ag composite devices welded with pure Bi were measured at 298 K as a function of relative thickness of x, where x is the ratio of thickness of Bi-Te compound to the interval between two thermocouples and the chemical compositions of the p- and n-type Bi-Te compounds used here are (Bi_0.25Sb_0.75)₂Te₃ and Bi₂(Te_0.94Se_0.06)₃, respectively. Consequently, the electrical resistivities ρ of the p- and n-type Ag/Bi-Te/Ag devices increased linearly with an increase of x, while the Seebeck coefficients α were enhanced significantly in the range from x = 0.03 to 0.10, so that their observed P values have a large local maximum at x = 0.06. The x-dependence of P values was found to be explained roughly with the simple model proposed here when some reduction in the thermal conductivity κ of Ag and Bi was taken into the calculation. The maximum P of the p- and n-type Ag/Bi-Te/Ag devices reached extremely large values of 27.8 and 88.3 mW/K²m, which are higher than 25.7 mW/K²m obtained for the previous n-type Ni/Bi/Cu device.     

Layered Pb/Ag films

Thin layered structures were produced by sequential vacuum evaporation of lead and silver.The layered samples showed strong [111] texture. The X-ray diffraction plots contained a series of additional satellite peaks characteristics of a superlattice. The experimental X-ray diffraction data and the results of calculations based on a simple model of a superlattice were compared.The influence of room temperature annealing on the crystal structure of the layered Pb/Ag samples was observed.     

Ag glasses based on Zn-phosphate

The partial substitution of Zn²⁺ for Ag⁺ in Ag₄P₂O₇ leads to the formation of a wide glassy domain of composition [Ag₄P₂O₇] _(1−y) [Zn₂P₂O₇] _(y) with 0.20y0.87. The introduction of AgI in these materials results in a new series of glasses of formula [(Ag₄P₂O₇)_(1−y) (Zn₂P₂O₇)_(y)] _(1−X) [AgI] _(x), which domain for the composition y = 0.25 corresponds to 0x 0.64. The structure as well as the thermal and electrical properties of these materials are compared with those of the [AgPO₃] _(1−X) [AgI] _(x) and [Ag₄P₂O₇] _(1−x) [AgI] _(x) glasses.     

Ag/SiO_2/Ag组成的三角形纳米柱的光学及传感特性

研究了一种Ag/SiO2/Ag组成的三角形纳米柱的LSPR消光光谱特性及其传感特性.时域有限差分（FDTD）法计算结果表明,三棱柱结构在中间夹层SiO2后,消光光谱峰值出现红移现象,并伴随着折射率灵敏度的增加.随着中间介质层厚度的增加,上下两层金属间表面等离子体耦合逐渐减弱,消光光谱峰值红移速度减慢.当介质层厚度为60nm时,金属层间的表面等离子体耦合消失,消光光谱与折射率灵敏度不再发生变化.对于实际制作时可能出现尖角钝化的三棱柱结构,中间介质层仍然表现出对其光学及传感特性的良好的调节作用.     

Standard thermodynamic properties of Ag3Sb and Ag6Sb evaluated by EMF measurements

The standard thermodynamic properties of the intermetallic compounds Ag₃Sb and Ag₆Sb (the minerals dyscrasite and allargentum, respectively) in the Ag-Sb system have been determined in the temperature range 350–500 K at atmospheric pressure using a solid-state galvanic cell (emf method). The results have been used to propose recommended standard thermodynamic functions of formation at 298.15 K and 10₅ Pa. The Gibbs energy, entropy, and enthalpy of Ag₃Sb(cr) are ?5934 ± 1277 J/mol, 195.89 ± 2.54 J/(mol K), and 841 ± 1046 J/mol, respectively, and those of Ag₆Sb(cr) are ?6637 ± 3064 J/mol, 332.40 ± 5.99 J/(mol K), and 2778 ± 2491 J/mol, respectively.