Sn–8Zn–3Bi solder paste and Sn–3.2Ag–0.5Cu solder balls were reflowed simultaneously on Cu/Ni/Au metallized ball grid array (BGA) substrates to investigate the interfacial bonding behaviors for multiple reflow cycles at two different soldering temperature of 210 and 240 °C. The different intermetallic compounds that formed at the interface after one reflow cycle were respectively the island-shaped Ag–Au-Cu-Zn (near the solder) compounds and the Ni–Sn–Cu-Zn (near the metallized pad) compounds in 210 or 240 °C soldering systems. Layered Ag–Au–Cu–Zn, Ag5Zn8, and Ag–Zn–Sn compounds were also observed within the solder near the interface after single reflow cycle. After ten reflow cycles, the Ag–Au–Cu–Zn compounds significantly decomposed, while the Ag3Sn and Ni–Sn–Cu–Zn compounds coarsened obviously.

The initial stages of the interaction between the Fe–Cr alloy metallic interconnect and Sr-doped LaMnO3 (LSM) electrode of solid oxide fuel cells (SOFC) were investigated under cathodic polarization at the temperature range of 700–900 °C. Cr deposits on the Y2O3–ZrO2 (YSZ) electrolyte surface increased with the polarization time. However, it was observed that at the early stages of the reaction, there is no preferential Cr deposition at the three-phase boundary areas at the LSM electrode/YSZ electrolyte interface region. With the decrease of the temperature the Cr deposition reduced significantly, probably due to the significant reduction in the partial pressure of the gaseous Cr species and the cationic diffusivities in the LSM electrode. The results clearly demonstrated that the deposition of Cr species at the LSM electrode/YSZ electrolyte is basically a chemical reaction and kinetically controlled by the nucleation reaction between the gaseous Cr species and the Mn2+ species generated under cathodic polarization.

A titania-based self-standing film with high transparency and flexibility was successfully prepared via a sol-gel process, in which a titanium tetraisopropoxide/isostearate complex (precursor), n-hexylammonium isostearate (catalyst), and o-xylene (solvent) were used. The sol obtained by the sol-gel reaction was floated on a water surface to form an unsupported film. This film was composed of a titania/isostearate nanocomposite with ordered layer structure. The basal spacings of the nanocomposites depended on the chain length of the carboxylate modifier.

We have characterized thermally annealed perovskite (CaTiO3) surfaces, both before and after aqueous dissolution testing, using scanning electron microscopy, cross-sectional transmission electron microscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. It was shown that mechanical damage caused by polishing was essentially removed at the CaTiO3 surface by subsequent annealing; such annealed samples were used to study the intrinsic dissolution behavior of perovskite in deionized water at RT, 90 °C, and 150 °C. Our results indicate that, although mechanical damage caused higher Ca release initially, it did not affect the long-term Ca dissolution rate. However, the removal of surface damage by annealing did lead to the subsequent spatial ordering of the alteration product, which was identified as anatase (TiO2) by both x-ray and electron diffraction, on CaTiO3 surfaces after dissolution testing at150 °C. The effect of Ca2+ in the leachant on the dissolution reaction of perovskite at 150 °C was also investigated, and the results suggest that under repository conditions, the release of Ca from perovskite is likely to be significantly slower if Ca2+ is present in ground water.

A microwave-hydrothermal process for the synthesis of crystalline zinc oxide powders has been developed in this study. Well-crystallized zinc oxide powders exhibiting different morphology, crystallinity, and particle size have been successfully prepared by controlling the process temperature and molarity of NH4OH in the starting solution. With increasing process temperature and NH4OH molarity during synthesis, the morphology of ZnO powders changes from flowerlike agglomeration to a well-developed rodlike shape. The band gap of ZnO powders increases with a decrease in the molarity of NH4OH during synthesis. Vacuum ultraviolet radiation (VUV) excited luminescence studies for ZnO powders reveal an excitation band at 161 nm possibly due to the absorption of O2− 2p electrons in the valence band. The VUV excitation band of ZnO powders observed at 161 nm will be useful for excitation of gas-discharged plasma display devices.

Cobalt nanoparticles were synthesized on silica thin films by heat treating Co/silica films spun on thermally oxidized Si substrates. The as-deposited films were calcined in vacuum (∼0.03 Torr) for 2 h at 500 °C, followed by reduction in hydrogen at 650 °C for up to 15 h. The reduction process is characterized as one of time-dependent evolution of nanoparticles in both physical appearance and phase nature, eventually leading to the formation of well-dispersed Co nanoparticles, as ascertained by x-ray photoelectron spectroscopy and scanning electron microscopy. Slow conversion of Co ions into metallic Co observed in this study is ascribed to the absence of a Co3O4 phase that forms predominantly during calcination in air. Atomic force microscopy revealed a marked increase in the surface roughness of the film due to the development of nanoparticles. A distinct duplex-layer structure was observed in the reduced film, which consisted of the upper layer laden with nanoparticles and the lower layer essentially particle-free. The growth of the upper layer appears to be controlled by the upward diffusion of Co2+ in the film during the reduction process.

The mechanical properties of intermetallic compounds in the Au–Sn system were investigated by nanoindentation. Measurements of hardness and elastic modulus were obtained for all of the confirmed room-temperature intermetallics in this system as well as the β phase (8 at.% Sn) and AuSn4. Overall, it was found that the Au–Sn compounds have lower hardness and stiffness than common Cu–Sn compounds found in solder joints. This finding is in contrast to common knowledge of “Au embrittlement” due to the formation of either AuSn4 or (Au,Ni)Sn4 intermetallic compounds. This difference in understanding of mechanical properties of these phases and the resulting joint strength is discussed in terms of reliability and possible failure mechanisms related to interface strength or microstructural effects. Indentation creep measurements performed on Au5Sn, Au–Sn eutectic (29 at.% Sn) and AuSn indicate that these alloys are significantly more creep resistant than common soft solders, in keeping with typical observations of actual joint performance.

This paper, based on extensive finite element simulations and scaling analysis, presents scaling functions for the inverse problem in nanoindentation with sharp indenters to determine material properties from nanoindentation response. All the inverse scaling functions were directly compared with results calculated using the large deformation finite element method and are valid from the elastic to the full plastic regimes. To relate the material properties to measurable indentation parameters a new nondimensional experimental parameter Λ=P/(DS) was introduced, where P is load, D is indentation depth, and S is contact stiffness. This parameter is monotonically related to the ratio of yield stress to modulus. The modulus, hardness and yield stress are presented as explicit functions of Λ and the strain hardening exponent. The error in the inverse modulus, hardness, and yield stress due to uncertainty of the strain hardening exponent was studied and is compared with that of the traditional Oliver–Pharr method. The method of determining the strain hardening exponent from measurement with an additional indenter with a different cone apex angle is described. For this, a scaling function with the strain hardening exponent as the only unknown was obtained. In this way, the modulus, hardness, yield stress and strain hardening exponent may be determined. Experimental results show the inversion method permits the modulus and hardness to be accurately determined irrespective of the effects of pileup or sink-in.

The initial oxidation behaviors of Cu–50 at.% Au (001) single-crystal thin film were studied by in situ ultra-high-vacuum transmission electron microscopy to model nano-oxidation of alloys with one oxidizing component and one inert component. The oxidation behaviors such as incubation time, oxide nucleation rate, oxide growth kinetics as well as nucleation activation energy were greatly changed by the addition of nonoxidizing Au. The reasons for these changes, such as Au segregation to the top surface, a decrease in Cu activity, and reduced lattice mismatch due to the addition of Au, were discussed, and a qualitative analysis of nucleation energetics was given.

Bi–Ca–Co–O polycrystalline materials with a layered structure were prepared. The synthesis of the sintered specimens from two starting compositions, Bi1.8Ca2Co2Oxand Bi2.5Ca2.5Co2Ox, revealed the latter is preferentially formed at high temperature(850 °C). The increase in sintering time was shown by growth of large platelike grains (up to 50 μm in diameter and several micrometers in thickness). The reaction mechanisms during the heat treatment and the preferential formation of the Bi2.5Ca2.5Co2Ox phase were observed by x-ray diffraction, thermogravimetry–differential thermal analysis, and scanning electron microscopy. These techniques supposed the presence of a liquid phase at high temperature, origin of a highly kinetic phase formation, and the growth of large grains. Interestingly the liquid phase reaction promotes an efficient stacking and sliding of grains during hot-forging treatment, and highly (00l) oriented materials were prepared. A relationship between thermoelectric performance, texture strength, and microstructure is clarified.

An important component of the slurries used in chemical mechanical planarization (CMP) is an appropriately chosen corrosion/dissolution inhibitor, which facilitates selective material removal from protrusions while protecting recessed regions of the surface. The present work demonstrates the utility of two environmentally benign anionic surfactants, sodium dodecyl sulfate (SDS) and ammonium dodecyl sulfate (ADS) as dissolution inhibitors. Using a standard slurry (1 wt% glycine with 5 wt% H2O2 at pH = 4.0) typically used for Cu CMP and combining measurements of open circuit potentials and contact angles with those of Cu removal rates, we show that both SDS and ADS suppress chemical dissolution and polish rates of Cu. The dissolution inhibition efficiencies of ADS and SDS measured in these experiments are found to be superior to those of benzotriazole (BTA), a traditional inhibiting agent used for copper CMP.

Glass composition 39PbO–1BaO–25TiO2–9.8Al2O3–24.2SiO2–1B2O3 (mol%) crystallized on heat treatment at ≥600 °C to form glass-ceramics whose majority phase was PbTiO3 (PT). At 600 °C, nano-size PT crystals (∼20–50 nm) with a c/a ratio of 1.000(1) were observed, but as heat-treatment temperature increased to 1000 °C, the crystal size and c/a ratio increased to ∼1.2 μm and 1.056(4), respectively. Permittivity measurements as a function of temperature revealed a broad peak at ∼400 °C associated with the nanocrystalline PT crystals, but it sharpened and increased in temperature as heat treatment temperature increased to 1000 °C. The causes of peak broadening and shift of Tc are believed to be due to either clamping of PT crystals by glass matrix, finite size effects due to their intrinsically small size, or the incorporation of dopant impurities such as Al, Si, or Ba ions in the PT phase.

W-rich particle-reinforced Ti-based bulk metallic glass (BMG) matrix composites with a compressive strength approaching 3 GPa and a fracture strain of approximately 12% were developed. In contrast to most existing BMG matrix composites, in which the improved ductility was obtained only at the expense of the strength, the composites developed in this study exhibited a significant enhancement in their strength, as well as an improvement in the plasticity. This improvement in the plasticity was attributed to the blocking and circumscription of the shear band propagation, leading to the formation of a large number of shear bands. Using a classical elasticity theory of inclusions, the improvement of the strength was interpreted as resulting from the generation of tensile residual stresses in the matrix due to the difference in the coefficient of thermal expansion between the W-rich particles and the BMG matrix.

Among many Sn-based intermetallics, Cu6Sn5 (η and η′) is ubiquitous in modern solder interconnects. Using the published structural models of η and η′ and also related structures, the total energies and equilibrium cohesive properties are calculated from first-principles employing electronic density-functional theory, ultrasoft pseudopotentials, and both the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation energy. The accuracy of our calculations is assessed through comparisons between theoretical results and experimental measurements for lattice parameters, elastic properties, and formation and transformation energies. The ambient-temperature experimental lattice constants of η and η′ are found to lie between the LDA and GGA level calculated zero-temperature lattice constants. The Wyckoff positions in the structural models of η and η′ agree very well with the ab initio results. The calculated formation energy of η′ lies between −3.2 and −4.0 kJ/mol, which is more positive by about 3 to 4 kJ/mol compared to reported experimental data obtained by solution calorimetry. Our systematic differential scanning calorimetry (DSC) experiments show that the η′ → η transformation enthalpy is 438 ± 18 J/mol, which is about 66% higher than the literature value. In view of our DSC results on heating and cooling, the nature of η′ → η and η → η′ is discussed. Our experimental bulk modulus of η and η′, and the heat of η′ → η transformation agree very well with the ab initio total energy calculations at the GGA level. Based on these results, we conclude that other isotropic elastic moduli (Young’s modulus, shear, and Poissons ratio) of η and η′ phases measured by pulse-echo technique are representative of their actual properties. The scatter in experimental elastic constants in the literature may be attributed to various factors, such as the measurement technique (pulse-echo versus nanoindentation), type of specimen (bulk, Cu6Sn5-layer in diffusion couple, thin-film), and anisotropy effects (particularly in Cu6Sn5-layer in diffusion couples).

Elastic deformation of coating/substrate composites was examined for axisymmetric indentations with three different geometries of flat-ended cylinder, sphere, and cone. Intensive theoretical considerations were made for the Boussinesq problems not only in its Fredholm integral equation of the second kind, but also in its Green function using the principle of superposition for the approximated contact stress distribution. The agreement and the disagreement between these two different numerical/analytical assessments for elastic surface deformations are discussed. Along with these theoretical considerations, experimental scrutiny was conducted for the theoretical predictions for spherical indentation by the use of a sol-gel-derived MeSiO3/2 film coated on a soda-lime glass plate. A novel technique is also proposed for estimating in a simultaneous manner the elastic moduli of both the coating film and of the substrate or the elastic modulus of the film and its thickness in spherical indentation tests.

A NiFe2O4 particle/organic hybrid was synthesized in situ from iron-organic and nickel organic compounds below 100 °C. A mixture of nickel (II) acetylacetonate (NA) and iron (III) 3-allylacetylacetonate (IAA) was hydrolyzed and polymerized yielding spinel oxide particle/oligomer hybrid. X-ray diffraction analysis revealed that the crystallinity of spinel particles was dependent upon the hydrolysis conditions of NA-IAA. Nanocrystalline nickel ferrite particles around 10 nm were uniformly dispersed in the organic matrix. The formation of nickel ferrite was confirmed by energy-dispersive x-ray and x-ray photoelectron spectroscopy. The saturation magnetization of hybrid increased with increasing water amount for hydrolysis. Nano-sized nickel ferrite particle/organic hybrid showed a BH curve with no remanence above 75 K. The magnetization versus H/T curves at 300, 200, and 75 K were superimposed on the same curve and satisfied the Langevin equation. The remanent magnetization and coercive field of the hybrid were 7.4 emu/g and 460 Oe, respectively, at 5 K.

Two-dimensional arrays of embedded channels with cross-sectional diameters of 1–3 μm were fabricated in silica-on-silicon thin film structures. The channel arrays were fabricated using void-forming borophosphosilcate glass (BPSG) deposited by plasma-enhanced chemical vapor deposition (PECVD) over templates patterned and etched using standard photolithographic methods and reactive ion etching. The sizeand shape of the channels could be controlled by adjusting the depth, width, and spacing of the template ridges, the dopant levels in the BPSG, and the annealing conditions. Optimization of the channel fabrication process through detailed investigation of the process variables is presented. Potential applications inphotonics, sensors, and microfluidics are discussed.

Oxyfluoride glasses (GeO2–PbO–PbF2) doped with erbium and/or ytterbium fluorides were prepared. Highly transparent glass-ceramics, containing β–PbF2 nanocrystallites, were successfully obtained by controlled glass devitrification and were studied as they could lead to promising optical applications. To characterize the samples, differential thermal analysis, x-ray diffraction, and transmission electron microscopy were performed, revealing a variation of the crystallites size, the crystallites number and β–PbF2 crystallization temperature according to the doping ion. Indeed, the analyses indicated differences between erbium and ytterbium fluorides in promoting the crystallization of the fluoride phase. Although both fluorides act as seeds for β–PbF2 heterogeneous nucleation, erbium fluoride has higher nucleation efficiency than ytterbium fluoride and runs the nucleation process in co-doped samples. Energy dispersive x-ray microanalysis insured high rare-earth segregation into the crystallites, proving the formation of a solid solution Pb1−x−yErxYbyF2 +x+y, also confirmed by the unit cell parameter study.

Measurement of electromigration parameters in the lead-free solder SnAg3.5 was carried out by utilizing U-groove solder lines and atomic force microscopy in the temperature range of 100–150 °C. The drift velocity was measured, and the threshold current densities of the SnAg3.5 solder were estimated to be 4.4 × 104 A/cm2 at 100 °C, 3.3 × 104 A/cm2 at 125 °C, and 5.7 × 103 A/cm2 at 150 °C. These values represent the maximum current densities that the SnAg3.5 solder can carry without electromigration damage at the three stressing temperatures. The critical products for the SnAg3.5 solder were estimated to be 462 A/cm at 100 °C, 346 A/cm at 125 °C, and 60 A/cm at 150 °C. In addition, the electromigration activation energy was determined to be 0.55 eV in the temperature range of 100–150 °C. These values are very fundamental for current carrying capability and mean-time-to-failure measurement for solder bumps. This technique enables the direct measurement of electromigration parameters of solder materials.

We report on the fabrication of self-organized titanium oxide nanotube arrays of enhanced surface area prepared by anodic oxidation of a pure titanium sheet in electrolyte solutions containing potassium fluoride (KF) or sodium fluoride (NaF). The effects of electrolyte composition and concentration, solution pH, and the anodic potential on the formation of nanotubes and dimensions of the resulting nanotubes are detailed. Although nanotube arrays of length greater than 500 nm are not possible with hydrofluoric acid containing electrolytes [G.K. Mor, O.K. Varghese, M. Paulose,N. Mukherjee, C.A. Grimes, J. Mater. Res. 18, 2588 (2003)], by adjusting the pH of a KF containing electrolyte to 4.5 using additives such as sulfuric acid, sodium hydroxide, sodium hydrogen sulfate, and/or citric acid, we could increase the length of the nanotube-array to approximately 4.4 μm, an order of magnitude increase in length. The as-prepared nanotubes are composed of amorphous titanium oxide. Independent of the electrolyte composition, crystallization of the nanotubes to anatase phase occurred at temperatures ⩾280 °C. Rutile formation occurred at the nanotube-Ti substrate interface at temperatures near 480 °C. It appears geometry constraints imposed by the nanotube walls inhibit anatase to rutile transformation. No disintegration of the nanotube array structure is observed at temperatures as high as 580 °C. The excellent structural and crystal phase stability of these nanotubes make them promising for both low- and high-temperature applications.