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Conventionally, Te has primarily been used to improve the machinability of steel and its alloys. In this work, Te was used to refine the grains of an oxide-dispersion-strengthened (ODS) steel produced by additive manufacturing (AM) with fixed processing parameters. Addition of Te to the raw powder produced an ODS steel with a fine-grained microstructure, in contrast to the ODS steel manufactured without Te. Moreover, the addition of Te resulted in superior yield strength and ultimate tensile strength, which was attributed to the combined effects of grain refinement and the finer nanoparticles (NPs) composed of Te-rich composite NPs and Cr-rich NPs. For the first time, the AM technique was used to obtain grain and nanoparticle sizes of ~3.4 µm and 6 nm, respectively, from the Te-added ODS steel

Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries, owing to their low cost and abundant raw materials. Among the several candidate materials for the anode, spinel-type Li4Ti5O12 (LTO) has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na+ intercalation properties. However, a low diffusion coefficient for Na+ and the insulating nature of LTO remains challenging for practical sodium-ion battery systems. Herein, we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in LTO. We demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured LTO. Optimized Cr doped LTO shows a superior reversible capacity of 110 mAh g−1 after 400 cycles at 1C, with a three-fold higher capacity (75 mAh g−1) at 10C compared with undoped LTO material. This suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.

Herein, we introduced surface modification of a Cu catalyst by employing CH4 pre-annealing, which changed the uniformly rough Cu surface; this resulted in formation of high-quality and uniform Bern...

We explore a phase engineering strategy to improve the electrochemical performance of transition metal sulfides (TMSs) in anode materials for lithium-ion batteries (LIBs). A one-pot hydrothermal approach has been employed to synthesize MoS

Single phase, crystalline NaFeTiO4 with tunnel structure is prepared by a solid state method and explored as a novel photocatalyst for the first time. Structural, optical and morphological properties of NaFeTiO4 are investigated by various characterization techniques such as X-ray diffraction (XRD), scanning & transmission electron microscopy (SEM & TEM), Energy dispersive X-ray spectroscopy (EDS), N2 adsorption-desorption study (BET), UV-vis, X-ray photoelectron, X-ray absorption (UV-vis DRS, XPS and XANES) and photoluminescence (PL) spectroscopy. The interfacial charge transfer ability of the prepared n-type NaFeTiO4 was also investigated by transient photocurrent response and electrochemical impedence spectroscopy which proved to be an efficient tool for better understanding of electronic properties of NaFeTiO4. The photocatalytic efficiency of NaFeTiO4 is evaluated for decomposition of methylene blue (MB) and Rhodamine B (RhB) dyes as well as for H2 evolution through water splitting reaction under visible light. NaFeTiO4 exhibits efficient charge separation properties, excellent photocatalytic activities and reusability.

Herein, the bulk micromachining of Si by a magnetically guided metal-assisted chemical etching (MACE) process is demonstrated. To improve the etching performance of Si, a trilayer metal catalyst (A...

The effect of the thicknesses of the Pt intermediate layer and FePt magnetic layer in CrV/Pt/FePt multilayers on the microstructure and magnetic properties for the perpendicular magnetic anisotropy was investigated. The Pt (0–4 nm) and FePt (7–28 nm) layers were deposited on a 90 nm-thick Cr94V6 underlayer at 350 °C, and the crystal structure and magnetic properties of the fabricated CrV/Pt/FePt multilayers were characterized. X-ray diffraction and vibrating sample magnetometer measurements revealed that the out-of-plane coercivity (Hc-out) and squareness increase when the Pt intermediate layer is deposited between CrV and FePt because it protects against diffusion of Cr and V atoms into the FePt magnetic layer during deposition. In addition, we confirmed that Hc-out and squareness decrease with increasing FePt layer thickness in the range of 7–28 nm. As a result, the maximum Hc-out, S, and squareness were obtained for a multilayer with a CrV thickness of 90 nm, Pt thickness of 2 nm, and FePt thickness of 7 nm. This paper shows that highly ordered FePt L10 (001) can be fabricated by sublayer thickness control.

Biochar (BC) is an inexpensive and widely available carbon-based material with a variety of applications. Zero valent iron nanoparticles (nZVI), on the other hand, are highly reactive species. However, agglomeration and difficulty of separation from the treated media are the major reported drawbacks associated with nZVI application for water treatment. In this study, BC was modified by a simple heat-treatment, producing hydrophilic heat-treated biochar (HBC) with enhanced absorptive features, and was impregnated with nZVI, producing BC/nZVI composite for efficient organic contaminant removal. Synthesis conditions of BC/nZVI composite were optimized by evaluating p-nitrosodimethylaniline (pNDA) bleaching efficiency of various BC/nZVI samples synthesized under different conditions of pH, ultrasonication amplitude, and iron concentration. Variously-synthesized HBCs were then used to synthesize HBC/nZVI composites, and were characterized for surface morphology, surface chemistry, and elemental composition. The best-performing HBC/nZVI for pNDA bleaching was then used for trichloroethylene (TCE) removal from water. Using HBC/nZVI or BC/nZVI composites, the pseudo-second order model fit indicated a chemisorption mechanism for organic contaminants removal. Using 250 mg L−1 of the best-performing HBC/nZVI, an 88% TCE reduction (initial concentration of 40 μg L−1) was achieved after 20 min at pH = 3.0, with a rate of 3.318 g mg−1 min−1.

Activated carbon (AC) is a widely used adsorbent with a limited selectivity for chromium species. In this study, polysulfide rubber (PSR) polymer was synthesized, characterized by FTIR, and coated on F400 granular AC to obtain AC-PSR. The material properties of this composite adsorbent were investigated using SEM, TEM, EDS, TGA, BET isotherm, and XPS. The effectiveness of AC-PSR for aqueous Cr(VI) removal was investigated, and compared against virgin AC. The results showed that despite a 23% decrease in the surface area of AC after PSR coating, AC-PSR had a higher capacity for Cr(VI) adsorption. Adsorption followed a pseudo-second-order biphasic diffusion model for both AC and AC-PSR. The reaction rate constants showed that despite faster initial kinetics between AC and Cr(VI) during the film diffusion step, AC-PSR exhibited faster kinetics during the intraparticle diffusion step. The Langmuir isotherm model was found to be the best model to describe the experimental data, which showed a higher adsorption capacity for AC-PSR (QM,AC = 3.472 mg/g vs. QM,AC-PSR = 8.929 mg/g) and a stronger binding between Cr(VI) and AC-PSR (bA,AC = 0.391 L/mg vs. bA,AC-PSR = 0.696 L/mg). Regenerated AC-PSR showed an 8% increase in Cr(VI) removal efficiency after the first cycle, and then maintained a ∼98% Cr(VI) removal for three additional successive cycles.

Nitrogen-doped porous carbons containing atomically dispersed iron are prime candidates for substituting platinum-based catalysts for oxygen reduction reaction (ORR) in fuel cells. These carbon catalysts are classically synthesized via complicated routes involving multiple heat-treatment steps to form the desired Fe-Nx sites. We herein developed a highly active Fesingle bondNsingle bondC catalyst comprising of exclusive Fe-Nx sites by a simplified solid-state synthesis protocol involving only a single heat-treatment. Imidazole is pyrolyzed in the presence of an inorganic salt-melt resulting in highly porous carbon sheets decorated with abundant Fe-Nx centers, which yielded a high density of electrochemically accessible active sites (1.36 × 1019 sites g−1) as determined by the in situ nitrite stripping technique. The optimized catalyst delivered a remarkable ORR activity with a half-wave potential (E1/2) of 0.905 VRHE in alkaline electrolyte surpassing the benchmark Pt catalyst by 55 mV. In acidic electrolyte, an E1/2 of 0.760 VRHE is achieved at a low loading level (0.29 mg cm−2). In PEMFC tests, a current density of 2.3 mA cm−2 is achieved at 0.90 ViR-free under H2–O2 conditions, reflecting high kinetic activity of the optimized catalyst.

Metastable phases—kinetically favored structures—are ubiquitous in nature. Rather than forming thermodynamically stable ground-state structures, crystals grown from high-energy precursors often initially adopt metastable structures depending on the initial conditions such as temperature, pressure, or crystal size. As the crystals grow further, they typically undergo a series of transformations from metastable to lower-energy phases and ultimately energetically stable phases, as described by Wilhelm Ostwald. Metastable phases, however, sometimes provide superior chemical and physical properties, and hence, discovering and synthesizing novel metastable phases are promising avenues for achieving innovations in materials science. The most common strategy for synthesizing a metastable material involves manipulating thermodynamic conditions such as temperature and pressure during the course of synthesis. However, the search for metastable materials has mainly been heuristic, on the basis of experiences, intuitions, or even speculative predictions. This limitation necessitates the advent of a new paradigm to discover novel metastable phases, i.e., by “rational design and synthesis” instead of a “rule of thumb,” and based on ab initio methods, i.e., the calculation of thermodynamic and kinetic properties of materials with various compositions, crystal structures, and crystal sizes. The design rule is embodied in the discovery of a metastable hexagonal close-packed (HCP) palladium hydride (PdHx), synthesized in a liquid cell environment using a transmission electron microscope (TEM). The metastable HCP structure is stabilized through a unique interplay among the precursor concentrations in the solution: a sufficient supply of hydrogen (H) favors the HCP structure on the sub-nanometer scale, and an insufficient supply of Pd inhibits further growth and subsequent transition toward the thermodynamically stable face-centered cubic (FCC) structure. The crystal structure was modulated (HCP or FCC) by adjusting the H concentration inside the TEM liquid cell, providing strong evidence for the crucial role of the H concentration. Monte Carlo simulations reveal that an unexpected inhomogeneous distribution of interstitial H atoms, distinct from the predominant occupation at the octahedral interstitial sites, is key to stabilizing nanoscale HCP PdHx. Furthermore, insufficient Pd brings a multi-step nucleation and growth pathway, deduced from in situ liquid cell TEM combined with atomic electron tomography, which maintains the metastable phase intact. These findings provide new thermodynamic insights into metastability-engineering strategy to be deployed in discovering new metastable phases.

Nanorod-shaped NaFeSnO4 having a tunnel-structure analogous to CaFe2O4 is proposed as a novel anode material for rechargeable sodium-ion batteries. The material shows a considerably high charge capacity of 179 mAhg-1 with low redox voltages, decent rate, and cycling performance. XANES results reveal Fe3+/Fe2+ as the active redox couple associated with the sodium insertion/extraction during cycling.

Metastable phases-kinetically favoured structures-are ubiquitous in nature

Light element identification is necessary in materials research to obtain detailed insight into various material properties. However, reported techniques, such as scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectroscopy (EDS) have inadequate detection limits, which impairs identification. In this study, we achieved light element identification with nanoscale spatial resolution in a multi-component metal alloy through unsupervised machine learning algorithms of singular value decomposition (SVD) and independent component analysis (ICA). Improvement of the signal-to-noise ratio (SNR) in the STEM-EDS spectrum images was achieved by combining SVD and ICA, leading to the identification of a nanoscale N-depleted region that was not observed in as-measured STEM-EDS. Additionally, the formation of the nanoscale N-depleted region was validated using STEM–electron energy loss spectroscopy and multicomponent diffusional transformation simulation. The enhancement of SNR in STEM-EDS spectrum images by machine learning algorithms can provide an efficient, economical chemical analysis method to identify light elements at the nanoscale.

Allotropy is a fundamental concept that has been frequently studied since the mid-1800s. Although the bulk allotropy of elemental solids is fairly well understood, it remains challenging to reliably produce an allotrope at the nanoscale that has a different crystal structure and accompanies a change in physical properties for specific applications. Here, we demonstrate a "heterostructure" approach to produce allotrope-like bismuth nanowires, where it utilizes the lattice constant difference between bismuth and tellurium in core/shell structure. We find that the resultant strain of [100]-grown Bi nanowires increases the atomic linear density along the c-axis that has been predicted from theoretical considerations, enabling us to establish a design rule for strain-induced allotropic transformation. With our >400-nm-diameter nanowires, we measure a thermoelectric figure of merit ZT of 0.5 at room temperature with reduced thermal conductivity and enhanced Seebeck coefficient, which are primarily a result of the rough interface and the reduced band overlap according to our density-functional calculations.

Use of p-nitroso dimethylaniline (pNDA) as a selective hydroxyl radical ( OH) probe compound has been extensively reported in the literature for evaluating the performance of the catalysts used in Advanced Oxidation Processes (AOPs). Some recent studies speculated that pNDA might be oxidized by other oxidizing species, and might also be directly reduced. This study, for the first time, investigates pNDA bleaching mechanism by an Fe0-containing composite, capable of causing both reduction and Fenton-like oxidation. The composite consisted of Santa Barbara-15 (SBA-15) mesoporous silica as the supporting medium for nZVI immobilization (nZVI/SBA-15). The quantity of iron in the composite was optimized by synthesizing four various nZVI/SBA-15 samples with different iron to silica weight ratios and comparing their pNDA bleaching efficiency. Kinetic studies showed a pseudo-second-order model for pNDA bleaching using all nZVI/SBA-15 samples. The effects of OH scavengers and dissolved oxygen concentration on pNDA bleaching rate were examined. FTIR analysis of pNDA solutions showed different molecular structures for pNDA bleached under different DO conditions, leading to the conclusion that pNDA is susceptible to reductive bleaching. Results demonstrated that when using pNDA as a probe for free radicals’ generation assessment, the reductive potential of the catalysts needs to be considered.

For Fe-based 18Cr10Mn0.4N0.5C(0&ndash, 2.17)Mo (in wt %) austenitic stainless steels, effects of Mo on pitting corrosion resistance and the improvement mechanism were investigated. Alloying Mo increased pitting and repassivation potentials and enhanced the passive film resistance by decreasing number of point defects in the film. In addition, Mo reduced critical dissolution rate of the alloys in acidified chloride solutions, and the alloy with higher Mo content could remain in the passive state in stronger acid. Thus, it was concluded that the alloying Mo enhanced pitting corrosion resistance of the alloys through increasing protectiveness of passive film and lowering pit growth rate.

Solid phase speciation of chromium in dry dust deposition and road paint was determined using transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS). Spherical black carbon aggregates in dry dust deposition contained discrete nano-sized lead chromate (PbCrO4) and zinc chromate (ZnCrO4), which likely originated from yellow traffic paint and zinc chromate primer (corrosion resistant pigment), respectively based on their main applications. Road marking paint samples from auto roads included lead chromate particles whose size, shape, composition and crystal structure were similar to those in dry dust deposition. A slight difference was found at the particle boundary. Namely, lead chromate in traffic paint was encapsulated by silica-bearing matrix, while discrete lead chromate in the black carbon of dry deposition was rarely enclosed within silica-bearing matrix. The Cr K edge X-ray absorption near edge structure (XANES) spectrum for dry deposition showed the characteristic pre-edge resonance peak similar to the spectra for the Cr(VI) standard and road paint, but the lower intensity. The amount of Cr(VI) accounted for approximately 45% of the total Cr in the dust sample. The solid phase speciation of Cr observed using TEM and their valence states determined using XANES were consistent with the chemical speciation determined using the sequential extraction. The contribution of this study is that XANES was applied to identify Cr valance states in urban dust deposition and zinc chromate was found as a Cr(VI) phase in dry dust deposition using TEM. These study results provide novel data on Cr speciation and Cr(VI)-containing mineral phases in dry dust deposition and their potential sources. Based on the wide use of lead and zinc chromate, atmospheric contamination with these solid phase speciation of Cr(VI) is expected in other cities in the world.

The in-situ heating transmission electron microscopy experiment allows us to observe the time- and temperature-dependent dynamic processes in nanoscale materials by examining the same specimen. The temperature, which is a major experimental parameter, must be measured accurately during in-situ heating experiments. Therefore, calibrating the thermocouple readout of the heating holder prior to the experiment is essential. The calibration can be performed using reference materials whose phase-transformation (melting, oxidation, reduction, etc.) temperatures are well-established. In this study, the calibration experiment was performed with four reference materials, i.e., pure Sn, Al-95 wt%Zn eutectic alloy, NiO/carbon nanotube composite, and pure Al, and the calibration curve and formula were obtained. The thermocouple readout of the holder used in this study provided a reliable temperature value with a relative error of

This article briefly reviews the results of recently reported research on high-temperature Pb-free solder alloys and the research trend for characterization of the interfacial reaction layer. To improve the product reliability of high-temperature Pb-free solder alloys, thorough research is necessary not only to enhance the alloy properties but also to characterize and understand the interfacial reaction occurring during and after the bonding process. Transmission electron microscopy analysis is expected to play an important role in the development of high-temperature solders by providing accurate and reliable data with a high spatial resolution and facilitating understanding of the interfacial reaction at the solder joint.

Many studies have reported the interfacial reaction of Sn-Ag/ electroless nickel immersion gold (ENIG). Various analysis techniques, such as scanning electron microscopy, electron probe microanalyzer, and transmission electron microscopy (TEM), have been used to examine interfacial reaction. Among them, TEM equipped with analytical attachments offers the most complete tool for characterizing the formation of intermetallic compounds (IMCs) at the interface. However, solders are typically soft and ductile, while IMCs tend to be quite hard and brittle, which has limited the level of success in preparing TEM samples. We utilized ultramicrotomy since it might offer a reasonable and relatively quick alternative in this case. Ultramicrotomy has been used for the preparation of TEM specimens from biological materials and extending a range of materials including polymers, coating layer, particles, and even metals (Becker & Bange, 1993; Glanvill, 1995; Howell et al., 1995). TEM sample making to section hard materials by ultramicrotomy are not new. Besides, it has been traditionally considered that the mechanical damage during sectioning by diamond knife might hinder unambiguous specimen characterization. However, this technique also has many advantages such as no ion beam irradiation damage, no chemical mixing, no differential thinning rate and the ease of preparation of many serial sections with large, thin areas of uniform thickness in a relatively short time (Quintana, 1997). The increasing acceptability of ultramicrotomy in materials science is evidenced by a number of recent paper giving results for different hard materials (Hwang & Suganuma, 2003).

An unconventional phase-change memory (PCM) made of In

We examined the electrical properties and microstructure of NiO produced using a sol-gel method and Ni nitrate hexahydrate () to investigate if this NiO thin film can be used as an insulator layer for resistance random access memory (ReRAM) devices. It was found that as-prepared NiO film was polycrystalline and presented as the nonstoichiometric compound with Ni interstitials (oxygen vacancies). Resistances-witching behavior was observed in the range of 0~2 V, and the low-resistance state and high-resistance state were clearly distinguishable ( orders). It was also demonstrated that NiO could be patterned directly by KrF eximer laser irradiation using a shadow mask. NiO thin film fabricated by the sol-gel method does not require any photoresist or vacuum processes, and therefore has potential for application as an insulating layer in low-cost ReRAM devices.

Background Endoscopic submucosal dissection is gaining popularity in the treatment of early gastric cancer. This study aimed to identify clinicopathological factors predictive of lymph node metastasis in patients with the poorly differentiated early gastric cancer to assess the feasibility of using endoscopic submucosal dissection for these cancers. Methods The records of patients with poorly differentiated early gastric cancer who had undergone gastric cancer surgery between January 2002 and December 2009 were reviewed. Associations between clinicopathological factors and the presence of lymph node metastasis were analysed by univariable and multivariable logistic regression analysis. Results Some 1005 patients were included in the analysis. Univariable analysis indicated that lymph node metastasis was associated with sex, ulceration, tumour size, depth of invasion, macroscopic type, lymphatic invasion and venous invasion. Logistic regression revealed that lymph node metastasis was significantly associated with sex, tumour size, depth of tumour invasion and lymphatic involvement. In the group with none of these risk factors (men with mucosal tumour no larger than 2 cm in size, with no lymphatic involvement), lymph node metastasis was present in four (3·2 per cent) of 124 patients. Conclusion In the present study 3·2 per cent of patients who were negative for all identified risk factors had lymph node metastasis. The use of endoscopic submucosal dissection should be considered carefully in the treatment of poorly differentiated early gastric cancer.

This study examined the ternary Ni2SnP layer in Sn-3.5Ag/EN-P solder joints by using in situ transmission electron microscopy (TEM). The TEM analyses confirmed that Sn from the solder diffused into the P-rich Ni layer through the ternary Ni-Sn-P layer. However, Ni was neither detected in the solder region nor formed an additional Ni3Sn4 IMC layer at the interface between the solder and the ternary layer during the in situ annealing in the TEM. This suggests that the ternary Ni-Sn-P layer acts as a diffusion barrier to Ni during the aging process. Copyright © 2012 John Wiley & Sons, Ltd.

We examined the formation and morphological evolution of germanide formed in a ternary Ni/Zr-interlayer/Ge system using ex situ and in situ annealing experiments. Ni germanide in the Ni/Zr-interlayer/Ge system remained stable at temperatures up to 550^oC whereas Ni germanide in a Ni/Ge system agglomerated and was unstable. Microstructural and chemical analyses of the Ni/Zr-interlayer/Ge system during and after in situ annealing in a transmission electron microscope confirmed that the Zr atoms were retained uniformly on the top region of the Ni germanide layer during the diffusion reaction. Ultimately, the level of agglomeration in the Ni germanide film was reduced by the Zr-interlayer, and the thermal stability of Ni germanide was improved.

Microwave treatment of multi-walled carbon nanotubes (MWCNTs) with nitric acid (HNO3) and 0.2 M sodium chlorate (NaClO3) can generate and enhance defects on the surfaces of MWCNTs. These defects are the important sites to load Pt nanoparticles (NPs). We investigated the defect induced Raman spectra and observed a decrease in the R-values (D-band/G-band peak ratio) and a slight up-shift of the both peaks as the amount of loaded Pt NPs increased. Using the Brunauer-Emmett-Teller (BET) method, we observed that the pore size distribution and the pore volume changed according to the amount of Pt NPs loaded. Fewer micropores and mesopores were observed on MWCNTs loaded with Pt NPs. Based on the pore size distribution calculated from the BET results, Pt NPs loaded mainly on pores/defects with a size of 2-8 nm. Transmission electron microscopy and Raman spectroscopy results confirmed that most well-crystallized Pt NPs loaded on the surface defect sites and pores spontaneously through the exchange of electrons between Pt and C atoms.

CdTe/Te core-shell heterostructures were fabricated by the vapor phase synthesis at low temperatures using a quartz tube furnace. Two step vapor-solid processes were employed. First, various tellurium structures such as nanowires, nanorods, nanoneedles, microtubes and microrods were synthesized under different deposition conditions. These tellurium nanostructures were then used as substrates in the second step to synthesize the CdTe/Te core-shell heterostructures. Using this method, various sizes, shapes and types of CdTe/Te core-shell structures were fabricated under a range of conditions. The temperature, pressure and gas flow rate were very important parameters for synthesizing these nanostructures in the vapor phase process. The morphology, crystal structure and orientation were characterized by field-emission scanning microscopy, field-emission transmission electron microscopy and X-ray diffraction. The vapor phase process at low temperatures appears to be an efficient method for producing a variety of Cd/Te hetero-nanostructures. In addition, the hetero-nanostructures can be tailored to the needs of specific applications by deliberately controlling the synthetic parameters.

This study examined the interfacial reaction in Sn–3.5Ag/electroless Ni(P) solder joints using in situ transmission electron microscopy (TEM). In situ TEM confirmed that the thickness of the ternary layer increased by approximately 70 nm. A new interfacial reaction layer (Ni3P) formed in the P-rich Ni layer/Ni(P) interface. Several Ni–P compounds that formed in the reflow process changed into the stable Ni3P phase. This suggests that the P-rich Ni layer acts as a diffusion barrier layer between the intermetallic compounds and the Ni(P) layer during the annealing process.

This study examined the interfacial reaction in Sn-3.5Ag-0.7Cu/electroless Ni (P) solder joints using various TEM techniques. TEM confirmed that three types of intermetallic compounds (Ag3Sn, (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4) formed in the solder joints. In addition, interfacial reaction layers between the IMCs and the electroless Ni (P) are composed of two reaction layers (ternary and P-rich Ni layers). The ternary layer is composed of orthorhombic Ni2SnP phase and the P-rich Ni layer is dominantly composed of Ni3P. Furthermore, Kirkendall voids were clearly observed in the ternary layer and P-rich Ni layer. The Sn has diffused preferentially along the grain boundaries in the (Ni,Cu)3Sn4 IMCs.

This study examined the ternary Ni2SnP layer in Sn–3.5Ag–0.7Cu/electroless Ni (P) solder joints using in situ transmission electron microscopy (TEM). TEM confirmed the formation of an Ni2P phase underneath the ternary Ni2SnP after reflowing. We can directly observe the Sn diffused into Ni2P to form Ni2SnP during annealing in TEM. These results suggested that the ternary Ni2SnP forms through the diffusion of Sn into Ni2P. In addition, small Kirkendall voids were newly formed in the ternary Ni2SnP layer after annealing in TEM.

This study examined the crystallization behavior of electroless Ni-P UBM with an medium phosphorous content (~15 at%) induced by a single and step heat treatment using in-situ transmission electron microscopy (TEM). Different heat treatment processes affected the crystallization behavior of electroless Ni-P UBM. After single heat treatment at 300°C for 60 min, the electroless Ni-P UBM contained Ni and Ni 3 P. In addition to Ni and Ni 3 P, more complex Ni-P compounds, such as Ni 12 P 5 and Ni 5 P 2 formed in the electroless Ni-P UBM resulting from a step heat treatment at 150°C for 60 min followed by 300°C for 60 min.

This study investigated a method for controlling the interfacial reaction between a Sn–3.5Ag–0.7Cu (wt.%) solder and an electroless nickel-immersion gold-plated Cu substrate through heat treatment. The interfacial reaction layer was controlled by heat treating of the electroless Ni–P plated layer. By applying a heat treatment, the thickness of the reaction layer (intermetallic compounds, P-rich Ni layer) was observed to be reduced. The formation of Ni2SnP, which significantly affects the mechanical reliability of solder joints, was suppressed.

Analytical electron microscopy (AEM) was used to examine the initial interfacial reaction layers between a eutectic Sn–3.5Ag solder and an electroless nickel-immersion gold-plated (ENIG) Cu substrate during reflow at 255 °C for 1 s. AEM confirmed that a thick upper (Au,Ni)Sn2 layer and a thin Ni3Sn4 layer had formed through the reaction between the solder and ENIG. The amorphous electroless Ni(P) plated layer transformed into two P-rich Ni layers. One is a crystallized P-rich Ni layer, and the other is an intermediate state P-rich Ni layer before the crystallization. The crystallized P-rich layer consisted of Ni2P and Ni12P5. A thin Ni2P layer had formed underneath the Ni3Sn4 layer and is believed to be a predecessor of the Ni2SnP ternary phase. A Ni12P5 phase was observed beneath the Ni2P thin layer. In addition, nanocrystalline Ni was found to coexist with the amorphous Ni(P) phase in the intermediate state P-rich Ni layer.

The formation and morphological evolution of the germanides formed in the Ni1−xTax/Ge (x=0 and 0.1) systems were examined using ex situ and in situ annealing experiments. It was observed that the Ni-germanide in the Ni0.9Ta0.1/Ge system remained stable at temperatures up to 550 °C whereas the Ni-germanide in the Ni/Ge system agglomerated and was unstable. Microstructural and chemical analyses of the Ni0.9Ta0.1/Ge system during and after in situ annealing in a transmission electron microscope confirmed that the Ta-rich layer was formed by the accumulation of Ta atoms on the interface between the Ni0.9Ta0.1 alloy film and the Ge substrate during the diffusion reaction, and a small amount of residual Ta was found in the Ni-germanide grains. Ultimately, the Ta-rich layer helps reduce the level of agglomeration in the Ni-germanide film and improves the thermal stability of Ni-germanide.

This study examined the morphological and compositional changes that occur in oxidized poly-Si 1− x Ge x film during electron-beam irradiation in a transmission electron microscope. Before irradiation, the oxide layer was composed of a mixture of SiO 2 and GeO 2 phases. However, during electron-beam irradiation, there were significant changes in the microstructure and elemental distribution. For the oxidized poly-Si 0.6 Ge 0.4 films, the agglomeration of GeO 2 was observed at the surface region. On the other hand, in the case of the oxidized poly-Si 0.4 Ge 0.6 films, the crystallization of GeO 2 occurred in the oxide layer. Ge lattice fringes and twinning were also observed in the oxide layer.

The interfacial reaction between a eutectic Sn-3.5wt.%Ag solder and an electroless nickel–immersion gold-plated Cu substrate during reflow was examined by transmission electron microscopy (TEM). During the initial reflowing, the amorphous, electroless Ni (P)-plated layer crystallized into two P-rich Ni layers: a Ni12P5 + Ni3P mixed upper layer and a Ni3P lower layer. No ternary Ni-Sn-P layer was observed in the initial stage. After subsequent reflow for 60 s, a ternary Ni2SnP layer (containing a small amount of the Ni3P phase) was formed between the Ni3Sn4 and P-rich Ni layers (Ni3P + Ni12P5 + Ni).