Solid Sn Research Articles

Enhancement of Sn plasma EUV emission by double-sided laser illumination

Advancements in state-of-the-art nanolithography technology over the past decade have been raising an ongoing demand for improvement of the power and efficiency of extreme-ultraviolet (EUV) light sources that stand at its heart. This study introduces a double-sided laser illumination scheme aimed at enhancing EUV emission from such a laser-produced Sn plasma source. Using a solid-state laser, experiments were conducted with suspended solid Sn targets of varying thicknesses, evaluating the resulting effect on EUV output intensity. A significant increase in EUV emission to the collection side was observed due to the addition of illumination of the other side, particularly for thinner targets. For targets with thicknesses of 60 and 20 nm, an increase between 50% and 150% in EUV emission was detected in comparison with single-sided illumination. Extrapolating to a long laser pulse that burns through the target, the enhancement is projected to be 17% for a 300 nm thick target. These results highlight a promising way for further improvement of output power and energy efficiency in next-generation EUV light sources.

Seeded Synthesis of Hollow PdSn Intermetallic Nanomaterials for Highly Efficient Electrocatalytic Glycerol Oxidation.

Intermetallic nanomaterials have shown promising potential as high-performance catalysts in various catalytic reactions due to their unconventional crystal phases with ordered atomic arrangements. However, controlled synthesis of intermetallic nanomaterials with tunable crystal phases and unique hollow morphologies remains a challenge. Here, a seeded method is developed to synthesize hollow PdSn intermetallic nanoparticles (NPs) with two different intermetallic phases, that is, orthorhombic Pd2 Sn and monoclinic Pd3 Sn2 . Benefiting from the rational regulation of the crystal phase and morphology, the obtained hollow orthorhombic Pd2 Sn NPs deliver excellent electrocatalytic performance toward glycerol oxidation reaction (GOR), outperforming solid orthorhombic Pd2 Sn NPs, hollow monoclinic Pd3 Sn2 NPs, and commercial Pd/C, which places it among the best reported Pd-based GOR electrocatalysts. The reaction mechanism of GOR using the hollow orthorhombic Pd2 Sn as the catalyst is investigated by operando infrared reflection absorption spectroscopy, which reveals that the hollow orthorhombic Pd2 Sn catalyst cleaves the CC bond more easily compared to the commercial Pd/C. This work can pave an appealing route to the controlled synthesis of diverse novel intermetallic nanomaterials with hollow morphology for various promising applications.

Direct Imaging of Surface Melting on a Single Sn Nanoparticle.

Despite previous studies, understanding the fundamental mechanism of melting metal nanoparticles remains one of the major scientific challenges of nanoscience. Herein, the kinetics of melting of a single Sn nanoparticle was investigated using in situ transmission electron microscopy heating techniques with a temperature step of up to 0.5 °C. We revealed the surface premelting effect and assessed the density of the surface overlayer on a tin particle of 47 nm size using a synergetic combination of high-resolution scanning transmission electron microscopy imaging and low electron energy loss spectral imaging. Few-monolayer-thick disordered phase nucleated at the surface of the Sn particle at a temperature ∼25 °C below the melting point and grew (up to a thickness of ∼4.5 nm) into the solid core with increasing temperature until the whole particle became liquid. We revealed that the disordered overlayer was not liquid but quasi-liquid with a density intermediate between that of solid and liquid Sn.

Radiation of extreme ultraviolet source and out-of-band from laser-irradiated low-density SnO<sub>2</sub> target

The extreme ultraviolet (EUV) lithography technology required for high-end chip manufacturing is the first of 35 “bottleneck” key technologies that China is facing currently. The high conversion efficiency EUV source and low out-of-band radiation play a significant role in the application of the EUV lithography system. In this work, the EUV source and out-of-band radiation are studied by using laser irradiated solid Sn target and low-density SnO<sub>2</sub> target. The result shows that a strong EUV radiation at a wavelength of 13.5 nm is generated when the laser irradiates the two forms of Sn targets. Owing to the self-absorption effect of the solid Sn target plasma, the maximum intensity of the wavelength is not located at the position of 13.5 nm, which is working wavelength of EUV lithography system. However, the peak radiation spectrum is located at the position of 13.5 nm with low-density SnO<sub>2</sub> target due to its weaker plasma self-absorption effect. In addition, the satellite lines are weaker in low-density SnO<sub>2</sub> target than in the solid Sn target, so that the spectrum efficiency of the EUV at 13.5 nm (2% bandwidth) is increased by about 20%. On the other hand, the experimental study of the out-of-band radiation is carried out. The out-of-band radiation spectral results show that the out-of-band radiation is mainly dominated by the continuum spectrum. Compared with the solid Sn target, the low-density SnO<sub>2</sub> target contains a part of the low <i>Z</i> element O (<i>Z</i> = 8), resulting in a low-intensity continuum spectrum. In addition, the collision probability of ion-ion and electron-ion both become low when the laser irradiates the low-density SnO<sub>2</sub> target, resulting in a short out-of-band radiation duration time. Therefore, the out-of-band radiation generated by the laser irradiated on the low-density SnO<sub>2</sub> target is weak based on the above reasons. The angular distribution of out-of-band radiation measurement results shows that the intensity of out-of-band radiation decreases with the angle increasing. A cosine function <inline-formula><tex-math id="M2">\begin{document}$A \cos ^\alpha \theta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20222385_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20222385_M2.png"/></alternatives></inline-formula> can fit the angular distribution of the total radiation.

FEATURES OF THE ELECTRICAL PROPERTIES OF HETEROJUNCTIONS N-GAAS-P-(GAAS)1 - X - У(GE2)X(ZNSE)Y

The optimal technological conditions for growing multicomponent epitaxial films of solid solutions (GaAs)1 - x - y(Ge2)x(ZnSe)y with specified physical properties by liquid-phase epitaxy have been determined. It has been established that the above conditions for growing thin films from a tin solution-melt at temperature intervals of 730-630, 650-550 °С with a substrate cooling rate of 1 deg/min are the most optimal. In this case, the films had a thickness of 10 μm and p-type conductivity. For ohmic contacts to such semiconductor solid solutions, Sn, Au, In, (In-Ga) and (Ge-Ag) alloys were used. It was determined that the mobility of current carriers depends on the composition, the structural perfection of the epitaxial layers and the ionization energy of the atoms of the constituent components have values of 0.19, 0.07, 0.029 eV. It has been established that in heterostructures of the n-GaAs-p-(GaAs)1 - x - y(Ge2)x(ZnSe)y type, obtained at Т = 7500 °С, the current transmission is determined by tunneling-recombination, and in the samples obtained at Т = 7300 °С, by currents limited volume charges. It was also determined that a region with a higher resistivity is formed at the heterointerface, the thickness of which, depending on the growth conditions of thin films, is from 0.2 to 0.5 μm.

Radvaniceite, GeS2, a New Germanium Sulphide, from the Kateřina Mine, Radvanice near Trutnov, Czech Republic

The new mineral radvaniceite, GeS2, was found on the burning coal mine dump of the abandoned Kateřina coal mine at Radvanice, near Trutnov, northern Bohemia, Czech Republic. It occurs as aggregates resembling cotton tufts up to 5 mm in size; they are composed of acicular crystals up to fibres about 1–5 μm thick and up to 3 mm in length. Individual fibres are distorted and partly resemble bent wires nucleated on rock fragments or on black, crumbly ash, in association with minerals of solid solutions of Bi-Sb and stangersite, herzenbergite, and greenockite. Radvaniceite was also observed as irregular grains in a range of 10–50 μm in size, forming part of earlier multicomponent aggregates upon which the above-described crystals grow. These aggregates are formed, in addition to radvaniceite, by minerals of Bi-Sb, Bi2S3-Sb2S3 and Bi2S3-Bi2Se3 solid solutions, Bi3S2, Bi-sulpho/seleno/tellurides, tellurium, unnamed PbGeS3, Cd4GeS6, GeAsS, Sn5Sb3S7, stangersite, greenockite, cadmoindite, herzenbergite, teallite, and Sn- and/or Se-bearing galena. Radvaniceite is formed under reducing conditions by direct crystallization from hot gasses (250–350 °C) containing Cl and F at a depth of 30–60 cm under the surface of a burning coal mine dump; the mine dump fire started spontaneously, and no anthropogenic material was deposited there. Acicular crystals up to fibres of radvaniceite are elastic to flexible; are white to yellowish grey in colour, with white streaks; are translucent in transmitted light; and have vitreous to adamantine lustre. Cleavage and fracture were not observed. The calculated density is 3.05 and 2.99 g·cm−3 for the empirical and ideal formulae, respectively. Radvaniceite is transparent under the microscope, with a very weak pleochroism (from colourless to pale greenish yellow), and has a refraction index > 1.8. Under reflected light, radvaniceite is light grey; bireflectance and pleochroism were not observed due to abundant, white to grey, internal reflections. Anisotropy in crossed polars is distinct with grey rotation tints. Reflectance values of radvaniceite in air (Rmin–Rmax, %) are: 15.4–18.8 at 470 nm, 16.1–20.4 at 546 nm, 16.4–20.8 at 589 nm, and 16.9–20.9 at 650 nm. The empirical formula, based on electron-microprobe analyses, is (Ge0.99Bi0.01)Σ1.00(S1.97Se0.03)Σ2.00. The ideal formula is GeS2, which requires Ge 53.10, S 46.90, total 100 wt. %. Radvaniceite is monoclinic, Pc, a = 6.8831(12), b = 22.501(3), c = 6.8081(11) Å, β = 120.365(9)°, with V = 909.8(4) Å3 and Z = 12. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I) (hkl)] are: 5.7395 (100) (11-1, 110), 5.2067 (16) (021), 3.3650 (33) (111, 11-2), 2.8417 (33) (022), 2.8236 (16) (170, 17-1), 2.8134 (20) (080) and 2.6257 (19) (240, 24-2). According to X-ray powder diffraction data and Raman spectroscopy, radvaniceite is a natural analogue of synthetic monoclinic low-temperature β-GeS2 with distorted GeS4 tetrahedra forming four corner-sharing tetrahedral chains, which are connected by corner-sharing tetrahedra in a three-dimensional structure. We named the mineral after its type locality, Radvanice, one of the past centres of coal mining in the Czech limb of the Intra-Sudetic Basin. This mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (number 2021-052).

The influence of Pb content on the interfacial free energy of solid Sn in eutectic Pb–Sn liquid mixtures using molecular dynamics simulations

ABSTRACT The solid–liquid interfacial free energy (γ) for binary Pb–Sn systems at different concentrations and crystal orientations is calculated using molecular dynamics (MD) simulation that employs a modified-embedded atom method interatomic potential. First, the solid–liquid interface is constructed in MD simulations according to its calculated phase diagram. Then, the capillary fluctuation method (CFM) is employed for the calculation of the solid–liquid interfacial stiffness. A novel systematic approach is proposed that eliminates the error in the linear approximation of the CFM. The results show that orientation of the solid Sn crystal does not have a significant influence on the value of the stiffness, which explains the experimentally observed spherical shape of Sn particles in eutectic liquid Pb–Sn mixtures. The calculated γ for pure Sn is in good agreement with experimental counterparts. In addition, this study finds that γ slightly increases with increasing the concentration of Pb in the eutectic liquid Pb–Sn mixture, which agrees with available experimental data.

Improvement of thermoelectric performance of SnTe-based solid solution by entropy engineering

SnTe is a good alternative to PbTe in the thermoelectric (TE) applications, in that it is a compound with no toxic element Pb. Besides, the compound SnTe has a relatively narrow bandgap (0.3–0.4 eV) and high Sn vacancy concentration (Sn<sub>v</sub>) as well. Accordingly, it gives a high carrier concentration (10<sup>21</sup> cm<sup>–3</sup>) at room temperature (RT), which is not favorable for thermoelectrics, therefore the regulation of both the electronic and phonon scattering mechanisms is strongly required. Up to date, there have been many approaches to improving its TE performance. The typical examples are those involving the valence band convergence, nanostructuring, substitutional and interstitial defects, and lattice softening, which are all practical and effective to improve the TE performance of SnTe. However, in this work the entropy is taken as an indicator to design the SnTe-based TE material with multicomponents and then optimize its TE performance. The detailed scheme involves the chemical composition design step by step. At first, SnTe alloys with 5% GaTe to form a solid solution Sn<sub>0.95</sub>Ge<sub>0.05</sub>Te, aiming to increase the solubility of the foreign species. The second step is to form another solid solution (Sn<sub>0.95</sub>Ge<sub>0.05</sub>Te)<sub>0.95</sub>(Ag<sub>2</sub>Se)<sub>0.05</sub> via the alloying Sn<sub>0.95</sub>Ge<sub>0.05</sub>Te with 5% Ag<sub>2</sub>Se. The purpose of this step is to reduce the p-type carrier concentration of the system, for the species Ag<sub>2</sub>Se is a typical n-type semiconductor. The last step is to form a series of solid solutions (Sn<sub>0.95–<i>x</i></sub>Ge<sub>0.05</sub>Bi<sub><i>x</i></sub>Te)<sub>0.95</sub>(Ag<sub>2</sub>Se)<sub>0.05</sub> by substituting different amounts of Bi on Sn in (Sn<sub>0.95</sub>Ge<sub>0.05</sub>Te)<sub>0.95</sub>(Ag<sub>2</sub>Se)<sub>0.05</sub>, to further enhance the configurational entropy (Δ<i>S</i>). Because of the above approaches, both the carrier concentration and thermal conductivity decrease while the highest TE figure of merit (<i>ZT</i>) increases from 0.22 for the pristine SnTe to ~0.8 for the alloy (Sn<sub>0.95–<i>x</i></sub>Ge<sub>0.05</sub>Bi<sub><i>x</i></sub>Te)<sub>0.95</sub>(Ag<sub>2</sub>Se)<sub>0.05</sub> (<i>x</i> = 0.075). This result proves that the entropy engineering is a practical way to improve the TE performance of SnTe, and at the same time it illustrates that it is very important to harmonize the entropy engineering with other electronic and phonon scattering mechanisms, in order to improve the TE performance of SnTe effectively.

Strained α-Sn thin films on highly lattice-mismatched Ge substrates

Strained α-Sn thin films and stanene (two-dimensional counterpart of α-Sn), which have attracted significant attentions due to their electronic properties as topological insulators, were mostly deposited on nearly lattice-matched substrates through molecular beam epitaxy. In this work, contrary to prior efforts, Sn thin films are deposited on highly lattice-mismatched Ge (100) substrates through physical vapor deposition of solid Sn sources. Three different methods, 1) Acetone/Isopropyl Alcohol (IPA), 2) Acetone/IPA/H2O(80°C), and 3) Hydrogen Peroxide (H2O2)/Hydrochloric Acid (HCl), are used to clean commercially available Ge (100) substrates. X-ray diffraction (XRD) characterizations indicate that compressively strained α-Sn thin films are formed on Ge substrates cleaned by Acetone/IPA/H2O(80°C) or H2O2/HCl, but no peak associated with crystalline α-Sn appears for thin films grown on Ge substrates cleaned by Acetone/IPA. Strained α-Sn thin films deposited on Ge substrates cleaned by Acetone/IPA/H2O(80°C) are further investigated using dielectric force microscopy (DFM). Although Ge substrates where α-Sn thin films are deposited are p-type, DFM images indicate that the α-Sn thin films are n-type. The α-Sn/Ge heterostructures that we demonstrate in this work might be promising in applications in advanced electronics and photonics.

Effect of Cooling Methods on Microstructure and Mechanical Properties of Hot-extruded Cu-15Ni-8Sn Alloy

The effect of cooling method on microstructures and mechanical properties of the hot-extruded Cu-15Ni-8Sn bars were investigated by optical microscope(OM), scanning electronic microscope(SEM), differential scanning calorimetry(DSC) and tensile testing. The results indicated that the content of solid solution atom Sn in the water-cooled alloy after hot extrusion is greater than that in the air-cooled alloy. The precipitation onset temperature and dissolution termination temperature of γ phase in the water-cooled alloy are 24 °C and 32 °C lower than that in the air-cooled alloy, respectively. Both water-cooled and air-cooled alloys are composed of γ phase and supersaturated solid solution α(Cu), and show the similar grain size about 23 μm. In the air-cooled alloy, a large number of dispersed rod-like and granular γ-phases are precipitated in the grains, while only granular γ phase is observed in water-cooled alloy with. The tensile strength, elongation and microhardness of the water-cooled and air-cooled alloys are 588±12 MPa and 855±41 MPa, 41.6±2.0% and 15.2±1.0%, 166±7 HV and 292±5 HV, respectively, while the former shows a typical ductile fracture mechanism and the latter has somewhat brittle fracture characteristics.

Low-cost and highly safe solid-phase sodium ion battery with a Sn–C nanocomposite anode

• Nanosized Sn particles are embedded in an amorphous carbon host derived from sucrose. • Na 3 Zr 2 Si 2 PO 12 ceramic-based hybrid solid electrolyte is prepared for sodium ion battery. • Sn–C-based solid sodium battery show high discharge capacities and Coulombic efficiency. With the use of a conducting ceramic-based solid-phase hybrid electrolyte, the batteries can maintain safe and stable operation during the reversible insertion/extraction of sodium ions by the suppression of sodium dendrites. Here, Sn–C nanocomposites are prepared by a simple one-pot synthesis process, and they have a unique structure in which nanosized Sn particles are embedded in an amorphous carbon host derived from sucrose. The Sn–C nanocomposite is used to fabricate a solid-phase sodium-ion battery with a Na 3 Zr 2 Si 2 PO 12 ceramic-based hybrid solid electrolyte. The Sn–C-based solid-phase sodium battery shows high electrochemical performance with a high discharge capacity of 669.9 mA h g −1 at 0.2 C with a Coulombic efficiency close to 100%. The electrochemical alloy mechanism of the Sn–C nanocomposite is investigated by X-ray photoelectron spectroscopy. The good electrochemical performance demonstrates the advantages of using the Na 3 Zr 2 Si 2 PO 12 ceramic-based hybrid solid electrolyte and Sn–C nanocomposite in solid-phase sodium ion batteries.

Precise determination of the effect of temperature on the density of solid and liquid iron, nickel, and tin

Abstract Density and thermal expansion coefficient of metals are fundamental characteristics to describe the equation of state. Especially for liquid metals, the reported data for density and thermal expansion coefficient vary in the literature, even at ambient pressure. To determine the density of solid and liquid metals precisely at high temperatures and ambient pressure, we have developed a high-temperature furnace. The densities of solid Sn, Ni, and Fe were determined from the sample image with an uncertainty of 0.11–0.7% in the temperature range of 285–1803 K with increments of 1–10 K. The density of solid Sn decreased linearly with increasing temperature up to 493 K, and then the decrease became drastic until the melting temperature (Tm) was reached. By contrast, for solid Ni and Fe, the densities decreased linearly with increasing temperature up to the Tm (1728 and 1813 K) without any drastic density drop near Tm. This suggests that Ni and Fe do not exhibit the “premelting effect.” The density of liquid Fe was determined with an uncertainty of 0.4–0.7% in the range of 1818–1998 K with temperature increments of 5 K. The obtained thermal expansion coefficient (α) of liquid Fe was well approximated as either a constant value of α = 2.42(1) × 10–4 K–1 or a linear function of temperature (T); α = 1.37(10) × 10–3 – [6.0(6) × 10–7]T [K–1] up to at least 2000 K.

Elucidating the effect of solid base on the hydrogenation of C5 and C6 sugars over Pt–Sn bimetallic catalyst at room temperature

Conversion of sugars into sugar alcohols at room temperature with exceedingly high yields are achieved over Pt–Sn/γ-Al2O3 catalyst in the presence of calcined hydrotalcite. pH of the reaction mixture significantly affects the conversion and selectivity for sugar alcohols. Selection of a suitable base is the key to achieve optimum yields. Various solid bases in combination with Pt–Sn/γ-Al2O3 catalysts were evaluated for hydrogenation of sugars. Amongst all combinations, the mixture (1:1 wt/wt) of Pt–Sn/γ-Al2O3 and calcined hydrotalcite showed the best results. Hydrotalcite helps to make the pH of reaction mixture alkaline at which sugar molecules undergo ring opening. The sugar molecule in open chain form has carbonyl group which can be polarized by Sn in Pt–Sn/γ-Al2O3 and Pt facilitates the hydrogenation. In the current work, effect of both; solid base and Sn as a promoter has been studied to improve the yields of sugar alcohols from various C5 and C6 sugars at very mild reaction conditions.

Coarsening of solidβ-Sn particles in liquid Pb-Sn alloys: Reinterpretation of experimental data in the framework of trans-interface-diffusion-controlled coarsening

Previously published data, not ours, on the coarsening of solid \ensuremath{\beta}-Sn particles in a liquid Pb-Sn matrix of near-eutectic composition are reanalyzed within the framework of the trans-interface-diffusion-controlled (TIDC) theory of coarsening. The data were obtained under conditions of microgravity from specimens heat-treated at 458 K and containing four equilibrium volume fractions ${f}_{e}$ equaling 0.10, 0.15, 0.20, and 0.30. We show that the rate constants $k({f}_{e})$ in the traditional coarsening equation ${\ensuremath{\langle}r\ensuremath{\rangle}}^{3}\ensuremath{\approx}k({f}_{e})t$ for the kinetics of growth of the average particle radius $\ensuremath{\langle}r\ensuremath{\rangle}$ are nearly independent of ${f}_{e}$, in disagreement with numerous theories wherein coarsening is controlled by diffusion in the host matrix phase. Atom transport in TIDC coarsening is instead controlled by slow diffusion through the diffuse interface, of width \ensuremath{\delta}, separating the dispersed particles from the matrix; the kinetics of this process is independent of ${f}_{e}$. Atomistic simulations were performed to estimate the properties of the solid-liquid (S-L) interface at 458 K, 2 K above the Pb-Sn eutectic temperature. The S-L interfaces normal to (001) and (010) of tetragonal \ensuremath{\beta}-Sn were examined and found to have nearly identical properties, including interface widths of \ensuremath{\sim}1.7 nm. In conjunction with the diffusivities in solid \ensuremath{\beta}-Sn and liquid hypereutectic Pb-Sn at 458 K, we estimate that TIDC coarsening should prevail for solid Sn particles \ensuremath{\sim}1700 \ensuremath{\mu}m in radius, far exceeding the maximum radius of \ensuremath{\sim}100 \ensuremath{\mu}m measured experimentally. The TIDC theory also predicts that the kinetics of growth obeys the equation ${\ensuremath{\langle}r\ensuremath{\rangle}}^{n}\ensuremath{\propto}t$. The temporal exponent $n$ was evaluated to be \ensuremath{\sim}2.5, as ascertained by analyzing data on the particle size distributions (PSDs; histograms) for the alloys with ${f}_{e}=0.15$, 0.20, and 0.30. The histograms were converted to experimental cumulative distribution functions (ECDFs) and analyzed using the Kolmogorov-Smirnov (K-S) test applied to the theoretical CDFs predicted by the TIDC theory. We report the first successful application of the K-S test to experimental PSDs concomitant with particle coarsening. From every aspect of the experimental data amenable to analysis, we conclude that the coarsening behavior of solid Sn particles in liquid hypereutectic Pb-Sn alloys is fully consistent with the predictions of the TIDC theory of coarsening.

Esterification of levulinic acid over Sn(II) exchanged Keggin heteropolyacid salts: An efficient route to obtain bioaditives

Abstract In this paper, we describe a process to add value to the biomass derivatives (i.e., levulinic acid), converting it to bioadditives over solid Sn(II) exchanged Keggin heteropolyacid salts. These solid catalysts are an attractive alternative to the traditional soluble and corrosive Bronsted acid catalysts. Among Sn(II) heteropoly salts, the Sn1.5PW12O40 was the most active and selective catalyst, achieving high conversions (ca. 90 %) and selectivity (90–97 %) for alkyl esters and angelica lactone, the main reaction products. The impacts of the main reaction parameters (i.e., catalyst load, temperature, and the molar ratio of alcohol to acid) were investigated. The use of renewable raw material, and an efficient and recyclable catalyst are the main positive features of this process. The Sn1.5PW12O40 catalyst was easily recovered and reused without loss activity.

Formation of intermetallic compounds in reaction between Cu–Ni alloys and solid Sn – a new look at the prominent effect of Ni

Diffusion-controlled interaction of pure Cu with Sn at 488 K results in the formation of ε-Cu3Sn and η-Cu6Sn5 intermetallic compounds, and small additives of Ni in the Cu-substrate (up to 1 at. %), do not influence phase composition of the diffusion zone. It was found that in the η-phase, Sn diffuses somewhat faster than Cu (and Ni) does, and diffusion porosity is developed in the vicinity of the substrate/reaction product interface.When a Cu–Ni alloy containing (5–25) at. % of Ni is involved in the interaction at 488 K, no ε-phase is formed and no pores can be found in the vicinity of the reaction interface. In these couples, ThO2-particles introduced as fiducial markers at the contact surface, end up after the interaction inside the (Cu,Ni)6Sn5 product layer close to the interface with Sn. The reaction layer growth follows a parabolic kinetics, and the growth rate of the (Cu,Ni)6Sn5 product in the Cu1-xNix/Sn (x = 0.05–0.25) couples is much higher than that of η-phase in binary Cu/Sn and ternary couples with lower Ni-content.TEM investigation revealed that reaction product in the Cu25Ni/Sn couple consists of domains of differently oriented unit cells of long-period superlattice formed in the (Cu,Ni)6Sn5 phase. In each domain, there is a periodic array of antiphase boundaries which provide a high density of short-circuit paths for diffusional transport resulting in the fast growth kinetics of the product intermetallic layer.

Formation of Intermetallic Compounds and Microstructure Evolution due to Isothermal Reactive Diffusion at the Interface Between Solid Co and Liquid Sn

Co has been studied extensively by many research groups as an alternative material for underbump metallization, since Co–Sn compounds show better mechanical properties than Cu–Sn compounds. Information on reactive diffusion at the solid/liquid interface is considerably important to form mechanically and electrically reliable solder joints. In the present study, the kinetics of the reactive diffusion between solid Co and liquid Sn was experimentally examined using semiinfinite Co/Sn diffusion couples prepared by an isothermal bonding technique. Isothermal annealing of the diffusion couple was conducted at temperatures in the range of 523 K to 583 K for various times up to 96 h. An intermetallic layer formed at the original Co/Sn interface in the diffusion couple during annealing. One or two intermetallic compounds among α-CoSn3, β-CoSn3, and CoSn2 were identified, depending on the annealing temperature. The total thickness of the intermetallic layer was proportional to a power function of the annealing time. The overall growth rate of the intermetallic layer did not increase with increasing annealing temperature but was dependent on the kind of compound formed at the interface. The overall growth rate at 583 K was much slower than at lower annealing temperatures, since two compounds (CoSn2 and CoSn3) were identified at the interface, while only CoSn3 formed at 523 K to 563 K. This indicates that the interdiffusion coefficient of CoSn2 is much smaller than that of CoSn3. Based on the exponent of the power function and the microstructure evolution at the moving interface, the layer growth of the compounds was controlled by volume diffusion with spheroidal growth.

Wetting and spreading behavior of Sn–Ti alloys on SiC

The isothermal wetting behavior of Sn–Ti alloys in contact with SiC were studied by the sessile drop method in the 900 °C–1000 °C temperature range, and the interfacial microstructures were characterized. Ti additions led the system to evolve from a non-wetting (θ = 151°) to a wetting state with the formation of interfacial layers (TiC and Ti5Si3). As the Ti concentration increased, more Ti5Si3 phases grew on the TiC layer and lower final contact angles were obtained. The lowest value θ = 20° was obtained at 1000 °C for the Sn-2.0Ti/SiC system. The Sn-5.0Ti melt kept the contact angle of 20° as well, whereas the formation of solid Sn–Ti intermetallics inhibited the kinetics of spreading. Lower temperatures had no influence on the final contact angles, only slowed down the spreading rate. The spreading of Sn–Ti melts on SiC consisted of three stages: (i) reaction-limited stage, (ii) transition stage and (iii) diffusion-limited stage. The activation energy of the first stage was calculated to be 210.3 kJ/mol. These results offer important information to optimize SiC brazing and for the preparing SiC-based composites.

Electrochemical performance and morphological evolution of hollow Sn microspheres

Using shell-like structures in lithium-ion battery (LIB) can limit the structural degradation/damage induced by the volumetric change during electrochemical cycling. In this work, we synthesize hollow Sn microspheres (Sn-HMSs) via a galvanic replacement reaction, and study the electrochemical performance of the lithium-ion cells with Sn-HMSs as the working electrode. The lithium-ion cells have a charge capacity of 205.9 mA h g−1 after 100 cycles at a current density of 100 mA g−1. In comparison with the charge capacities of 148 mA h g−1 of solid Sn nanospheres and 516.1 mA h g−1 of hollow Sn nanospheres, the results reported in this work reveal the importance of shell-like structures in the retention of the energy storage for LIBs and the size effect on the energy storage. The smaller the hollow Sn spheres, the better is the cycle performance. There are two modes of structural degradation/damage contributing to the capacity loss during electrochemical cycling; one is the disintegration of the Sn-HMSs, and the other is the fracturing of the electrode layer.

Tailoring band structure and band filling in a simple cubic (IV, III)-VI superconductor

Superconductivity and its underlying mechanisms are one of the most active research fields in condensed-matter physics. An important question is how to enhance the transition temperature $T_{\rm c}$ of a superconductor. In this respect, the possibly positive role of valence-skipping elements in the pairing mechanism has been attracting considerable interest. Here we follow this pathway and successfully enhance $T_{\rm c}$ up to almost 6 K in the simple chalcogenide SnTe known as topological crystalline insulator by doping the valence-skipping element In and codoping Se. A high-pressure synthesis method enabled us to form single-phase solid solutions Sn$_{1-x}$In$_{x}$Te$_{1-y}$Se$_{y}$ over a wide composition range while keeping the cubic structure necessary for the superconductivity. Our experimental results are supported by density-functional theory calculations which suggest that even higher $T_{\rm c}$ values would be possible if the required doping range were experimentally accessible.