Phase Equilibria in the Ni-Sn-Zn System at 500°C

The isothermal section of the Ni-Sn-Zn ternary system at 500°C was investigated by means of x-ray diffraction (XRD), and scanning electron microscopy with energy-dispersive spectrometry (SEM/EDS). A new ternary compound with a composition of Ni₃₆Sn₄₂Zn₂₂ (in at.%) was discovered in the present study. The space group of this compound is P [`(4)] \overline{\textit{4}} 3m with lattice parameter a = 0.88283(4) nm. Two ternary phases, i.e., τ₁ and τ₂, which are derived from α′-Ni₃Sn₂ and β-NiZn, respectively, were observed to be present at 500°C. The solubility of Sn in Ni₂Zn₁₁ was determined to be about 3.5 at.%, and that of Zn in Ni₃Sn to be about 5 at.%.     

Phase Equilibria of the Sn-Ni-V System at 800°C

Ternary Sn-Ni-V alloys were prepared and annealed at 800°C for 60 days. The annealed alloys were metallographically examined, and the equilibrium phases formed were identified on the basis of compositional determinations and x-ray diffraction analysis. The isothermal section of the ternary Sn-Ni-V system at 800°C was proposed. Two ternary compounds, VNi₂Sn and V₂NiSn, were found in the system. V₂NiSn is nearly a stoichiometry compound, while VNi₂Sn has a wide composition range at 800°C. It spans 24.6 at.% to 49.6 at.% V, 50.6 at.% to 31.2 at.% Ni, and 19.2 at.% to 24.8 at.% Sn. VNi₂Sn (30V-45Ni-25Sn) has a congruent melting temperature of 1095.6°C. Moreover, the maximum solubility of V in Ni₃Sn₂ can reach 10.3 at.%, and that in Ni₃Sn is 1.9 at.%. Up to 4.2 at.% Ni dissolves in V₃Sn.     

The Isothermal Section of the Sn-Sb-Ni Ternary System at 270°C

Phase equilibria of the Sn-Sb-Ni ternary system at 270°C are experimentally determined in this work. Experimental results reveal both the Sn₃Sb₂ and β-SnSb phases, and thus the phase relationship near the Sn-rich corner differs from that in the 250°C isothermal section. Instead of a liquid + Ni₃Sn₄ + β-SnSb three-phase region, liquid + Ni₃Sn₄ + Sn₃Sb₂, Ni₃Sn₄ + Sn₃Sb₂ + τ, and Sn₃Sb₂ + β-SnSb + τ three-phase regions are found near the Sn-rich corner. A ternary phase (τ) is found, with stoichiometry of Ni(Sn_1?x ,Sb _x )₃, x = 0.5 to 0.78. Additionally, the Ni₃Sn₂ and NiSb phases form a continuous solution. The Ni₃Sn and Ni₃Sb phases have different structures, and thus they do not form a continuous phase region. The Ni₃Sb phase has an extended Sn solubility of 14.9 at.%, while the maximum Sb solubility in the Ni₃Sn phase is 3.2 at.%.     

Effects of Minor Amounts of Zn on the Sn-Zn/Ni Interfacial Reactions and Phase Equilibria of the Ternary Sn-Zn-Ni System at 250°C

This study investigated the effects of minor Zn additions (less than 1 wt.%) to pure Sn on the phase formation and microstructural evolution at the interfaces between Ni and Sn-Zn solders. When the Zn content was less than 0.3 wt.%, the reaction product was Ni₃Sn₄, which had no Zn solubility. By contrast, for reactions with more than 0.4 wt.% Zn, one high-Zn-containing phase (about Sn-35 at.%Ni-20 at.%Zn) was formed, which was proven to be a ternary intermetallic compound, the τ-phase. In addition to composition analysis, x-ray diffraction (XRD) analysis revealed that the crystallographic structure of the τ-phase was different from that of Ni₃Sn₄. Furthermore, a partial isothermal section in the Sn-Zn-Ni ternary system (less than 40 at.% Ni) at 250°C was experimentally determined to contain 12 different Sn-Zn-Ni alloys. Three three-phase regions were identified: Ni₃Sn₄ + τ + liquid, Ni₅Zn₂₁ + τ + liquid, and Ni₅Zn₂₁ + Zn + liquid. The equilibrium phase boundaries for liquid separately with Ni₅Zn₂₁, τ, and Ni₃Sn₄ were highly consistent with the Zn concentrations where the phase transitions occurred in the interfacial reactions.     

Experimental Determination and Thermodynamic Modelingof the Sn-Rich Corner of the Ternary Ni-Pd-Sn PhaseDiagram at 250°C

The Sn-rich portion of the phase diagram for the Ni-Pd-Sn ternary system was preliminarily obtained by interpolation of the three constituent binary systems using the Muggianu method. Based on this proposition, 23 Ni-Pd-Sn alloys were prepared and annealed at 250°C. The annealed alloys were analyzed by scanning electron microscopy, electron probe microanalysis, electron backscatter diffraction, and x-ray diffraction. All the binaries adjacent to the Sn-rich corner (i.e., PdSn₄, PdSn₃, PdSn₂, and Ni₃Sn₄) were found to have remarkable ternary solubility. The experimental results presented herein, together with a thermodynamic interpolation of the ternary system based on the results from the binary systems, were used to calculate the ternary phase diagram using the calculation of phase diagrams (CALPHAD) method. A substitution model was used to describe the Gibbs free energies of the liquid and solid solution phases, and a sublattice model was used to describe intermetallic compounds. A consistent set of thermodynamic parameters was obtained, ultimately leading to a better fit between the calculated results and the experimental data for this system.     

High-Dose Phosphorus-Implanted 4H-SiC: Microwave and Conventional Post-Implantation Annealing at Temperatures ≥1700°C

Semi-insulating 4H-SiC ⟨0001⟩ wafers have been phosphorus ion implanted at 500°C to obtain phosphorus box depth profiles with dopant concentration from 5 × 10¹⁹ cm⁻³ to 8 × 10²⁰ cm⁻³. These samples have been annealed by microwave and conventional inductively heated systems in the temperature range 1700°C to 2050°C. Resistivity, Hall electron density, and Hall mobility of the phosphorus-implanted and annealed 4H-SiC layers have been measured in the temperature range from room temperature to 450°C. The high-resolution x-ray diffraction and rocking curve of both virgin and processed 4H-SiC samples have been analyzed to obtain the sample crystal quality up to about 3 μm depth from the wafer surface. For both increasing implanted phosphorus concentration and increasing post-implantation annealing temperature the implanted material resistivity decreases to an asymptotic value of about 1.5 × 10⁻³ Ω cm. Increasing the implanted phosphorus concentration and post-implantation annealing temperature beyond 4 × 10²⁰ cm⁻³ and 2000°C, respectively, does not bring any apparent benefit with respect to the minimum obtainable resistivity. Sheet resistance and sheet electron density increase with increasing measurement temperature. Electron density saturates at 1.5 × 10²⁰ cm⁻³ for implanted phosphorus plateau values ≥4 × 10²⁰ cm⁻³, irrespective of the post-implantation annealing method. Implantation produces an increase of the lattice parameter in the bulk 4H-SiC underneath the phosphorus-implanted layer. Microwave and conventional annealing produce a further increase of the lattice parameter in such a depth region and an equivalent recovered lattice in the phosphorus-implanted layers.     

Vapor-Assisted Surface Activation Method for Homo- and Heterogeneous Bonding of Cu, SiO2, and Polyimide at 150°C and Atmospheric Pressure

Homo- and heterogeneous bonding of Cu, SiO₂, and polyimide, by using a single vapor-assisted surface activation method at 150°C and atmospheric pressure, is highly feasible and will be of practical use in three-dimensional heterointegration of thin, flat interconnection layers. Since it is necessary to achieve good bondability to diverse materials in a single process in order to maintain bumpless structures, we have to create a compatible bridging layer. Bridging layers, based on Cu hydroxide hydrate and silanol and hydroxyl groups formed from SiO₂ and polyimide, respectively, were prepared by introducing water onto the activated surfaces at atmospheric pressure. The growth rate of the bridging layers was tunable via absolute humidity, and exposure of 8 g/m³ was used. Heating at 150°C, after exposure to humidity, caused tight adhesion between the mating surfaces for all combinations of starting materials with voidless amorphous interfacial (bridging) layers. Because of the well-controlled layer thickness, low electrical resistivity of ～4 × 10^?8 Ω m was obtained at the Cu–Cu interface.     

Study of the Effects of Zn Content on the Interfacial Reactions Between Sn-Zn Solders and Ni Substrates at 250°C

The interfacial reactions of Ni with Sn-Zn alloys with 1 wt.% to 9 wt.% Zn at 250°C were examined. The Zn content greatly affected the intermetallic compounds formed and microstructural evolution. A continuous Ni₅Zn₂₁ layer was formed for the Sn-Zn/Ni couples with a Zn content higher than 5 wt.%. A stable reaction layer existed at the interface and grew thicker with time. When decreasing to 3 wt.% Zn, two thin reaction layers of Ni₅Zn₂₁ and (Ni,Zn)₃Sn₄ were simultaneously observed initially, and then an extremely large faceted Ni₅Zn₂₁ phase was formed near the boundary between the Ni₅Zn₂₁ layer and the solder. Furthermore, when the Zn content was lower than 2 wt.%, the dominant phase changed to (Ni,Zn)₃Sn₄. The Zn concentration of the solder gradually decreased with reaction, and thus the interfacial stability was reduced. Subsequently, a large amount of (Ni,Zn)₃Sn₄ grains were dispersed into the molten solder, and finally the reaction product at the interface changed to Ni₃Sn₄.     

ZTE ADSL:Victory in Athens,Chinese Telecom Equipment Wins at the Olympics

While Chinese athletes were fiercely competing at the 2004Olympics, capturing a magnificent 32 gold medals for China,the ADSL broadband system constructed by ZTE Corporationfor this great event was extremely successful, providing ath-letes, referees, journalists and spectators from all over theworld with quality broadband services in 16 venues and newscenters.     

Formation of electrically active centers in silicon irradiated with electrons and then annealed at temperatures of 400–700°C

The effect of irradiation with electrons on the formation of quenched-in donors in silicon is studied. It is found that n-and p-type regions are formed in the bulk of single-crystal silicon as a result of irradiation with electrons and subsequent annealing at a temperature of 450°C. The concentration of charge carriers in the regions of both types increases as the radiation dose and the annealing duration increase, which indicates that not only quenched-in donors but also quenched-in acceptors are formed. Nonuniformity in the distribution of the acceptor and donor centers correlates with fluctuations of the oxygen concentration in silicon.     

Dielectric Spectroscopy and Mechanism of the Semiconductor–Metal Phase Transition in Doped VO2:Ge and VO2:Mg Films

Semiconductors - The frequency dependences of the dissipation factor tanδ(f) and the Cole–Cole diagrams for germanium- and magnesium-doped vanadium-dioxide films in the range of...     

Electrical characterization and reliability of submicron SOI CMOS technology in the extended temperature range (to 300 °C)

I-V characteristics and reliability parameters for the set of hardened SOI MOSFET's with special layouts and tungsten metallization to provide additional thermal tolerance for high-temperature SOI CMOS IC's are investigated in the temperature range up to 300 °C. The reliability aspects under test for MOSFET's are threshold voltage shift, subthreshold slope and mobility degradation, gate leakage current rise; for tungsten metallization (contacts, conductor lines and vias) I-T and R-T characteristics, failure time. The SOI MOSFET standard compact SPICE model BSIMSOI with traditional temperature limit of 150 °C is modified to be used for CMOS IC simulation in the extended temperature range up to 300 °C. The results indicate that the 0.5–0.18 μm SOI MOSFET's with tungsten metallization have stable electrical behavior that makes them possible to be used during implementation of HT CMOS IC's (to 300 °C).     

Gibbs random fields on a lattice: Definitions,existence, uniqueness,and phase transitions (a review of proceedings of the seminar on statistical physics at the faculty of mechanics and mathematics of the Moscow state university in 1962–1994)

The Moscow Grand Seminar on Statistical Physics is one of the first seminars in the world devoted to rigorous methods in statistical physics. The achievements of the seminar can be appreciated in full measure from publications by the leaders of the seminar (R.L. Dobrushin, V.A. Malyshev, R.A. Minlos, Ya.G. Sinai). This paper presents a review (far from complete) of the proceedings of the seminar. The emphasis is made on the fundamental definitions and most important results.     

Light emitting diodes for the spectral range λ=3.3–4.3 µm fabricated from InGaAs and InAsSbP solid solutions: Electroluminescence in the temperature range of 20–180°C (Part 2)

Light-emitting diodes (LEDs) based on p-n homo-and heterostructures with InAsSb(P) and InGaAs active layers have been designed and studied. An emission power of 0.2 (λ=4.3 µm) to 1.33 mW (λ=3.3 µm) and a conversion efficiency of 30 (InAsSbP, λ=4.3 µm) to 340 mW/(A cm²) (InAsSb/InAsSbP double heterostructure (DH), λ=4.0 µm) have been achieved. The conversion efficiency decreases with increasing current, mainly owing to the Joule heating of the p-n homojunctions. In DH LEDs, the fact that the output power tends to a constant value with increasing current is not associated with active region heating. On raising the temperature from 20 to 180°C, the emission power of the (λ=3.3 and 4.3 µm) LEDs decreases, respectively, 7-and 14-fold, to become 50 (at 1.5 A) and 7 µW (at 3 A) at 180°C.     

Electroluminescence at a wavelength of 1.5 μm in Si:Er/Si diode structures doped with Al,Ga, and B acceptors

Si:Er layers in diode structures were doped with Al, Ga, or B during growth by sublimation molecular-beam epitaxy. As a result, a sharp increase in the electroluminescence intensity at a wavelength of 1.5 μm was observed in diodes with thick bases (as large as 0.8 μm).     

Band Structure and Processes in the Electronic System of (Bi2 – xSbx)Te3 (0 < x < 2) Crystals,According to Optical Studies in the Infrared Range

Semiconductors - A decrease in the resonance frequency of plasma oscillations of free carriers ωp, observed in p-type Bi2 – xSbx (0 &lt; x &lt; 2) crystals with increasing...     

Light emitting diodes for the spectral range of λ=3.3–4.3 μm fabricated from the InGaAs-and InAsSbP-based solid solutions: Electroluminescence in the temperature range of 20–180°C

Light emitting diodes (LEDs) with λ_max=3.4 and 4.3 µm (t=20°C) were studied at elevated temperatures. It is demonstrated that LEDs operating in the temperature range t=20–180°C can be described using the classical concepts of injection radiation sources and the processes of charge carrier recombination. The temperature dependences of reverse currents in the saturation regions of current-voltage characteristics are consistent with the increase in the intrinsic-carrier concentration according to the Shockley theory. The emission spectra are described on the assumption of the direct band-to-band transitions, spherically symmetric bands, and thermalized charge carriers. The current-power characteristics are proportional to I ^3/2 suggesting that the contribution of the nonradiative Auger recombination is dominant. The radiation power decreases exponentially with the temperature which is characteristic of the CHSH and CHCC processes.