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We realized the room temperature direct bonding method for polyethylene 2, 6 naphthalene dicarboxylate (polyethylene naphthalate, PEN) film by means of surface activated bonding method using nano-adhesion layer.

The influence of diffusion on bonding micro-bumps at low temperatures in solid state was studied. The contamination was detected to act as a barrier layer on diffusion during bonding. The diffusion between Au and Sn occurred even at low temperatures by performing surface activation process before bonding and was effective on improving the bonding quality. The increase of bonding strengths of Au-to-Au micro-bumps were slow followed with bonding time, which appeared a logarithmic rate law. 100% bond yield was achieved and the die shear strength was higher than 10 MPa at low temperatures by performing surface activation process before bonding.

A Monte-Carlo computer code for the simulation of particle transport in metallic solids has been developed. Electrons or bare ion projectiles can be used. The code is able to calculate a wide variety of phenomena such as electronic energy loss, electronic energy loss straggling, particle-induced yield of emitted electrons or the statistical distribution of the number of emitted electrons per incident projectile. The theoretical models used in the simulation partially follow the basic work of Ganachaud and Cailler. However, for the loosely bound outer electrons of copper, the classical model of core ionization as it has been used by previous authors breaks down. Therefore, a fully quantum- mechanical description has been used in this work. For aluminum and copper the simulation results are compared with experimental and theoretical data. Excellent agreement is found.

Clusters of lithium atoms ranging in size from Li4 to Li40 and bulk metallic solids, including surfaces, are investigated through first principles electronic structure calculations, which are based upon density functional theory and the electron localization function (ELF). It is found that large lithium ppi-type contributions in the electronic wavefunction cause the electrons to localize in interstitial regions, which leads to multicenter bonding for both the clusters and the solids, including their surfaces. For the smaller clusters these stabilizing ppi interactions also lead to short Li-Li interatomic distances, which in conjunction with the longer bonds induces "distance alternation" in the range from 2.45 A to 3.15 A. This consequence of the additional ppi interactions is absent in simple solids due to symmetry. The electronic structure of the clusters is topologically insensitive to deformations that do not affect their general shape, but changes significantly upon isomerization. The ramifications upon dynamic properties is that the clusters are quasi-rigid at low temperatures and retain their shape though the distance alternation pattern is suppressed. The picture which emerges for bonding in the bulk solid is that the metallic state arises from the presence of a large number of partially occupied multicenter bonds. For nanoscale clusters only the surface of these clusters exhibits strong localization, whereas their interiors display localization properties similar to the bulk metallic solid. On the other hand, localized states similar to those of the clusters ("dangling bonds") are found on the (001) surface of body-centered cubic (bcc) and face-centered cubic (fcc) lithium solids.

Ab initio calculations based on the density-functional pseudopotential approach have been used to study the electronic structure and chemical bonding in layered machinable Ti3SiC2 ceramic. The calculations reveal that all three types of bonding-metallic, covalent and ionic-contribute to the bonding in Ti3SiC2 The high electric conductivity is attributed to the metallic bonding parallel to the basal plane and the high modulus and high melting point are attributed to the strong Ti-C-Ti-C-Ti covalent bond chains in the structure.

The solid-state structures of a l-(φ-ammoniopropyl)-2-(2-thienylcarbonyl)-cyclopentadienide (2) and a l-(φ-ammoniopentyl)-2-(4-methoxybenzoyl)-cyclopentadienide (3) have been determined. Both betaines self-assemble by NH ··· O hydrogen bonds, but the motifs are different. In the ammoniopropyl case, both intramolecular and intermolecular hydrogen bonds of this type exist, the latter bond being responsible for the formation of infinite chains. In the ammoniopentyl case, intermolecular hydrogen bonds build up a two-dimensional network which contains centrosymmetric dimers held together by NH ··· O=C-aryl hydrogen bonds.

Studies on SiO 2 –SiO 2 bonding with hydrofluoric acid (HF) are described. This method has a remarkable feature that bonding can be obtained at room temperature. Advantages of this method are low thermal damage, low residual stress and simplicity of the bonding process, which are expected for the packaging and assembly of micro-electro-mechanical systems (MEMS). The bond characteristics were measured under different bonding conditions of HF concentration, applied pressure, another chemicals for bonding and so on. The bond strength depends on the applied pressure during bonding. To achieve reliable bonding, HF concentration of higher than 0.5 wt.% and a large applied pressure of 1.3 MPa are required. The bonding is also observed using KOH solution in stead of HF. Transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS), radioactive isotope (RI) analysis and electron probe micro analysis (EPMA) were applied to evaluate the bonded interface. The results of these analysis indicated that an interlayer of a silicon oxide complex including hydrogen and fluorine atoms is formed between bonded SiO 2 to SiO 2 . The thickness of the interlayer depends strongly on the applied pressure during bonding. Large bond strength is obtained when the interlayer is thin. The bonding mechanism is expected when the SiO 2 at both surfaces is dissolved in HF solution, and that the interlayer, which is a binding layer, is formed between substrates by resolidification of dissolved silicon dioxide. Formation of the interlayer plays very important roles for the characteristics of HF-bonding.

Graphite was bonded to nickel under joining compressive stress of 3 to 33 MPa in a vacuum at temperatures within the range of 973 to 1273 K using an RF-induction furnace. The influence of joining conditions on the bending strength of the graphite/nickel joint, and changes in the microstructure and hardness of nickel near the joining interface, were investigated. Thermal stress induced in the joint was estimated using the finite element method. On the basis of these results, the influence of thermal stress on the bending strength of the joint was examined Completion of the graphite/nickel joint depends on both joining compressive stress and joining temperature. At high joining temperature, good solid-state bonding under relatively low joining compressive stress becomes feasible. Axisymmetric thermoelastic finite element analysis suggests that the maximum tensile thermal stress is induced at a distance of 0.64 mm from the joining interface on the surface of graphite anal is increased with increasing joining temperature. The position of fracture in a bending test corresponds approximately to that of the maximum tensile thermal stress. Part of the thermal stress in practical joints is relaxed and less than that calculated using the finite element method. The bending strength of the joint increases with decreasing residual tensile stress on the surface of graphite. Relaxation of the maximum tensile thermal stress depends on the amount of carbon which diffuse into nickel. This may be related to changes in plasticity of both nickel and graphite, that is, changes in the amount of carbon that dissolves in nickel to supersaturation and the point defects introduced in graphite.

Bonding between silver and ceramics like Al2O3, ZrO2, MgO, AlN, sapphire or quartz glass is obtained by a “liquid phase bonding process” based on the pseudo-binary eutectic between Ag and CuO (at 1 mol %). It melts 15 K below the melting point of pure Ag in air. Excellent wetting between the eutectic liquid and the ceramic surfaces gives mechanically strong, reliable bonds. The bonding mechanism is similar to the well known direct copper bonding (DCB)-process. Our new process is simple and works at 1219±2 K in plain air. It therefore has the potential of massive cost reductions compared to the more complicated DCB-process.

Gorsky effect involvements in regard to the diffusion of hydrogen in metallic solids has meant that, in addition to operations of concentration gradients, expansion effects of interstitials themselves can promote a reverse direction diffusion flux component. In cases where concentrations of Hydrogen interstitials have already been present in diffusion membranes, such strain gradients can produce experimentally observable overall long range uphill effects. Specific quantitative evidence of this behaviour has been recorded in the case of hydrogen diffusion in Palladium, Palladium⧸Platinum and Palladium⧸Silver, and has been shown to influence calculations of hydrogen diffusion coefficients 1 , 2 . There now also seem strong possibilities that such strain gradient production can have important influences in phase transition and other solid state processes.

The calculation of temperature fields that develop in rubbing metallic pairs is customary performed under the assumption of a steady state and; that heat is released at the interface of the rubbing pair. These assumptions have several drawbacks as they neglect the role of the subsurface structural deformations which gives rise to internal heat generation. This paper introduces a solution for the transient temperature fields developed within two rubbing metallic solids with internal heat generation that varies exponentially with the distance from the nominal contact surface. The results indicate that in contrast to the customary models, the maximum temperature appears at some distance in the subsurface region. A result that is supported by the experimental observations of different authors.

Hydrogen reaches the mimimum electrical conductivity of a metal at 140 GPa (1.4Mbar), 0.6g cm−3 (ninefold compression of initial liquid-H2 density) and 3000 K in the fluid phase. The quest for metallic hydrogen over the past 100 years is reviewed briefly. Possible scientific and technological uses of metastable solid metallic hydrogen (MSMH) are speculated upon in the unlikely event that the metallic fluid can be quenched to MSMH at ambient pressure and temperature: a quantum, mostly diatomic, metallic solid with novel physical properties, including room-temperature superconductivity; a very light-weight structural material; a fuel, propellant, or explosive, depending on the rate of release of stored energy; a dense fuel for higher energy yields in inertial confinement fusion; and an aid in the synthesis of novel hard materials. Some of the formidable difficulties to synthesize MSMH are discussed.

A great number ofin situ observations proved that at normal temperature and pressure there exists a nonlinear oscillation phenomenon in the solid alloys. This kind of oscillation phenomenon exhibits fluid-like character in localized areas, fluctuating with crystal rotation, cell’s moving, expansion and contraction.

Graphite was bonded to SUS304 steel under a compressive stress of 25 MPa in a vacuum over a temperature range from 873 to 1023 K using a RF-induction furnace. The bending strength of the graphite/SUS304 steel joint, and changes of microstructure and hardness near the joining interface of SUS304 steel, were investigated. Thermal stress induced in the joint was estimated with a finite element method. On the basis of these results the influence of thermal stress on the bending strength of the joint was examined. Good solid state bonding becomes feasible when the joining temperature exceeds 923 K. Axisymmetric thermoelastic finite element analysis suggests that maximum tensile thermal stress is induced at a distance of 0.64 mm from the joining interface on the surface of the graphite and is increased with increasing joining temperature. The position of fracture in a bending test specimen corresponds approximately to that of the maximum tensile thermal stress. A part of the thermal stress is released with the deformation of SUS304 steel and graphite. The bending strength of the joint increases with decreasing residual tensile stress on the surface of graphite. Relaxation of thermal stress depends on the amount of carbon atoms which diffuse into SUS304 steel. This may be related to the changes in plasticity of SUS304 steel and graphite, that is, the changes in the amounts of Cr 23 C 6 precipitated in SUS304 steel and point defect introduced in graphite.

We have investigated low-temperature bonding of Si and SiO 2 by the surface activation method in vacuum. In the method, Ar beam etching is used to create a clean surface which has strong bonding ability. The specimens are bonded in the vacuum without exposing them to the atmosphere. The strength of Si/Si bonding prepared at room temperature by the method is equivalent to the bulk strength. SiO 2 /SiO 2 bonding by the method is twice as strong as conventional bonding before annealing. In addition, the bonding prepared by Ar beam is stronger than that prepared by reactive molecule beam etching such as H 2 O and NH 3 . The influence of surface oxidation was examined by exposing an etched Si surface to residual gas in the vacuum chamber. Adsorption of reactive molecules such as H 2 O on the etched surface causes reduction of bonding strength, whereas Ar gas does not affect the bonding. These results mean that a clean surface etched by Ar beam has strong bonding ability even at room temperature.

The polariton modes of spheroidal microcrystals of dispersive materials are investigated over a wide range of spheroid sizes and eccentricities by using the T-matrix method. The method is applied to phonon-polaritons in ionic dielectric solids and to plasmon-polaritons in metallic solids. The main effects of retardation, observed when the particle size increases, are: the surface polariton peaks broaden and shift to lower frequencies; subsidiary peaks owing to higher-order surface modes appear in the spectrum. The method is applied to the interpretation of three sets of previously published experimental optical data for Ag spheroids.

The results of tests of quasi-static and dynamic finite thermoelastoplastic plane shear is discussed. Use is made of a new shear device in which loading and displacements are controlled in compression. Using the thermovision technique the temperature changes of the sheared paths have been registered for various shear rates. The rate-independent constitutive relations are formulated for elastic-plastic metallic solids at finite strain. The constitutive relations are considered for an adiabatic process with combined isotropic-kinematic hardening. The analogous initial-boundary-value problem as in the experiment of simple shear is formulated for finite deformations. An exceptional homogeneity of the permanent strain and temperature fields is observed in experiments and numerical simulations, over the total length of the specimens, when the strain is less than 70%. For the largest deformations the zones of strain localization are observed

Graphite was bonded to S45C steel by using a RF-induction furnace, and bending strength, microstructure and concentration profile of carbon of graphite/S45C steel joint were investigated. Thermal stress induced in the joint was estimated by an X-ray stress analysis and a finite element method. On the basis of these results the influence of thermal stress on the bending strength of the joint was examined in connection with the diffusion of carbon atoms. Austenite phase contributes greatly to solid-state bonding of the graphite/steel system. Therefore good diffusion bonding becomes feasible when joining temperature exceeds eutectoid transformation temperature A 1 . Axisymmetrix thermoelastic finite element analysis suggests that the increase in carbon concentration near the joining interface of S45C steel has no influence on the maximum tensile stress induced on the surface of graphite. Bending strength of the joint increases with decreasing residual thermal stress on the surface of graphite. Relaxation of thermal stress is increased to a maximum when the amounts of carbon atoms that diffuse into S45C steel reach an optimum value. Point defects introduced in graphite during annealing seem to be pertinent to thermal stress relief.

A low temperature bonding process was developed for the fabrication of microchip devices for liquid and heterogeneous phase chemical analysis. Photolithographically etched microchannels on glass substrates were closed by bonding a glass cover plate using a spin-on sodium silicate layer as an adhesive. Good channel sealing was achieved by curing at 90°C for 1 h or room temperature overnight. The fluidic performance of the device was evaluated by monitoring the electroosmotic flow on the chip. The results compared well with those obtained from devices made by high temperature direct bonding of the substrate and cover plate. The dielectric and mechanical strength for bonds, created using the low and high temperature methods, were compared. A dielectric strength of 400 kV cm−1 was obtained for the sodium silicate bonding and 1100 kV cm−1 for the high temperature bonding. Mechanical strength measurements gave a surface energy value of ≈2.7 J m−2 for sodium silicate bonding, compared to 6.5 J m−2 for direct bonding. The mechanical strength of glass bonds obtained with sodium silicate at low temperature was comparable to that reported for the sodium silicate bonding of silicon wafers at >200°C or by conventional direct bonding of oxidized silicon at 1400°C. The low temperature bonding performance is adequate for microfabricated fluidic devices that employ electrokinetic transport phenomena. The reduced temperature of the bonding process will allow chemical surface modification prior to bonding.

We present an expression for the partition of friction-induced heat between two rubbing members. The expression stems from a variable conductivity solution of the heat equation and incorporates the influence of the thermal capacity of the sliding pair on heat distribution. The current formulation yields matching predictions to those of constant conductivity expressions in the case of sliding materials with similar properties.

In an attempt to understand the hysteresis phenomena better, tests were made on a series of VxNb1 − x (x = 0.1, 0.2, 0.3), (Nb1 − xFex)1 − yCry (x, y = 0.15, 0.14 and 0.20, 0.08) and (Nb1 − xFex)1 − xCrx (x = 0.05, 0.07) solid solution alloys and Zr(FexCr1 − x)2 (x = 0.55, 0.75) intermetallic compounds. A pronounced hysteresis was observed for all the alloys used. It was seen that, as the temperature increases the hysteresis effect as measured by the ratio ( P f P d ), where Pf is the plateau pressure for hydride formation and Pd is the plateau pressure for hydride decomposition, decreases. The hysteresis effect was also affected by the number of hydriding/dehydriding cycles. The hysteresis becomes smaller as the number of cycles increases. The hysteresis effect in the solid solution alloys can be explained in terms of the elastic strain energy. The change in hysteresis in the intermetallic compounds upon cycling is explained in terms of attrition (i.e. decreasing particle size) of the Zr(FexCr1 − x)2.

An amorphous alloy is defined as a solid with the lack of a long-range atomic order. The failure of the Bloch theorem is immediately deduced from this definition and can explain the possession of high electrical resistivities in amorphous alloys. However, studies of the local atomic structure of amorphous alloys have been extensively carried out since early 1980's and have led to the conclusion that certain short range order always develops in amorphous alloys. As its natural consequence, attention has been directed to its effect on various physical properties in the last decade. The discovery of quasicrystals in 1984 has certainly stimulated the research along this line, since quasicrystals are characterized by the absence of the translational symmetry but with the well-developed atomic order. In the present article, we demonstrate clearly how the short-range atomic structure affects the electron transport properties by analyzing the data associated with the metal-insulator transition for amorphous V-Si alloys. A unified picture for the electron transport mechanism for metallic solids, which include amorphous alloys, quasicrystals, approximants and crystals, is proposed.

X-ray crystallographic and computational studies are reported for a series of boranthrenes, substituted with halogen atoms. The role of competitive hydrogen (O—H...O, O—H...F, C—H...O) and halogen (Cl...Cl, O...Br, F...F) bonding interactions on the molecular arrangement in the crystal structures is discussed. The structural analysis and calculations reveal that the O—H...O hydrogen bond in the unsubstituted derivative 5,10-dihydroxy-5,10-dihydroboranthrene, C12H10B2O2, is of moderate strength (ca−20 kJ mol−1), but weaker than that in the related thiophene derivative 4,8-dihydro-4,8-dihydroxy-p-diborino[2,3-b:5,6-b]dithiophene, C8H6B2O2S2(ca−40 kJ mol−1). This is due to shielding of the OH group by the H atoms in the β-position of the boranthrene unit. Structural diversity derived from the flexibility of the O—H...O hydrogen bond facilitates the occurrence of other competitive interactions. For instance, in the 1,6-difluoro derivative, C12H8B2F2O2, the crystal packing results from O—H...F and F...F interactions. In turn, the 1,6-dibromo derivative, C12H8B2Br2O2, is dominated by Br...O halogen-bond interactions. In the most interesting case, the 1,6-dichloro derivative, C12H8B2Cl2O2, molecular disorder leads to the formation of two different supramolecular arrangements co-existing in the crystal lattice, one based on the Cl...Cl and C—H...O bonds, and the other stabilized by O—H...O hydrogen bonds. Calculations performed with density-functional theory (DFT;CRYSTAL09) andPIXELmethodologies show that both lattices are characterized by similar energy values (ca−100 kJ mol−1). A mixed arrangement with random or short-range-ordered molecular orientations can also be expected.

We present a simple revision of the VV10 nonlocal density functional by Vydrov and Van Voorhis [J. Chem. Phys. 133, 244103 (2010)] for dispersion interactions. Unlike the original functional our modification allows nonlocal correlation energy and its derivatives to be efficiently evaluated in a plane wave framework along the lines pioneered by Roman-Perez and Soler [Phys. Rev. Lett. 103, 096102 (2009)]. Our revised functional maintains the outstanding precision of the original VV10 in noncovalently bound complexes and performs well in representative covalent, ionic, and metallic solids. DOI: 10.1103/PhysRevB.87.041108

Complex Metallic Alloys (CMAs) are metallic solids of high structural complexity, consisting of large numbers of atoms in their unit cells. Consequences of this structural complexity are manifold and give rise to a variety of exciting physical properties. The impact that such structural complexity may have on the lattice dynamics will be discussed. The surprising dynamical flexibility of Tsai-type clusters with the symmetry breaking central tetrahedron will be addressed for Zn6Sc, while in the Ba-Ge-Ni clathrate system the dynamics of encaged Ba guest atoms in the surrounding Ge-Ni host framework is analysed with respect to the experimentally evidenced strong reduction of lattice thermal conductivity. For both systems experimental results from neutron scattering are analyzed and interpreted on atomistic scale by means of ab initio and molecular dynamics simulations, resulting in a picture with the respective structural building blocks as the origin of the peculiarities in the dynamics.

The canonical hole set for non-metallic solids has been defined in order to provide a more specific and quantitative description of the interstitial structure of non-crystalline solids. Although a broad set of construction criteria would allow an indefinitely large number of polyhedra, considering regular-faced convex polyhedra, prisms, and antiprisms, the canonical hole set for non-metallic solids is a total of 126 polyhedra. As expected, this number is substantially larger than the total of eight Bernal holes for metallic solids. An even more compact set for non-metals (28 convex polyhedra and 16 prisms and antiprisms) is possible by considering only ‘simple’ polyhedra which can not be further dissected. A simple application of this approach is the description of cristobalite, a crystalline analog for vitreous silica, in which the interstices are relatively undistorted truncated tetrahedra. A substantially more complex application is the description of wollastonite, a crystalline analog for CaSiO3 glass, in which the interstices are relatively distorted tetrahedra, square pyramids, and triangular prisms.

A new non-equilibrium state of metal materials induced by irradiation has been found in preceding studies of the authors by the method of X-ray investigation. Now the morphology peculiarities accompanying this transition are described. There are three stages and three groups of microstructures depending on irradiation parameters. These are essentially different whether the microstructure corresponds to a state within a specific interval of the transition or out of this interval. There are some signs of microstructures observed which are similar to the structural elements in heavily deformed metals, in particular, the rotation mode and the appearance of hydrodynamical flow.

The importance of local structure to the physical properties of alloys is receiving increasing attention. Recent measurements of the short-range nanoscale structure in metallic solid solution alloys reveal both the local chemical order and the chemically sensitive near-neighbor distances. These measurements are made possible by intense and tunable synchrotron X radiation; X-ray energy is adjusted to vary the x-ray scattering contrast between atoms in the solid solution. We discuss the local structures in NilFe binary alloys and compare the observed structures to trends calculatedfrom first principles cluster models that identify the role of the local bonding. The small cluster models are found to exhibit trends in agreement with measured Ni-Fe, Ni-Ni and Fe-Fe near neighbor distances. From the cluster models we infer the mechanisms responsible for the observed average lattice and pair correlation lengths in NiFe alloys.

An oxide-free, covalently bonded interface of InP/silicon wafer pairs has been realized at low temperature by B2H6 plasma treatment of bonding surfaces in the reactive ion etch mode followed by a HF dip and room temperature bonding in air. The bonding energy reaches InP fracture surface energy of 630 mJ/m2 at 200 °C. A total B-doped amorphous layer of about 15 A with peak concentration of ∼2×1020 cm−3 was detected at the bonding interface. The release of hydrogen at low temperature from B–H complexes and subsequent absorption of the atomic hydrogen by the amorphous layer at the bonding interface is most likely responsible for the enhanced bonding energy.

We have performed cluster calculations in a study of the bonding nature in the CeO2 crystal using the relativistic discrete-variational Xα method. The electron charge distribution of CeO2 is compared with those of ZrO2 and CaF2. The charge density in the metal atomic region indicates stronger covalency for CeO2 than that in Zr for ZrO2. The repulsion between the metal and oxygen ionic cores is, however, strong and superior to the covalent interaction, and thus the ionic character determines the static bonding nature in the CeO2 crystal. A population analysis shows that the mixed interaction due to the independent ionic and covalent contributions arises from the ionic Ce 5s, 5p and covalent Ce 4f, 5d orbitals which are proximate to each other in the bond region.

GdTe is a fee antiferromagnetic metal. By substituting Gd3+ by non-magnetic divalent or trivalent rare-earth ions we generate magnetically diluted solid solutions in which the free-carrier concentration (n) and/or the lattice parameter depend on the substitution rate. In this paper, we report on the magnetic properties of the metallic La1−xGdxTe solid solution where n does not depend significantly on x. The evolution of the Neel temperature with x is discussed and compared with the evolution observed in the Yb1−xGdxTe system, where the free-carrier concentration varies with composition. In (La1−zYz)1−xGdxTe, we are able to control independently the free-carrier concentration and the lattice parameter. The comparison of the Neel temperature for these three solid solutions at the same Gd concentration gives evidence that the decrease of the Neel temperature vs. x in both La-based solid solutions is a pure spin-dilution effect. The fact than TN is smaller in metallic solid solutions than in Yb1−xGdxTe is due to a shift in the wavevector (≈kF) of the oscillations in the Ruderman-Kittel-Kasuya-Yoshida interaction.

A new type of electron self-trapping is described, which can occur even if the bare single-electron energy level is independent of the surrounding local atomic configuration coordinates. Such a self-trapping can be realized in soft local structures in non-metallic solids, e.g., semiconductors. Hybridization of states in the interband gap is decisive for the self-trapping, providing actually the related coupling between an electron (hole) and a localized soft motion mode in the surrounding atomic configuration. In this sense, unlike the well-known polaronic self-trapping, the self-trapping under discussion is entirely of quantum mechanical origin.

A novel processing approach and experimental design to achieve as‐cast bulk amorphous materials are investigated. By sudden decompression of a melt that is seeded with a volatile liquid, the dispersed ‘‘foaming’’ liquid vaporizes, taking its latent heat of vaporization from the melt, thereby homogeneously cooling the melt. Due to a high decompression rate, a sufficient cooling rate may be produced to yield an amorphous solid foam. The resulting ‘‘foam glass’’ is expected to be an open solid bulk structure that may possess glass properties and low density. These foam glass materials should be free of structural defects, and may have many potential applications. The ultimate goal for this form glass processing is to produce bulk amorphous metallic solids. This approach differs from other processes used in the production of metals with a porous structure. A description of the approach, the processing design and techniques, as well as some evaluation of foam processing with the organic p‐terphenyl as a sample...

We report a photoemission study of Cs on hydrogenated amorphous silicon (a-Si: H) at room temperature. The alkali adsorbate bonds covalently with the amorphous substrate, but remains neutral at all time. The Cs a- Si covalent bonding is strong, in contrast to the crystalline counterpart where the bonding is weak, and highly polarized. Surface disordering facilities in this strong covalent bonding further lessens the adsorbate-adsorbate interaction, resulting in the absence of Fermi emission.

The effects of preparation of silicon surfaces in hydrofluoric acid solutions, prior to direct wafer bonding, is investigated. Surface analysis with atomic force microscopy, electron spectroscopy for chemical analysis, and estimation of the surface particle density is made. This is related to results from room temperature bonding experiments. A diluted (1–10%) solution is most favorable for hydrophobic silicon wafer bonding. The subsequent water rinse should be omitted, or performed in a careful way, to avoid particle contamination. solutions generally are not favorable for bonding. The initial room temperature bonding is attributed to the relatively weak van der Waals forces, which makes the bonding sensitive to the surface roughness and particle density. The surface chemistry appears to have a second order influence in hydrophobic bonding.

The Embedded Atom Method (EAM) was combined with the quasiharmonic approximation to determine the enthalpies and the free energies of mixing for a number of binary f.c.c. and b.c.c. metallic solid solutions. In each case, the EAM potential functions were determined using only the data for the constituent elements. It was found that when two f.c.c. elements are mixed to form an f.c.c. solid solution, the combination of the EAM and the quasiharmonic methods gives a fairly good assessment of the thermodynamic properties of the solid solution. On the other hand, when an f.c.c metal and an b.c.c. metal are combined to produce either an f.c.c. or an b.c.c solid solution, the same approach fails to predict correctly the enthalpies and the free energies of the mixing. However, at least over a composition range reasonably good predictions can still be obtained for the relative thermodynamic stability of the f.c.c. and the b.c.c. structures which is of interest in the analysis of diffusionless phase transformations, such as the martensitic transformation.

Atomic processes induced by electronic excitation in the bulk and on surfaces of insulators are surveyed, emphasizing the difference in the atomic processes induced in different types of solids. The phenomena treated involve local lattice modification in the bulk and atomic emission from the surfaces. First the relaxation of holes and excitons in halides and oxides are compared and the way how the self-trapping of excitons leads to formation of defects is discussed. It is argued also that the self-trapping of holes and excitons is favorable in amorphous materials and the difference in the behaviors of holes and excitons in crystalline and amorphous SiO2 is discussed. The relaxation of excitons on surfaces of ionic crystals and consequent atomic emission processes are argued. The relaxation of densely generated excitons and electron-hole pairs in the bulk is also discussed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A new method of preparation of bulk amorphous solids is successfully applied to the semiconductor solid solutions Ge1−x (GaSb) x .The method consists in the solid-state disordering of a high-pressure phase on decompression. Large mutual solubility can be achieved for high-pressure phases of Ge and GaSb. Amorphization of metallic solid solutions occurs on decompression even at room temperature. Some data concerning the structure and stability of the amorphous semiconducting solid solutions a-Ge1−x (GaSb) x are presented.

The bonding of metal electrodes and insulator hybrid interfaces is one of the key techniques in three-dimensional integration technology. Metal materials such as Cu or Al are easily directly bonded by surface activated bonding at room temperature, but insulator materials such as SiO2 or SiN are not. Using only Si ultrathin films, we propose a new bonding technique for SiO2/SiO2 bonding at room temperature. Two SiO2 surfaces, on which Si thin films were deposited, were contacted in vacuum. We confirmed that the thickness of the layer was about 7 nm by transmission electron microscopy observation and that the layer was non crystalline by electron energy loss spectroscopy analysis. No metal material was found in the bonding interface by energy-dispersive X-ray spectroscopy analysis. The surface energy was about 1 J/m2, and the bonding strength was more than 25 MPa. This bonding technique was successfully realized to enable SiO2/SiO2 bonding without a metal adhesion layer.

By introducing a nanometer-scale H trapping defective silicon layer on bonding surfaces, the bonding surface energy of bonded oxide-free, HF dipped, hydrophobic silicon wafers can reach a silicon fracture surface energy of 2500 mJ/m2 at 300 to 400 °C compared with 700 °C conventionally achieved. Adding boron atoms on bonding surfaces can reduce the surface hydrogen release temperature but would not increase the bonding energy unless a defective layer is also formed. This indicates that, in order to achieve high bonding energy, the released hydrogen must be removed from the bonding interface. Many prebonding treatments are available for low-temperature hydrophobic wafer bonding including the formation of an amorphous silicon layer by As+ implantation, by B2H6 or Ar plasma treatment, or by sputter deposition, followed by an HF dip and room temperature bonding in air. The interface amorphous layer may be recrystallized by annealing at elevated temperatures, e.g., at 450 °C for As+-implanted samples.

An ideal low temperature bonding method was studied. Cu cones were prepared by electroless plating. Heating and pressure were used in the bonding process between Cu cones and Sn-3.0Ag-0.5Cu solder. It's a solid state bonding method because the bonding process was performed below the melting point of solder. Shear strength was measured by bonding tester. Morphologies of Cu cones, fracture surfaces and bonding interfaces were analyzed by field emission scanning electron microscope. Results showed that bonding strength was superior with proper bonding conditions. Mechanical interlock produced by insertion was a key success factor. Fast solid state diffusion also played an important role during the bonding process.

We demonstrate solid liquid interdiffusion bonding by gallium and gold as bonding material and show the bonding at 40°C. Because of the low melting point of gallium of 29.8°C several difficulties for processing the gallium exists. We could successful develop deposition, structuring and bonding processes.

Electrophilicity and hardness have been shown to be adequate in constructing structure-stability diagrams. Maximum hardness principle and minimum electrophilicity principle provide a rough guide toward locating the domains of stability and reactivity in a fitness landscape. Bonding in solids, aromaticity, magic alkali clusters, bond—stretch isomers, multivalent superatoms, etc. have been analyzed within this purview.

We describe a technique for measuring the pressure and density of a metallic solid, shocklessly compressed to multi-megabar pressure, through x-ray radiography of a magnetically driven, cylindrical liner implosion. Shockless compression of the liner produces material states that correspond approximately to the principal compression isentrope (quasi-isentrope). This technique is used to determine the principal quasi-isentrope of solid beryllium to a peak pressure of 2.4 Mbar from x-ray images of a high current (20 MA), fast (~100 ns) liner implosion.

Notwithstanding the substitutional disorder, the Fermi surface of metallic alloys can be measured and computed. We show that, from the theoretical point of view, it is defined as the locus of the peaks of the Bloch Spectral Function (BSF). Such Fermi surfaces, on varying the atomic concentrations, may undergo changes of their topology, known as Electronic Topological Transitions (ETT). Thus, for instance, pockets of electrons or holes may appear or disappear, necks may open or close. ETTs cause anomalous behaviours of thermodynamic, transport and elastic properties of metals and constitute a fascinating field in the study of Fermi liquid systems. Although ETTs could be studied on pure systems as a function of the thermodynamic variables, nevertheless such a study would often require extreme conditions, and would lead to experimental difficulties. On the other hand, it is possible to explore the variations of atomic concentration, i.e. the valence electron per atom ratio, in metallic solid solutions with a relative experimental ease. In this paper we review the theoretical techniques for the determination of Fermi surfaces in metallic solid solutions and discuss some examples of ETTs, namely LiMg, ZrNb, NbMo, MoRe, AgPd, CdMg, NiW and NiTi alloys, also in connection with experimental data as thermoelectric power, resistivity, elastic constants and electron-phonon coupling and with the determinations of the electron momentum distribution function from Compton scattering and positron annihilation experiments. We show that the ab initio calculations of the electronic structure for the quoted systems, together with a careful determination of the BSF, are able to predict quantitatively ETTs at those concentrations where physical quantities display anomalies, so confirming directly ETT theory. Although it is not the purpose of the present review to give a full account of electronic structure calculation schemes, however, we briefly discuss the ideas and the main physical approximations underlying theories of substitutional disorder in alloys. We shall pay some more attention to the Coherent Potential Approximation (CPA) in the Korringa-Kohn-Rostoker (KKR) multiple scattering framework and the Hohenberg and Kohn Density Functional Theory in the Local Density Approximation (LDA) for the exchange-correlation potential. The above choice is supported by the numerical versatility of the LDAKKRCPA theory, and, more important, by the a fortiori evidence that essentially equivalent results are obtained from different theoretical frameworks, provided the same basic physical approximations are used. Accordingly, when convenient, we present new LDAKKRCPA determinations of the Fermi surfaces, as for the ZrNbMoRe series.

Creep behaviour and dislocation substructure as a function of strain was investigated for two solid solution alloys and the pure components in the KBr-Kl system. The creep characteristics for the KBr-Kl alloys are in good agreement with creep behaviour observed in other ionic and class I metallic solid solution alloys, where the creep rate is controlled by a viscous dislocation glide process. The creep resistance of the KBr-KI alloys is higher than that for the pure components at the same value of homologous temperature. The dislocation substructure of the KBr-Kl alloys and pure components at large strains consists of well defined subgrains. Subgrain formation is shifted to larger strains in the alloys compared to the pure components as a result of solute drag forces on dislocations during glide.