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In the effort to develop atomistic models capable of accurately describing nanoscale systems with complex interfaces, it has become clear that simple treatments with rigid charge distributions and dispersion coefficients selected to generate bulk properties are insufficient to predict important physical properties. The quantum Drude oscillator model, a system of one-electron pseudoatoms whose “pseudoelectrons” are harmonically bound to their respective “pseudonuclei,” is capable of treating many-body polarization and dispersion interactions in molecular systems on an equal footing due to the ability of the pseudoatoms to mimic the long-range interactions that characterize real materials. Using imaginary time path integration, the Drude oscillator model can, in principle, be solved in computer operation counts that scale linearly with the number of atoms in the system. In practice, however, standard expressions for the energy and pressure, including the commonly used virial estimator, have extremely large variances that require untenably long simulation times to generate converged averages. In this paper, low-variance estimators for the internal energy are derived, in which the large zero-point energy of the oscillators does not contribute to the variance. The new estimators are applicable to any system of harmonic oscillators coupled to one another (or to the environment) via an arbitrary set of anharmonic interactions. The variance of the new estimators is found to be much smaller than standard estimators in three example problems, a one-dimensional anharmonic oscillator and quantum Drude models of the xenon dimer and solid (fcc) xenon, respectively, yielding 2–3 orders of magnitude improvement in computational efficiency. [ABSTRACT FROM AUTHOR]

We have studied the depth dependence and temperature behavior of the ordering of smectic-A films close to the smectic A-nematic transition, deposited on grated glass. X-ray grazing incidence geometry in reflection mode through the glass substrate was used to characterize the samples. Our results indicate the presence of a structure similar to the helical twist grain boundary phase. The structure has two maxima, one close to the glass-liquid crystal interface and another about 8 μm above the surface. The structure at 8 μm is the one that dominates at higher temperatures. In addition, we find that order is preserved to temperatures close to the nematic-isotropic transition temperature for the deeper gratings. We find also a dependence of the orientation of the structure with the depth of the grating and the elastic constant of the liquid crystal. [ABSTRACT FROM AUTHOR]

This article studies theoretically and experimentally the recombination at the amorphous/crystalline silicon interface of a heterojunction with intrinsic thin layer (HIT) structure without metallization. We propose a physical model to calculate the interface recombination rate under illumination. This model calculates the effective lifetime τeff as a function of the average excess minority carrier concentration 〈Δn〉. In order to test the model, we prepared a set of HIT structures. The dependence of τeff vs 〈Δn〉 of the samples is measured using the quasi-steady-state photoconductance technique. By fitting our model to the experimental data, we determine the a-Si:H/c-Si interface parameters and the doping density of the amorphous layer. [ABSTRACT FROM AUTHOR]

We propose a ray optics model to calculate the trapping force on a dielectric particle located on the interface between two media and illuminated by a focused evanescent field beam. Such a focused evanescent beam is produced by a high numerical aperture objective with a central obstruction whose size satisfies the total internal reflection condition on the interface. The dependence of the lifting force on the obstruction size, the particle size, and the distance of the particle from the interface is revealed. [ABSTRACT FROM AUTHOR]

A three-dimensional transient temperature field model (TTFM) is proposed for the general problem of laser-induced out-of-equilibrium annealing of a bilayer device, which is made up of a bulk material covered by a transparent layer. The TTFM solves the moving-boundary problem with a deterministic relation between the interface velocity and temperature in contrast to preceding problem-dependent models, which use an interface-tracking heuristic algorithm. The TTFM is the first step to model many temperature-driven phenomena such as diffusion and segregation in laser annealing. Both computed transient temperature field and melted-zone dimensions of a SiO2/Si example device, which is irradiated by a focused visible (532 nm) laser, are in very good agreement with experimental measurements. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a theory of behavior of foreign solid inclusions in a liquid being crystallized. Methodology of the study; Results and discussion on the study; Conclusions.

Focuses on a study which measured the root-mean-square width of the buried crystalline/amorphous silicon(001)/silicon oxide[sub2] interface. Properties of metal-oxide semiconductor devices; Reverse correlation of interface width and oxide thickness; Difference between the rate of smoothing for wet and dry oxides.

The orientation ratio (OR) is a key issue to achieve high density in longitudinal recording media. Recent recording media have seed layers which exclusively promote small grain growth of the recording layer. In this paper, the effect of seed layers on OR was investigated by the use of various seed materials deposited twice. OR tends to decrease as the thickness of the seed layer is increased; however, the degree of decrease is quite different with seed material. A seed material with small Young’s modulus is preferable for a large OR. These results suggest that OR depends on the interface stress which is relieved as seed layer thickness is increased. Moreover, the relation between the stress in the seed layer and OR was also considered with a multilayer model. [ABSTRACT FROM AUTHOR]

GaN pyramid arrays have been successfully synthesized by selective photo-assisted chemical etching in a K 2 S 2 O 8 /KOH solution. A detailed analysis of time evolution of surface morphology has been conducted, which describes an etching process of GaN pyramids. Room temperature cathodoluminescence images indicate that these pyramids are composed of crystalline GaN surrounding dislocations, which is caused by the greater recombination rate of electrons and holes at dislocation than that of crystalline GaN. The Raman results show a stress relaxation in GaN pyramids compared with unetched GaN. The optical property of both unetched GaN and GaN pyramids has been studied by photoluminescence. The formation mechanism and feature of GaN pyramids are also rationally explained. [ABSTRACT FROM AUTHOR]

Well-crystalline homogeneous α-Fe 2 O 3 nanopeanuts were synthesized, characterized and utilized as an effective photocatalysts for the photocatalytic degradation of toxic and harmful organic dyes, i.e. Congo red (CR), Eosin red (ER) and methylene blue (MB). The nanopeanuts were synthesized by facile one-step hydrothermal process without employing any templates and characterized in detail in terms of their morphological and structural properties. The detailed characterizations confirmed the well-crystallinity, large-scale growth and rhombohedral crystal structure of the synthesized nanopeanuts. Further, the detailed growth processes of prepared nanopeanuts were studied by examining the effects of reaction time, temperature and amounts of hexamethylenetetramine (HMT) on the shapes and sizes of the products. Thus, based on the observed experimental evidences, a possible growth mechanism for the formation of nanopeanuts was also proposed. Finally, the nanopeanuts were used as efficient visible-light driven photocatalyst for the photocatalytic degradation of organic dyes and the observed degradation rates were MB (57%) < ER (63%) < CR (93%) under visible-light irradiation. Interestingly, it was seen that the photocatalytic degradation of nanopeanuts was higher than other α-Fe 2 O 3 nanostructures such as nanospindles and commercial α-Fe 2 O 3 which revealed that the prepared α-Fe 2 O 3 nanopeanuts are excellent visible-light driven photocatalyst for the photocatalytic degradation of harmful and toxic organic dyes. [ABSTRACT FROM AUTHOR]

Rapid solidification occurs under large driving force of transformation from the metastable undercooled liquid phase to the stable crystalline state. Using a formalism of extended irreversible thermodynamics, a phase-field model of rapid solidification in binary systems is derived. An entropy approach together with a grand potential density of a binary system is used to obtain the main governing equations of the model. Special attention is paid to equations of a rapidly solidifying binary system which are accompanied by essential deviations from local equilibrium in the transport of the conservative variables (such as inner energy and mass) and in the dynamics of non-conservative variables (such as phase field). The obtained equations are analyzed and compared with recent models and outcomes based on the grand potential approach to solidification. [ABSTRACT FROM AUTHOR]

In the present paper, crystallization behavior and glass forming ability (GFA) of Cu64Zr36 bulk metallic glass (BMG) were studied based on the crystal phase competition. Electrical resistivity and X-ray diffraction results indicate that Cu64Zr36 glass underwent a two-stage crystallization process, during which Cu10Zr7 and Cu51Zr14 crystals precipitate at first and then there are only Cu10Zr7 and Cu8Zr3 phases at the end of the second stage. Intriguingly, it was found that it is the competing phase Cu10Zr7 that weakens GFA of the Cu64Zr36 alloy, because the Cu10Zr7 precipitate is fully restrained in the cast rod when substituting Zr with 7.5at%Ti and thereby its diameter with fully amorphous structure is enlarged from 1 mm to 2 mm. [ABSTRACT FROM AUTHOR]

The general problem of two-phase transport in phase-field models is analyzed: the flux of a conserved quantity is driven by the gradient of a potential through a medium that consists of domains of two distinct phases which are separated by diffuse interfaces. It is shown that the finite thickness of the interfaces induces two effects that are not present in the analogous sharp-interface problem: a surface excess current and a potential jump at the interfaces. It is shown that both effects can be eliminated simultaneously only if the coefficient of proportionality between flux and potential gradient (mobility) is allowed to become a tensor in the interfaces. This opens the possibility for precise and efficient simulations of transport problems with finite interface thickness. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis, characterization and investigation of the mesogenic, thermo-morphologic and thermotropic properties of a new chiral liquid crystalline compound are presented in this work. This new compound has prolate molecules and exhibits the chiral smectic C* mesophase in a sufficiently large temperature interval. Two types of solid crystalline phases have been found in this compound. Typical textures and temperatures of the direct and reverse phase transitions, taking place in the compound, are given. Typical peculiarities for the first-order transition between the smectic C* mesophase and isotropic liquid have been observed. [Copyright &y& Elsevier]

Abstract: In this paper, the principle of a solution for “thermal” connection between two solids is analyzed. We shows results given by the solution applied to the mechanical behaviour of a γ/γ′ two-phase material and to “artificial” structures obtained from modern techniques for epitaxial deposit. It appears that the use of a true or fictitious thermal loading constitutes a simple “connection” procedure, but is particularly coherent with the mechanics of two-phase crystalline materials with different lattice parameters. It would be interesting to apply the model to real structures, with misfit and interfacial dislocations. [Copyright &y& Elsevier]

Abstract: Porous titanium and tantalum coatings were produced on cast cobalt–chromium alloy substrate plates (Co-28 Cr-6 Mo ASTM designation F75)) using the additive manufacturing process Selective Laser Melting (SLM). Both tantalum and titanium coatings where successfully produced, however, a poor interface bond was observed with the titanium coatings on the cobalt–chrome alloy. This was due to a eutectic reaction leading to the formation of a low melting point phase βTi(CoCr) which cracks during cooling, rather than the formation of titanium carbide, as previously reported. This cracking makes titanium an unsuitable material to coat cobalt–chromium alloys using SLM. Tantalum coatings, however, showed considerably improved performance in terms of interface compatibility when compared to titanium and therefore a Co–Cr/Ta system would seem feasible for the manufacture of porous structured devices when a bi-material approach is required. This would allow the advantages of a highly biocompatible structured coating to be combined with the mechanical performance of a less biocompatible substrate. [Copyright &y& Elsevier]

Mechanical properties of Ti/Al–7Si assemblies produced by insert moulding were studied with a classical push-out test and a variant that is the circular-bending test. Special care has been taken for controlling both the reactivity at the Ti/Al–7Si interface and the metallurgical health of the Al–7Si matrix. Mechanical tests until complete debonding have been completed with interrupted tests, metallographic characterizations and FEM analysis of elastic stress state. A mean shear strength of the interface of about 120 MPa was obtained. When the Ti insert is solely fretted in the matrix, without chemical interaction between Ti and the Al–7Si alloy, the mean shear strength is significantly lower (48 MPa). This result clearly shows that chemical interaction at the interface (formation of a thin TiSi layer at the Ti side and a thick Al3Ti(Si) layer at the Al–7Si alloy side) improves the mechanical properties of the assembly. It is also shown that the failure sequence is characterized both by crack propagation from bottom to top and matrix yielding from top to bottom. Actually, interface damaging begins by crack initiation at the specimen bottom face (not at the top face and under the indenter) in a nearly pure mode I solicitation at a radial tensile stress of about 100 MPa. [ABSTRACT FROM AUTHOR]

Void formation and compositional change in nitrogen doped Ge2Sb2Te5 (NGST) films during repeated phase transformations were examined. Stable reversible switching behavior between the crystalline and melt-quenched phase of NGST films containing 5% nitrogen was examined using laser irradiation on a nanosecond time scale. Transmission electron micrographs indicated that with repeated phase transformation, void formation and subsequent coalescing and movement to the top and bottom interfaces with SiO2 layers in NGST occurred in both amorphous and crystalline states. Moreover, void formation at the grain boundaries of crystalline NGST was clearly observed. Compositional change around voids also occurred, which was confirmed using energy dispersive spectroscopy. Void formation and compositional change during repeated reversible switching can cause serious issues related to the reliability of NGST materials during actual phase-change random access memory device operations. [ABSTRACT FROM AUTHOR]

This article provides a concise discussion of thermodynamic and kinetic contributions to microstructure stabilization by dopant atoms located at interfaces in metallic nanocrystalline materials and an overview of recent molecular dynamics simulations used to study the behavior of dopant-modified interfaces in nanocrystalline copper. Molecular dynamics simulations show that antimony dopant atoms randomly positioned at copper grain boundaries can retard grain growth, in agreement with proposed thermodynamic and kinetic predictions. Simulations of uniaxial tensile deformation show a maximum in the flow strength at a grain size of 15 nm and that antimony dopants at the grain boundaries do not appreciably impact the nucleation of partial or full dislocations during uniaxial tensile deformation in nanocrystalline copper. [ABSTRACT FROM AUTHOR]

Novel bulk glassy samples of the pseudoternary chalcohalide Ge–S–AgI system have been prepared. Glasses have been obtained by monotemperature synthesis in evacuated ampoules and standard melt-quenching technique. The glass-forming region in the system determined by X-ray diffraction is situated in the S-rich region on the Ge–S side (S/Ge = 1.2, 1.5, 2 and 3) with AgI content up to 20 mol.%. Some physicochemical properties of the amorphous materials and their compositional dependence have been investigated. In addition, the theoretical average coordination number (Z), the total constraints per atom (Nco), the radial (Na) and axial (Nb) strength of the bonds have been calculated and related to the experimental results. [ABSTRACT FROM AUTHOR]

The effects of material interface curvature on deflagration of a homogeneous solid energetic material (EM) is studied in a limit when the radius of curvature is much larger than the deflagration front thickness. Under the assumption of quasi-steady burning, a method of matched asymptotics is employed do derive first-order curvature corrections to the mass flux across the gas-solid interface as well as to the interface temperature. As an illustration, a problem of quasi-steady spherical particle deflagration is solved numerically and the simulation results are used to verify those obtained through asymptotic analysis. An algorithm for a fully-coupled unsteady solver suitable for EM deflagration simulation is presented. Numerical solution of the unsteady spherical particle deflagration is used to show that the assumption of quasi-steady deflagration is valid. [ABSTRACT FROM AUTHOR]

We have modeled the electrical properties of three magnetotunnel junctions (MTJs) using a density functional theory (DFT), non-equilibrium Green's functions (NEGFs) based commercial code. We find results similar to those in the literature, and propose investigations into the effects of perturbations to the exact positions of the atoms in these structures. [ABSTRACT FROM AUTHOR]

The interfaces between liquid or solid Pb islands and single- or poly-crystalline Cu substrates are investigated. EBSD (Electron backscattered diffraction) analyses show that when Pb is solidified from droplets, a cube-on-cube orientation relationship prevails between the Pb crystals and each Cu grain surface, whatever its surface orientation, even though the lattice parameter of Pb is 1.37 times larger than that of Cu. Scanning electron microscope (SEM) and atomic force microscope (AFM) analyses show that during annealing of Pb droplets, ridges develop at the droplet-substrate triple lines, indicating that the interfaces evolve towards equilibrium by diffusional processes. These features are discussed in comparison with experiments and calculations performed on Pb nanocrystals embedded in Al, another fcc solid with a lattice parameter smaller than that of Pb. It is proposed that the cube-on-cube orientation relationship results from the solidification of Pb along the {111} planes of the solid Cu/liquid Pb interface which have developed by diffusion during the process of equilibration of the interface shape. [ABSTRACT FROM AUTHOR]

The article focuses on a study involving liquid crystal interfaces. The author revealed that the Bristol project focused on molecular orientation at the free surface of molecular fluids. He also stressed that the theoretical investigation on surface structure of liquid crystals used molecular cylindrical symmetry as its starting point.

The thermal properties, crystalline structure and shape memory effects of poly( l-lactide) (PLLA) and poly( l-lactide-co-ε-caprolactone) (PCLA) copolymers are systematically investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and tensile tests. The effects of the deformation strain on the shape recovery rate and recovery stress are also revealed. The polymers have the PLLA crystal and the amorphous phase, which are served as the fixed phase and reversible phase, respectively. The shape recovery rate and the recovery stress are significantly affected by the compositions and the deformation strain. With the increase of the deformation strain, the shape recovery rate decrease and higher shape recovery rate can be obtained in the polymers which have higher ε-CL content. However, the variation of recovery stress with the deformation strain is quite different and the maximum recovery stress of all polymers exceeds 3 MPa. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are carried out to analyze the structure and mechanical behavior of Cu nanowires with lateral dimensions of 1.45-2.89 nm. The calculations simulate the formation of nanowires through a "top-down "fabrication process by "slicing" square columns of atoms from single-crystalline bulk Cu along the [001], [010], and [100] directions and by allowing them to undergo controlled relaxation which involves the reorientation of the initial configuration with a ...001... axis and {100} surfaces into a new configuration with a ...110... axis and {111} lateral surfaces. The propagation of the planes is primarily responsible for the lattice rotation. The transformed structure is the same as what has been observed experimentally in Cu nanowires. A pseudoelastic behavior driven by the high surface-to-volume ratio and surface stress cit the nanoscale is observed for the transformed wires. Specifically, the relaxed wires undergo a reverse transformation to recover the configuration it possessed as part of the bulk crystal prior to relaxation wizen tensile loading with sufficient magnitude is applied. The reverse transformation progresses with the propagation of a single twin boundary in reverse to that observed during relaxation. This process has the diffusionless nature and the invariant-plane strain of a martensitic transformation. and is similar to those in shape memory alloys in phenomenology. The reversibility of the relaxation and loading processes endows the nanowires with the ability for pseudoelastic elongations of up to 41% in reversible axial strain which is well beyond the yield strain of the approximately 0.25% of bulk Cu and the recoverable strains on the order of 8% of most bulk shape memory materials. The existence of the pseudoelasticity observed in the single-crystalline, metallic nanowires here is size and temperature dependent. At 300 K, this effect is observed in Wires with lateral dimensions equal to or smaller than 1.81 × 1.81 nm. As temperature increases, the critical wire size for observing this effect increases. This temperature dependence gives rise to a novel shape memory effect to Cu nanowires not seen in bulk Cu. [ABSTRACT FROM AUTHOR]

The formation of the interface between the GaAs(100) single-crystal surface and PTCDA and NTCDA organic semiconductors is investigated. The method of total current spectroscopy makes it possible to trace the formation of the interfacial electronic structure. The two organic materials and the GaAs substrate are bonded together when the π electron cloud of an aromatic ring spreads toward the substrate. This modifies the electronic states of interfacial organic molecules and generates a dipole at the interface. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

Abstract: . A crystalline interface is often covered by a dense network of linear defects with a (pseudo) biperiodic geometry. The elastic field of this network is calculated by thinking the interface as paved by adjacent Somigliana dislocations. The analysis of a portion of an erratic zigzag line of a (001)Si low angle twist boundary, observed in two-beam transmission electron microscopy, is given as an example. To cite this article: A. Boussaid et al., C. R. Physique 6 (2005). [Copyright &y& Elsevier]

The most widely used memory materials for rewritable phase-change optical disks are the GeTe—Sb2Te3 pseudobinary compounds. Among these compounds, Ge2Sb2Te5 crystallizes into a cubic close-packed structure with a six-layer period (metastable phase) in the non-thermal equilibrium state, and a trigonal structure with a nine-layer period (stable phase) in the thermal equilibrium state. The structure of the stable phase has Ge/Sb layers in which Ge and Sb are randomly occupied, as does the structure of the metastable phase, while the conventionally estimated structure had separate layers of Ge and Te. The metastable and stable phases are very similar in that Te and Ge/Sb layers stack alternately to form the crystal. The major differences between these phases are: (i) the stable phase has pairs of adjacent Te layers that are not seen in the metastable phase and (ii) only the metastable phase contains vacancies of ca 20 at. % in the Ge/Sb layers. [ABSTRACT FROM AUTHOR]

We study the all time regularity of the free-boundary problem associated to the deformation of a compact weakly convex surface Σ in ℝ3, with a flat side, by its Gaussian Curvature. We show that under certain necessary regularity and non-degeneracy initial conditions the interface separating the flat from the strictly convex side, remains smooth on 0

The compatibility of different approximations to the Helmholtz free energy F is analysed in order to provide the consistent definition of the order parameters for liquid crystalline phases. In particular the diagrammatic expansion theory is compared to the weighted, also modified weighted, density approximations. The weight function w is shown to be proportional to the Mayer function. The explicit form of the weight function for the system of non-uniaxial polar molecules is given and the interaction terms of the polar and orientational order parameters in the free energy expansion are discussed. [ABSTRACT FROM AUTHOR]

The nematic-isotropic phase transitions in mixtures of rod-like and disc-like molecules are studied by a mean field theory. We consider both attraction and hard-core repulsion for the model molecules, thermotropic phase transitions are found from the isotropic to one of the two types of uniaxially symmetric nematic phases: optically positive N+ and negative N-. On the other hand, biaxially symmetric nematic phase is shown to be always less stable than the uniaxial phase. We predict that re-entrant phase transition occur for the lyotropic system. [ABSTRACT FROM AUTHOR]

We theoretically study interfacial properties between two coexisting phases in mixtures of a flexible polymer and a low molecular weight liquid crystal. By numerically solving Eular equations for concentration and orientation order parameters, we calculate order parameter profiles and interfacial tensions between coexisting nematic-isotopic and isotropic-isotropic phases at equilibrium. [ABSTRACT FROM AUTHOR]

Shows that the interfacial profile between two bonded wafers can be directly determined using X-ray reflectivity without resorting to standard model-fitting of the data. Attempt to solve the phase problem inherent to any structure determination by scattering technique; Use of a known silicon/silicon oxide interface which acts as a phase reference for the reflected signals.

Shapes of the interface between the L1 and cubic Pn3m phases in the mixture C12EO2/water are studied. The concave and convex variants of the interface are realised using Pn3m crystals surrounded by the L1 phase and L1 inclusions on surfaces and in the bulk of the Pn3m phase. It is shown that both variants of the Pn3m/L1 interface contain the (111)-type facets in coexistence with everywhere else rough surfaces. The matching between facets and curved parts of the interface is angular. In the vicinity of the upper limit of the L1 + Pn3m coexistence domain, additional (200)-type facets appear on the interface. The influence of the contact angle at glass walls on shapes of crystals and of inclusions is discussed. [ABSTRACT FROM AUTHOR]

The general formulation of double refraction or internal double reflection with different directions of propagation vector and wave vector in a uniaxial crystal is analysed in terms of Huygens' principle. Then double refraction and double reflection along the sequential interfaces in a crystal are discussed. On this basis, a configuration of electro-optic 1× N optical switch with modulators and birefringent crystal slabs integrated in a single block of crystal is suggested, which is simple and compact in construction, low in loss and insensitive to environment. Finally, calculations are given which lead to a proposed design of a 1×4 switch. [ABSTRACT FROM AUTHOR]

Examines the atomic structure of the interfaces in amorphous-crystalline tungsten obtained in situ by ultrafast quenching to low temperatures from the liquid phase, using methods of field ion microscopy. Establishment of a high degree of localization of imperfections and interfacial incoherence.

The surface abundance of lithium on the Sun is 140 times less than the protosolar value, yet the temperature at the base of the surface convective zone is not hot enough to burn—and hence deplete—Li (refs 2, 3). A large range of Li abundances is observed in solar-type stars of the same age, mass and metallicity as the Sun, but such a range is theoretically difficult to understand. An earlier suggestion that Li is more depleted in stars with planets was weakened by the lack of a proper comparison sample of stars without detected planets. Here we report Li abundances for an unbiased sample of solar-analogue stars with and without detected planets. We find that the planet-bearing stars have less than one per cent of the primordial Li abundance, while about 50 per cent of the solar analogues without detected planets have on average ten times more Li. The presence of planets may increase the amount of mixing and deepen the convective zone to such an extent that the Li can be burned. [ABSTRACT FROM AUTHOR]

Band offsets of the Ge/GeO2 interface are calculated through a hybrid density functional scheme. We first generate a model of disordered GeO2 through ab initio molecular dynamics to describe the oxide component. For addressing the interface, we then consider an atomistic model in which amorphous GeO2 is connected to crystalline Ge through a suboxide transition region showing regular structural parameters. The band offsets are obtained through the application of an alignment scheme, which reproduces the experimental band gaps of the interface components. The calculated valence band offset of 3.7 eV favors the low-energy side of the range of measured offsets. [ABSTRACT FROM AUTHOR]

Epitaxial Bi(111) films on the Si(100)-(2×1) surface were studied by two different scanning probe techniques, to obtain information on the buried interface. Ballistic electron emission microscopy reveals that the transmission across the Schottky barrier depends on the type of substrate terrace. The thermovoltage in scanning tunneling microscopy exhibits alternating signals for substrate step edges, which can be related to SA and SB steps, characteristic for the uncovered Si(100)-(2×1) surface. In addition to information about the growth mode of Bi, it was found that typical features of the Si(100)-(2×1) surface reconstruction are maintained. [ABSTRACT FROM AUTHOR]

We report the relationship between the formation of Ni-silicide compounds and the change of the electrical behavior under different post-annealing conditions. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), micro-Raman spectroscopy and X-ray diffraction (XRD) techniques were employed to study the formation of the various Ni-silicide compounds at the interface between Ni and 4H-SiC. Also, the electrical properties of the device were analyzed based on its current-voltage (I-V) characteristics under the same conditions. In our experiments, Ni2Si began to form at a post-annealing condition about 700°C. However, a good Ohmic behavior was observed at a post-annealing condition of 1000°C. [ABSTRACT FROM AUTHOR]

This letter introduces a modified effective medium formulation for composites where the characteristic length of the inclusion is on the order of or smaller than the phonon mean free path. The formulation takes into account the increased interface scattering in the different phases of the nanocomposite and the thermal boundary resistance between the phases. The interface density of inclusions is introduced and is found to be a primary factor in determining the thermal conductivity. The predictions are in good agreement with results from Monte Carlo simulations and solutions to the Boltzmann equation. [ABSTRACT FROM AUTHOR]

First-principles calculations of the atomic and electronic structure of crystalline CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) are performed to understand the effect of B on spin-dependent transport in these junctions. The authors find that it is energetically favorable for B atoms to reside at the crystalline CoFeB/MgO interface rather than remain in the bulk of the crystalline CoFeB electrode. The presence of B at the interfaces is detrimental to tunneling magnetoresistance (TMR) because it significantly suppresses the majority-channel conductance through states of Δ1 symmetry. Preventing B segregation to the interfaces during annealing should result in an enhanced TMR in CoFeB/MgO/CoFeB MTJs. [ABSTRACT FROM AUTHOR]

In this work, we investigate the electronic and optical properties of self-assembled InN/GaN quantum dots. The one-particle states of the low-dimensional heterostructures are provided by a tight-binding model that fully includes the wurtzite crystal structure on an atomistic level. Optical dipole and Coulomb matrix elements are calculated from these one-particle wave functions and serve as an input for full configuration interaction calculations. We present multiexciton emission spectra and discuss in detail how Coulomb correlations and oscillator strengths are changed by the piezoelectric fields present in the structure. Vanishing exciton and biexciton ground state emission for small lens-shaped dots is predicted. [ABSTRACT FROM AUTHOR]

Improving the performance of superconducting qubits and resonators generally results from a combination of materials and fabrication process improvements and design modifications that reduce device sensitivity to residual losses. One instance of this approach is to use trenching into the device substrate in combination with superconductors and dielectrics with low intrinsic losses to improve quality factors and coherence times. Here, we demonstrate titanium nitride coplanar waveguide resonators with mean quality factors exceeding two million and controlled trenching reaching 2.2 μm in the silicon substrate. Additionally, we measure sets of resonators with a range of sizes and trench depths and compare these results with finite-element simulations to demonstrate quantitative agreement with a model of interface dielectric loss. We then apply this analysis to determine the extent to which trenching can improve resonator performance. [ABSTRACT FROM AUTHOR]

The article focuses on the effects of adding and reducing atoms in copper-niobium multilayer nanocomposites forming two flaw-free interfaces between copper (Cu) and niobium (Nb). Study shows that radiation striking crystalline materials may damage their structure and other properties through the generation of vacancies or interstitials. It reveals that the first interface exists from the combination of the face-centered cubic Cu (111) plane and body-centered cubic Nb (110) plane. Other interface needs a straining and rotating of the Cu (111) to make it a 0.5% less dense in the interfacial area.