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Heterogeneous integration is considered as the key technology to create large, complex System in Package (SiP) assemblies of separately manufactured, smaller components. Proper control of the uniformity of each process step constitutes one of the main challenges during integration of the different components into a higher-level assembly. In this context, processes that create thick layers by electrochemical deposition are especially susceptible to variations across the substrate. Such processes include copper pillar and bump as well as tin-silver applications. Insufficient coplanarity of electrolytic copper would result in significant reliability issues or evolution of stress in the package. Upcoming hybrid bump designs with features of different dimensions pose additional challenges to the electrolytic copper and tin-silver processes. Purposeful adjustment of differences between the heights of pillars of different diameters may be required after the copper process step in order to obtain the best uniformity for the complete stack with tin-silver on top. In addition to coplanarity, the electrolytic process should allow modification shape of the individual pillar or bump. In this context, a versatile copper electrodeposition process will be discussed that allows adjustment to a broad variety of uniformity parameters and combinations thereof. In combination with suitable tin-silver deposition processes, this process is expected to significantly improve the reliability of copper pillars and bumps for advanced packaging applications.

The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of with central electron temperatures were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of a temperature of with was transiently accomplished, which corresponds to with a peak diamagnetic energy of and volume-averaged normalized plasma pressure . The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above line integrated density and central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

Wendelstein 7-X (W7‐X) is the world’s largest superconducting nuclear fusion experiment of the optimized stellarator type. In the first Operation Phase (OP1.1) helium and hydrogen plasmas were studied in limiter configuration. The heating energy was limited to 4 MJ and the main purpose of that campaign was the integral commissioning of the machine and diagnostics, which was achieved very successfully. Already from the beginning a comprehensive set of diagnostics was available to study the plasma. On the path towards high-power, high-performance plasmas, W7‐X will be stepwise upgraded from an inertially cooled (OP1.2, limited to 80 MJ) to an actively cooled island divertor (OP2, 10 MW steady-state plasma operation). The machine is prepared for OP1.2 with 10 inertially cooled divertor units, and the experimental campaign has started recently. The paper describes a subset of diagnostics which will be available for OP1.2 to study the plasma edge, divertor and scrape-off layer physics including those already available for OP1.1, plus modifications, upgrades and new systems. The focus of this summary will be on technical and engineering aspects, like feasibility and assembly but also on reliability, thermal loads and shielding against magnetic fields.

Équipe 107 : Physique des plasmas chauds; International audience; In JET-ILW dedicated melt exposures were performed using a sequence of 3MA/2.9T H-Mode JET pulses with an input power of P-IN = 23 MW, a stored energy of similar to 6 MJ and regular type I ELMs at Delta W-ELM = 0.3 MJ and f(ELM) similar to 30 Hz. In order to assess the risk of starting ITER operations with a full W divertor, one of the task was to measure the consequences of W transients melting due to ELMs. JET is the only tokamak able to produce transients/ ELMs large enough (>300 kJ per ELM) to facilitate melting of tungsten. Such ELMs are comparable to mitigated ELMs expected in ITER. By moving the outer strike point (OSP) onto a dedicated leading edge the base temperature was raised within similar to 1 s to allow transient ELM-driven melting during the subsequent 0.5 s. Almost 1 mm (similar to 6 mm(3)) of W was moved by similar to 150 ELMs within 5 subsequent discharges. Significant material losses in terms of ejections into the plasma were not observed. There is indirect evidence that some small droplets (similar to 80 mu m) were ejected. The impact on the main plasma parameters is minor and no disruptions occurred. The W-melt gradually moved along the lamella edge towards the high field side, driven by j x B forces. The evaporation rate determined is 100 times less than expected from steady state melting and thus only consistent with transient melting during individual ELMs. IR data, spectroscopy, as well as melt modeling point to transient melting. Although the type of damage studied in these JET experiments is unlikely to be experienced in ITER, the results do strongly support the design strategy to avoid exposed edges in the ITER divertor. The JET experiments required a surface at normal incidence and considerable pre-heating to produce tungsten melting. They provide unique experimental evidence for the absence of significant melt splashing at events resembling mitigated ELMs on ITER and establish a unique experimental benchmark for the simulations being used to study transient shallow melting on ITER W divertor PFUs

The continuous scaling of transistor size towards deep submicron level demands an inevitable replacement of SiO 2 with a low-k dielectric material. Doping of methyl groups in SiO 2 network reduces the dielectric constant by replacing oxygen atoms bonded with silicon and creating a lower polarizable silicon methyl bond in the network. Further reduction in dielectric constant is possible by introducing porosity in the dense low-k network. The detailed knowledge about atomic structure of such low-k materials is a must for understanding their electronic and optical properties. In this study, electron diffraction and (density functional based tight binding) DFTB calculations are used to investigate the structure of dense and porous low-k dielectric materials. The radial distribution function (RDF) obtained from electron diffraction technique contains information about the short-range order present in the material. Bond lengths and bond angles determined from RDF indicate a significant modification occurring in the SiO 2 network after doping with methyl groups. The local density of the materials is also derived from radial distribution function. It depends on the number and distances of nearest neighbors and was found to be decreased in these low-k materials compared with amorphous SiO 2 .

A group of edge diagnostics and modelling has been developed for investigation of synergy between 3D edge physics and plasma-wall interactions on Wendelstein 7-X (W7-X). Two endoscopes have been designed for visible and ultraviolet spectroscopy and tomography of the plasma edge, along with infrared thermography of the divertor tiles. 2D profiles of impurities (e.g. helium, carbon) will be measured by two endoscopes viewing the island divertor region in the plasma edge with a spatial resolution of

In this study, the dielectric response of low-k dielectric materials has been characterized by electron energy loss spectroscopy. A widely accepted fast Fourier transform based Kramers–Kronig method (Johnson, 1975) [3] has been used to derive the high-frequency response of these materials. We used three different low-k dielectric materials to find out the effect of porosity and carbon content on the dielectric response of materials. Amorphous SiO 2 and SiC:H samples are used for comparison. All samples were deposited by plasma-enhanced chemical vapor deposition technique. A Lorentzian-based oscillator model has been used to determine the eigen-energy of excitations by fitting the measured loss function. The model is specially designed to let all oscillator parameters move freely and find their most probable position by using a least square fitting analysis procedure. The band gap for amorphous SiO 2 which corresponds to the first absorption peak in the imaginary part of dielectric function is found to be at around 9 eV. We observed that in the case of dense low-k material, there appears a finite density of states (DOS) inside the band gap of SiO 2 , whereas the inclusion of porosity into dense low-k network diminishes the in-gap DOS and widens the band gap to around 10 eV.

Density functional theory (DFT) and density functional tight binding (DFTB) molecular dynamics (DFTB/MD) simulations of embedding and relaxation of buckminsterfullerene C60 molecules chemisorbed on (001) and (111) surfaces and inside bulk silicon lattice were performed. DFT calculations of chemisorbed fullerenes on both surfaces show that the C60 molecule deformation was very small and the C60 binding energies were roughly ∼4 eV. The charge analysis shows that the C60 molecule charges on (001) and (111) surfaces were between -2 and -3.5 electrons, respectively, that correlates well with the number of C-Si bonds linking the fullerene molecule and the silicon surface. DFT calculations of the C60 molecule inside bulk silicon confirm that the C60 molecule remains stable with the deformation energy values of between 11 and 15 eV for geometries with different C60 configurations. The formation of some C-Si bonds causes local silicon amorphization and corresponding electronic charge uptake on the embedded fullerene cages. Charge analysis confirms that a single C60 molecule can accept up to 20 excessive electrons that can be used in practice, wherein the main charge contribution is located on the fullerene's carbon atoms bonded to silicon atoms. These DFT calculations correlate well with DFTB/MD simulations of the embedding process. In this process, the C60 molecule was placed on the top of the Si(111) surface, and it was further exposed by a stream of silicon dimers, resulting in subsequent overgrowth by silicon.

The parameterisation of accurate and transferable repulsive potentials is a key ingredient for the self-consistent-charge density functional tight-binding method (SCC-DFTB). In the conventional parameterisation scheme the balanced description of different chemical environments involves significant human effort and chemical intuition. In this work, we propose an in situ parameterisation method with reduced transferability but maximal accuracy for the chemical and physical environment under investigation. Starting from an initial guess, we used iterative Boltzmann inversion to successively improve the repulsive potentials. The corrections were extracted iteratively from the differences in the radial distribution functions with respect to a density functional reference calculation. With this protocol convergence was reached within a few iterations involving only minimal human input. We applied this new scheme to liquid water at ambient conditions, a particularly challenging case for conventional SCC-DFTB. Th...

In the present work we describe a kinetic Monte-Carlo method (KMC) in the framework of the lattice gas model for the simulation of the adsorption in multicomponent systems from a liquid solution. The algorithm is subsequently used for an investigation of the influence of an adhesion promoter additive on the adsorption of amine-curing epoxide components on the aluminium oxide surface. The KMC method is coupled to the Metropolis algorithms to accelerate the simulations and take into account effects of various adsorption sites and neighboring adsorbates. An inclusion of the bulk diffusion in the simulation scheme allows to study the distribution of components in the solution near the interface. Parameters used in the simulations are reaction barriers and reaction energies for the surface complex formation. They were calculated in previous works by using density functional based tight binding (1–3). Results of the simulations show that the small additions of the adhesion promoter (˜2%), which adsorption is mo...

The results of a comprehensive and systematic ab initio based ground-state search for the structural arrangement of oxygen vacancies in rutile phase ${\mathrm{TiO}}_{2}$ provide new insights into their memristive properties. We find that O vacancies tend to form planar arrangements which relax into structures exhibiting metallic behavior. These metastable arrangements are structurally akin to, yet distinguishable from, the Magn\'eli phase. They exhibit a more pronounced metallic nature but are energetically less favorable. Our results confirm a clear structure-property relationship between segregated oxygen vacancy arrangement and metallic behavior in reduced oxides.

Marton Voros1, Adam Gali1,2, Efthimios Kaxiras3, Thomas Frauenheim4, and Jan M. Knaup*,3,4 1 Department of Atomic Physics, Budapest University of Technology Economics, 1111 Budapest, Hungary 2 Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest, Hungary 3 Department of Physics, Harvard University, 17 Oxford St., Cambride, MA, 02138, USA 4 Bremen Center for Computational Materials Science, University of Bremen, Am Fallturm 1, 28359 Bremen, Germany

The high heat flux ion beam test facility MARION (Material Research ION Beam test Stand) has been used for ion source conditioning and material testing within the IEK-4 for several years. Mainly small samples have been tested in the past by perpendicular irradiation. In these experiments only 25% of the available power density of MARION (>80 MW/m 2 ) was used so far. The activation of these resources for material testing was realized in the first test phase of the new tungsten divertor element for the JET tokamak. The enhancement of MARION by a new protection scraper is shown. During the last experiments the need of a more flexible handling of the sample itself and of the facility became clear. Based on those experiences an upgrade concept was developed to prepare MARION for future demands allowing the handling of much bigger prototypes. Additionally main emphasis is given to the access to improved (surface) diagnostics for all orientations of the target.

In the frame of the ITER-like Wall (ILW) for the JET tokamak, a divertor row made of bulk tungsten material has been developed for the position where the outer strike point is located in most of the foreseen plasma configurations. In the absence of active cooling, this represents a formidable challenge when one considers the temperature reached by tungsten (TW,surf > 2000 °C) and the vertical gradient ∂T/∂z = 5 × 104 K/m. As the development is drawing to an end and most components are in production, actual 1:1 prototypes are exposed to an ion beam with a power density around 7 MW/m2 on the plasma-facing surface. Advantage is taken of the flexibility of the Marion facility to bombard the tungsten stack under shallow angles of incidence (∼6°) with a powerful beam of ions and neutrals (>70 MW/m2 on axis). The shallow angles are important, with respect to the toroidal wetted surface, for properly simulating the expected performance under actual tokamak conditions. The M arion tests have been used to validate for a few typical cases the thermal calculations that were steadily developed along with the tungsten tile and, at the same time, to gather information on the actual temperatures of individual components. The latter is an important factor to a finer estimation of the power handling capabilities.

Atomistic simulations show that organosilicates, used as low permittivity dielectric materials in advanced integrated circuits, can be made substantially stiffer than amorphous silica, while maintaining a lower mass density. The enhanced stiffness is achieved by incorporating organic cross-links to replace bridging oxygen atoms in the silica network. To elucidate the mechanism responsible for the enhanced stiffness, the conformational changes in the network upon hydrostatic and shear loading are examined. The structural and mechanical impact of terminal methyl groups is also assessed quantitatively and compared with continuous random network theory.

Organosilicate glasses (OSG) are of great technological interest as low-k dielectrics. We use ab initio simulations to analyze the influence of the C/Si ratio in OSG on the density and elastic properties of pore-free material to gain a detailed understanding of the origins of these properties in this class of materials. We find that the addition of carbon to amorphous silica leads to a stiffening of the material by removing the bending degrees of freedom of Si-O-Si bonds. This transition in mechanisms of stiffness, leads to a distinctly nonlinear behavior of the bulk and elastic modulus over the C/Si ratio. Experimental results do not contradict our findings, however dominant pore effects impede conclusive comparison.

We use the Density Functional based Tight-Binding (SCC-DFTB) method in a Quantum Mechanics/Molecular Mechanics embedding scheme to simulate single SiC quantum dots of different shapes and with diameters of up to 1 nm, embedded in a block of α -Quartz with cell vectors of a = 15 nm and c = 13 nm. First results show that during the annealing process three recurring motives appear at the SiC/SiO2 interface of the embedded nanocrystals: Si-Si bonds often in Si interstitial-like configurations, C-C bonds involving all possible combinations of sp3 and sp2 hybridized carbon and threefold coordinated oxygen atoms. All of these defects, alone or in complexes, may play a crucial role in quenching the luminescence of these embedded nanocrystals. Detailed studies of the spectroscopic properties if the point defects identified in this work is indicated (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Computer-assisted design of functional materials requires methods that are able to simultaneously describe these with the necessary accuracy at the relevant time and length scales. One such possibility is the combination of classical interatomic force fields with density-functional based tight-binding (DFTB), an efficient and accurate quantum method. We employ this combination to study porous silicon dioxide functionalized with imidazole, which is used as an additive to polymer electrolyte membranes (PEM) for fuel cells applications. We analyze the water density and the dynamics of the functional groups at different temperatures by molecular dynamics simulation, whereas we calculate DFTB free energy barriers for proton transport reactions within the functionalized surface at different water contents. Combining both results, a macroscopic picture of the proton diffusion is drawn. Furthermore, we simulate the adsorption reactions of different components of an epoxide adhesive system on gamma alumina, using a direct coupling of DFTB and classical modeling. This yields direct chemical insight, how water and excess protons at the interface weaken the adhesion between epoxy polymers and natively oxidized aluminium.

Recently, Wang et. al. formulated a criterion for identifying the source of deep interface sates at the SiC/SiO2 interface, based on the known inefficiency of H2 passivation. We apply this criterion to a variety of excess carbon defects at the interface, which we have predicted to be energetically feasible. We find that, also with respect to this criterion, the simple C split interstitials are the most likely cause of the deep interface states among the examined defects.

From the viewpoint of application in power electronics, SiC possesses the greatest advantage of having SiO2 as its native oxide. Unfortunately, the usual thermal oxidation produces an unacceptably high density of interface states, with a complex energy distribution. Deep states are assumed to be caused by carbon excess at the interface, while the slow electron traps, called NIT, with especially high density near the conduction band of 4H-SiC (which would be the best polytype for power devices), are expected to originate from oxide defects near the interface. Unlike the case of the Si/SiO2 interface, simple hydrogen passivation does not help to reduce the high trap density. A possible passivation method for both deep states and NIT is post-oxidation annealing or oxidation in the presence of NO or N2O molecules. Here we present systematic and sophisticated theoretical calculations on a model of the 4H-SiC/SiO2 interface, in order to establish the main reaction routes and the most important defects that are created during dry oxidation, and may give rise to the observed interface traps. We also investigate the effect of nitrogen in suppressing them.

Preliminary results of a systematic theoretical study on the reactions of NO with a model 4H-SiC/SiO2 interface are presented. We show, that nitridation is a complex process, in which the balance between various mechanisms depends on doping and temperature. For weakly doped (1015-16 cm-3) n-type SiC, the crucial effect is an additional oxidation without creation of excess carbon at the interface.

The performance of popular molecular dynamics (MD) thermostat algorithms in constant temperature simulations of equilibrium systems is well-known. This is not the case, however, in the context of nonequilibrium chemical systems, such as chemical reactions or nanoscale self-assembly processes. In this work, we investigate the effect of popular thermostat algorithms on the "natural" (i.e., Hamiltonian) dynamics of a nonequilibrium, chemically reacting system. By comparing constant-temperature quantum mechanical MD (QM/MD) simulations of carbon vapor condensation using velocity scaling, Berendsen, Andersen, Langevin, and Nose-Hoover chain thermostat algorithms with natural NVE simulations, we show that efficient temperature control and reliable reaction dynamics are mutually exclusive in such a system. This problem may be circumvented, however, by placing the reactive system in an inert He atmosphere, which is itself described using NVT MD. We demonstrate that both realistic temperature control and dynamics consistent with natural NVE dynamics can then be obtained simultaneously. In essence, the thermal energy created by the natural dynamics of the NVE subsystem is drained by the thermostat acting on the NVT atmosphere, without adversely affecting the dynamics of the reactive system itself.

The high density of interface electron traps in the SiC/SiO2 system, near the conduction band of 4H-SiC, is often ascribed to graphitic carbon islands at the interface, although such clusters could not be detected by high resolution microscopy. We have calculated the electronic structure of a model interface containing a small graphite-like precipitate of 19 carbon atoms, with a diameter of ~7 Å, corresponding to the experimental detection limit. The analysis of the density of states shows only occupied states in the band gap of 4H-SiC near the valence band edge, while carbon related unoccupied states appear only well above the conduction band edge.

In this paper a test structure is introduced, which allows the evaluation of the quality of an anodic bond interface in terms of surface energy. It is based on the creation of small non-bonded areas in the vicinity of small steps in the bond interface. Using finite element analysis simulations it was possible to calculate the surface energy of the monitored bonding processes. The test structure was used to investigate the influence of anodic bonding parameters (temperature and voltage) on the surface energy.

The density of interface traps (Dit) in thermally oxidized SiC is unacceptably high for MOS device fabrication. The most severe problem is posed by the extremely high concentration of slow acceptor states near the conduction band edge of 4H-SiC. These states are attributed to near interface traps originating from (probably intrinsic) defects in the oxide. Here a systematic theoretical search is presented for possible defects in the oxide with an appropriate acceptor level. Supercell calculations using a hybrid functional approach (and resulting in a correct gap) on defects in alpha-quartz exclude the oxygen vacancy and the oxygen interstitial, as possible candidates. In contrast, these calculations predict interstitial silicon to have an acceptor level in the appropriate range. The carbon interstitial in silica has an acceptor level somewhat deeper than that. Occupation of these levels give rise to significant rearrangement of the environment, leading to a more extended defect structure.

Reactions of oxygen molecules with an initially perfect 4H-SiC/SiO2 interface are studied by first principle model calculations. We show that the most likely route of reactions in the oxidation process produces carbon interstitials at the interface, which can easily be emitted into the oxide. As a result, a stationary concentration of carbon interstitials is present at the interface with a gradient decreasing toward the oxide. The electronic structure of these defects may explain many of the observed features in the distribution of interface states.

Recent shock-wave experiments with deuterium [1, 2] in a regime where a plasma phase-transition has been predicted [3] and their theoretical interpretation are the matter of a controversial discussion (see e.g. [4–8]). In this paper, we apply 'wave packet molecular dynamics' (WPMD) simulations to investigate warm dense hydrogen. The WPMD method was originally used by Heller for a description of the scattering of composite particles such as simple atoms and molecules [9]; later it was applied to Coulomb systems by Klakow et al [10, 11]. In the present version of our model the protons are treated as classical point-particles, whereas the electrons are represented by a completely anti-symmetrized Slater sum of periodic Gaussian wave packets. We present recent results for the equation of state of hydrogen at constant temperature T = 300 K and of deuterium at constant Hugoniot E − E0 + 1/2(1/n − 1/n0)(p + p0) = 0, and compare them with the experiments and several theoretical approaches.

With the aid of Wave Packet Molecular Dynamics (WPMD) simulations we investigate hydrogen under extreme conditions. In this model the protons are treated as classical point-particles, whereas the electrons follow a pseudo-hamiltonian dynamics. For the simulations we use up to 4000 particles in a periodically continued cubic box. The equation of state, i.e. the pressure as function of the temperature for an electron density n = 2.10 29 m -3 is rather flat between 5000 K and 12000 K. In this regime the molecules dissociate. Above 20000 K we observe another structure in p(T), which is associated with ionization. The linear mixing model shows a similar behaviour of the pressure, but at lower absolute values. The PIMC treatment seems to overestimate the effect of dissociation, while the tight-binding model shows no structure at all. Independent structure information is obtained from proton pair correlation functions. Below 500 K we observe a dominant molecular peak and pronounced long-range correlations. This indicates a molecular crystal which can indeed be verified by inspecting the particle positions.

Recent laser shock-wave experiments by Da Silva et al. [1] with deuterium in a regime where a plasma phase-trasition has been predicted [6] are topic of many current discussions (e.g. [2, 3, 4, 5]). In this paper we apply Wave Packet Molecular Dynamics (WPMD) simulations to the equation of state of deuterium at constant hugoniot E - Eo + 1/2(V - V 0 )(p+ p 0 ) = 0 and compare them with the experiments and several theoretical approaches. The WPMD method was originally used by Heller for a description of the scattering of composite particles like simple atoms and molecules [7]; later it was applied to Coulomb systems by Klakow et al. [8, 9]. In the current version of our model the protons are treated as classical point-particles, whereas the electrons are represented by a completely anti-symmetrized Slater-sum of periodic Gaussian wavepackets.

Recent multiple-shock experiments of hydrogen at very high pressures show a transition from nonconducting to metallic behaviour at about 140 GPa and a temperature of approximately 3000 K [1]. We simulate hydrogen at various densities and temperatures in the region of this transition. As a theoretical tool we employ “Wave Packet Molecular Dynamics” simulations. This method was originally used by Heller for a description of the scattering of composite particles like simple atoms and molecules [2]; later it was applied to Coulomb systems by Klakow et al. [3]. From the simulations we can extract for example energies, pressure, structure information like pair-correlations and auto-correlation functions of current and velocity as well as the resulting transport coefficients. In this work we show the equation of state and proton-proton pair correlation functions for a constant electron number-density n = 2.016 × 1029m−3 (rs = 2). We compare our results with other theoretical approaches: Path Integral Monte Carlo simulations of Magro et al. [5], Tight Binding Molecular Dynamics calculations of Lenosky et al. [7], and analytical approaches via dissociation model by Nagel et al. [8] and the linear mixing model by Ross [9].

Vacancy dynamics in oxides are vital for understanding redox reactions and resulting memristive effects or catalytic activity. We present a method to track and drive vacancies which we apply to metadynamics simulation of oxygen vacancies (V${}_{\mathrm{O}}{}^{2+}$) in rutile, demonstrating its effectiveness. Using the density-functional based tight-binding method, it is possible to explore the free energy hyperplane of oxygen vacancies in TiO${}_{2}$. We show that the migration of V${}_{\mathrm{O}}{}^{2+}$ in TiO${}_{2}$ is governed by the jump with the highest degree of topological interconnection. Free energy profiles are consistent with minimum energy paths.

For the dynamic behaviour of a target under irradiation with dense particle beams, it is essential to study static and transport properties of matter over a wide range of densities and temperatures. Of particular interest are the formation of neutral atoms and molecules through recombination in a dense plasma, and the eventual emergence of ordered structures, as well as the delocalization and the lowering of the continuum edge that precurses the transition to a metallic state. As a theoretical tool, we employ wave packet molecular dynamics, in which electrons are represented by Gaussian wave packets, whose parameters follow pseudo-Hamiltonian dynamics. To exclude artifacts from the finite size of the simulation box, about 103 particles must be simulated. For reasons of numerical economy, the wave function is only pairwise symmetrized at present. As stationary observables, we study the energy-resolved electron-proton pair distribution function for hydrogen and the spectral density of the electrons. With increasing density, we observe the delocalization of the states and the lowering of the continuum edge. As a dynamical observable, we consider the stopping of ions. In comparison with classical point particles, the finite width of the wave packet leads to a smoothing of the singular Coulomb potential and a reduction of the stopping power. This is confirmed by actual calculations of the stopping of ions in matter.

We simulate the thermodynamics and kinetics of the drift/diffusion of oxygen vacancy defects in rutile TiO2, using the density-functional based tight-binding (DFTB) method. Both static and dynamic simulations have been performed. Results indicate that DFTB is well suited to examine the dynamic behavior of oxygen vacancies in TiO2. Detailed analysis shows, that strong model size dependence in relative diffusion barrier heights between different diffusion processes requires great care in defect diffusion simulations in TiO2. Thermodynamic results on the influence of an external electric field show that, due to the large dielectric constant, the coulomb driving force on oxygen vacancy diffusion is very small. Dynamic simulation of the influence of electric fields on the diffusion requires the use of advanced molecular dynamics acceleration schemes.

In this paper we apply Wave Packet Molecular Dynamics simulations to the equation of state of hydrogen. This method was originally used by Heller for a description of the scattering of composite particles like simple atoms and molecules [J. Chem. Phys. 62 (1975) 1544] [1]; later it was applied to Coulomb systems by Klakow et al. [Phys. Lett. A 192 (1994) 55; J. Chem. Phys. 101 (1994) 10 766] [2,3]. In the present version of the method the protons are treated as classical point particles, whereas the electrons are represented by a completely anti symmetrized Slater sum of periodic Gaussian wave packets. In contrast to other ab-initio methods [Phys. Rev. Lett. 85 (2000) 1890; Phys. Rev. E 63 (2001) 066404] [10,11] the Slater sums can be evaluated by a numerically stable and affordable matrix inversion [Nucl. Instrum. and Meth. A 464 (2000) 267] [5].

Organosilicate glasses (OSGs) are used as low-k intermetal dielectrics for advanced integrated circuits. In this application, the material must fulfill two conflicting requirements: It has to have low density to reduce the dielectric constant while being sufficiently mechanically stable to withstand thermomechanical and other stresses during subsequent steps of integrated circuit manufacture. Recent experimental advances in improving the mechanical and electrical properties of these materials have not yet been systematically studied theoretically at the ab initio level due to the large model sizes necessary to realistically describe amorphous materials. In this paper we employ the density-functional-based tight-binding method to achieve an accurate description of OSG properties at different compositions. We analyze the influence of composition and local network defects on the density and bulk modulus of nonporous OSG. We find that the dependence of density and that of mechanical stiffness on chemical composition are of different natures. This difference is traced to a transition between mechanisms of elastic deformation in silica glass and in silicon hydrocarbide, which is also the reason for the two materials' different sensitivities to network defects.

Organosilicate glasses (OSG), also known as SiCOH or carbon-doped oxide are used as low-k inter-metal dielectrics for integrated circuits. The material must fulfill two conflicting requirements: It has to have low density to reduce the dielectric constant and be mechanically stable enough to withstand mechanical stress during subsequent production steps. Experimental advances in improving their mechanical and electrical properties have not yet been theoretically examined at the ab initio level, due to the relatively large model sizes necessary for amorphous materials. We employ the density-functional based tight-binding (DFTB) method to achieve an accurate description of OSG properties at different compositions. We analyze the influence of composition and topological defects on the density and bulk modulus of non-porous OSG. We find that the dependence of density and stiffness on chemical composition is of different nature. This difference is traced to a transition between different mechanisms of elastic deformation in silica glass and in silicon hydrocarbide, which is also the reason for different sensitivity to topological defects in the two materials.

Oxide materials might form the basis for the next technological revolutions in fields such as electronics, photovoltaics or heterogeneous catalysis by enabling the production of inexpensive, high capacity and fast nonvolatile memories, neuromorphic computers and control systems, and efficient energy conversion devices. All these possible applications have in common that they promise to expand the limits of existing technologies by exploiting the inherent material-level complexity of oxides. However, the enhanced opportunities of this added complexity come at the price of significantly greater difficulties in understanding the materials' properties and their implications. Among many, the peculiar and variable mixture of ionic and covalent bonding behavior and the relative ease of changing the oxygen content of many compounds lead to fascinating effects. Furthermore, a deep level of understanding of the materials properties and their relation to synthesis is crucial for eventual applications. In recent years, an enormous amount of work has been devoted to the development of new experimental and theoretical tools, which have enabled much improved understanding of oxide behavior. Materials science is now becoming able to predict and engineer the behavior of oxide materials and explore brave new worlds of functionality. The recent advances in functional oxide science and technology prompted us to hold the CECAM workshop on “Functional Oxides for Emerging Technologies” at the Bremen Center for Computational Materials Science in October 2013, and it was during the preparation for this workshop that the Focus Issue on functional oxides was conceived. The three Review@RRL articles introduce the reader to innovative, low energy electron microscopy [1], controllable electric conduction at oxide interfaces [2], and ionic switching based RRAM [3]. The 20 original Letters present exciting new research on the topics of transport properties [4], super-reducible oxides [5], ferroelectricity [6], point defects [7], memory applications [8–10], bulk properties [11–14], interfaces [15–17], surfaces [18–20] and catalytic properties [21–23]. We sincerely hope that you will find our collection of articles from the forefront of functional oxide research to be informative and that reading our Focus Issue inspires you to come up with more and even better ideas and insights. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A plug for the ITER core charge exchange recombination spectroscopy (core CXRS) is located in the upper port 3. It transfers the light emitted by interaction of plasma ions with the diagnostic neutral beam (DNB). The plug consists of a main shell, a shielding cassette and a retractable tube. The tube carries the first mirror (M1) with a shutter and allows multiple replacements of M1. A large uncertainty in the M1 lifetime has initiated a new design option with M1 located as far as possible from the first wall. A fast shutter has been proposed to enhance M1 protection. It operates consistently with a pulsed DNB and uses elastic hearings. Three-point attachment scheme of blanket shield modules (BSMs) has been suggested. It is capable to react electromagnetic loads caused by eddy- and halo-currents for any BSM option with a good design margin. The concern has been raised with regards to the forces caused by halo current and applied to the entire plug. Possible solutions are either to shunt and support the plug to the port in the frontal part, or re-attach all BSM in this belt from the plugs to the vacuum vessel. (C) 2009 Elsevier B.V. All rights reserved.

In the frame of the ITER-like wall project, a new row of divertor tiles has been developed which consists of 96 bulk tungsten load-bearing septum replacement plates (LB-SRP). Exposed to the outer strike point for most ITER-relevant, high triangularity configurations, they shall be subject to high power loads (locally 10 MW/m 2 and above). These conditions are demanding, particularly for an inertially cooled design as prescribed. The expected erosion rates are high as well as the risk of melting, especially with transients and repetitive ELM loads. The development is also a real challenge with respect to the inevitable excursions of the tungsten material through the so-called DBTT, ductile-to-brittle transition temperature. A lamella design has been selected to fulfil the requirements with respect to the thermo-mechanical and electromagnetic loads during disruptions (∂ T /∂ z ≤ 5 × 10 4 K/m vertically, induction rate of change ∂ B /∂ t ≤ 100 T/s, and I halo ≤ 18 kA/module). Care is taken to act on refractory metals solely with compressive forces to a large extent. The dedicated clamping concept is described. Results of a test exposure to an electron beam around 70 MJ/m 2 substantiate the resort to ‘high temperature’ materials like – among others – high-grade Nimonic ® alloys, molybdenum or ceramic coatings.

Apical plasma membrane vesicles were prepared from human organ donor colon mucosal scrapings. These vesicles were enriched 10-fold in cysteine-sensitive alkaline phosphatase activity compared to starting homogenates, and showed minimal contamination of microsomal, mitochondrial or basolateral membranes. Transport studies using [22Na] uptake into proximal colonic vesicles demonstrated Na+ and H+ conductances, Na+/H+ exchange and amiloride inhibition of Na+ uptake. The isolation of these apical vesicles will permit detailed study of human colonic transport processes.

Chemical reactions at solid/liquid or solid/gas hybrid interfaces govern the morphogenesis of growing solid state phases. In order to understand the polymorphism of solids, the understanding of the mechanisms and kinetics of these reactions is of crucial importance, as is an insight into the morphology of said surfaces on an atomistic scale. Ab initio simulations are a valuable tool to obtain these data, especially in materials design, where many possible materials for an application may have to be examined. In such cases the fabrication of all these materials for examination and characterization can be extremely time consuming and expensive. We present methods to determine surface properties and reaction energetics from ab initio simulations and demonstrate their potential using three examples: reaction energetics for the adsorption of adhesive component molecules on alumina surfaces, the functionalization of a silica surface with a fluorocarbon layer and the investigation of the wetting behavior of the functionalized surface, and the calculation of reaction energetics for a proton transfer process in the bacterial reaction centre of photosynthesis, including quantum mechanical effects as well as solvent and continuum electrostatic influences from the surrounding medium.

We calculate the minimum energy paths and reaction energies of the adsorption of the epoxide adhesive components diglycidylesterbisphenol A (DGEBA), diethyltriamine (DETA), and the adhesion promoter 3-aminopropylmethoxysilane (AMEO) at two different sites on a model of the native Al2O3 surface, using the nudged elastic band algorithm in conjunction with self-consistent charge-density functional based tight binding. Our results show that the chosen combination of methods is well suited to obtain an overview of the reaction mechanisms and kinetics of the adsorption of organic molecules on inorganic surfaces. The obtained MEP-s show that there is preference for the adsorption of the adhesion promoter, AMEO, over the resin, DGEBA, while the adsorption of the curing agent, DETA, is unfavorable. Our approach also gives an insight into the ranges of the mechanical and electronic influences of the adsorption process on the interface, which neither full ab initio methods nor force field approaches can provide. These results will help to develop a quantum mechanics-molecular mechanics multiscale embedding scheme for more detailed studies of organic/inorganic hybrid interface reactions.

A systematic study of the level positions of intrinsic and carbon defects in ${\mathrm{SiO}}_{2}$ is presented, based on density functional calculations with a hybrid functional in an $\ensuremath{\alpha}$-quartz supercell. The results are analyzed from the point of view of the near interface traps (NIT), observed in both $\mathrm{SiC}∕{\mathrm{SiO}}_{2}$ and $\mathrm{Si}∕{\mathrm{SiO}}_{2}$ systems, and assumed to have their origins in the oxide. It is shown that the vacancies and the oxygen interstitial can be excluded as the origin of such NIT, while the silicon interstitial and carbon dimers give rise to gap levels in the energy range inferred from experiments. The properties of these defects are discussed in light of the knowledge about the $\mathrm{SiC}∕{\mathrm{SiO}}_{2}$ interface.

Possible defect structures, arising from the interaction of ${\mathrm{O}}_{2}$ molecules with an ideal portion of the $\mathrm{SiC}∕\mathrm{Si}{\mathrm{O}}_{2}$ interface, have been investigated systematically using density functional theory. Based on the calculated total energies and assuming thermal quasiequilibrium during oxidation, the most likely routes leading to complete oxidation have been determined. The defect structures produced along these routes will remain at the interface in significant concentration when stopping the oxidation process. The results obtained for their properties are well supported by experimental findings about the $\mathrm{SiC}∕\mathrm{Si}{\mathrm{O}}_{2}$ interface. It is found that carbon-carbon bonds can explain most of the observed interface states but not the high density near the conduction band of $4H$-SiC.

Hydrogen, being composed of the simplest atom, is a material whose properties have attracted attention since long. It was as early as 1935 that the existence of a metallic phase at high pressures has been postulated. Since then this problem has been intensely studied, not only as a basic challenge in many-body physics but also because of important astrophysical implications. Recent experiments with multiple shock waves show a remarked increase of the conductivity by four orders of magnitude for pressures between 93 and 180 In these experiments neither the density nor the temperature have been measured independently. Instead they were calculated by computationally simulating each measurement using a standard equation of state for hydrogen in the molecular fluid phase. Relating the resistivity to a density-dependent band gap and to the temperature, the data have thus been interpreted in terms of a continuous transition from a semiconducting to a metallic diatomic fluid at 140 GPa and 3000 K. However, this view does not comply with several theoretical investigations using different advanced many-body methods which all predict a first-order phase transition. A chemical picture has been employed in [5] where hydrogen is described as a mixture of H2, H, H + and free electrons where the properties of molecules, atoms and ions change with increasing density because of the polarization due to strong coupling. Hierarchical schemes based on the hypernetted chain (HNC) equations allow to account for both longand short-range correlations in fluids and these have been applied to the hydrogen problem. Using the equation of state emerging therefrom and corresponding models for the conductivity, the results of the multiple shock wave experiments have been interpreted as a first-order transition between molecular and metallic phases. This view is supported by path-integral Monte Carlo (PIMC) studies of hydrogen which show a decreasing pressure P(T) as the temperature is raised between 5000 K and 10000 K at densities around This drop in pressure is due to the decrease in electron kinetic energy density upon the breaking of the molecular bonds during the dissociation of the H2 molecules. A tight binding calculation shows no such drop in pressure, on the other hand. Here we investigate the problem of a phase transition in hydrogen at high pressures on the basis of extensive numerical simulations of the equation of state, pair correlation functions and charge transport coefficients. To this end, we employ an efficient quantum mechanical simulation scheme, the wave-packet molecular dynamics (WPMD). The technical simplifications of the scheme allow to use much larger samples which, in turn, help to pin down