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Heterojunctions have received much interest as a way to improve semiconductors' electrical and optical properties. The impact of the interface on the electrical and optical properties of g-Cpt>3N4/SnS2 was explored using first-principles calculations in this study. The results show that, at the hetero-interface, a conventional type-II band forms, resulting in a lower band gap than that in the g-C3N4 and SnS2 monolayers. When there is no high barrier height, the averaged microscopic and averaged macroscopic potentials can be used to accomplish efficient carrier transformation. Furthermore, the polarization direction affects the absorption spectra. All of these discoveries have significant implications for the development of g-C3N4-based optoelectronics. [ABSTRACT FROM AUTHOR] more...

With the enhancement of integration and functionality of high-power electronic devices, heat dissipation has become a critical bottleneck limiting performance improvement. In particular, under high power density conditions, interface thermal resistance has emerged as a prominent factor in overall thermal management. In this paper, the interfacial energy transport characteristics of Si/Ge is investigated based on the Boltzmann Transport Equation (BTE). The quality of interfacial energy transport is analyzed using Boltzmann statistical entropy and the losses that occur at the interface during energy transmission is also explored. The results indicate that the mismatch and high degree of localization of interface phonons increase the irreversible loss of energy phonons during transport across the interface, which leads to a significant entropy increase at the interface. Furthermore, the degree of irreversibility in energy loss is related to the thermal transport pathway; the lower the phonon matching at the interface, the greater the thermal transport resistance and the larger the irreversible loss. This research offers a comprehensive analysis of the irreversibility of energy loss, providing novel theoretical frameworks and research avenues for enhancing energy efficiency in high-power electronic devices. [ABSTRACT FROM AUTHOR] more...

Heterogeneous composites consisting of Bi6Cu2Se3.6Cl0.4O6 and Bi2O2Se are prepared according to the concept of modulation doping. With prominently increased carrier mobility and almost unchanged effective mass, the electrical transport properties are considerably optimized resulting in a peak power factor ≈1.8 µW cm−1 K−2 at 873 K, although the carrier concentration is slightly deteriorated. Meanwhile, the lattice thermal conductivity is lowered to ≈0.62 W m−1 K−1 due to the introduction of the second phase. The modified Self‐consistent Effective Medium Theory is utilized to explain the deeper mechanism of modulation doping. The enhancement of apparent carrier mobility is derived from the highly active phase interfaces as fast carrier transport channels, while the reduced apparent thermal conductivity is ascribed to the existence of thermal resistance at the phase interfaces. Ultimately, an optimized ZT ≈0.23 is obtained at 873 K in Bi6Cu2Se3.6Cl0.4O6 + 13% Bi2O2Se. This research demonstrates the effectiveness of modulation doping for optimizing thermoelectric properties once again, and provides the direct microstructure observation and consistent theoretical model calculation to emphasize the role of interface effects in modulation doping, which should be probably applicable to other thermoelectrics. [ABSTRACT FROM AUTHOR] more...

Introduction: Magnetic resonance imaging-linear accelerator radiotherapy is an innovative technology that requires special consideration for secondary electron interactions within the magnetic field, which can alter dose deposition at air–tissue interfaces. As part of ongoing quality assurance and quality improvement of new radiotherapy technologies, the purpose of this study was to evaluate skin dose modelled from the treatment planning systems of a magnetic resonance imaging-linear accelerator and a conventional linear accelerator, and then correlate with in vivo measurements of delivered skin dose from each linear accelerator. Methods: In this prospective cohort study, 37 consecutive glioma patients had treatment planning completed and approved prior to radiotherapy initiation using commercial treatment planning systems: a Monte Carlo-based algorithm for magnetic resonance imaging-linear accelerator or a convolution-based algorithm for conventional linear accelerator. In vivo skin dose was measured using an optically stimulated luminescent dosimeter. Results: Monte Carlo-based magnetic resonance imaging-linear accelerator plans and convolution-based conventional linear accelerator plans had similar dosimetric parameters for target volumes and organs-at-risk. However, magnetic resonance imaging-linear accelerator plans had 1.52 Gy higher mean dose to air cavities (P <.0001) and 1.10 Gy higher mean dose to skin (P <.0001). In vivo skin dose was 14.5% greater for magnetic resonance imaging-linear accelerator treatments (P =.0027), and was more accurately predicted by Monte Carlo-based calculation (ρ = 0.95, P <.0001) versus convolution-based (ρ = 0.80, P =.0096). Conclusion: This is the first prospective dosimetric comparison of glioma patients clinically treated on both magnetic resonance imaging-linear accelerator and conventional linear accelerator. Our findings suggest that skin doses were significantly greater with magnetic resonance imaging-linear accelerator plans but correlated better with in vivo measurements of actual skin dose from delivered treatments. Future magnetic resonance imaging-linear accelerator planning processes are being designed to account for skin dosimetry and treatment delivery. [ABSTRACT FROM AUTHOR] more...

Complex hydrides, such as LiBH4, are a promising class of ion conductors for all-solid-state batteries, but their application is constrained by low ion mobility at room temperature. Mixing with halides or complex hydride anions, i.e., other complex hydrides, is an effective approach to improving the ionic conductivity. In the present study, we report on the reaction of LiBH4 with LiBF4, resulting in the formation of conductive composites consisting of LiBH4, LiF and lithium closo-borates. It is believed that the in-situ formation of closo-borate related species gives rise to highly conductive interfaces in the decomposed LiBH4 matrix. As a result, the ionic conductivity is improved by orders of magnitude with respect to the Li-ion conductivity of the LiBH4, up to 0.9 × 10−5 S cm−1 at 30 °C. The insights gained in this work show that the incorporation of a second compound is a versatile method to improve the ionic conductivity of complex metal hydrides, opening novel synthesis pathways not limited to conventional substituents. [ABSTRACT FROM AUTHOR] more...

We construct a new spatial finite-difference discretization for a regularized 3D Navier–Stokes–Cahn–Hilliard system of equations. The system can be attributed to phase field type models and describes flows of a viscous compressible isothermal two-component two-phase fluid with surface effects; the potential body force is also taken into account. In the discretization, the main sought functions are defined on one and the same mesh, and an original approximation of the solid wall boundary conditions (homogeneous with the discretization of equations) is suggested. The discretization has an important property of the total energy dissipativity allowing one to eliminate completely the so-called spurious currents. The discrete total mass and component mass conservation laws hold as well, and the discretization is also well-balanced for the equilibrium solutions. To ensure that the concentration C remains within the physically meaningful interval (0, 1), the non-convex part of the Helmholtz free energy is taken in a special logarithmic form (the Flory–Huggins potential). The speed of sound can depend on C that leads to different equilibrium mass densities of the "pure" phases. The results of numerical 3D simulations are also presented including those with a gravitational-type force. The positive role of the relaxation parameter is discussed too. [ABSTRACT FROM AUTHOR] more...

La2/3Sr1/3MnO3 (LSMO) thin films of various thicknesses (6, 8, 10, 20, and 30 nm), capped by 7 nm‐thick Pt layer, are grown by pulsed laser deposition on SrTiO3 (001) substrates. X‐ray diffraction revealed that LSMO films are (001) oriented. Vibrating sample magnetometer is used to determine the magnetization at saturation and the magnetic dead layer thickness. This latter is around 3.4 nm, significantly thicker compared with the one induced at interfaces of Pt with ferromagnetic transition metals. Microstrip line ferromagnetic resonance (MS‐FMR) is used to extract the gyromagnetic ratio, which is found to increase with LSMO thickness. MS‐FMR revealed that the in‐plane magnetic anisotropy is dominated by a uniaxial contribution for the Pt capped film, whereas the noncapped 10 nm‐thick LSMO layer shows a fourfold anisotropy. Furthermore, the thickness dependence of the effective magnetization reveals the existence of a second‐order perpendicular anisotropy term, which is thickness‐dependent, and of a weak uniaxial interface anisotropy. The Gilbert damping coefficient is found to vary linearly with the inverse of the effective LSMO thickness due to spin pumping leading to relatively low spin mixing conductance of LSMO/Pt interface. [ABSTRACT FROM AUTHOR] more...

The high‐κ polymer P(VDF‐TrFE‐CFE) is applied in the dielectric layer of a thin film transistor based on graphene, inducing a considerable overall performance improvement compared with conventional SiO2 or ordinary polymer PMMA dielectrics. A systematical study reveals the reason for this improvement to be the strong screening effect on the Coulomb scattering in the dielectric‐semiconductor interface, which originates from the high‐κ value of P(VDF‐TrFE‐CFE). This positive effect is dominant enough to compensate for the adverse effects induced by the application of P(VDF‐TrFE‐CFE), including the large surface roughness and strong phonon scattering. A prototype transistor fabricated on a plastic substrate shows similar superior performance and sustainability upon bending operation, testifying the adaptability of P(VDF‐TrFE‐CFE) in a flexible graphene transistor. This study proposes a high‐κ polymer dielectric that is valid for high‐performing transistors based on 2D semiconductor materials. [ABSTRACT FROM AUTHOR] more...

Domain switching pathways fundamentally control performance in ferroelectric thin film devices. In epitaxial bismuth ferrite (BiFeO3) films, the domain morphology is known to influence the multiferroic orders. While both striped and mosaic domains have been observed, the origins of the latter have remained unclear. Here, it is shown that domain morphology is defined by the strain profile across the film–substrate interface. In samples with mosaic domains, X‐ray diffraction analysis reveals strong strain gradients, while geometric phase analysis using scanning transmission electron microscopy finds that within 5 nm of the film–substrate interface, the out‐of‐plane strain shows an anomalous dip while the in‐plane strain is constant. Conversely, if uniform strain is maintained across the interface with zero strain gradient, striped domains are formed. Critically, an ex situ thermal treatment, which eliminates the interfacial strain gradient, converts the domains from mosaic to striped. The antiferromagnetic state of the BiFeO3 is also influenced by the domain structure, whereby the mosaic domains disrupt the long‐range spin cycloid. This work demonstrates that atomic scale tuning of interfacial strain gradients is a powerful route to manipulate the global multiferroic orders in epitaxial films. [ABSTRACT FROM AUTHOR] more...

The physical aging behavior, time‐dependent densification, of thin polystyrene (PS) films supported on silicon are investigated using ellipsometry for a large range of molecular weights (MWs) from Mw = 97 to 10,100 kg mol−1. We report an unexpected MW dependence to the physical aging rate of h < 80‐nm thick films not present in bulk films, where samples made from ultra‐high MWs ≥ 6500 kg mol−1 exhibit on average a 45% faster aging response at an aging temperature of 40 °C compared with equivalent films made from (merely) high MWs ≤ 3500 kg mol−1. This MW‐dependent difference in physical aging response indicates that the breadth of the gradient in dynamics originating from the free surface in these thin films is diminished for films of ultra‐high MW PS. In contrast, measures of the film‐average glass transition temperature Tg(h) and effective average film density (molecular packing) show no corresponding change for the same range of film thicknesses, suggesting physical aging may be more sensitive to differences in dynamical gradients. These results contribute to growing literature reports signaling that chain connectivity and entropy play a subtle, but important role in how glassy dynamics are propagated from interfaces. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1224–1238 [ABSTRACT FROM AUTHOR] more...

Superconductivity at the two-dimensional limit in crystalline films with only one unit cell thick or one quantum well channel has become a frontier in the field of superconductivity. In this paper, we briefly review the recent experimental detections of superconductivity at the two-dimensional limit and corresponding Berezinskii-Kosterlitz-Thouless (BKT) transitions using imaging, spectroscopy and transport techniques, such as one-monolayer Pb/In films on Si(lll) substrates, one-unit-cell FeSe films on SrTiO3 (001) substrates, and two-monolayer Ga films on GaN(0001) substrates. Due to anisotropy, quantum size effects from dimension limitation, and interface effects between the film and the substrate, superconducting parameters such as critical temperature, Bardeen-Cooper-Schrieffer (BCS) ratio and critical magnetic fields in thin films can be significantly different from those in corresponding bulk materials. Furthermore, considering quasi-two-dimensional layered structure in high-Tc superconductors and dissipation problem in electronic integrated circuits, the investigation of superconductivity at the two-dimensional limit is expected not only to reveal new physical phenomena or properties, but also to further understand high-Tc superconductivity and explore new high-Tc superconductors, as well as to develop new generation of dissipationless electronic devices and low-dissipation integrated circuits. [ABSTRACT FROM AUTHOR] more...

This paper deals with the universal model describing plane strain bending of a multilayered sector of a cylindrical tube which can have residual deformations as well as nano-scale effects. In order to model the response of the sector at the nano-scale, the Gurtin-Murdoch theory is employed. Residual deformations of the layers, such as prestretch or precompression, are introduced into the model of finite bending using the multiplicative decomposition rule for corresponding deformation gradients. Numerous coupled nonlinear effects exhibited by the sector are discussed. [ABSTRACT FROM AUTHOR] more...

The catalytic activity for the oxygen reduction reaction (ORR) of a hexagonal boron nitride (h-BN) monolayer deposited on a Au(111) surface and decorated by a small planar Au8 cluster has been studied theoretically using density-functional theory. It is shown that gold nanoparticles (Au-NP) deposited on the h-BN/Au(111) surface can provide catalytically active sites for effective ORR at the perimeter interface with the support. Stabilization of oxygen at the perimeter interface between Au-NP and h-BN/Au(111) support promotes OOH* dissociation opening effective 4-electron pathway of ORR with formation of H2O. It is suggested that increase in the perimeter interface area between the supported Au-NP and the surface would result in increase of the ORR activity. Such increase in the perimeter interface area can be achieved by decreasing the size of Au-NP. Our calculations demonstrate the principal ability to functionalize inert materials such as stand-alone h-BN monolayer or Au surface for the ORR and open new way to design effective Pt-free catalysts for fuel cell technology.? [ABSTRACT FROM AUTHOR] more...

The governing equation of screw dislocations in heterostructures is constructed using image method. The interface type (-1 ≤ γ ≤ 1) and distance between dislocation and interface h are considered in the new equation. The Peierls-Nabarro equations for screw dislocations in bulk and semi-infinite materials can be recovered when γ = 0 and γ = -1. The soft (γ < 0) and hard (γ > 0) interfaces can enhance and reduce the Peierls stress of screw dislocations near the interface, respectively. The interface effects on dislocations decrease with the increasing of distance h. The Al/TiC heterostructure is investigated as a model interface to study the unstable stacking fault energy and dislocation properties of the interface. The mismatch of lattice constants and shear modulus at the interface results in changes of the unstable stacking fault energy. Then, the changes of the unstable stacking fault energy also have an important effect on dislocation properties, comparing with γ and h. [ABSTRACT FROM AUTHOR] more...

Purpose Hypofractionated partial breast irradiation ( HPBI) involves treatment to the breast tumor using high doses per fraction. Recent advances in MRI-Linac solutions have potential in being applied to HPBI due to gains in the soft tissue contrast of MRI; however, there are potentially deleterious effects of the magnetic field on the dose distribution. The purpose of this work is to determine the effects of the magnetic field on the dose distribution for HPBI tumors using a tangential beam arrangement ( TAN), 5-beam intensity-modulated radiation therapy ( IMRT), and volumetric modulated arc therapy ( VMAT). Methods Five patients who have received HPBI were selected with two patients having bilateral disease resulting in a total of two tumors in this study. Six planning configurations were created using a treatment planning system capable of modeling magnetic field dose effects: TAN, IMRT and VMAT beam geometries, each of these optimized with and without a transverse magnetic field of 1.5 T. Results The heart and lung doses were not statistically significant when comparing plan configurations. The magnetic field had a demonstrated effect on skin dose: for VMAT plans, the skin (defined to a depth of 3 mm) D1cc was elevated by +11% and the V30 by +146%; for IMRT plans, the skin D1cc was increased by +18% and the V30 by +149%. Increasing the number of beam angles (e.g., going from IMRT to VMAT) with the magnetic field on reduced the skin dose. Conclusion The impact of a magnetic field on HPBI dose distributions was analyzed. The heart and lung doses had clinically negligible effects caused by the magnetic field. The magnetic field increases the skin dose; however, this can be mitigated by increasing the number of beam angles. [ABSTRACT FROM AUTHOR] more...

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Purpose: To quantify and explain the backscatter dose effects for clinically relevant high atomic number materials being irradiated in the presence of a 1.5 T transverse magnetic field. Methods: Interface effects were investigated using Monte Carlo simulation techniques. We used GPUMCD (v5.1) and geant4 (v10.1) for this purpose. GPUMCD is a commercial software written for the Elekta AB, MRI linac. Dose was scored using GPUMCD in cubic voxels of side 1 and 0.5 mm, in two different virtual phantoms of dimensions 20 ? 20 ? 20 cm and 5 ? 5 ? 13.3 cm, respectively. A photon beam was generated from a point 143.5 cm away from the isocenter with energy distribution sampled from a histogram representing the true Elekta, MRI linac photon spectrum. A slab of variable thickness and position containing either bone, aluminum, titanium, stainless steel, or one of the two different dental filling materials was inserted as an inhomogeneity in the 20 ? 20 ? 20 cm phantom. The 5 ? 5 ? 13.3 cm phantom was used as a clinical test case in order to explain the dose perturbation effects for a head and neck cancer patient. The back scatter dose factor (BSDF) was defined as the ratio of the doses at a given depth with and without the presence of the inhomogeneity. Backscattered electron fluence was calculated at the inhomogeneity interface using geant4. A 1.5 T magnetic field was applied perpendicular to the direction of the beam in both phantoms, identical to the geometry in the Elekta MRI linac. Results: With the application of a 1.5 T magnetic field, all the BSDF's were reduced by 12%-47%, compared to the no magnetic field case. The corresponding backscattered electron fluence at the interface was also reduced by 45%-64%. The reduction in the BSDF at the interface, due to the application of the magnetic field, is manifested in a different manner for each material. In the case of bone, the dose drops at the interface contrary to the expected increase when no magnetic field is applied. In the case of aluminum, the dose at the interface is the same with and without the presence of the aluminum. For all of the other materials the dose increases at the interface. Conclusions: The reduction in dose at the interface, in the presence of the magnetic field, is directly related to the reduction in backscattered electron fluence. This reduction occurs due to two different reasons. First, the electron spectrum hitting the interface is changed when the magnetic field is turned on, which results in changes in the electron scattering probability. Second, some electrons that have curved trajectories due to the presence of the magnetic field are absorbed by the higher density side of the interface and no longer contribute to the backscattered electron fluence. [ABSTRACT FROM AUTHOR] more...

Carbon nanotubes (CNTs)/Al interface interaction is critical to the mechanical properties of CNT-reinforced Al matrix composites. In this study, the effect of different defects (oxygen and carbon adatoms, n-type N substitution and p-type B substitution) on the interactions between a (5, 5) CNT and an Al (111) surface is studied based on first-principles total energy calculations. It is found that the defects can enhance the interaction between the CNT and Al (111) surface in different degree due to the different valence electron configurations of the interfacial defect atoms, as well as the different influences of the defects on the electronic structures of the CNT. The results are helpful for the improvement of the interfacial interactions between CNTs and Al matrix via the introduction of the defects at the interface to enhance the mechanical properties of CNT-reinforced Al matrix composites. [ABSTRACT FROM AUTHOR] more...

The acidity of a compound is a fundamental property that dictates molecular speciation and reactivity in solution. Measurements of acidity of simple molecules in interfacial environments are rarely carried out but assumptions often are made that the difference is sufficiently small that the change can be ignored. The effect of oil-surfactant-water interfaces in reverse micellar systems on the p Ka value of the anilinium ion was measured using titrations by NMR spectroscopy as the size of the bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane reverse micelles decreased. The p Ka was observed to drop from 4.85±0.02 to 4.62±0.02 in water as the reverse micelle decreased from w0 10 to 4 (that is down to a reverse micellar radius of about 2 nm). NOSEY experiments demonstrated that the aniline moiety resides within the surfactant interface with the amine/ammonium moiety protruding into the waterpool bridging the interface. The presence of the aniline was found to have modest and variable effect on the size of the reverse micelles as observed using dynamic light scattering. Our experimental results provide information important to theoretical studies, which explore interface phenomena and provide a framework for information on such simple molecules. These studies quantitate the small but significant effect on the p Ka values upon placement of an aromatic amine molecule at a hydrophilic-hydrophobic interface. [ABSTRACT FROM AUTHOR] more...

Many research activities have contributed to extend the homogenization schemes and variational bounds to account for surface stresses, in the case of matrix-inclusion composite materials. The nanostructure of clay-based and cement-based materials rather exhibits a disordered granular-like morphology which is usually well described by using the self-consistent scheme. Within this context, this paper proposes an extension of Kroener's self-consistent scheme incorporating the physics of surface stress. The poromechanical coupling is also considered through the concept of disjoining pressure. Closed-form solutions for the homogenized elastic and poroelastic moduli that are derived and simplified expressions of these moduli are reported for asymptotic cases. [ABSTRACT FROM AUTHOR] more...

The effective behavior of a solid made from a periodic distribution of inclusions in a matrix is investigated. Inclusions and matrix are linearly elastic or viscoelastic of Kelvin-Voigt type (and possibly rigid for the inclusions) while the link between them can be pure adhesion or viscous friction with bilateral contact or involve a very thin viscoelastic layer. As long as one constituent is viscoelastic, the effective behavior is no longer of Kelvin-Voigt type but with memory. [ABSTRACT FROM AUTHOR] more...

To extend classical micro and nanomechanics of inclusions and inhomogeneities from bulk phase only to interface-featured multi-phase, we formulated a solution procedure for evaluating the significance of interface stress on embedded nanoparticles. The methodology allows, for instance, analytical determination of the influential effects of interface stress on elastic fields of both nanoparticles and matrices within the general framework of continuum theory of bulk and interface elasticity. A thorough curvilinear analysis of a general Euclidean interface is performed with the aid of field theory and applied to facilitate the integration of displacement continuity and traction jump boundary conditions of interface elasticity into the classical formulation of displacement potentials. For illustration purposes, the solution methodology is applied to a spherical nanoparticle embedded in an infinite substrate subjected to most general far-field tension and eigenstrain loads. The developed model extends the solution limit of interface-induced length-scale effects on embedded ellipsoidal nanoparticles to the solution availability of their corresponding classical counterparts, provided that interface material properties are given. [ABSTRACT FROM PUBLISHER] more...

Correlations of the exchange bias and surface roughness in bilayer structures of a ferromagnetic (NiFe)/antiferromagnetic (IrMn) type (F/AF structures) with varying thickness and sequence of deposition of the AF layer are studied using the angular dependence of the resonance field of the ferromagnetic resonance (FMR). It is found that the roughness of the samples in structures with an AF layer deposited on top of an F layer (TS type) is higher than in structures with an AF layer located at the bottom (BS type). The possible causes of differences in the behavior of the exchange bias as a function of surface roughness in samples with the different location of the AF layer are discussed. [ABSTRACT FROM AUTHOR] more...

Pulse laser deposited La2/3Sr1/3MnO3 ultrathin films on SrTiO3 substrates were characterized by polar and longitudinal Kerr magneto-optical spectroscopy. Experimental data were confronted with theoretical simulations based on the transfer matrix formalism. An excellent agreement was achieved for a 10.7 nm thick film, while a distinction in the Kerr effect amplitudes was obtained for a 5 nm thick film. This demonstrated the suppression of ferromagnetism due to the layer/substrate interface effects. A revised, depth-sensitive theoretical model with monolayer resolution described the experimental data well, and provided clear cross-section information about the evolution of ferromagnetism inside the film. It was found that the full restoration of the double-exchange mechanism, responsible for the ferromagnetic ordering in La2/3Sr1/3MnO3, occurs within the first nine monolayers of the film. Moreover, all the studied films exhibited magneto-optical properties similar to bulk crystals and thick films. This confirmed a fully developed perovskite structure down to 5 nm. [ABSTRACT FROM AUTHOR] more...

Recent experiments show that certain self-assembled polymer nanocomposites exhibit colossal dielectric constants (∼4000 at 20 Hz), as compared to eight for the polymer matrix, even for small filler volume fractions (∼7%). However, reasons for this are not well understood. In this work, two possible explanations are systematically evaluated: (i) presence of interface zones with dielectric constants much greater than that of the matrix and (ii) charge injection from filler surfaces into the dielectric at matrix–filler interfaces. Linear, isotropic composites with periodic and random arrangements of spherical, conducting nanofillers are considered. While finite element analyses on unit cells are used to compute quasi-static dielectric properties of periodic composites, standard homogenization theories are used for investigating random composites. A novel two-parameter, non-local model is used to describe the charge injection. It is shown that both the effects improve the overall dielectric constants but in very different ways. While charge injection leads to a drastic increase in effective dielectric constant even for small filler volume fractions (∼1%), high dielectric constant interface zones significantly alter the overall properties only at percolation volume fractions. Charge injection appears to be the likely reason for the colossal dielectric constants observed experimentally in self-assembled nanocomposites. [ABSTRACT FROM AUTHOR] more...

A series of samples consisting of alternating stripes of ZnO grown by molecular-beam epitaxy (MBE) and radio-frequency (rf) sputtered Ga-doped ZnO stripes was laterally microstructured with a self-aligned pattern transfer method. We measured as a function of temperature the Seebeck coefficient S and the electrical resistivity ρ in-plane of the samples with the transport direction perpendicular to the stripe direction. Throughout the series the bar width and hence the number of interfaces was kept constant, but the interface profile was varied yielding different interface lengths and geometries. The dependence of S, ρ and the power factor S2/ ρ on the interface length at room temperature were simulated using an empirical network model and it was demonstrated that the macroscopic transport coefficients are very sensitive to the interface region and that even this rather simple modelling yields useful information about the interface region. [ABSTRACT FROM AUTHOR] more...

Magnetron sputtered thin films of Cu, Nb, and Cu-Nb multilayers with 2.5 and 5 nm nominal layer thickness were deposited on Si and implanted with 4He+ and 3He+ ions. Secondary ion mass spectroscopy and nuclear reaction analysis, respectively, were used to measure the 4He+ and 3He+ concentration profile with depth inside the films. Cross-sectional transmission electron microscopy was used to characterize the helium bubbles. Analysis of the contrast from helium bubbles in defocused transmission electron microscope images showed a minimum bubble diameter of 1.25 nm. While pure Cu and Nb films showed bubble contrast over the entire range of helium implantation, the multilayers exhibited bubbles only above a critical He concentration that increased almost linearly with decreasing layer thickness. The work shows that large amounts of helium can be trapped at incoherent interfaces in the form of stable, nanometer-size bubbles. [ABSTRACT FROM AUTHOR] more...

In order to evaluate the effectiveness of CdTe surface passivating layers, HgCdTe photoconductors with and without CdTe sidewall passivation were fabricated. As expected, photoconductors with CdTe sidewall passivation demonstrated significantly higher responsivity in comparison with those without sidewall passivation, indicating the effectiveness of molecular-beam epitaxially (MBE)-grown CdTe as a passivation layer in reducing surface recombination velocity. Characterization of the responsivity differences between photoconductors with and without sidewall CdTe passivation offers a potential method for measuring the interface/surface recombination velocity. This has been demonstrated in this paper by extracting the value of the surface recombination velocity using the Synopsys Sentaurus commercial modeling package to fit experimental responsivity data for fully and partially passivated devices. [ABSTRACT FROM AUTHOR] more...

In this paper an algorithm for calculating 3-D dose distributions within the brain is introduced and adapted to the demands of modern radiosurgery. The dose calculation with this model is based on a 3-D distribution of the primary photon intensity which is calculated with a ray casting algorithm. A prelocated matrix takes into account field sizes as well as modifying elements as collimator positions (MLC), blocks, wedges and compensators. Monte Carlo precalculated monoenergetic kernels from 0.1 MeV to 50 MeV were at our disposal. The components of the spectrum were either determined by deconvoluting depth dose curves measured in water or analyzed with a Ge-Li detector system in the case of60Co. The calculated fluence distribution has to be superposed to the complete kernel containing the spatial energy deposition. Inhomogeneities and tissue interface phenomena (σe, Z) have been investigated. The divergence of the rays and the curved surface of the patient are taken into account. Assuming homogenous media, it is possible to shorten the computation time by using the Fast Fourier Transformation (FFT) delivering a first overview within seconds.The algorithm was evaluated and verified under specific conditions of small fields as used in radiosurgery and compared to dose measurements and Monte Carlo calculations. In using both the fast algorithm (FFT) for mainly homogenous conditions on one hand and the very precise superposition for inhomogeneous cases on the other, this algorithm can be a very helpful instrument especially for critical locations in the skull. [ABSTRACT FROM AUTHOR] more...

The huge increase in the superconducting transition temperature of FeSe induced by an interface to SrTiO3 remains unexplained to date. However, there are numerous indications of the critical importance of specific features of the FeSe band topology in the vicinity of the Fermi surface. Here, we explore how the electronic structure of FeSe changes when located on another lattice matched substrate, namely a Si(001) surface, by first-principles calculations based on the density functional theory. We study non-magnetic (NM) and checkerboard anti-ferromagnetic (AFM) magnetic orders in FeSe and determine which interface arrangement is preferred. Our calculations reveal interesting effects of Si proximity on the FeSe band structure. Bands corresponding to hole pockets at the Γ point in NM FeSe are generally pushed down below the Fermi level, except for one band responsible for a small remaining hole pocket. Bands forming electron pockets centered at the M point of the Brillouin zone become less dispersive, and one of them is strongly hybridized with Si. We explain these changes by a redistribution of electrons between different Fe 3 d orbitals rather than charge transfer to/from Si, and we also notice an associated loss of degeneracy between d x z and d y z orbitals. [ABSTRACT FROM AUTHOR] more...

The present work focuses on the study of exchange-biased magnetic core/shell nanoparticles at the atomic scale. The nanoparticles (NPs) consist of a perfectly epitaxial crystalline cobalt oxide (CoO) shell on a magnetite (Fe3O4) core. The numerical core/shell is built by taken into account the spinel structure of the core (Fe3O4) and the face-centered cubic structure of the shell (CoO). Two different configurations of core/shell NPs were examined: homogeneous and inhomogeneous core/shell. Our magnetic simulations are based on a 3D classical Heisenberg model. Monte Carlo simulations performing single spin rotation are used to investigate the effect of exchange bias on the spin configurations and hysteresis loops of core/shell nanoparticles. The numerical results reveal, as expected, a significant hysteresis loop shift obtained for a weak interface coupling. In addition, the magnetization reversal is not perfectly uniform in space when the interfacial coupling is different from zero. Finally, the increase in the magnetic interfacial coupling produces an increase in coercive field and a decrease in the exchange bias field. [ABSTRACT FROM AUTHOR] more...

Depth profiles obtained under Cs bombardment of samples of crystalline lithium niobate (LiNbO3) covered with a thin layer of metal display some artifacts related to metal/LiNbO3 interface effects. The altered yields of Li and Nb secondary ions in the first 50 nm after erosion of the metal layer can be interpreted in terms of different stopping powers between metal and LiNbO3. In this study, two typical samples are investigated and the artifacts are qualitatively explained by comparing experimental profiles and simulations performed with the transport of ions in matter code. The similarity between experiment and simulation suggests that the ballistic interpretation of the artifacts is appropriate. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR] more...