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A bi-layers stack consisting of a semiconductor thin film of a varied thickness and a very thin Pd layer (SiC/Pd/c-Si).was deposited onto c-Si by e-beam evaporation at room temperature. The multi-layers structure was subjected to a thermal annealing process at near eutectic temperature of the Si – Pd phase. It is noticed, through top view SEM and cross-section STEM analyses, that the sandwiched Pd metal layer dewets from the interface with the c-Si substrate in well dispersed nanoparticles and it diffuses inward onto the top few monolayers of the substrate; at times it permeates shallowly through the SiC semiconductor top layer. The size distribution of the nanoparticles was found to be closely linked to the thickness of the top semiconductor layer. On the other hand, the top SiC layer was found to form islands protruding above the surface, when the film was very thin. When thicker, the semiconductor SiC layer retained its integrity and remained unaffected. An optical model of the resulting metal-dielectric mixed layer is proposed.

We report the influence of reactive oxygen (O2) and argon (Ar) plasma based ITO:Zr bi-layers for silicon heterojunction (SHJ) solar cells. The purpose of reactive O2 sputtered ITO:Zr was to improve the Hall mobility and work function while the Ar based ITO:Zr films play an important role to maintain good electrical characteristics. The thickness of reactive O2 based ITO:Zr films was fixed at 15 nm while Ar based films was varied from 65 to 125 nm, respectively. ITO:Zr bi-layers with the thickness of 15/105 nm deposited by O2 and Ar plasma, respectively, showed lowest resistivity of 2.358 × 10−4 Ω cm and high Hall mobility of 39.3 cm2/V · s. All ITO:Zr bi-layers showed an average transmittance of above 80% in the visible wavelength (380–800 nm) region. Work function of ITO:Zr bi-layers was calculated from the X-ray photoelectron spectroscopic (XPS) data. The ITO:Zr work function was enhanced from 5.3 eV to 5.16 eV with the variation of ITO:Zr bi-layers from 15/65 to 15/125 nm, respectively. Front barrier height in SHJ solar cells can be modified by using TCO films with high work function. The SHJ solar cells were fabricated by employing the ITO:Zr bi-layer as front anti-reflection coating. The SHJ solar cells fabricated on ITO:Zr bi-layer with the thickness of 15/105 nm showed the best photo-voltage parameters as; Voc = 739 mV, Jsc = 39.12 mA/cm2, FF = 75.97%, η = 21.96%.

The influence of thickness of silver-magnesium fluoride bi-layers on the sensitivity of SPR based fiber optic sensor has been experimentally examined. The sensitivity is enhanced with increasing ma...

INTRODUÇÃO: O uso de materiais cerâmicos como estratégia restauradora enfrenta algumas problemáticas, como interferências entre a porcelana e zircônia, sendo a primeira utilizada como cerâmica de cobertura e a segunda como infraestrutura ou coping. OBJETIVO: revisar a literatura sobre coroas cerâmicas bi-layer, através dos tipos de cerâmicas, processamento cerâmico e tensão residual. METODOLOGIA: As bases de dados para esta revisão foram Bireme, Pubmed, Scielo e Bibliotecas Virtuais. As palavras-chaves foram buscadas no Mesh, quanto aos critérios de inclusão são Estudos, Laboratoriais e Clínicos, Revisão Sistemática e Metanálise, artigos científicos e literatura específica sobre o tema, literatura em inglês e português. Já os critérios de exclusão foram carta ao editor, caso clínico e artigo de opinião, literaturas que não abordasse o tema em estudo e artigos que abordem outras cerâmicas odontológicas. A literatura e os artigos foram selecionados por meio de resumos e abstracts. CONSIDERAÇÕES FINAIS: Tensão residual em coroas cerâmicas bi-layers, com infra-estrutura em zircônia e cobertura em porcelana, ocorrem pela ação de diversos fatores como coeficiente de expansão térmica, velocidade de resfriamento, processamento e espessura da cerâmica de cobertura.

We have measured the relative orientation of rotated graphene bi-layers (RGBs) deposited by chemical vapor deposition and found that there are spontaneously occurring preferred orientations. Measurements were performed using selected area electron diffraction patterns on various regions of the RGBs. These orientations minimize the complexity of the lattice defined by the set of all possible Burgers vectors. By using a precise definition of singularity, we have been able to show that all non-singular preferred orientations are special in the sense that their angular distance Δθ to the closest singular orientation also complies with the definition of singularity. Our results show that these special interfaces, named secondary singular interfaces, have simpler displacement fields compared to other non-singular RGBs, implying that interfacial dislocations have fewer Burgers vectors to choose from. Since all observed orientations were found to be either singular or secondary singular, we found evidence that RGBs starting out with rotation angles far from singular orientations re-orient themselves into a nearby secondary singular state in order to simplify their strain fields. Secondary singular orientations also account for the spontaneous formation of high Σ interfaces, although the lack of a precise definition of singularity caused them to remain unnoticed.

Investigations of single and bilayers of bismuth are one of the most thrusting areas of research in contemporary condensed matter physics and material sciences. This is because such ultrathin layers of bismuth host interesting exotic electronic properties, which are important from both fundamental science and future application perspectives. In the past, many inorganic processes for the synthesis of single and bi-layers of bismuth were reported using physical and chemical vapor deposition techniques. The ultrathin films deposited are found to interact electronically with the substrates due to their proximity to the substrate surface. We introduce a new and easy organic channel for the synthesis of the bismuth multi-bilayers in ambient conditions. Bismuth stearate multi-bilayer thin films are deposited on the hydrophobic silicon and hydrophilic glass substrates using the Langmuir-Blodgett technique. Optical absorption spectroscopy measurements in the infrared region provided information on various bond structures present in those bismuth stearate thin films. Specular x-ray reflectivity (XRR) experiments and their analysis of such thin films unambiguously show the highly periodic stacking of bismuth bilayers along the surface-normal directions within the multilayer film structure. Model-based microstructural analysis of the XRR data further shows that each bilayer of bismuth is well separated (3.5 nm) from other bismuth bilayers by hydrocarbon chains. At these separations, the electronic states of the bismuth bilayers are expected to be non-interacting with each other. The morphology of the surface obtained from field emission scanning electron microscopy supports the XRR analysis. A bandgap of 3.2 eV was obtained for such bismuth stearate thin films from the optical spectroscopy measurements in the UV-visible range. The large separations between the bismuth-bilayers and between the substrate and the bismuth bilayers are expected to minimize the electronic interactions between them.

Mismatched lattice-constants at a van-der-Waals epitaxy interface often introduce in-plane strains to the lattice of the epitaxial layer, termed epitaxy-strain, where the strains do not follow the intra-layer Poisson's relation. Here, we presented the magnetic phase diagrams of the CrSe2 and CrTe2 mono- and bi-layers under epitaxy-strain up to 8 %, as predicted using density-functional-theory calculations. They show that the in-plane epitaxy-strain manipulates either the intra- or inter-layer magnetism of them. The in-plane strain varies the interlayer distance, defined using an inter-layer Poisson's ratio, which governs the inter-layer magnetism in two opposite ways depending on the in-plane magnetism. The tunability of the intra-layer magnetism is a result of competing intra-layer Cr-Cr super-exchange interactions. A graphene substrate was introduced to examine the validity of our diagrams in practice. Our work also gives a tentative explanation on the controversially reported magnetizations in CrSe2 and CrTe2 epitaxial mono- or bi-layers under epitaxy-strains.

Surface, the front face of any materials or object. Surface properties define the physical appearance, chemical reactivity or stability, optical, friction, mechanical properties etc. To study and manipulate the surface properties is the dire need in present scenario. At present with modern instruments, better understanding of different biological phenomena particularly stability, pattern formation and small scale deformation of membranes have been gained. In the present article a two-dimensional film which is in a frictional contact with the substrate which developed between the film and the substrate using the contact interactions is studied. Surface morphology and stability evolution of a thin elastic film subjected to in-line axial force is investigated. The instability of the 2D thin film under different elastic conditions and boundary conditions is examined using finite element simulation. The response to perturbation in which surface of the film becomes unsteady and forms a wavy pattern without any simultaneous mass transport. A complete picture stability/bifurcation is obtained for different elastic modulus ratios of film and substrate. Result revealed that the wavelength is directly proportional to elastic modulus of the film. The growth rate of perturbations is also analysed. The pattern instability in the thin films which are fixed on a substrate by adhesive forces decreases with the decrease in elastic modulus of the film. Study revealed that the morphology of the film is independent of forces exerted however seems dependence on the nature of the film. The film shows stability in its pattern when its elastic modulus is same as substrate elastic modulus or the ratio of modulus is close to unity. This study will be helpful in in choosing the surface coating to coat over the base material, design material of required properties coating life and estimating the life of coating.

Warping of layered wood-based panels is still a challenging problem in the development of thin engineered wood products. Wood as an anisotropic and hydrophilic material tends to change its volume and mechanical properties with changing moisture content. Besides the wood components, also the mechanical properties of certain adhesives are sensitive to moisture changes. A moisture load onto the adhered wood is resulting in different stress and strain states between the adherends. It is expected that adhesives with different moisture-related properties participate differently to this interaction. To observe an adhesive-related warping, thin spruce/HDF (Picea abies and high-density fibreboard) bi-layers with identical material geometries were manufactured under laboratory conditions, using different wood adhesive systems, which are currently used in furniture and flooring industry [polyurethane (PUR), emulsion polymer isocyanate (EPI), polyvinyl acetate (PVAc), urea formaldehyde (UF) and ultra-low emitting formaldehyde amino adhesive (ULEF)]. The bi-layers were exposed to certain relative humidity conditions, and the resulting deformation was measured with a high-precision laser distance detector. Moisture-dependent warping of the bi-layers was obtained in relation to the used adhesive systems. As a result of the study, it can be shown that initial warping after panel manufacturing strongly depends on the adhesive curing characteristics and, especially, on the amount of water that is released into the wood adherend. For the post-setting panel warping, a differentiation into two adhesive groups became visible: rigid and flexible adhesives. Rigid adhesives (UF and ULEF) showed a higher degree of warping compared to the group of flexible adhesives (PUR, EPI and PVAc).

In this paper, we report results on the processing of cadmium zinc sulfide (CdxZn1-xS) ternary compound starting from the deposition of cadmium sulfide (CdS)/zinc sulfide (ZnS) bi-layers buffer configuration and a subsequent thermal annealing for its application to thin film solar cells. The impact of different CdS/ZnS bi-layers buffer configurations as effective alternative to the single CdS buffer layer, as well as the physical and chemical properties of the equivalent CdxZn1-xS ternary compound are presented and discussed. Results on physical properties optimization of CdxZn1-xS ternary compound for future applications to thin film solar cells are presented.

The accurate and speedy detection of COVID-19 is essential to avert the fast propagation of the virus, alleviate lockdown constraints and diminish the burden on health organizations. Currently, the methods used to diagnose COVID-19 have several limitations, thus new techniques need to be investigated to improve the diagnosis and overcome these limitations. Taking into consideration the great benefits of electrocardiogram (ECG) applications, this paper proposes a new pipeline called ECG-BiCoNet to investigate the potential of using ECG data for diagnosing COVID-19. ECG-BiCoNet employs five deep learning models of distinct structural design. ECG-BiCoNet extracts two levels of features from two different layers of each deep learning technique. Features mined from higher layers are fused using discrete wavelet transform and then integrated with lower-layers features. Afterward, a feature selection approach is utilized. Finally, an ensemble classification system is built to merge predictions of three machine learning classifiers. ECG-BiCoNet accomplishes two classification categories, binary and multiclass. The results of ECG-BiCoNet present a promising COVID-19 performance with an accuracy of 98.8% and 91.73% for binary and multiclass classification categories. These results verify that ECG data may be used to diagnose COVID-19 which can help clinicians in the automatic diagnosis and overcome limitations of manual diagnosis.

The quality of a semiconductor, which strongly affects its performance, can be estimated by its photoluminescence, which closely relates to the defect and impurity energy levels. In light of this, it is necessary to have a measurement method for photoluminescence properties with spatial resolution at the sub-micron or nanoscale. In this study, a mapping method for local photoluminescence properties was developed using a focused synchrotron radiation X-ray beam to evaluate localized photoluminescence in bi-layered semiconductors. CuO/Cu2O/ZnO semiconductors were prepared on F:SnO2/soda-lime glass substrates by means of electrodeposition. The synchrotron radiation experiment was conducted at the beamline 20XU in the Japanese synchrotron radiation facility, SPring-8. By mounting the high-sensitivity spectrum analyzer near the edge of the CuO/Cu2O/ZnO devices, luminescence maps of the semiconductor were obtained with unit sizes of 0.3 μm × 0.3 μm. The devices were scanned in 2D. Light emission 2D maps were created by classifying the obtained spectra based on emission energy already reported by M. Izaki, et al. Band-like structures corresponding to the stacking layers of CuO/Cu2O/ZnO were visualized. The intensities of emissions at different energies at each position can be associated with localized photovoltaic properties. This result suggests the validity of the method for investigation of localized photoluminescence related to the semiconductor quality.

Thin films of noble metals, such as gold, have high visible transparency and infrared reflectance. The former is due to the presence of surface plasmons, and the latter is due to the large density of free electrons. Gold thin films have a transmittance peak at 520 nm, which is closely matched to the maximum emission of solar radiation. These properties have been utilized in several applications, including energy-saving transparent heat mirrors that consist of a bi-layer of a thin gold film over-coated with a dielectric layer. These coatings transmit light and reflect heat. For such an application, the transmittance of the thin gold film needs to be enhanced; this is achieved by the dielectric layer that functions as an antireflective coating. In this work, the dielectrics were metal oxides that are transparent in the visible range. The selection criteria based on the band gap, and refractive index were first imposed to identify potential metal oxides. This resulted in the choice of ten metal oxides (CeO2, HfO2, MoO3, Nb2O5, NiO, SnO2, Ta2O5, TiO2, WO3, and ZrO2). The bi-layer performance was then optimized theoretically. The gold-metal oxide layers were subsequently fabricated, and their optical spectra were measured over the ultraviolet–visible-near infrared ranges. The performance of the heat mirrors was assessed in terms of their visible and solar transmittance and reflectance. A figure of merit was defined to evaluate the suitability of the oxides. The optical properties suggest that tungsten oxide (WO3) is the best oxide; however, hafnium oxide (HfO2) has the best performance for solar energy applications.

Processed meat products have been increasingly consumed, a highlight being dried-cured coppa, commonly purchased sliced, making it more susceptible to bacterial deterioration and lipid oxidation. The aim of this work was to produce and apply bi-layers films based on gelatin (in both layers) with addition of nisin and/or Pitanga leaf hydroethanolic extract (PLHE) only in the food contact thinner layer, in order to evaluate their effect on the refrigerated storage of sliced dried-cured coppa. Dried-cured coppa slices covered with active films were vacuum-packaged and stored under refrigeration for 120 days. Every 30 days, samples were tested for moisture content, water activity, pH, color parameters, lipid oxidation by TBARS and peroxide index methods, and microbiological analysis. The different film formulations presented no influence on the water activity, pH and color parameters of sliced dried-cured coppa. However, they significantly affected moisture content, bacterial count and lipid oxidation. The addition of both active compounds - nisin and PLHE - in the food contact thinner layer was observed to have the most favorable effect.

Cu wires are coated by porous/dense Ni bi-layers as current collectors through electroless plating and hydrogen bubble dynamic template electrodepostion methods. The unique coaxial composite current collectors can be beneficial from the high electrical/thermal conductivity of metal Cu core and high corrosion resistance of dense metal Ni coating as well as porous Ni substrate for growth of active materials. Furthermore, the metal wire current collectors have excellent flexibility and mechanical strength. Highly flexible solid-state fiber supercapacitors are then fabricated by binder-free integrated electrodes of hierarchical MnCo2O4 nanothorns grown on porous/dense Ni bi-layers coated Cu wires. The fiber supercapacitors reach capacitance of 20.6 mF cm−1 (54.8 mF cm−2) and energy density of 4.8 μWh cm−1 (12.8 μWh cm−2) at a power density of 32.25 μW cm−1 (110 μW cm−2). Moreover, the twist fiber supercapacitors show good rate capability and cycling stability. The outstanding performances of the fiber supercapacitors might be attributed to the hierarchically nanothorns MnCo2O4 active materials and the unique porous/dense Ni coated Cu wire current collectors. Our results can provide a novel strategy to design flexible nanostructure fiber supercapacitors for energy storage applications in future wearable electronics.

38th European Photovoltaic Solar Energy Conference and Exhibition; 451-453, We fabricated and analyzed CZTSe: Ge bi-layers solar cells to accurately evaluate the electrical structure at hetero and back contact junctions by modulus spectroscopy. Two separate built-in potentials of hetero and back contact junctions are extensively investigated to describe qualitative each junction model of CZTSe: Ge bilayers devices. Fabricated devices are analyzed with an equivalent circuit model, and LEVM/LEMW software resolved two different parallel circuit branch components. Modeling with LEVM/LEMW software accurately fits our model to modulus and impedance spectra in the given testing frequency domain. Using TCAD numerical simulations, we examine a variety of device models with a set of built-in potentials for appropriate parallel circuits with two capacitance and two resistance (R2=0.99). Our study shows that heterojunction built-in potential is 801 meV, which is ~10 % smaller than a theoretical value, 894 meV. Conversely, the built-in potential of the back contact junction is 428 meV. Total built-in potential is 373 meV

Maraging steels are martensitic steels hardened by precipitation during thermal aging, with good machining properties and high strength and corrosion resistance. It is well suited for applications which require high strength-to-weight material, being used in aerospace, aeronautics and nuclear industries. A protective and corrosion resistant oxide layer can be formed during age hardening if treated in steam atmosphere. This work aims to use grazing incidence X-ray diffraction (GIXRD) to evaluate qualitatively the thickness of the layers formed during this process. GIXRD and scanning electron microscopy (SEM) were employed to identify and order the layered structure formed on four specimens of maraging steel grade 300 with different surface finishes that were previously solution annealed twice at (950 ± 5) °C for 1 h, air-cooled, and submitted to oxidation process under positive pressure around 1.5 kPa of steam at (480 ± 5) °C for 6 h followed by forced air cooling. The diffraction patterns were measured employing CuKα radiation and parallel beam, in step scan mode, using incident angles varying from 0.2º to 4.0º and 20º < 2θ < 85º. The results revealed the formation of two layers, the innermost was formed by γ-iron (austenite – fcc) phase followed by a mixture of oxides (hematite and magnetite) on the top, regardless of surface finish, which was confirmed by the SEM analysis that also allowed the measurement of the average layer’s thickness of oxides (1.130 ± 0.094) µm and austenite (0.507 ± 0.090) µm phases, and corroborated the qualitative thicknesses analysis made from GIXRD results.

We have investigated and modeled the complex phenomenon of boron (B) redistribution process in strongly doped silicon bilayers structure. A one-dimensional two stream transfer model well adapted to the particular structure of bi- layers and to the effects of strong-concentrations has been developed. This model takes into account the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method, using in-situ nitrogen- doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P+) layer. To avoid long redistributions, thermal annealing was carried out at relatively lowtemperatures (600 °C and 700 °C) for various times ranging between 30 minutes and 2 hours. The good adjustment of the simulated profiles with the experimental secondary ion mass spectroscopy (SIMS) profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders kinetics.

The authors acknowledge the financial support in part from NRF-NRFI2016-08 and in part from TUBITAK 115F279 and 117E713. H.V.D. gratefully acknowledges support from TUBA. O.E. acknowledges TUBITAK for the financial support through BIDEB 2211 program. The authors thank Mr. Mustafa Guler for TEM imaging of the as-synthesized CQWs and preparation of the TEM cross-sectional sample and Dr. Gokce Celik for her help on the ellipsometric measurements. This study demonstrates an ultra-thin colloidal gain medium consisting of bi-layers of colloidal quantum wells (CQWs) with a total film thickness of 14 nm integrated with high-index dielectrics. To achieve optical gain from such an ultra-thin nanocrystal film, hybrid waveguide structures partly composed of self-assembled layers of CQWs and partly high-index dielectric material are developed and shown: in asymmetric waveguide architecture employing one thin film of dielectric underneath CQWs and in the case of quasi-symmetric waveguide with a pair of dielectric films sandwiching CQWs. Numerical modeling indicates that the modal confinement factor of ultra-thin CQW films is enhanced in the presence of the adjacent dielectric layers significantly. The active slabs of these CQW monolayers in the proposed waveguide structure are constructed with great care to obtain near-unity surface coverage, which increases the density of active particles, and to reduce the surface roughness to sub-nm scale, which decreases the scattering losses. The excitation and propagation of amplified spontaneous emission (ASE) along these active waveguides are experimentally demonstrated and numerically analyzed. The findings of this work offer possibilities for the realization of ultra-thin electrically driven colloidal laser devices, providing critical advantages including single-mode lasing and high electrical conduction. Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) 115F279 117E713 BIDEB 2211 Turkish Academy of Sciences NRF-NRFI2016-08

Geometrical instability leading to cambering is recorded during co-sintering of zirconia dense/porous bi-layered planar structures. Sintering strain in the bi-layers rises mainly from mismatch between the different porosity volume fractions at the layers and their interface. In this paper, we analyze the model case of dense taped of 8 mol% Y 2 O 3 -stabilized ZrO 2 laminated on ca. 400 μ thick 3 mol% Y 2 O 3 doped zirconia porous tapes, with homogenous spherical porosity of 13 vol%, 46 vol%, and 54 vol%. Sintering stress during densification is evaluated from the shrinkage rates and viscoelastic behavior during sintering by thermo-mechanical analysis, using cyclic loading dilatometry. The camber development of the bi-layers is measured by in-situ optical dilatometry. In accordance with the model prediction, cambering can be controlled tuning the porosity while achieving a synergetic effect between densification and formation of open porosity at the bilayers.

We report the formation of Bi clusters in Ga(P1-x,Bix) layers during an in situ (scanning) transmission electron microscopy ((S)TEM) annealing investigation. The non-destructive temperature regime in dependence on the tertiarybutylphosphine (TBP) pressure in the in situ cell was investigated to ensure that the results are not distorted by any destructive behaviour of the crystal during the thermal treatment. The following annealing series of the Ga(P92.6Bi7.4) and Ga(P96.4Bi3.6) layers reveals that the threshold temperature at which the Bi clustering takes place is 600 °C in the Ga(P92.6Bi7.4) layer. Further thermal treatments up to 750 °C show a relationship between the Bi fraction in the Ga(P1-x,Bix) layer and the initial temperature at which the Bi clustering takes place. Finally, we investigate one Bi cluster at atomic resolution conditions. In these conditions, we found that the Bi cluster crystallized in a rhombohedral phase, aligning with its {101} planes parallel to the Ga(P,Bi) {202} planes.

37th European Photovoltaic Solar Energy Conference and Exhibition; 710-712, In this contribution, we propose an AC response equivalent circuit model to describe the impedance spectroscopy of CZTSe nanoscale Ge bi-layers solar cells. A developed equivalent circuit of CZTSe Ge bi-layers solar cells reflects a realistic device structure, involving the contact & bulk resistance, resistance and capacitance of one heterojunction interface, two effective back-contact interfaces, and a buffer interface. The impedance model is characterized by proposing an equivalent circuit that includes series and parallel resistance and constant phase element to accurately model the device structure. The Sentaurus TCAD simulation is performed to confirm the structure of a proposed device model. The in-house MATLAB simulator, connected to external TCAD simulation tools are designed for the accurate impedance model with the simulated structures to illustrate the effectiveness of impedance models of CZTSe Ge bi-layers solar cells, associated with MoSe2 interfacial defects.

Twisted two-dimensional bi-layers offer exquisite control on the electronic bandstructure through the interlayer rotation and coupling, enabling magic-angle flat-band superconductivity and moir\'e excitons. Here, we demonstrate how analogous principles, combined with large anisotropy, enable extreme control and manipulation of the photonic dispersion of phonon polaritons (PhPs) in van der Waals (vdW) bi-layers. We experimentally observe tunable topological transitions from open (hyperbolic) to closed (elliptic) dispersion contours in twisted bi-layered {\alpha}-MoO3 at photonic magic angles, induced by polariton hybridization and robustly controlled by a topological quantity. At these transitions the bilayer dispersion flattens, exhibiting low-loss tunable polariton canalization and diffractionless propagation with resolution below {\lambda}0/40. Our findings extend twistronics and moir\'e physics to nanophotonics and polaritonics, with great potential for nano-imaging, nanoscale light propagation, energy transfer and quantum applications., Comment: Nature, in press

Evolution of interface microstructure with addition of more number of layers has been investigated on Cr/Ti multilayer which is important for application as a mirror or monochromator in the “water window” soft X-ray spectral regime. Two sets of Cr/Ti multilayers at moderate and low bi-layer thickness regime have been prepared for this purpose using Ion Beam Sputtering technique. In one set, Cr/Ti multilayer with 25, 50, 60 and 100 numbers of bilayers with moderate bi-layer thickness of 3.8 nm have been deposited. In another set, four samples each having low bilayer thickness of 2.4 nm with 25, 50, 75 and 100 number of bi-layers have been prepared and the multilayers have subsequently been characterized with Specular X-ray reflectivity and diffuse X-ray scattering measurements at grazing incidence with hard X-rays. It is observed that cumulative effect of interface imperfections became more pronounced with increasing number of bilayers resulting in continuous increase in the interface width in both the thickness regimes; however, its evolution is not exactly same for the two sets of samples. Diffuse X-ray scattering result reveals that for the first set of samples, interface imperfections are dominated by interface roughness with no change in the interface diffusion with increase in number of layers, while for the second set, both interface roughness as well as interface diffusion contribute towards the cumulative accumulation of interface imperfections which is also confirmed by cross-sectional Transmission Electron Microscopy. Finally, performance of the multilayers in water window regime has been checked by soft X-ray reflectivity measurements using synchrotron radiation. The above results have direct implication in utilisation of these multilayers over a wide bi-layer thickness regime required to cover the full ‘water-window’ spectrum.

Cuprous halides (CuX with X = Cl, Br, I), intensely studied about four decades ago by experimentalists for excitons, are again drawing attention of researchers recently. Potential of cuprous halide systems for device applications has not yet been fully explored. We go beyond the one-particle picture to capture the two-particle physics (electron-hole interaction to form excitons). We have deployed the full tool kit of many-body perturbation technique, GW approximation + Bethe Salpeter equation, to unfurl the rich excitonic physics of the bulk as well as layers of CuX. The negative spin-orbit contribution at the valence band top in CuCl, compared to CuBr and CuI, is in good agreement with experiments. We note that CuX have exceptionally strong excitons, defying the linear fit (between the excitonic binding energy and band gap) encompassing many semiconductors. The mono- and bi- layers of cuprous halides are predicted to be rich in excitons, with exceptionally large binding energies and the resonance energies in UV/visible region. Hence this work projects CuX layers as good candidates for optoelectronic applications. With advancement of technology, we look forward to experimental realization of CuX layers and harnessing of their rich excitonic potential.

Theoretical analysis of surface plasmon resonance (SPR) based fiber optic sensor with bi layers of ITO-Pt is carried out. Sensitivity and figure of merit (FOM) of sensor increase with increase in Pt layer thickness for all thicknesses of ITO layers. Though, for a fixed thickness of Pt layer, sensitivity and FOM are reduced with increase in ITO layer thickness. 50 nm ITO–25 nm Pt based SPR sensor reveals maximum sensitivity and FOM.

Aluminum alloy 1050 strips are roll-bonded with interlayer Al2O3 particles. The effect of rolling parameters on the bond strength, such as the content of Al2O3 particles, plastic deformation, and rolling temperature are investigated by peel test. It is established that higher bond strength can be obtained by increasing the rolling temperature, reducing the thickness, and decreasing the alumina content. The peeling surface of samples versus alumina content is characterized by scanning electron microscopy.

This paper aims at developing a simplified analytical model, as verified by the Hilbert-Riemann theoretical solution of interfacial cracks, to study the thermal stress distributions in solar cell laminated structures under thermal loadings. The interface thermal failure problem is analyzed in terms of the packaging materials and solar cell materials of simulated models, maximum interfacial normal stress, and stress critical point. It provides some guidance for the design and optimization of solar modules.

We report a ferromagnetic resonance study of an electrically insulating magnetic bi-layer consisting of two yttrium iron garnet (YIG) films epitaxially grown on both sides of a non-magnetic gadolinium gallium garnet (GGG) slab. We show that standing transverse sound waves couple the coherent magnetization dynamics of the two YIG films half millimeter apart through the magnetoelastic interaction, periodically modulating the microwave absorption as a function of frequency. Constructive and destructive interferences between the dynamics of the two YIG layers is observed. This long range coherent coupling by phononic angular momentum currents through non-magnetic dielectric waveguide brings new functionalities to insulator hybrid spin circuits and devices.

We observe the signature of zero-field ground-state skyrmions in BiSb topological insulator / MnGa bi-layers by using the topological Hall effect (THE). We observe a large critical interfacial Dzyaloshinskii-Moriya-Interaction energy (5.0 pJ/m) at the BiSb/MnGa interface that can be tailored by controlling the annealing temperature of the MnGa template. The THE was observed at room temperature even under absence of an external magnetic field, which gives the strong evidence for the existence of thermodynamically stable skyrmions in MnGa/BiSb bi-layers. Our results will give insight into the role of interfacial DMI tailored by suitable material choice and growth technique for generation of stable skyrmions at room temperature.

In this paper, we present structural and luminescence studies of silicon-rich silicon oxide (SRO) and SRO-Si3N4 bi-layers for integration in emitter-waveguide pairs that can be used for photonic lab-on-a-chip sensing applications. The results from bi and mono layers are also compared. Two clearly separated emission bands are respectively attributed to a combination of defect and quantum confinement–related emission in the SRO, as well as to defects found in an oxynitride transition zone that forms between the oxide and the nitride films, while ruling out quantum-confinement phenomena in the silicon nitride, This work has received funding from the CONACyT of Mexico; and from the Spanish National MINECO-DGI project, grant number: TEC2011-29045-C04-01, We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

In this paper, we present structural and luminescence studies of silicon-rich silicon oxide (SRO) and SRO-Si 3 N 4 bi-layers for integration in emitter-waveguide pairs that can be used for photonic lab-on-a-chip sensing applications. The results from bi and mono layers are also compared. Two clearly separated emission bands are respectively attributed to a combination of defect and quantum confinement⁻related emission in the SRO, as well as to defects found in an oxynitride transition zone that forms between the oxide and the nitride films, while ruling out quantum-confinement phenomena in the silicon nitride.

Interplay between intrinsic bi-layers and overlying doped layers in a-Si:H/c-Si heterojunction solar cells was investigated. Insertion of the more porous intrinsic a-Si:H layer at the a-Si:H/c-Si interface is beneficial to mitigate the degradation of the surface passivation after p-layer deposition. This interfacial layer was also applied to SHJ solar cells, and a notably high V$_{OC}$ of 0.742 as well as a high conversion efficiency of 22.2% was achieved.

The presence of Schottky barrier near back contact limits the hole movement which influences the current-voltage characteristics and deteriorates the Voc-deficit as well. In this work, a set of CZTSe solar cells were fabricated by DC magnetron sputtering and investigated for the back contact interface between CZTSe/MoSe$_{\mathbf {2}}$ and Mo metal contact in an effort to improve a back contact barrier. By incorporating nanoscale Ge bi-layers below and below the absorber, a barrier height is considerably improved. To extract a back contact barrier height, a temperature-dependent behavior of CZTSe: Ge bi-layer devices is characterized and compared to CZTSe monolayer devices.

Here, we investigated the influence of grain formation on the magnetization reversal of SmCo5/Co at low temperature. A set of SmCo5/Co bi-layer samples were fabricated under identical conditions on MgO(100) and glass substrates with a Cr underlayer. Analysis of each magnetic layer by an Atomic Force Microscope (AFM) reveals that MgO(100) results small and uniform grain formation of 23 nm in contrast to 57 nm on glass, and x-ray diffraction studies show that the sample on MgO(100) has high crystallinity with SmCo5(11 0) phase. At room temperature, both samples exhibit good hard magnetic properties with coercivity (HC) of 13.2 kOe and 12.5 kOe, and energy products (BH)max of 14.5 MGOe and 5.3 MGOe for samples on MgO(100) and glass, respectively. Low temperature hysteresis measurements show an exchange decoupling at low temperatures for the sample on glass, and this is due to the formation of large grains on glass that reduces the effective inter-grain exchange coupling between phases., 13 pages, 5 figures

The nano technology development requires efficient multifunctional low dimensional materials. In this work, the full-potential linearized augmented plane wave (FP-LAPW) method and semiclassical Boltzmann transport theory are applied to investigate the structural, electronic, optical and thermoelectric properties of the CaO monolayer and bilayers with AA and AB stacking. These two-dimensional (2D) materials are indirect gap semiconductors with band gap of 2.619, 2.290 and 2.857 eV, respectively. CaO monolayer and bilayers appear to be prospective materials for applications in the ultraviolet detector and absorber of the optoelectronic devices provided that they show wide absorption band with high absorption coefficient. Simulations demonstrate that the in-plane polarized incident light may be more efficient to excite the electronic transitions than the perpendicular polarization. Finally, the thermoelectric properties of layers at hand including Seebeck coefficient, electrical conductivity, electronic thermal conductivity and power factor are determined and discussed. Studies suggest that the AA-stacking may be the most promising candidate for the thermoelectric applications. Results presented here may be a good theoretical guidance for the low-dimensional wide band gap semiconductors.

We investigate different mechanical effects which accompany the nerve pulse propagation by using mathematical modeling. The propagation process is composed by three connected phenomena: (i) the action potential (electrical signal) which is usually considered when nerve pulses are discussed, (ii) the mechanical wave propagating in the biomembrane and (iii) the pressure wave in the axoplasm inside the axon. The main goal of the present study is to investigate numerically how the mechanical wave is generated by the action potential and how the characteristics of the system are reflected in the emerging wave ensemble. %the existence and characteristics of the mechanical wave influence the parameters of an action potential part of the wave ensemble. The key characteristics for the coupled model system are: (i) the velocity of the peak of the mechanical pulse is associated with the velocity of the action potential regardless of the sound velocity value in the lipid bi-layer, (ii) the velocity of the front and the shape of the mechanical wave depends on sound velocity in the lipid bi-layer, (iii) the shape of the mechanical wave can have an effect on the velocity and shape of the action potential., Comment: The Tenth IMACS International Conference on Nonlinear Evolution Equations and Wave Phenomena: Computation and Theory, March 29 - April 01, 2017. Georgia, USA

To improve the corrosion resistance of mild steel, in this work, bi-layers of BTSE (bis-(triethoxysilyl) ethane) and Ppy coatings have been deposited via adsorption and electrodeposition, respectively. The anticorrosive properties of these bi-layers have been evaluated in an aggressive medium like 3% NaCl, and compared with the layers of BTSE and Ppy in a separate way. In spite of the aggressive solution, it was evaluated a poor behaviour of both Ppy and BTSE coatings using potential measurements, EIS and SEM techniques. A better behaviour was expected because the preparation of the bi-layers Ppy/BTSE and BTSE/Ppy showed a protective behaviour using SEM and salt spray tests. However, EIS results predicted an evolution of these coatings for long immersion times being evident the oxidation of the steel.

In this study, organic photovoltaic cells based on planar heterojunctions using small-molecules were fabricated. Two cell configurations were used, planar heterojunctions based on a classical electron donor/electron acceptor couple and planar heterojunctions using three active layers, one donor, one acceptor and a central ambipolar layer. The donor is a thiophene derivative called BSTV, the acceptor is the fullerene while the ambipolar material is a phthalocyanine dye, the SubPc. After studying the performances of cells based on the couples SubPc/C60, BSTV/C60 and BSTV/SubPc, we explore the dependence of the short circuit current and the external quantum efficiency on the SubPc interlayer thickness in cells with three active layers. By comparison with the optimum couple SubPc/C60 the ternary structure BSTV/SubPc/C60 exhibits higher short circuit current but smaller fill factor. Nevertheless, for an optimum interlayer thickness of 12.5 nm, the ternary structure allows an improvement of the cell efficiency of 11% by comparison with the highest result obtained with the best couple. As shown by optical measurements, long range Foster energy transfer from the larger band gap donor, BSTV, to the smaller band gap, SubPc, is possible. Therefore, the increase of Jsc is attributed to two-step exciton dissociation process. Excitons produced in the outer BSTV layer are transferred to the SubPc central layer and then dissociated at the interface.