Layers Of Different Thicknesses Research Articles

Broadband Tamm plasmon polariton

A broadband Tamm plasmon polariton localized at the interface between the Bragg mirror and a thin metallic layer has been theoretically and experimentally investigated. The possibility of a localized state formation has been demonstrated and energy coefficients at the Tamm plasmon polariton wavelength have been predicted in the framework of the coupled mode theory. The metallic layer material and thickness corresponding to the maximum coupling between the incident radiation and the Tamm plasmon polariton has been determined. Experimental reflectance and transmittance spectra of the structure consisting of the Bragg mirror and chromium layers of different thicknesses have been measured. The analysis of the energy spectra shows the existence of the wavelength range with the near-unity absorption coefficient inside the Bragg mirror bandgap. The use of chromium as a metal results in the broadband Tamm plasmon polariton excitation. It is demonstrated that the experimental data is in a good agreement with the calculation.

Thin-Film Gd-Doped Ceria Sr-Barrier Layers for Electrolyte Supported SOFCs

In order to prevent detrimental reaction during manufacturing and enable the use of high performing La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode in electrolyte supported solid oxide cells, Ce0.8Gd0.2O2-δ (GDC) barrier layer is implemented between the cathode and the electrolyte. It is of great interest to manufacture thin and dense GDC layer at low temperature to avoid unfavorable reactions. GDC layers deposited through Electron-Beam Physical Vapor Deposition (EB-PVD) were investigated to address this challenge. Dense GDC barrier layers of different thickness were deposited onto yttria-stabilized zirconia (YSZ) electrolyte. Samples coated with GDC thin-film, with and without LSCF cathode, were thermally treated to simulate further cell and stack processing steps. XRD and SEM were applied to evaluate the phase composition, thermomechanical stability, morphology and microstructural changes. It is found that the 0.5 µm GDC layer remains crack-free and adherent to the substrate after the simulated thermal cycles.

Growth and Characterization of Undoped Polysilicon Thick Layers: Revisiting an Old System

Thick layer of polycrystalline silicon (poly-Si) grown by Atmospheric Pressure Chemical Vapor Deposition (APCVD) is still a reference material in a number of applications, despite the high thermal budget of this technique. This work presents a material study of undoped poly-Si layers of different thicknesses, using different characterization techniques such as secondary electron microscope in backscattered detection configuration, electron backscattering diffraction imaging, secondary ion mass spectrometry and spreading resistance profiling. The poly-Si layers, grown at 1000 °C by APCVD on thermal oxide, were found to have a columnar microstructure with [110] main orientation. By correlating layer purity, grain size and electrical resistivity, no straightforward relation between grain size and resistivity could be found. The layers resistivity is found almost independent on thickness and thus grain size. The possible reasons for such difference with previous other works are discussed taking into account the grain size determination uncertainty and the electrical characterization limitations.

Optimization of Transparent Organic Light-Emitting Diodes by Simulation-Based Design of Organic Capping Layers.

In this work, we use the transfer matrix method to optimize TPBi capping layers deposited on organic light emitting diodes with respect to light extraction and transmittance. The green transparent organic light emitting diodes comprise three organic semiconductors (CBP, Ir(ppy)₃ and TPBi) forming an efficient simplified phosphorescent organic light emitting diode stack. A transparent cathode of 2 nm Cs₂CO₃, 2 nm Al and 16 nm Au is deposited by thermal evaporation. The diode stack as well as the capping layer are deposited by organic vapor phase deposition. The refractive indices and extinction coefficients of all materials in the transparent organic light emitting diodes (glass, indium tin oxide, organic semiconductors and cathode) are determined using spectroscopic ellipsometry combined with optical transmittance and reflectance measurements. With these spectrally resolved data, we calculate the transmittance of transparent organic light emitting diodes with TPBi capping layers of different thicknesses. The results were validated with high accuracy in the visible spectral range and beyond (360 nm-1000 nm) by a series of experiments. By choosing a TPBi capping layer of optimized thickness (here 50 nm), we fabricated transparent organic light emitting diodes with an optical transmittance which was strongly enhanced from 47% (reference without capping layer) to 65%, measured at 555 nm.

Study of Thermal Stress in Nano Silver Bonded Silicon Substrates for High Temperature Applications

Abstract The silver nanoparticle paste is a promising material for high temperature die-attach applications. In this paper, the finite element method is used to study the relationship between the thickness of the sintered silver layer and the thermal stress in the sintered silver joint. Silicon chips are bonded together with sintered silver layers of different thicknesses. In the experimental study, strain gauges are attached onto the surface of the upper silicon and used to estimate the effects of the nano silver die-attach layer. The results show that the average stress in the silver layer at the interface decreases with the increasing thickness of the silver layer, while the stress on the silicon surface increases with the increasing thickness of the silver layer.

High photostability and luminescent efficiency of quantum dots: ultrathin epitaxial Al self-passivation layer with a homogeneous ligand

Semiconductor quantum dots (QDs) have aroused extensive interest in various applications because of their excellent optical and electronic properties. However, long-term photostability of the CdSe QDs has always posed application challenges. This study discusses the high-quality QDs synthesized using an uncomplicated coating method. The ultrathin epitaxial Al self-passivation layer is coated with a homogeneous ligand to maintain high luminescent efficiency and photostability of the QDs. The time-dependent intensity responses of the CdSe/CdS, CdSe/CdS/Al, and CdSe/CdS/CdS/Al QDs were verified under continuous irradiation using a single-particle one-watt blue light-emitting diode (LED). The CdSe/CdS photoluminescence (PL) intensity rapidly decreased under the blue LED illumination, whereas that of the CdSe/CdS/CdS/Al QDs remained almost unchanged for 300 min. The PL spectra of the three samples in 10–300 K were verified by comparing the temperature-dependent full-width at half-maximum of their emission energies and luminescent intensities. The mechanism of the temperature-dependent non-radiative relaxation of CdSe QDs coated with CdS layers of different thicknesses evolved from the thermal activation of carrier trapping by surface defects/traps in the CdSe QDs to the thermal escape of carriers in the core/shell QDs, assisted by multiple longitudinal–optical phonons. The luminescence mechanism was almost independent of the Al epitaxial growth layer.

Development of a method for optimization calculation of a group of sound-insulating panels for airborn noise protection

Various designs and procedures for calculating soundproof panels for protecting premises against airborne noise were considered. These procedures make it possible to calculate single-layer, two-layer and three-layer panels. Single-layer panels may consist of homogeneous solid and thin materials. Two-layer panels may consist of two thin layers of different thickness and an air gap. Three-layer panels can be made of two thin layers of different thickness and a sound-absorbing material between them. These procedures enable calculation and optimization of individual structures of sound-proofing panels independently of each other. The problem of simultaneous penetration of noise from one source into several adjacent rooms was considered. When using the procedures considered in references, maximum effect is unattainable. In this regard, a method of optimization calculation of a group of sound-proofing panels aimed at achievement of the most advantageous value of the objective function was proposed. The method is based on a random search resting on random distribution of typical structures and procured materials among panels. Choice of the best result is made proceeding from a result of checking fulfillment of limiting conditions. The following options of the objective function were proposed: the excessive noise load, the total index of noise reduction in rooms, the total cost of sound-proofing panels and the number of panels made. Recommendations were given on the choice of the objective function option taking into account concrete production conditions. The result of optimization consists in the choice of design of the panel for each room and distribution of available materials among them. Formulation of the optimization problem with various options of the objective function and limitations has been considered. Efficiency of using this method was confirmed by almost 24 % lower cost of panels compared to the separate panel designing using conventional methods.

Bethe-Salpeter-based simulations of multiple scattering from bounded media

Here we present results of Monte Carlo simulations employing an effective numerical approach, based upon a description of radiative transfer in terms of the Bethe-Salpeter equation. We develop a simulation algorithm which presents a stochastic calculation of the multi-fold spatial integrals of the Bethe-Salpeter iterative solution. The algorithm is a modification of the widely known MCLM method with a signal registration recipe resulting in a significant reducing of sampling volume. For isotropic scattering the obtained results exhibit an excellent agreement with the known theoretical solution. We simulate backscattering from layers of different thickness for the Henyey-Greenstein or Rayleigh-Gans scattering patterns.

Fabrication of thin sandwiched 142,150Nd targets for HYRA spectrometer experiments

Abstract Sandwiched 142 , 150 Nd targets of thickness ( ∼ 100– 150 μ g /cm 2 ) have been fabricated between two carbon layers of different thickness ( ∼ 30 μ g /cm 2 and ∼ 10 μ g /cm 2 ) using the thermal evaporation technique in the diffusion pump based coating unit at the target lab of Inter University Accelerator Center (IUAC), New Delhi. Thickness and purity measurement of the targets have been confirmed by using the Rutherford backscattering spectrometry (RBS) technique and energy dispersive X-ray fluorescence (EDXRF) measurement present at IUAC, New Delhi and Panjab University, Chandigarh, respectively. These targets have been successfully used in a recent experiment to measure evaporation-residue (ER) cross section and spin distribution of ERs in the hybrid recoil mass analyzer (HYRA) facility present at IUAC.

Thickness-Dependent Resistive Switching Behavior of KCu7S₄/CuxO/Au Device.

We report the fabrication of KCu7S₄/CuxO/Au devices with interfacial CuxO layers of different thicknesses through the spontaneous oxidation of Cu film during deposition. Deposition was conducted with an electron-beam evaporation system under the deposition rate and the chamber pressure of 0.1 Å s-1 and 9.8×10-3 Pa, respectively. X-ray diffraction and X-ray photoelectron spectroscopy characterizations reveal that the interfacial CuxO layers mostly comprise Cu₂O and CuO. Electrical characterization reveals that the devices exhibit remarkably thickness-dependent resistive switching behavior. After undergoing an electroforming process under a high compliant current of 1000 μA, the KCu7S₄/16 nm CuxO/Au device exhibits stable bipolar resistive switching behavior with the set voltage of 0.58 V and reset voltage of -0.21 V, whereas the KCu7S₄/32 nm CuxO/Au device only shows a hysteresis loop in the forward voltage regime. These findings are ascribed to the existence of high-insulation CuO, which is difficult to be softly broken down. Therefore, the depositional condition of Cu film and the thickness of the interfacial layer should be appropriately controlled for the effective performance of devices with Cu electrodes. The results may also provide guidance for the improvement of the performance and stability of Cu-based nonvolatile memory devices.

Method to Extract Interface and Bulk Trap Separately Over the Full Sub-Gap Range in Amorphous InGaZnO Thin-Film Transistors by Using Various Channel Thicknesses

We propose an experimental method to decompose the interface (insulator/channel) trap density ( ${D}_{\mathrm {it}}$ ) and sub-gap density-of-state in the entire defect ( ${g}_{\mathrm {tot}}$ ) of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). This method involving various active layers of different thicknesses is used for determining the origin of defects and for process optimization. These results can be used to determine clearly the contributions to the origin of the defect. Oxygen-related and deep states near the conduction band minimum ( ${E}_{{C}}$ ) were strongly affected by the interface region. Tail states near ${E}_{C}$ , on the other hand, were strongly influenced by the active layer. The proposed method provides physical insight and key guidelines for optimizing the performance of a-IGZO TFTs.

ZnO/Carbon nanowalls shell/core nanostructures as electrodes for supercapacitors

In this work, carbon nanowalls (CNW) were coated with zinc oxide (ZnO) for use as supercapacitor electrodes. The ZnO layers of different thicknesses were deposited using pulsed laser ablation in oxygen reactive atmosphere. The performance of the CNW-ZnO electrodes was found to be dependent on the thickness of ZnO deposit, which in turn influences the specific capacitance and capacitance retention of the CNW-ZnO electrodes. The areal capacitance of the CNW-ZnO measured in mild electrolyte of 1 M KCl was as high as 4.3 mF·cm−2 at a current density of 0.2 mA·cm−2 and 1.41 mF·cm−2 at a scan rate of 10 mV·s−1 with an enhanced capacitance stability over 26,000 cycles. Such results demonstrate the potential use of ZnO nanostructures for low cost and high performance material for electrochemical capacitors.

Sticking Properties of Silicates in Planetesimal Formation Revisited

Abstract In the past, laboratory experiments and theoretical calculations showed a mismatch in the derived sticking properties of silicates in the context of planetesimal formation. It has been proposed by Kimura et al. that this mismatch is due to the value of the surface energy assumed, supposedly correlated to the presence or lack of water layers of different thickness on a grain’s surface. We present tensile strength measurements of dust aggregates with different water content here. The results are in support of the suggestion by Kimura et al. Dry samples show increased strengths by a factor of up to 10 over wet samples. A high value of γ = 0.2 J m−2 likely applies to the dry low pressure conditions of protoplanetary disks and should be used in the future.

Effect of myocardial heterogeneity on ventricular electro-mechanical responses: a computational study

BackgroundThe heart wall exhibits three layers of different thicknesses: the outer epicardium, mid-myocardium, and inner endocardium. Among these layers, the mid-myocardium is typically the thickest. As indicated by preliminary studies, heart-wall layers exhibit various characteristics with regard to electrophysiology, pharmacology, and pathology. Construction of an accurate three-dimensional (3D) model of the heart is important for predicting physiological behaviors. However, the wide variability of myocardial shapes and the unclear edges between the epicardium and soft tissues are major challenges in the 3D model segmentation approach for identifying the boundaries of the epicardium, mid-myocardium, and endocardium. Therefore, this results in possible variations in the heterogeneity ratios between the epicardium, mid-myocardium, and endocardium. The objective of this study was to observe the effects of different thickness ratios of the epicardium, mid-myocardium, and endocardium on cardiac arrhythmogenesis, reentry instability, and mechanical responses during arrhythmia.MethodsWe used a computational method and simulated three heterogeneous ventricular models: Model 1 had the thickest M cell layer and thinnest epicardium and endocardium. Model 2 had intermediate layer thicknesses. Model 3 exhibited the thinnest mid-myocardium and thickest epicardium and endocardium. Electrical and mechanical simulations of the three heterogeneous models were performed under normal sinus rhythm and reentry conditions.ResultsModel 1 exhibited the highest probability of terminating reentrant waves, and Model 3 exhibited to experience greater cardiac arrhythmia. In the reentry simulation, at 8 s, Model 3 generated the largest number of rotors (eight), while Models 1 and 2 produced five and seven rotors, respectively. There was no significant difference in the cardiac output obtained during the sinus rhythm. Under the reentry condition, the highest cardiac output was generated by Model 1 (19 mL/s), followed by Model 2 (9 mL/s) and Model 3 (7 mL/s).ConclusionsA thicker mid-myocardium led to improvements in the pumping efficacy and contractility and reduced the probability of cardiac arrhythmia. Conversely, thinner M cell layers generated more unstable reentrant spiral waves and hindered the ventricular pumping.

Численное решение задачи об изгибе трехслойной пластины с идеально упругопластическим заполнителем с несущими слоями разной толщины

Численное решение задачи об изгибе трехслойной пластины с идеально упругопластическим заполнителем с несущими слоями разной толщины

The effect of platinum-aluminide coating features on high-temperature fatigue life of nickel-based superalloy Rene®80

Low cycle fatigue is the most important failure mode in Aviation/Industrial engine rotary turbine parts. In this paper, the influence of Pt-aluminide coating parameters on high temperature low cycle fatigue behavior of superalloy Rene?80 which is used to manufacture turbine blades, has been investigated. For this purpose, initial platinum layers of different thicknesses (2?m and 8?m) were coated on fatigue specimens. Then the aluminizing process was performed with two conditions of low temperature-high activity and high temperature-low activity. The results of microstructure investigations performed by scanning electron microscope and X-ray diffraction phase analysis indicated a three-layer structure for the coating (bi-phase (Ni,Pt)Al+PtAl2, single-phase (Ni,Pt)Al and interdiffusion zone) with different chemical compositions at both thicknesses of the platinum layer and using both aluminizing methods. Also, the results of low cycle fatigue tests at 871?C, R=0 and strain rate of 2?10 -3 s-1 showed a decline in fatigue properties in coated specimens as compared to uncoated sample, at total strains of 0.4, 0.8, and 1.2%. This reduction was lower in the low temperature-high activity with platinum layer thickness of 2?m, while it was more significant in the high temperature-low activity with the platinum layer thickness of 8?m. The fractography studies on coated and uncoated specimens indicated a mixed mode of ductile and brittle fracture.

Increasing accuracy and reliability of ground base settlement calculation

The article presents the sequence of soil foundations for deformations calculation, taking into account their deformation anisotropy. The calculations were made by the finite element method using the experiment and its mathematical planning. It was found that one can use the numerical experiment results (coefficients tables of soil anisotropy) and calculate soil base sediment and layers of different thickness, using any of the existing methods after determining the index of the soil deformation anisotropy and authenticity, thereby increase their accuracy and reliability.

Ignition temperatures of dust layers and bulk storages in hot environments

In many industrial installations, particulate solids (cereals, agri-food products, coal, plants, etc.) are stored or processed. Self-heating of these products, which can lead to fires and explosions, can occur in a variety of situations. Examples include large storage at room temperature, formation of a layer on a hot surface, layer deposited on a surface – insulating or conductive – in a hot environment or even storage of product exposed to heating on one side.The main parameters that determine the occurrence of self-heating are the size of the container, the temperature, the residence time and the characteristics of the product. Depending on the type of situation encountered and these implementation conditions, the analysis of self-heating risks must be based on specific models and/or parameters.This paper presents the different variants and combinations of the theoretical model from the theory of thermal runaway to represent self-heating, taking into account in particular the symmetry or asymmetry of heating, reagent consumption and boundary conditions. It also discusses their adaptation to the previous identified industrial situations.Nine products were chosen to be representative of those used in the different considered industrial situations. They were subjected to self-heating basket tests in isothermal ovens in order to determine the parameters for applying the described theoretical models. These results were compared with the results of self-heating tests in layers of different thicknesses in a hot environment, on an insulating or conductive plate, using a specially developed test protocol, as well as with the results of standardized tests of minimum ignition temperature in 5 mm layers.This led to the proposal of the most appropriate theoretical model to represent the self-heating phenomenon for each of the four identified industrial situations.This analysis can promote better design of industrial equipment and production conditions (temperatures, volumes or product flows …) in order to prevent fires and explosions.

Effect of transverse compression on superconducting properties of high-temperature superconducting wires

We designed a transverse loading device that can apply a more uniform compressive force perpendicular to superconducting tape than previously designed equipment. The effective compressive length and width reached up to 100 and 20 mm, respectively. The critical current (IC) and/or transport AC losses of the superconducting tape during transverse compression could be measured using this equipment. We used YBa2Cu3O7−x-coated conductor (YBCO CC) specimens with copper stabilizing layers of different thickness to investigate the characteristics of the critical current and transport AC losses under transverse compression loading. For comparison, several Bi-2223/Ag samples were also tested. A critical stress was observed for the compression process (the same as that for axial tension), and beyond this stress, IC degraded irreversibly. For the transport AC losses behavior of the YBCO CC and Bi-2223/Ag specimens, below the critical stress value, the AC losses remained almost unchanged with the increase of the compressive stress at the same current; while above the critical stress value, at increasing compressive stress, the AC losses increased rapidly and the normalized AC losses for normalized current decreased.

Coherent Excitation of Gigahertz Range Vibrations in Single Crystal Diamond with a Built-In Graphitized Layer

The paper presents the results of experimental observations of stimulated low-frequency Raman scattering (SLFRS) on acoustic eigenvibration of graphitized layers of different thicknesses in single-crystal diamond volume excited by a nanosecond laser pulse.