FEATURES STUDIES OF TRANSITION LAYERS IN SEMICONDUCTOR HETEROSYSTEMS

Studies of spectral characteristics in Schottky's contact specimens showed that photemf generated by mono­chromatic light, according to the formation mechanism, has a predominantly lateral nature, that is, in a hetero­system there are at least two areas separated by a potential barrier along the interface, with different conductivity levels. The feature of the photoemf spectral characteristics is a variations its appearance when changing the thermal annealing temperature of the studied heterosystems. A significant characteristic and a small amplitude of the characteristic indicates the formation of a transition layer, relatively homogeneous and with insignificant, compared with the volume of GaAs, the doping concentration. If the spectral characteristic has one maximum and amplitude, which several times exceeds the amplitude of a significant characteristic, which means the formation of a transition layer in the Schottky contact depletion area with high conductivity, compared with a quasine-neutral region of a semiconductor. The distribution of lateral photoemf along the sample also has a significant character. In order to obtain the correct results relative to the heterosystem transition layer, it is necessary to measure spectral acute characteristics at a distance from the point change sign of the emf that several times the diffusion length of non-equilibrium charge carriers in GaAs. The problem of the formation of a metal-semiconductor contact and other heterosystems accompanied by the occurrence of heterogeneous transition layers, always paid attention. The use of the proposed photovoltaic method allows to establish the degree of homogeneity of semiconductor layers, components of the structure and predict the redistribution of current density flowing through the physical scope of the device.

Thermal Spray Multilayer Ceramic Structures with Potential for Solid Oxide Cell Applications

The objective of this paper is to manufacture free-standing solid oxide cells (SOCs) through the atmospheric plasma spray process (APS), without the aid of a metallic support nor the need for a post-process heating treatment. A five-layered cell was fabricated. Fused and crushed yttria-stabilized zirconia (YSZ) powder in the 5–22 μm particle size range was used in order to achieve a dense electrolyte layer, yet still permitting satisfactory ionic diffusivity. Nickel oxide (NiO) powder that was obtained by in-house flame spray (FS) oxidation of pure nickel (Ni) powder was mixed and sprayed with the original Ni-YSZ feedstock, so as to increase the porosity content in the supporting electrode. Two transition layers were sprayed, the first between the support electrode and the electrolyte (25% (Ni/NiO)–75% YSZ) and the second at the electrolyte and the end electrode interface (50% YSZ–50% lanthanum strontium manganite (LSM)). The purpose of intercalation of these transition layers was to facilitate the ionic motion and also to eliminate thermal expansion mismatches. All the as-sprayed layers were separately tested by an in-house developed acetone permeability comparative test (APCT). Electrodes with adequate porosity (25–30%) were obtained. Concerning electrolytes, relatively thick (150–200 µm) layers derived from fused and crushed YSZ were found to be impermeable to acetone, while thinner YSZ counterparts of less than 100 µm showed a low degree of permeability, which was attributed mostly to existent microcracks and insufficient interparticle cohesion, rather than to interconnected porosity.

Electron and ion velocity distribution functions across one-dimensional tangential discontinuities: particle-in-cell simulations

<div><span>Tangential discontinuities are finite-width current sheets separating two magnetized plasmas with different macroscopic properties. Such structures have been measured in-situ in the solar wind plasma by various space missions. Also, under certain conditions, the terrestrial magnetopause can be approximated with a tangential discontinuity. Studying the microstructure of tangential discontinuities is fundamentally important to understand the transfer of mass, momentum and energy in space plasmas. The propagation of solar wind discontinuities and their interaction with the terrestrial magnetosphere play a significant role for space weather science. In this paper we use 1d3v electromagnetic particle-in-cell simulations to study the kinetic structure and stability of one-dimensional tangential discontinuities. The simulation setup corresponds to a plasma slab configuration which allows the simultaneous investigation of two discontinuities at the interface between the slab population and the background plasma. The initial discontinuities are infinitesimal and evolve rapidly towards finite-width transition layers. We focus on tangential discontinuities with and without perpendicular velocity shear. Three-dimensional velocity distribution functions are computed in different locations across the discontinuities, at different time instances, for both electrons and ions. We emphasize the space and time evolution of the velocity distribution functions inside the transition layers and discuss their deviation from the initial Maxwellian distributions. The simulated distributions show similar features with the theoretical solutions provided by Vlasov equilibrium models. </span></div>

Development of an integrated game theory-optimization subground stratification model using cone penetration test (CPT) measurements

The continuous cone penetration test (CPT) measurements provide an advantageous liable rapid tool for stratification and soil behavior classification that can be employed in the sustainable design of the infrastructures. However, the CPT measurements are often interpreted by geotechnical experts because of the involved complexities and uncertainties. In this study, a novel stratification and soil type behavior (SBT) classification model is developed to identify the transition and thicker layers by integrating the geotechnical knowledge with the three submodels of (a) locally estimated scatterplot smoothing (LOESS), (b) a game theory model known as Nash–Harsanyi (N–H) bargaining, and (c) grey wolf optimizer (GWO). The LOESS and integrated N–H bargaining-GWO models are, respectively, used to approximate the outliers in CPT measurements and identify the SBT and layer changes. Attractively, in the proposed model, the engineer has the opportunity to judge on the precision of the stratification profile regarding their own preferences in a project. Solving simple algebraic equations, high speed, identifying thick and the interlayer transition layers, and small required training data are the other advantages of the developed model. Finally, the applicability of the proposed model has been assessed in an example. The compared estimated and two other models’ stratification profiles highlighted the potential of the proposed model to identify thin transition layers.

Профильный анализ пленок ферритов-гранатов методом оптической эмиссионной спектроскопии тлеющего разряда

Annotation.The paper presents the results of experiments on the application of the method of optical emission spectroscopy of a glow discharge for the profile analysis of vacuum-deposited single and two-layer films of multicomponent garnet ferrites of various compositions before and after crystallization annealing. The presence of internal and external transition layers was revealed, and the modification of their elemental composition during crystallization, as well as the different sequence of synthesis of individual components in ferrite-garnet heterostructures, was investigated.

Optics of Inhomogeneous Thin Films with Defects: Application to Optical Characterization

This review paper is devoted to optics of inhomogeneous thin films exhibiting defects consisting in transition layers, overlayers, thickness nonuniformity, boundary roughness and uniaxial anisotropy. The theoretical approaches enabling the inclusion of these defects into formulae expressing the optical quantities of these inhomogeneous thin films are summarized. These approaches are based on the recursive and matrix formalisms for the transition layers and overlayers, averaging of the elements of the Mueller matrix using local thickness distribution or polynomial formulation for the thickness nonuniformity, scalar diffraction theory and Rayleigh-Rice theory or their combination for boundary roughness and Yeh matrix formalism for uniaxial anisotropy. The theoretical results are illustrated using selected examples of the optical characterization of the inhomogeneous polymer-like thin films exhibiting the combination of the transition layers and thickness nonuniformity and inhomogeneous thin films of nonstoichiometric silicon nitride with the combination of boundary roughness and uniaxial anisotropy. This characterization is realized by variable angle spectroscopic ellipsometry and spectroscopic reflectometry. It is shown that using these optical techniques, the complete optical characterization of the mentioned thin films can be performed. Thus, it is presented that the values of all the parameters characterizing these films can be determined.