Properties Of Multilayer Structures Research Articles

Microstructure, Adhesion, and Properties of Multilayer Structure WC/W/MCrAlY Coating on γ‐TiAl Alloy Prepared by Plasma Surface Metallizing Technique and Microwave Plasma Chemical Vapor Deposition

The WC coatings with a multilayer structure are synthesized on a γ‐TiAl alloy by the combined treatments of plasma surface metallizing technique and microwave plasma chemical vapor deposition. The morphology, microstructure, and phases of the coatings are examined by a white light profilometer, scanning electron microscope, and X‐ray diffraction analysis techniques. The formation of tungsten carbide coating leads to high hardness and good wear resistance. Because of a W transition layer and MCrAlY bonding layer, the good adhesion is achieved between coatings and substrate. This result provides a new approach for designing refractory metals and/or their carbide coatings on metals/alloys substrates, for example, WC and/or W coating on TiAl alloy and titanium alloys.

Features of the two-stage formation of macroporous and mesoporous silicon structuresя

The aim of this work was the formation of multilayer structures of macroporous silicon and the study of their structural, morphological, and optical properties in comparison with the properties of multilayer structures of mesoporous silicon. The paper presents the results of the development of techniques for the formation of multilayer structures of porous silicon por-Si by stepwise change in the current with two-stage modes of electrochemical etching.The data on the morphology, composition, and porosity of macroporous and mesoporous silicon samples were obtained using scanning electron microscopy, IR spectroscopy, and X-ray reflectivity. It was shown that with the two-stage growth of porous silicon layers, the depth of the boundary between the layers of the structure was determined by the primary mode of electrochemical etching, while the total layer thickness increased with an increase in the current density of electrochemical etching.A comparative analysis of the relative intensity and fine structure of vibrational modes of IR spectra indicated a significantly more developed specific pore surface and greater sorption capacity of mesoporous silicon as compared to macroporous silicon.
 
 
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Occurence of Characteristic Peaks in Phononic Multilayer Structures

In this paper the acoustic transmission properties of multilayer structures was analyzed. Were compared binary and aperiodic (Severin, Thue-Morse) superlattices, Calculations were performed using the Transfer Matrix Method (TMM) algorithm. As a superlattice environment in the simulation the water was used. The material used to construct the structure was a PNM-0.38PT piezoelectric. Multilayer types have been selected so that the total number of layers for a given generation is equal in all structures.

Magneto-Optical Response Amplification In Multi-Layer Nanocomposite-Semiconductor Structures

The spectral and field dependences of the Transversal Kerr Effect (TKE) for (Co40Fe40B20)Z(SiO2)100-Z/Si (or С) multilayer (ML) nanocomposite-semiconductor structures were studied depending on the concentration of the nanocomposite layer ferromagnetic phase (Z), chemical of semiconductor layer and its thickness. It was found that under certain conditions an addition of thin nonmagnetic semiconductor layer leads to the increase of a multilayer magneto-optical (MO) response and softening of the magnetic properties of ML structure, up to the appearance of ferromagnetic (FM) ordering. The observed anomalous changes in magnetic and MO properties are well correlated with abrupt changes in the electric properties of ML structures. Decreasing of ferromagnetic phase concentration Z in the nanocomposite layer as well as increasing of the semiconductor layer thickness led to the disappearance of anomalous behavior in the MO properties. The results obtained are discussed taking into account the formation of a new magnetic phase on the FM granule-semiconductor interface.

A study of the heat-removal process at the semiconductor–ceramics interface in solar cells by the laser thermal-wave method

The influence of the solder layer between a semiconductor solar cell and heat-removing ceramics on the nonstationary heat-transfer processes has been investigated by the laser thermal-wave method. A theoretical model taking into account the presence of additional thermal resistance and thermal capacitance at the soldered junction is proposed. Different soldering modes are considered. It is shown that the laser thermal- wave methods within the developed model allow one to correctly estimate the thermophysical properties of multilayer structures.

Optical Polarization Conversion and Phase Manipulation Properties of Multilayer Structure of Alternating SiC and Dielectric Nanofilms at Wavelength 10.6 μm

Optical Polarization Conversion and Phase Manipulation Properties of Multilayer Structure of Alternating SiC and Dielectric Nanofilms at Wavelength 10.6 <i>μ</i>m

Investigation of dielectric properties of multilayer structures consisting of homogeneous plastics and liquid solutions at 75–110 GHz

Abstract. In this paper, we demonstrate an active 3-D millimeter wave (mmW) imaging system used for characterization of the dielectric function of different plastic materials and liquid solutions. The method is based on reflection spectroscopy at frequencies between 75 and 110 GHz, denoted as W-band, and can be used to investigate homogeneous dielectric materials such as plastics or layered structures and liquid solutions. Precise measurement of their dielectric properties not only allows for characterization and classification of different fluids, but also for reliable detection and localization of small defects such as voids or delamination within multilayer structures built from plastic materials. The radio frequency (RF) signal generation is based on circuits that have been designed and fabricated at the Fraunhofer Institute for Applied Solid State Physics (IAF) using a 100 nm InGaAs mHEMT process (Tessmann et al., 2006; Weber et al., 2011).

Polycyanurate binder for spheroplastics

The approach to the development of the composition and the requirements to the physicochemical and technological properties of binders used as the polymeric base for syntactic foams are formulated. The main advantages and drawbacks of the binders used for spheroplastic fabrication, such as epoxy, polyurethane, phenolic, and oligoester compounds, are discussed. The rheological properties and heat resistance of the polycyanurate binder developed at the All-Russia Research Institute of Aviation Materials are studied. The binder is characterized by long working life in the temperature interval up to 150°C. The results obtained and the properties of multilayer structures with the spheroplastic based on this binder show that the suggested polycyanurate binder is suitable for fabrication of spheroplastics.

Optical Properties of Multilayer Structure of Alternating SiC and SiO2 Nanofilms at a Wavelength of 10.6 m

Optical Properties of Multilayer Structure of Alternating SiC and SiO₂ Nanofilms at a Wavelength of 10.6 m

Analysis of defect layers’ insertion effect on optical transmission properties of multilayer structures based on one-dimensional photonic crystals

In this paper, we are interested in the analysis of the transmission spectrum of several multilayer structures based on one-dimensional photonic crystals (1D PCs) infiltrated with different kinds of defect materials, such as bismuth oxide (Bi2O3), lithium niobate (LiNbO3), and E7 liquid crystal (LC). A 1D PC acting as a multichannel filter is constructed by inserting multiple Bi2O3 defect layers, while a localized mode is moved by applying various electric fields on a LiNbO3 defect layer inserted in the middle of a 1D PC structure used as a tunable device. A localized mode is also tuned by applying different magnetic fields on an E7 LC phase shifter inserted between SiO2/TiO2 alternative layers.

Optical Properties of Multi-Layer Structures of Nanometric Polymer Photonic Crystals

Photonic crystals are attracting a lot of attention due to their ability to manipulate and guide the light. Sandwiching 3-dimensional styrene-based photonic crystals between polymeric multi-layer films such as polystyrene and polymethyl methacrylate is reported in this article. Polystyrene and polymethyl methacrylate solutions and a suspension of polymeric nano particles were cast using a specially designed spin-casting machine to produce a periodic multi-layer structure. In the next step, the optical properties of multi-layer structures were investigated via spectrophotometric techniques. A film of styrene-based nano particles has a blue-green reflection, which being affected by the suspension particles sandwiched between polystyrene and polymethyl methacrylate layers, shifts to red whereas the multi-layer structure demonstrates a green color. Moreover, the effects of the observer's viewing angle on the color shift were studied by means of goniospectrophotometric technique.

Near-Perfect Reflection in Multilayer Structures with a Highly Absorptive Metallic Film and a Truncated Photonic Crystal Containing Defects

We have theoretically investigated the optical properties of multilayer structures composed of a highly absorptive metal film and a photonic crystal with defects. It is found that when the photonic crystal containing defects is asymmetric, multiple near-perfect reflection peaks at defect wavelengths will appear within the total absorption broadband of the multilayer because of the highly absorptive metal film, while the high transmission peaks appear when the photonic crystal with defects is nearly symmetric. Such properties are significant for designing particular multichannel reflection and transmission filters in the visible and near infrared regions.

Exact analytical representations for broadband transmission properties of quarter-wave multilayers

The formalism of the scattering matrix is applied to describe the transmission properties of multilayered structures with deep variations of the refractive index and arbitrary arrangements of the layers. We show that there is an exact analytical formula for the transmission spectrum, which is valid for the full spectral range and which contains only a limited number of parameters for structures satisfying the quarter-wave condition. These parameters are related to the poles of the scattering matrix, and we present an efficient algorithm to find them, which is based on considering the ray propagation inside the structure and subsequent application of the harmonic inversion technique. These results are significant for analyzing the reshaping of ultrashort pulses in multilayered structures.

Influence of Si on the magnetic properties of multilayer nanostructures with composite magnetic layers

The static and dynamic properties of multilayer structures [(Co45Fe45Zr10)m(Al2O3)100 − x]x/(a-Si)y with various magnetic phase concentrations and for different thicknesses x and y were measured. It was shown that for samples with comparatively thick composite layers and thin interlayers (x/y > 8), the silicides that form play no significant role and the magnetic properties are determined by the composites. With an increase in the thickness of the interlayers, more granules form silicides. This reduces the concentration of the magnetic phase, influencing the samples’ resonance fields and magnetization.

Effect of small magnetic corrections to susceptibility on the angular dependences of the reflectivity of polarized X-rays from multilayer structures

During the last fifteen years, a new method for investigating the magnetic properties of multilayer structures—Xray resonant magnetic scattering (XRMS)—has been actively developed at all synchro� trons. Having the same magnetic sensitivity and ele� mental selectivity as Xray magnetic circular or linear dichroism (XMCD or XMLD), XRMS allows for the reconstruction of the features of magnetic ordering and the depth profile of the magnetic moments of res� onant atoms in multilayer nanofilms (see, e.g., (1-5)). This information is very important for testing and cre� ating spintronic devices. Another problem that can be solved with XRMS is the experimental determination of the refraction of waves in the medium, i.e., the absolute values of Xray susceptibility, including magnetic corrections near the absorption edges. This information is almost absent in the existing databases for the scattering amplitudes and refractive indices of various materials. The prob� lem of the determination of the optical constants for X rays near the absorption edges is of fundamental interest for the theory of solids. Furthermore, this information is necessary for processing experimental spectra and angular dependences of XRMS in order to obtain depthselective information on the magnetic structure.

ZrO2 Layer Thickness Dependent Electrical and Dielectric Properties of BST/ZrO2/BST Multilayer Thin Films

ABSTRACTRecently, high K materials play an important role in microelectronic devices such as capacitors, memory devices, and microwave devices. Now a days ferroelectric barium strontium titanate [BaxSr1-xTiO3, (BST)] thin film is being actively investigated for applications in dynamic random access memories (DRAM), field effect transistor (FET), and tunable devices because of its properties such as high dielectric constant, low leakage current, low dielectric loss, and high dielectric breakdown strength. Several approaches have been used to optimize the dielectric and electrical properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant, loss tangent, and leakage current in the multilayer thin films. Also it is shown that the properties of multilayer structure are found to depend strongly on the sublayer thicknesses. In this work the effect of ZrO2 layer thickness on the dielectric, ferroelectric as well as electrical properties of BST/ZrO2/BST multilayer structure is studied. The multilayer Ba0.8Sr0.2TiO3/ZrO2/Ba0.8Sr0.2TiO3 film is deposited by a sol-gel process on the platinized Si substrate. The thickness of the middle ZrO2 layer is varied while keeping the top and bottom BST layer thickness as fixed. It is observed that the dielectric constant, dielectric loss tangent, and leakage current of the multilayer films reduce with the increase of ZrO2 layer thickness and hence suitable for memory device applications. The ferroelectric properties of the multilayer film also decrease with the ZrO2 layer thickness.

Calculation for the Acoustic Absorption Coefficient of Multilayered Materials by an Improved Extended Transfer Matrix Method

This paper describes an improved extended transfer matrix method to evaluate the acoustic absorption coefficient of multi-layered structure with viscoelactic materials for perpendicular incidence plane acoustic. Here, the dynamic behavior of viscoelastic materials is taken into account. By comparing the calculated and measured results, it is shown that the results calculated by the improved extended transfer matrix method are in good agreement with the results measured. This improved extended transfer matrix method can accurately estimate the sound properties of multilayered structures with viscoelastic materials.

Modeling a-SiC:H Tandem Pinpin and Pinip Photodiodes for Color Sensor Application

The present paper reports the optical properties of multilayer structures composed by p-i-n cells based on a-SiC:H or a-Si:H material. Different structures are studied in order to obtain image sensors that accomplish color filtering in addition to image pattern recognition. A simple theoretical model is developed to explain sensors behavior and to derive the optical-readout experimental procedure. Electrical models for the sensors are established for simulation purposes and to compare photocurrent signals with experimental data. A numerical simulation of the JV characteristic and of the spectral response is also presented in order to show possible future optimization of the device. Two main structures are studied, namely p-i-n/p-i-n and p-i-n/n-i-p tandem cells.

Optical properties of multilayer structures

The possibility of using the ellipsometry method for investigation of the optical properties of multilayer films and structures is shown. The optical properties of structures HfO2/SiO2/Si, HfO2/Si, ZrO2/Si, Ta2O5/Si, and Al2O3/Si are studied. It is found that a layer of hafnium silicate is formed at the interface between the HfO2 film and Si. Annealing of the structures in oxygen shows that oxides studied are oxygen-permeable and that the thickness of SiO2 at the film-substrate interface increases. The growth rate of SiO2 layers depends on the chemical nature of an oxide. Al2O3 films are impermeable for oxygen diffusion. The production of layers of alloys (Al2O3) x (HfO2)1 − x is optimized, which allows one to obtain layers with a homogeneous distribution of elements over the thickness.

Local cathodoluminescent study of the multilayers semiconductors nanostructures

Local cathodoluminescent (CL) method has been used for the investigation of the luminescent properties of multilayer heterostructure (ZnMgSSe–CdSe) and a structure for HEMT transistors based on GaAs–Al x Ga(1−x)As–In x Ga(1−x)As. One of the most important possibilities of the cathodoluminescent method is that of depth examination of the emission properties of semiconductors structures. The electron energy changing from 1 to 30 keV, the cathodoluminescence emission generation depth varies from 10 nm to several microns, depending on the materials. This permits one to study the luminescent properties of multilayer structure with depth. Our investigation showed that CL method can be used not only for study the luminescent properties of different semiconductors layers but for the characterization of the charge carriers transport in such multilayer structure and investigation of the potential profile of the quantum channel.