Structure Of Thin Layers Research Articles

The effect of the process gas mixture ratio on the structure and composition of TiC and TiCN thin layers prepared by cathodic arc deposition on tool steel

The presented research introduces the possibilities of setting the parameters of the deposition of thin coatings so that the desired surface properties are achieved. For the examined TiCN and TiC thin coatings, applied by the cathodic arc method (Arc-PVD), the dependence was revealed between the hardness of the coatings, the residual stress, and the wear resistance, which significantly affect the service life of the coated parts. The statistical analysis of the results shows the optimal ratio between nano-hardness and internal stress, at which the least wear of the layer occurs (the ratio of hardness and magnitude of compressive stress must be approximately equal to 10). The research is focused on predicting the utility properties of thin TiCN coatings to reduce the wear of modified surfaces.

Application of Modular Maximum of Wavelet Transform in the Paint-coat Damage Detection

The reflected waves of each interface might obliterate each other and be indistinguishable in the conventional ultrasonic testing of the multi-interface heterogenous thin-layer structure. Aiming at this problem, the method of dealing with signals by the modular maximum of wavelet transform is put forward and the detection testing for the embedded defects of test pieces is implemented. The test results show that this method can judge whether there is a defect by identifying the time point of .

Data-driven suppression of short-period multiples from laterally varying thin-layered overburden structures

Marchenko multiple elimination methods remove all orders of overburden-generated internal multiples in a data-driven way. In the presence of thin beds, however, these methods have been shown to underperform. This is because the underlying inverse problem requires the information about short-period internal multiple (SPIM) imprint on the inverse transmission to be correctly constrained. This has been addressed in 1.5D media with energy conservation and minimum-phase reconstruction. Extending the applications to two dimensions and, hence, making the step toward field data were believed to be hampered by the need for a multidimensional minimum-phase reconstruction which is (1) not unique and (2) no algorithm has been found to perform this in practice on band-limited data. Here, we address both of these problems with an approach that includes solving the Marchenko equation with a trivial constraint, evaluating the energy conservation condition of its solutions to find the spatially dependent error syndrome, using the 1.5D minimum-phase reconstruction for each shot gather to find the spatially dependent constraint, and finally using that inside another run of the Marchenko equation solver to find a much-improved result. We find that the method works because in 2D media the expression of SPIMs in the inverse transmission coda is approximately 1.5D. We then investigate a class of models and synthetic data sets to verify where the 1.5D approximation starts breaking down. Our analysis indicates that this approach could perform very well in settings with moderate lateral variations, which also is where the (short-period) internal multiples are most difficult to differentiate from primary reflections.

Optical response of SrTiO3 thin films grown via a sol-gel-hydrothermal method

The polycrystalline SrTiO3 thin films were prepared by the sol-gel-hydrothermal method on glass substrates. The synthesis pathway was initiated by preparing a clear TiO2 solution using the sol-gel method. This clear solution was then deposited on a glass substrate using the dip coating technique, followed by the transformation of a thin layer of TiO2 into SrTiO3 by the hydrothermal method. The crystal structure, bond interactions, and band gap energy of SrTiO3 thin layers were characterized using X-ray Diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), and UV–Vis Diffuse Reflectance Spectroscopy (UV-DRS). The XRD patterns of all SrTiO3 thin layers indicated the perovskite structure of the samples. The FTIR spectrum showed an interaction of the silanol groups on the surface of the glass substrate with Ti–O–Ti of SrTiO3 layers. The characteristics of the UV-DRS spectrum were influenced by the thickness of the SrTiO3 layer formed on the glass substrate. The findings of this work provide insights for producing SrTiO3 layers with specified thickness and morphology.

Development of a flexible thin-film radio-absorbing structure for UHF and SHF microwave range

A broadband printed thin-layer radio absorbing structure based on an array of coupled dipole antennas has been developed and created. The resulting material can be used to solve the problems of shielding electromagnetic waves and reduce the level of electromagnetic emission from various devices in the 4-7 GHz frequency range, as well as to create building radio shielding materials. Keywords: radar absorbing screen, magnetron sputtering, array of printed antennas.

Разработка гибкой тонкопленочной радиопоглощающей структуры для УВЧ- и ближнего СВЧ-диапазонов

A broadband printed thin-layer radio absorbing structure based on an array of coupled dipole antennas has been developed and created. The resulting material can be used to solve the problems of shielding electromagnetic waves and reduce the level of electromagnetic emission from various devices in the 4-7 GHz frequency range, as well as to create building radio shielding materials.

A Local Iterative Approach for the Extraction of 2D Manifolds from Strongly Curved and Folded Thin-Layer Structures.

Ridge surfaces represent important features for the analysis of 3-dimensional (3D) datasets in diverse applications and are often derived from varying underlying data including flow fields, geological fault data, and point data, but they can also be present in the original scalar images acquired using a plethora of imaging techniques. Our work is motivated by the analysis of image data acquired using micro-computed tomography ([Formula: see text]) of ancient, rolled and folded thin-layer structures such as papyrus, parchment, and paper as well as silver and lead sheets. From these documents we know that they are 2-dimensional (2D) in nature. Hence, we are particularly interested in reconstructing 2D manifolds that approximate the document's structure. The image data from which we want to reconstruct the 2D manifolds are often very noisy and represent folded, densely-layered structures with many artifacts, such as ruptures or layer splitting and merging. Previous ridge-surface extraction methods fail to extract the desired 2D manifold for such challenging data. We have therefore developed a novel method to extract 2D manifolds. The proposed method uses a local fast marching scheme in combination with a separation of the region covered by fast marching into two sub-regions. The 2D manifold of interest is then extracted as the surface separating the two sub-regions. The local scheme can be applied for both automatic propagation as well as interactive analysis. We demonstrate the applicability and robustness of our method on both artificial data as well as real-world data including folded silver and papyrus sheets.

Structural stability evolutions of CH4 and CO2 hydrate-sand nanoparticle systems

Despite solid hydrate and mineral particle substances appear extensively in the Earth’s natural environments and engineering applications, physical interactions between hydrates and minerals remain mysterious at the atomic scale due to the experimental challenges at high pressure and low temperature. Herein, particle physical interactions between hydrates and sands are reported using large-scale classical molecular dynamics simulations. Simulation results show that potential energies of nonbonded interactions between different counterparts in hydrate-sand nanoparticle systems exhibit distinctive behaviors, indicative of complex intrinsic interactions among them. Interestingly, both methane and carbon dioxide hydrate nanoparticles are characterized by a thin water layer structure on their surfaces. Molecular structural evolutions of both hydrate and sand nanoparticles are demonstrated in a combination of translational and rotational motions, resulting from van der Waals and Coulombic electrostatic interactions. Moreover, the rotational motion of nanoparticles also depends on thermal fluctuations. Furthermore, hydrate and sand nanoparticles are finally assembled together, accompanied by sintering processes of gas hydrates on sand nanoparticles in good agreement with previous experimental findings. This work quantitatively highlights particle physical interactions between hydrates and sands at the atomic scale, which is of critical importance to understand internal structural evolutions and mechanical stability of gas hydrate systems.

Effects of argon/nitrogen sputtering gas on the microstructural, crystallographic and piezoelectric properties of AlN thin films

The growth of highly crystalline c-plane AlN ‹002› is extremely difficult, entailing high temperature and ultra-high vacuum condition. In sputtering technique, the addition of nitrogen into argon sputtering gas can significantly assist the formation of AlN ‹002› at low temperature. We incorporated purified nitrogen gas and observed the consistent formation of single crystal ‹002› AlN thin film layer sputter-deposited on Mo/Si substrate from the AlN ceramic target. Small presence of oxygen content within AlN crystal relates to the preferential growth of AlN ‹002›. High oxygen content in AlN thin film due to the use of unpurified nitrogen and argon only sputtering gas prefers the formation of AlN ‹100›. Different AlN crystal structure has shown distinct thin film properties and piezoelectric response. This work provides a method to control the crystal structure of the sputter-deposited AlN thin film layer, either c-plane AlN ‹002›, a-plane AlN ‹100› or polycrystalline AlN.

Comparative analysis of the electronic energy structure of nanocrystalline polymorphs of Y2O3 thin Layers: Theory and experiments

The results of fabrication and characterization of atomic structure of nanocrystalline thin layers of Y2O3 in cubic and monoclinic phases is reported. Experimental data demonstrate crystalline ordering in nanocrystalline films with average grain size of ∼ 10–14 nm both for cubic and monoclinic studied structures. Density Functional Theory (DFT) based simulations demonstrate insignificant differences of electronic structure of these phases in the bulk and on the surfaces. Theoretical modeling also pointed out the significant broadening of valence and conductive bands caused by means of energy levels splitting in agreement with experimental data (X-ray photoelectron and photoluminescence spectra). The presence of various intrinsic and extrinsic defects (including surface adsorption of carbon mono- and dioxide) does not promote visible changes in electronic structure of Y2O3 surface for both studied phases. Optical absorption and luminescence measurements indicate insignificant bandgap reduction of Y2O3 nanocrystalline layers and the very little contribution from defect states. Simulation of extrinsic compression and expanding demonstrate stability of the electronic structure of nanocrystalline Y2O3 even under significant strain. Results of comprehensive studies demonstrate that yttrium oxide based nanocrystalline layers are prospective for various optical applications as a stable material.

Emitter layer optimization in heterojunction bifacial silicon solar cells

Silicon solar cells continue to dominate the market, due to the abundance of silicon and their acceptable efficiency. The heterojunction with intrinsic thin layer (HIT) structure is now the dominant technology. Increasing the efficiency of these cells could expand the development choices for HIT solar cells. We presented a detailed investigation of the emitter a-Si:H(n) layer of a p-type bifacial HIT solar cell in terms of characteristic parameters which include layer doping concentration, thickness, band gap width, electron affinity, hole mobility, and so on. Solar cell composition: (ZnO/nc-Si:H(n)/a-Si:H(i)/c-Si(p)/a-Si:H(i)/nc-Si:H(p)/ZnO). The results reveal optimal values for the investigated parameters, for which the highest computed efficiency is 26.45% when lighted from the top only and 21.21% when illuminated from the back only.

Decrypting the Influence of Axial Coordination on the Electronic Microenvironment of Co-N 5 Site for Enhanced Electrocatalytic Reaction

Decrypting the Influence of Axial Coordination on the Electronic Microenvironment of Co-N ₅ Site for Enhanced Electrocatalytic Reaction

Mesoporous Ultrathin g‐C3N4 with Surface Defects Activates Peroxodisulfate for Tetracycline Removal under Visible Light: Synergy and Mechanism

AbstractMetal‐free catalysts combined with a persulfate‐based advanced oxidation process (PS‐AOP) are considered to be a promising purification technology. In this study, porous thin layers of g‐C3N4 with nitrogen defects are synthesized by a simple method. Multiple characterization methods demonstrate the porous thin layer structure and the N defects of P‐CNx‐1. Photoelectrochemistry tests show that the combination of morphological modulation and defect engineering produces an excellent photocurrent response. The P‐CNx‐1/PS/Vis system shows the best tetracycline (TC) removal efficiency degrading 74.2% of TC within 90 min, and the degradation kinetics are significantly improved. Optimal degradation conditions such as catalyst dosage, persulfate (PS) dosage, initial TC concentration, and initial pH are investigated. Cyclic and anionic experiments demonstrate the excellent stability of P‐CNx‐1 and its ability to treat complex aqueous bases. Mechanistic experiments show that ˙OH/SO4˙−/˙O2−/h+/1O2 are all involved in the degradation of TC. Liquid chromatography‐mass spectrometry (LC‐MS) suggests possible degradation pathways for TC. This work aims to provide new ideas for the application of metal‐free g‐C3N4 in PS activation.

Acoustic properties of honeycomb like sandwich acoustic metamaterials

Low frequency noise has strong penetrability and has always been an important part of environmental pollution. Limited by the law of mass, traditional lightweight porous materials are difficult to effectively control low-frequency noise. Based on the characteristics of honeycomb structure, Helmholtz resonator and acoustic metamaterials, a kind of honeycomb like sandwich acoustic metamaterials is proposed. This structure combines the lightweight characteristics of honeycomb sandwich structure and Helmholtz resonance characteristics. The finite element models of honeycomb and Helmholtz resonators element are established. The transmission loss (TL) characteristic shows that Helmholtz resonators element will be a TL peak in a narrow frequency band than honeycomb element. The effects of neck diameter, neck length and cavity volume of Helmholtz resonator on its TL are analyzed. The TL of single and multiple Helmholtz resonators are compared. Furthermore, The TL of honeycomb panel and honeycomb like sandwich acoustic metamaterials are analyzed. The results show that the different TL peaks can be introduced into honeycomb like sandwich acoustic metamaterials with different neck diameters. Each Helmholtz resonators element plays an active role in its own frequency band. The sound insulation performance of the honeycomb like sandwich acoustic metamaterials is tested by impedance tube experiment. Excellent sound insulation ability is confirmed. The reasonable design of honeycomb like sandwich acoustic metamaterials structural parameters can solve the problem of low-frequency noise of thin-layer lightweight structure.

Enhancement of reflectance reduction of solar cells by a silicon nanoparticle layer on a textured silicon substrate

To reduce the surface reflectance of Si solar cells, a structure has been developed in which a silicon nanoparticle (SiNP) layer is formed on a pyramid-like structure to simultaneously exploit multiple reflections and refractive index changes. The high refractive index of Si leads to the high reflectance of polished Si wafers. A conventional pyramid-like structure is formed on the surface of the Si wafer to reduce reflections using multiple reflections; however, the resultant sample reflectance is high because of the refractive index difference between air and Si. Nevertheless, although the reflectance of a SiNP layer on a polished Si wafer is high, the short-wavelength reflectance is <10 %. Our SiNP layer was then formed on a textured Si wafer by spin coating with a succession of changes to the spin-coating speed. In this manner, the reflectance after each speed change drastically decreased to <10 %, while the short-circuit current increased from 25.2 to 34.1 mA cm−2. The extremely thin SiNP layer and pyramid-like structure are promising as antireflective layers for solar cells.

Stability improvement of inverted organic solar cells with thin organic protective layer

Encapsulation is one of the methods to prevent organic devices from degradation. We design a facile, effective bilayer structure of ∼250 nm thick as protective layer for organic solar cells (OSCs). This bilayer structure is composed of a free-radical scavenging 3-Hydroxyflavone (3-HF) film underneath a hydrophobic polyvinylidene difluoride (PVDF) layer. Devices packaged with this 3-HF/PVDF bilayer show better storage stability and light-soaking stability than those with individual layer. As obtained, the power conversion efficiencies of packaged devices remain 96.1%, 86.5%, and 69.7% of their original values after two months storage in relative humidity environment of 20%, 50%, and 77% at room temperature, respectively. The result can be understood as the cooperative effect of water molecule repelling property of PVDF and oxygen elimination ability of 3-HF. The purposed idea can be generalized to other organic devices to extend their shelf life and serve as a design guideline for developing thin encapsulation materials for wearable technology with simple processing and good performance. • Designing an organic thin double layer structure to encapsulate organic solar cells. • Hydrophobic outer layer can repel moisture and the free-radical scavenging inner layer is important for oxygen. • The 3-HF/PVDF double layer can effectively retard device degradation in various storage and light-soaking conditions. • The proposed idea is general and can be applied to other organic devices as well. • The design idea can be a useful guideline for developing thin encapsulation materials for wearable electronics.

Synthesis of Silver Nanoparticles-Modified Graphitic Carbon Nitride Nanosheets for Highly Efficient Photocatalytic Hydrogen Peroxide Evolution.

As a promising metal-free photocatalyst, graphitic carbon nitride (g-C3N4) is still limited by insufficient visible light absorption and rapid recombination of photogenerated carriers, resulting in low photocatalytic activity. Here, we adjusted the microstructure of the pristine bulk-g-C3N4 (PCN) and further loaded silver (Ag) nanoparticles. Abundant Ag nanoparticles were grown on the thin-layer g-C3N4 nanosheets (CNNS), and the Ag nanoparticles decorated g-C3N4 nanosheets (Ag@CNNS) were successfully synthesized. The thin-layer nanosheet-like structure was not only beneficial for the loading of Ag nanoparticles but also for the adsorption and activation of reactants via exposing more active sites. Moreover, the surface plasmon resonance (SPR) effect induced by Ag nanoparticles enhanced the absorption of visible light by narrowing the band gap of the substrate. Meanwhile, the composite band structure effectively promoted the separation and transfer of carriers. Benefiting from these merits, the Ag@CNNS reached a superior hydrogen peroxide (H2O2) yield of 120.53 μmol/g/h under visible light irradiation in pure water (about 8.0 times higher than that of PCN), significantly surpassing most previous reports. The design method of manipulating the microstructure of the catalyst combined with the modification of metal nanoparticles provides a new idea for the rational development and application of efficient photocatalysts.

Electrolyte-Layer-Tunable ATR-SEIRAS for Simultaneous Detection of Adsorbed and Dissolved Species in Electrochemistry.

A balanced detection of both adsorbates and dissolved species is very important for the clarification of the electrochemical reaction mechanism yet remains a major challenge for different modes of electrochemical infrared (IR) spectroscopy. Among others, conventional attenuated total reflection-surface-enhanced IR absorption spectroscopy (ATR-SEIRAS) is far less sensitive to low-concentration solution species than to surface species. We report herein an electrochemical wide-frequency ATR-SEIRAS with a novel thin-layer flow cell design, fulfilling the simultaneous detection of the variations of surface and solution species. This setup consists of a silicon wafer (with one side micromachined and the other side metallized), a thin-layer electrolyte structure with tunable thickness and flow rate, and a tilt-correction system based on laser collimation, enabling a well-controlled mass transport within the electrolyte layer and the spectral differentiation of solution species from adsorbates. Using acidic methanol oxidation on a Pt film electrode as a model system, besides SEIRA bands for adsorbed CO and formate intermediates, IR spectral signals for dissolved products CO2, formic acid, and methyl formate can be readily identified for a quiescent electrolyte layer of ∼20 μm, which are otherwise undetected with conventional ATR-SEIRAS, as indicated by the trend of spectral features with increasing thickness or flow rate.

Overcoming the trade off between the permeation and rejection of TFN nanofiltration membranes through embedding magnetic inner surface functionalized nanotubes

Today, one of the most imortant environmental problems is the treatment of industrial wastewaters containing heavy metal ions and salts. In this research, thin-film nanocomposite (TFN) membranes were developed through incorporation of modified titanate nanotube (TNT) and halloysite nanotube (HNT) into the polyamide (PA) active layer to improve the performance of the NF membranes. At first, the internal surface of the nanotubes was coated with different polymers to lessen the inner diameter of the nanotubes. Then, the inner surface coated nanotubes were magnetized through placing Fe3O4 on their outer surface. In case of magnetized nanotubes, the fabrication of the membranes was done in the absence and in the presence of the external magnetic field, which made the nanotubes to align in a regular pattern across the PA layer, smoothing the membranes' surface and lowering the contact angle. It is expected that the magnetized nanotubes can make suitable arrangement in the structure of thin layer in the presence of the magnetic field and show better performance. The nanotubes act as the channels for water transport and in case of inner coated nanotubes, reject more ions through the steric hindrance. The pure water permeation of the membranes, modified with polystyrene inner coated TNT and HNT increased by 71.23% and 80.27%, respectively compared to the pristine TFC membrane without any significant changes in the rejection of Na+ and Cu2+; a suitable trade-off between the permeation and the ion rejection. In addition, the membranes modified by magnetized polyaniline inner coated TNT and HNT showed 36.24% and 75.62% more water permeation compared to the pristine TFC membranes while the rejections of Na+ and Cu2+ have not been changed remarkably. The results of this research showed that inner coating and magnetization of the nanotubes can be considered as a novel method to enhance the efficiency of TFN membranes for wastewaters treatment.

Energy-band-structure calculation by below-band-gap spectrophotometry in thin layers of non-crystalline semiconductors: A case study of unhydrogenated [formula omitted]-Si

We have in depth analyzed the refractive-index behavior and optical absorption of below-band-gap light, in order to calculate the basic parameters of the energy-band structure of thin layers of non-crystalline semiconductors. By carrying out a semi-empirical determination of the influence of the finite (non-zero) width of the valence and conduction electronic bands, we find the dependence of the index of refraction upon the photon energy, n(E), which goes just one order beyond the Wemple–DiDomenico two-level single-oscillator expression, and we simultaneously obtain the spectral dependence of the absorption coefficient, α(E). By model fitting the measured normal-incidence transmittance spectrum, we demonstrate that with a highly-sensitive double-beam spectrophotometer, it can be accurately determined the energy distance, EM,Sol, between the corresponding ‘centers of mass’ of the bonding and anti-bonding electronic bands, and also a reasonable estimate of the so-called effective width, Δeff, of both valence and conduction bands. We have used this devised optical approach with a series of uniform and non-uniform thin layers of unhydrogenated fully a-Si, grown by RF-magnetron-sputtering deposition, onto room-temperature transparent glass substrates. The advantages of our novel approach are mainly due to the additional attention paid to the roles of the weak-absorption Urbach tail and the thickness non-uniformity of the studied a-Si films. We have also used a universal normal-incidence transmission expression reported by the authors in an earlier paper, which can be applied even to strongly-wedge-shaped semiconductor layers. Together with the use of the improved Solomon formula for the normal optical dispersion of the refractive index, the complete approach with all its elements constitutes the main novelty of the present paper, in comparison with other existing works.