Thin Metal Layer Research Articles

Plasmonic Hinge Modes in Metal-Coated Nanolasers.

Plasmonic lasers have traditionally been built on flat metal substrates. Here, we introduce substrate-free plasmonic lasers created by coating semiconductor particles with an optically thin layer of noble metal. This architecture supports plasmonic "hinge" modes highly localized along the particle's edges and corners, exhibiting Purcell factors exceeding 100 and Q-factors of 15-20 near the plasmon resonance frequency. We demonstrate hinge-mode lasing in submicron CsPbBr3 perovskite cubes encapsulated with conformal 15-nm-thick gold shells. The lasing is achieved with 480-nm nanosecond pumping at 10 pJ/μm2 through the translucent gold layer, producing a line width of 0.6 at 538 nm. Their rapidly decaying evanescent fields outside the gold coating show distinct sensitivities to long- and short-range external perturbations. Our results suggest the potential of these novel laser modes for sensing and imaging applications.

Investigating Gold Deposition with High-Power Impulse Magnetron Sputtering and Direct-Current Magnetron Sputtering on Polystyrene, Poly-4-vinylpyridine, and Polystyrene Sulfonic Acid.

Fabricating thin metal layers and particularly observing their formation process in situ is of fundamental interest to tailor the quality of such a layer on polymers for organic electronics. In particular, the process of high power impulse magnetron sputtering (HiPIMS) for establishing thin metal layers has sparsely been explored in situ. Hence, in this study, we investigate the growth of thin gold (Au) layers with HiPIMS and compare their growth with thin Au layers prepared by conventional direct current magnetron sputtering (dcMS). Au was chosen because it is an inert noble metal and has a high scattering length density. This allows us to track the growing nanostructures via grazing incidence scattering. In particular, Au deposition on the polymer polystyrene (PS) with the respective structural analogues poly-4-vinlypyridine (P4VP) and polystyrene sulfonic acid (PSS) is studied. Additionally, the nanostructured layers on these different polymer films are further probed by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray reflectometry (XRR), and four-point probe measurements. We report that HiPIMS leads to smaller island-to-island distances throughout the whole sputter process. Moreover, an increased cluster density and an earlier percolation threshold are achieved compared to dcMS. Additionally, in the early stage, we observe a significant increase in coverage by HiPIMS, which is favorable for the improvement of the polymer-metal interface.

Numerical investigation on the formation of focusing effect in the IVR strategy

The “focusing effect” is the main challenging issue to the success of the IVR strategy, since the heat flux to the RPV wall could be significantly larger in the thin metal layer region than that in the oxide layer region. This paper numerically investigates the formation of focusing effect using validated CFD approach. The influences of the top cooling condition, layer height and material properties on the formation of focusing effect are investigated. Results indicate that, enhancing the top cooling mitigates the focusing effect. For the insufficiently-cooled top radiation situation, reducing the pool height significantly increases the focusing effect. For the sufficiently-cooled top surface (e.g., with top water cooling), the focusing effect is not formed for all the cases regardless of the pool height. It demonstrates/supports the benefit of adding in-vessel flooding to IVR strategy as a supplementary measurement. It means that once the in-vessel flooding could be established in engineering to allow for a sufficient top cooling, the focusing effect would not likely be formed regardless of the pool height. It also confirms enhancing top cooling condition an efficient way to reduce focusing effect. As two main influential material properties, the effects of thermal conductivity and viscosity are also investigated. Either decreasing the thermal conductivity or increasing the viscosity (e.g., by addition of other materials) may reduce the focusing effect. Since IVR is a widely adopted severe accident mitigation strategy, this study could provide some insights in the formation of focusing effect and help inspiring or supporting possible new engineering features for a safety IVR design.

Effects of sintering temperature on the microstructure and mechanical properties of double-hard-phase TiB2–TiC cermets

The mechanical properties and microstructure of double-hard-phase TiB2–25-wt.%-TiC–20-wt.%-CoNi cermets prepared at different temperatures were investigated by performing scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The results showed that the transverse rupture strength, indentation fracture toughness, hardness, and relative density of the cermets reached the maximum values of 1654 MPa, 11.06 MPa m1/2, 90.1 HRA, and 99.42 %, respectively, when the sintering temperature was 1462 °C. Solid- and liquid-phase sintering occurred at temperatures below and above 1354.5 °C, respectively. The cermets were composed of TiB2, TiC, TiB, and CoNi phases when sintered at 1440 °C and below, but the TiB phase disappeared when sintered at 1462 °C and above. Both TiB2 core–(Ti, Co, Ni)B rim and TiC core–(Ti, Co, Ni)C rim structures appeared in cermets sintered at 1440 °C and above. In addition, a few TiC core–(Ti, W)C inner–(Ti, W, Co, Ni)C outer double rim structures were formed. A coherent interface was found between the (Ti, Co, Ni)B rim and TiB2 core. A thin CoNi amorphous metallic layer existed at the interface between the (Ti, Co, Ni)C rim and TiC core. In addition, amorphous CoNi was observed in the interfacial region between the CoNi binder and (Ti, Co, Ni)C rim phase and inside the CoNi binder phase. These multi-interface and core–rim structures resulted in excellent strength and toughness of the cermets.

A new method for estimating nanoparticle deposition coverage from a set of weak-contrast SEM images

Imaging nanomaterials in hybrid systems is critical to understanding the structure and functionality of these systems. However, current technologies such as scanning electron microscopy (SEM) may obtain high resolution/contrast images at the cost of damaging or contaminating the sample. For example, to prevent the charging of organic substrate/matrix, a very thin layer of metal is coated on the surface, which will permanently contaminate the sample and eliminate the possibility of reusing it for following processes. Conversely, examining the sample without any modifications, in pursuit of high-fidelity digital images of its unperturbed state, can come at the cost of low-quality images that are challenging to process. Here, a solution is proposed for the case where no brightness threshold is available to reliably judge whether a region is covered with nanomaterials. The method examines local brightness variability to detect nanomaterial deposits. Very good agreement with manually obtained values of the coverage is observed, and a strong case is made for the method's automatability. Although the developed methodology is showcased in the context of SEM images of Polydimethylsiloxane (PDMS) substrates on which silicone dioxide (SiO2) nanoparticles are assembled, the underlying concepts may be extended to situations where straightforward brightness thresholding is not viable.

Mixed phase iron oxides thin layers by atmospheric-pressure chemical vapor deposition method

This paper provides a simple method for producing a metal oxide thin layer methodology by atmospheric pressure chemical vapor deposition (APCVD) synthesis over stainless steel substrates. This methodology enables the formation of thin iron oxide layers at its performance at various temperatures of 330 °C, 430 °C, and 530 °C. The deposition arises from thermal decomposition of the iron organometallic precursor Fe3(CO)12, forming a thin layer of iron oxide is, by the ozone present in the reaction chamber promoting the deposition of the iron oxide particles over the substrate. The Raman characterization suggest that at 330 °C, a mixture of hematite and magnetite is predominant on the as deposited substrates, also hematite modes show to be more pronounced as the band at 300 cm-1 narrows. Conversely, magnetite is prominent at higher synthesis temperatures, exhibiting a more intense Eg5 mode at 680 cm-1. The particles exhibit a uniform morphology, with both metal oxide phases coexisting. The average diameter of the particles is 50 nanometers as scanning electronic microscopy shows in a transversal sample section.•The formation of particles is attributed to the combination of iron ions +2 and +3 in the deposition process and their interaction with oxygen in the given synthesis parameters at atmospheric pressure chemical vapor deposition (APCVD).

Disentangling different interfacial effects of reduced thin layer magnetizations

Abstract Thin buried magnetic layers ranging from thicknesses of a few atomic monolayers to several nanometers are omnipresent in the fields of magnetism and spintronics. For the functionality and fine tuning of devices build with such layers, exact knowledge of the depth dependent magnetic properties is essential. Especially the interfacial magnetic properties are important. Hence, understanding how magnetism is affected by structural variations, such as thickness or interface roughness, is mandatory. In this study, we use x-ray resonant magnetic reflectometry and magnetometry to study the high-resolution depth dependent magnetization profiles of thin magnetic transition metal layers sandwiched between an oxide and chromium layer. Compared to bulk materials, the room temperature saturation magnetization of these layers is reduced by up to 67%. These reductions are extremely sensitive to small structural variations. From the magnetic depth profiles, we disentangle different effects contributing to the magnetization reduction and the exact magnetic properties of the interface.

Study of effect of nanomaterial above the add layer on performance parameters of plasmonic structure

In this paper, we explored the effect of adding a nanomaterial layer above the add layer on performance parameter of the considered plasmonic structures (conventional, four and five layer SPR sensors). These structures are stimulated by the COMSOL Multiphysics. We have considered LiNbO3 as an add layer over a thin film of gold. Further, Graphene, Black Phosphorene, Mxene, MoS2 MoSe2, WS2 and WSe2 as nanomaterial are considered over add-layer. First, we optimised the thickness gold and LiNbO3. After that, we calculated reflectance and magnetic field dependent performance parameters, i.e., shift in resonance angle (∆θr), full beam width (FBW), sensitivity (S), detection accuracy (DA), quality factor (Q. F.), figure of merit (FoM), field intensity at different interfaces (metal-sensing medium (M-S), metal-dielectric (M-D), dielectric-sensing medium (D-S), dielectric-nanomaterial (D-N), nanomaterial-sensing medium (N-S), and penetration depth (PD) for the considered plasmonic structures. The minimum ∆θr is obtained for conventional structure i.e. 1.492° and maximum ∆θr is obtained for WS2 as nanomaterial used in five layer SPR sensor i.e., 2.052°. Moreover, FBW is also maximum for five layer SPR sensor with WS2 as nanomaterial i.e., 6.8430°. Moreover, PD has maximum value for conventional SPR sensor i.e., 190.894 nm, 175.94 nm for four layer SPR sensor and less than 175.94 nm for five layer SPR sensor. This comparative study will help to choose add-layer with nanomaterial over add layer and metal thin film layer in a SPR sensor for the detection of analyte or molecules present in the sensing medium.

New correlations for focusing effect evaluation of the light metal layer in the lower head of a nuclear reactor in case of severe accident

In case of a severe accident (SA) in a nuclear reactor, the core heats up and materials melt and relocate to the lower head of the vessel. In such configuration, stratification occurs between the oxide and metal phases present in the melt. When the metal phase is lighter than the oxide phase, the maximum heat flux applied to the vessel wall is concentrated at the location of this top metal layer, creating the so-called “focusing effect”. The modelling of the focusing effect is essential for SA codes to properly evaluate the vessel failure time or to demonstrate the vessel integrity, when In Vessel Retention (IVR) strategy is implemented. However, existing correlations used in SA codes for focusing effect modelling have some limitations: if the thickness of the metal layer becomes very small, they predict an extremely high heat flux. Moreover, they were validated with tests using water, whereas the Prandtl number was found to play a significant role in this heat transfer.In this paper, the focusing effect is studied based on 3D Direct Numerical Simulations (DNS) of a cylindrical metal layer, covering all possible metal layer characteristics in terms of geometry and boundary conditions, especially for its top surface where the intensity of radiative heat transfer may vary. The analysis of the fluid behavior and the quantitative results obtained allow to derive new correlations and a new model based on the radial profile of the mean temperature of the system and on the radial profile at the top surface. Results at reactor scale confirm the overestimation of existing 0D model used in SA codes for a thin metal layer and highlight the relevance of the proposed model for focusing effect evaluation during transient situations.

Dynamic reflectivity of an opto-acoustic three-layer transducer for picosecond ultrasonic measurements

We present an analysis of a three-layered structure used for both launching and detecting picosecond acoustic waves. To enhance the optical sensitivity to the acoustic disturbances, a cavity is designed, which acts as a Fabry–Perot interferometer. We use analytic modeling based on dual optical and acoustic transfer matrix formalism to analyze the coupled optical and acoustic wave propagation. Assuming a three-layer transducer made of an optical cavity sandwiched between two thin metallic layers, the model allows for mastering of the coupled optical and acoustic responses, which leads to an optimum design of the structure, and it highlights the various acoustic contributions to the reflectivity changes. The sensitivity of this three-layered structure to acoustic disturbances is compared to the numerical predictions we performed for the standard opto-acoustic transducer made of a single metallic layer.

Application of Spectral Ellipsometry for Dielectric, Metal and Semiconductor Films in Microelectronics Technology

The article reviews model-based and model-free approaches to solving problems of spectral ellipsometry related to the measurement of thicknesses and optical parameters of thin layers of dielectrics, metals and semiconductors in microelectronics application. Model-based approaches employ a priori information about the dispersion relation in form of the Cauchy, Drude, Drude—Lorentz and Tautz—Lorentz. Model-free approaches can use any smooth multivariate functional dependence describing a smooth spectral curve. Also, machine learning can be used to implement the model-free approach, which is well suited for determining the thickness of multilayer structures and their optical characteristics and allows to significantly increase the speed of data processing.

Explosively driven Richtmyer–Meshkov instability jet suppression and enhancement via coupling machine learning and additive manufacturing

The ability to control the behavior of fluid instabilities at material interfaces, such as the shock-driven Richtmyer–Meshkov instability, is a grand technological challenge with a broad number of applications ranging from inertial confinement fusion experiments to explosively driven shaped charges. In this work, we use a linear-geometry shaped charge as a means of studying methods for controlling material jetting that results from the Richtmyer–Meshkov instability. A shaped charge produces a high-velocity jet by focusing the energy from the detonation of high explosives. The interaction of the resulting detonation wave with a hollowed cavity lined with a thin metal layer produces the unstable jetting effect. By modifying the characteristics of the detonation wave prior to striking the lined cavity, the kinetic energy of the jet can be enhanced or reduced. Modifying the geometry of the liner material can also be used to alter jetting properties. We apply optimization methods to investigate several design parameterizations for both enhancing or suppressing the shaped-charge jet. This is accomplished using 2D and 3D hydrodynamic simulations to investigate the design space that we consider. We also apply new additive manufacturing methods for producing the shaped-charge assemblies, which allow for the experimental testing of complicated design geometries obtained through computational optimization. We present a direct comparison of our optimized designs with experimental results carried out at the High Explosives Application Facility at Lawrence Livermore National Laboratory.

Wytwarzanie ochronnych struktur kompozytowych za pomocą technologii infuzji w celu zapewnienia odporności na fale uderzeniowe

The paper presents the results of experiments on the use of infusion of polymer binders into a pre-constructed skeleton of reinforcing structures. Currently, three-layer structures with an average layer of aluminum honeycombs are considered to be one of the effective structural elements that ensure the damping of the blast wave. As an alternative middle layer, it is possible to offer elements of various shapes (cylinders, cubes, etc.) and geometries made of modern composites that are well-proven under the impact of a shock wave. These are, as is known, metal-polymer composites, i.e. materials containing, in addition to polymer binder and fabric filler, thin layers of metal. In order to form a solid structure that perceives an explosive load, an attempt was made to use RFI technology to obtain individual elements with which two steel sheets are connected. Aramid, glass fabrics and aluminum thin (0.5, 0.15, 0.05 mm) plates were used in the experiments. For the implementation of the infusion process, an epoxy resin was used, suitable in its technological parameters for this process. The use of this resin leads to the minimization of non-nourished areas and pores. In this case, the uniformity of the product obtained from the composite material is achieved. It should be added that RFI technology differs from other polymer processing technologies in the following significant advantages: the possibility of abandoning expensive equipment, reducing energy costs for equipment and its maintenance, and complete rejection of the use of prepregs. However, there are a number of difficulties that are associated with the technological process of infusion, these primarily include the rheological requirements of the binder: at room temperature, the resin should have a low viscosity, and in the practice of fillers, the viscosity should have rather low values. Below are some preliminary plans for the development of this technology in order to obtain a product that provides attenuation of the blast wave.

Spin‐Thermoelectric Generation Associated with Magnetization Dynamics in the Insulator‐Based Generators Fabricated from Liquid Phase Epitaxial Yttrium Iron Garnet, Bi‐Substituted YIG and Bi‐ and Al‐Substituted YIG Films

An insulator‐based spin‐thermoelectric (STE) generator is composed of a thin paramagnetic metal (PM: Pt) layer for generating the STE voltage VSTE via the inverse spin Hall effect and a ferrimagnetic insulator (FMI) film or slab used for producing spin‐wave spin currents due to a temperature gradient . Yttrium iron garnet (YIG) is a key material used for the FMI of STE generators. We examined in detail the ferromagnetic resonance (FMR) properties of YIG (Y3Fe5O12), Bi‐substituted YIG (Y3‐xBixFe5O12) and Bi‐ and Al‐substituted YIG (Y3‐xBixFe5‐yAlyO12) films grown by liquid phase epitaxy (LPE). Bi‐substituted YIG films exhibited the large FMR damping and high STE voltage when the films were incorporated in the STE generator. The LPE‐grown Y2.35Bi0.65Fe5O12 film exhibited the FMR linewidth ΔH of 30 mT and the VSTE of 70 μV for the ∇T of . This paper comprehensively presents the origin of the STE generation in the insulator‐based generators on the basis of the results of FMR and STE measurements. To clarify the origin of STE generation in the generators fabricated from single crystal YIG (YIG, Bi‐substituted YIG and Bi‐ and Al‐substituted YIG) films grown by LPE, three principal factors are explained: (a) thermal energy transfer from the phonon system to the spin system, which strengthens the heat excitation of spin precession, through the spin–orbit coupling enhanced by the growth‐induced magnetic anisotropy of LPE‐grown YIG films, (b) in the YIG films incorporated in the STE generators, the generation of spin‐wave spin currents owing its origin to the ferromagnetic spin exchange interaction acting between neighboring spins due to , and (c) how the spin currents pumped into the Pt layer from the YIG film at the Pt/YIG bilayer interface are affected by the magnetization processes of single crystal YIG films. It is concluded that the STE generation of insulator‐based STE generators can be explained from a viewpoint of the spin dynamics under the effect of in the Pt/YIG bilayer structure. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

The microstructure and mechanical properties of steel-bonded TiB2 modified by adding Mo2C

In this study, the microstructure and interface of steel-bonded TiB2 were adjusted by adding Mo2C, so as to improve its comprehensive mechanical properties. The addition of Mo2C led to the formation of two kinds of core-rim structures, including TiB2 core-(Ti, Fe, Ni, Cr, Mo)B rim, and TiC core-(Ti, Fe, Ni, Cr, Mo)C rim. Micro - nano scale of TiB2, TiC and (Mo, Cr)C particles were formed in the steel-bonded TiB2. The introduction of Mo element caused the redistribution of elements in Fe-based binder phase, and two types of binder phases were generated, one was Ni-rich binder phase, and the other was Cr-rich binder phase. A full coherent interface was formed between the core and rim phase, and the amorphous metal thin layer was formed between the rim and binder phase. A coherent interface was formed between TiB2 and (Mo, Cr)C phase, (Mo, Cr)C and Ni-rich binder phase, as well as TiB2 and Ni-rich binder phase. Both the coherent interface and amorphous metal thin layer greatly enhanced the interface bonding strength, and improved the strength and toughness of the steel-bonded TiB2. The steel-bonded TiB2 with 6.0 wt% Mo2C exhibited excellent comprehensive mechanical properties, and its relative density, hardness, transverse rupture strength and fracture toughness were 99.94 ± 0.06%, 92.3 ± 0.5 HRA, 1278 ± 37 MPa and 10.90 ± 0.28 MPa·m1/2, respectively.

Modeling of laser generation in a Fabry–Pérot-Tamm structure with a nematic liquid crystal layer

In the presented work, the possibility of controlling laser generation using a nematic liquid crystal (NLC) in a hybrid layered structure consisting of a thin metal layer (Ag), a layer of NLC doped with a light-absorbing dye, and a distributed Bragg reflector (DBR) with a rectangular refractive index profile is theoretically studied. Spectral dependencies of the reflection, transmission, and absorption coefficients of light as well as the localization coefficient of the light field in NLC within the photonic bandgap of the DBR are obtained. Narrow dips in the reflection coefficient and peaks in the transmission coefficient are achieved due to the excitation of plasmons at the Ag-NLC interface. The dependence of the spectral position and magnitude of the plasmonic dips/peaks and the enhancement of the light field in the NLC medium on the thickness and orientation of the NLC layer as well as the impact of a light-absorbing dye doping are investigated. Theoretical calculations of the temporal dependencies of luminescence pulses for pumping pulses of different power settings (below, above, and at the threshold of laser generation) and different values of light absorption in the dye-doped NLC medium are performed, taking into account the peculiarities of the optical properties of the dye-doped NLC.

Simulation of ageing and wear effect on graphene THz passive components using finite element method

In the growing scenario of 2D material-based metamaterials and metasurfaces for Terahertz (THz) applications, assessing the impact of ageing and wear due to environmental stressors on the components’ performance is becoming mandatory to understand the long-term reliability of novel technologies. This paper introduces approaches to assess the ageing and wear effects on THz passive components through numerical simulations. For this purpose, common techniques for introducing 2D materials and thin metal layers in numerical models are discussed. As a case study, this work explores the effects of graphene degradation and reflective metal ageing on the electromagnetic response of a graphene-enhanced reflective grating for THz absorption and modulation by finite element (FE) analysis. The developed FE model is validated against experimental data obtained through THz Time-Domain Spectroscopy. By computing the device’s transmission, reflection, and absorption spectra for degrading graphene and metal conductive properties, this work provides insights into the influence of ageing and wear on THz passive components.

Designing black mirrors

Black mirrors, or total absorbers, are related to neutral density (ND) filters. ND filters are primarily concerned with transmittance, whereas a black mirror has no transmittance and endeavors to reduce the reflectance to zero in the wavelength band of interest by absorbing all the light. Metal layers must be used for the absorptance capabilities and dielectric layers to create the interference phases, which maximize the electric field at the absorbing layers. Very thin metal layers, whose indices of refraction vary with the thickness and require special software handling in the design process, are required. The procedures and an additional viewpoint on designing black mirrors are discussed here.

Not all that glitters is gold: Glitter causes acute toxicity to nauplii of Artemia sp.

Glitter has been reported as a relevant pollutant, as it is widely used in cosmetic and textile products and craftwork, and often associated with domestic sewage. The particular glitter is composed of thin layers of plastic and metal. This study assessed the acute toxicity of glitter dispersions in the brine shrimp Artemia sp. Nauplii of Artemia sp. that were exposed to glitter dispersions (0.01, 0.1, 1, 10, and 100 mg/L), obtained by diluting a stock solution in seawater; the control consisted of filtered seawater only. Three replicates were used per treatment and consisted of glass tubes filled with 10 mL of the test solution, and ten nauplii aging over 48 h. After 48 h, the survivors were counted and examined under a microscope. The mean size of glitter particles was 3.94 (±0.98) µm; approximately 44 % of particles were in the range of very fine sand, and 27 % coarse silt. Significant lethal effects (p < 0.05) occurred from 0.1 mg/L (Lowest Observed Effect Concentration - LOEC); the lethal concentration to 50 % organisms (LC50-48h) was 0.350 (0.348 - 0.351) mg/L. The exposed organisms also exhibited patches in their digestive tracts, and particles were stranded in their appendices. The results indicate the toxic potential of glitter to brine shrimp. This investigation indicates the need for further studies on the toxicity of glitter to marine invertebrates. Highlights Glitter includes particles of sizes similar to those of marine microalgae Exposure to glitter suspensions caused toxicity in brine shrimps from 0.1 mg/L The nauplii of Artemia were more sensitive to glitter than echinoderm embryos Metallic parts of the glitter were observed in the digestive tract of the brine shrimp nauplii

Interaction of H-Wave with the Thin Metal Layer with Generalized Boundary Conditions

Interaction of H-Wave with the Thin Metal Layer with Generalized Boundary Conditions