Intermediate Metal Layer Research Articles

Increasing the adhesion of graphene on quartz through fluorination

Graphene was the first 2D-material ever discovered, and its unique properties open up for many applications. Due to its high mechanical resistance and transparency, it has been investigated as a coating for optical devices such as windows or lenses. A particular focus has been as an anti-icing coating where graphene functionalized with fluorine atoms, so-called fluorinated graphene, has been demonstrated to inhibit ice formation. However, to function as a durable coating the adhesion between graphene and the underlying substrate must be strong. Up till now it has not been possible to deposit graphene/functionalized graphene on a transparent substrate, such as SiO2, with strong adhesion, without an intermediate metal layer (that gradually makes it opaque). Through optical and electron microscopy observation of surfaces scratched with a sapphire tip, we show how a transparent, functionalized graphene coating with improved adhesion can be created through fluorination of graphene transferred onto a quartz substrate (α-SiO2). The fluorination leads to an increase in adhesion of approximately 3 times compared to unfluorinated graphene adhered to the same substrate. Comparing this with reported adhesion energies for graphene on SiO2 gives an estimated adhesion energy between 0.03J/m2 and 9J/m2 for graphene fluorinated on SiO2.

Improving the color gamut of gold nanostructures using vertical tandem nano-disks

Metallic nanoparticles have been used in structural coloration applications since they provide an alternative for the synthesis of color filters, with extended color gamut, enhanced color saturation, and brightness. These optical properties can be further improved when integrating nanoparticles into coupled dimers that give rise to enhanced hybridized plasmon resonances. In this contribution, gold nano-disks are split into Au/SiO2/Au layered structures to enhance its plasmon resonances and evaluate its improved performance as reflective color filters. To do so, the reflectance spectra of the layered disks were obtained with numerical simulations, identifying high amplitude peaks in the visible band and low-amplitude peaks in the near infrared one, related to the hybridized resonances. By choosing the appropriate size of the intermediate dielectric and metallic layers, as well as the near-field coupling, peaks can be tuned along the visible and near infrared bands, respectively. The chromatic coordinates of the addressed nanostructures obtained from the reflectance spectra show that the nanostructures hold color gamut that extends toward magenta, orange, yellowish, and reddish shades of colors.

RETRACTED: A droplet-based electricity generator with high instantaneous power density, high efficiency, and reliable long-term stability

Droplet-based electricity generators (DEGs) have recently revolutionized the prospects for energy harvesting from raindrops. However, achieving high instantaneous power density, high efficiency, and reliable long-term stability remains challenging. Here, we propose a DEG with an intermediate metal electrode underneath the dielectric layer (IM-DEG) for substantial instantaneous outputs, high efficiency, and improved long-term stability. This intermediate metal layer not only plays a vital role as additional charge storage but also opens up a new route to inject negative charges into the dielectric layer from below to further increase the surface charge density. Unlike other ion injection techniques that inject negative charges from the top of the dielectric materials, in our case, the negative charges injected from below tend to remain in the dielectric layer without leaking to the upper electrode or droplets, resulting in elevated electrical performance and improved long-term stability. The IM-DEG's instantaneous peak voltage, power density, and energy conversion efficiency reach 836 V, 6.92 kW/m2, and 32.69%, respectively, while the instantaneous peak voltage drops less than 3% after 1000 h of a continuous flow of droplets. This method offers substantial electrical outputs with high efficiency and reliable long-term stability, paving the way for the future of raindrop energy harvesting.

A broadband second-order bandpass frequency selective surface for microwave and millimeter wave application.

This paper presents a frequency selective surface (FSS) with a wideband second-order bandpass response in the dual-band of microwave and millimeter wave. The overall structure consists of three layers of metal pattern and two layers of thin dielectric substrate. The top and bottom metal layers have capacitive patches with integrated curled Jerusalem cross slot resonators, while the intermediate metal layer has an inductive grid structure with cross-shaped slot resonators. The incorporated slot resonators play a pivotal role in achieving the desired transmission poles or zeros, which enable a wideband second-order filtering response in the dual-band and a quick roll-off at the passband edges, increasing the efficacy of electromagnetic shielding. To fully investigate the structure's frequency response, an equivalent circuit model of the structure is created, spanning the complete frequency range of 5-50 GHz. Physical samples are created and measured to confirm the suggested approach's efficacy. The passband center frequencies of the FSS are found at f1 = 19.42 GHz and f2 = 42.78 GHz, and the - 3dB bandwidth is 4.34 GHz (17.25-21.59 GHz) and 8.54 GHz (38.51-47.05 GHz), respectively. The simulation results align well with the experimental data. The transmission response rapidly transitions from the passband to the stopband at the passband boundaries.

микромеханические характеристики плазменных теплозащитных покрытий после термической выдержки и циклического деформирования

For plasma heat-protective coatings with a ceramic layer based on zirconium dioxide, the influence of the duration of high-temperature exposure (1100 °C, 2—100 h) and subsequent cyclic deformation in the elastic region, as well as the ratio of the thicknesses of the ceramic and intermediate metal layers on the micromechanical characteristics (Young's modulus, kinetic hardness parameters, plastic deformation and creep) and flexural strength, assessed by instrumental indentation, has been studied. It was that in the case of thermal exposure lasting up to 2 hours, the Young's modulus, the characteristics of kinetic hardness and the strength of the coating were significantly reduced, and the proportion of energy spent on plastic deformation, as well as creep, increased. With an exposure duration of 50 hours or more, the kinetic microhardness characteristics increase, and the plasticity characteristics decrease. The greatest strength of the coating was obtained when the ratio of the thicknesses of the metal sublayer and the ceramic layer was 0.2—0.3. Keywords: heat-protective coating, thermal operating time, deformation aging, kinetic microindentation, micromechanical properties.

Reconfigurable coherent perfect absorption of different polarized electromagnetic fields through vanadium-dioxide based asymmetry transmissive meta-surfaces sandwiched with graphene meta-gratings

We demonstrate coherent perfect absorption (CPA) of different linearly polarized electromagnetic fields using an asymmetry transmissive meta-surface consisting of two outermost VO2-metal layers and symmetrical graphene meta-gratings, as well as an intermediate C-slit metallic layer. Such a five-layered cascaded VO2-metal-graphene meta-surface can perfectly trap either the x- or the y-polarized signal fields when interacting with the x-polarized control wave by imposing specific Fermi level over the graphene together with conducting- or insulating-state VO2 at 3 THz. On the other hand, y-polarized control wave can also interfere with either x- or y-polarized signal fields when the CPA of the electromagnetic wave operates at 3.65 THz. Our design, using asymmetry transmissive meta-surfaces for more advanced coherent control of different linearly polarized electromagnetic fields with the assistance of tunable materials, should pave the way for building up multipolar and multifunctional absorbers.

Preparation and mechanism of Cu-GO laminated composite films with high thermal conductivity by intermediate nickel and silver layers via electrodeposition and ultrasonic spraying method

The graphene oxide-Cu (GO-Cu) laminated composite films with nickel and silver intermediate layers were prepared by electrodeposition, ultrasonic spraying and subsequent annealing heat treatment. The influences of current density of Cu plating, the silver ion concentration and electrodeposition time of nickel plating on the morphology, microstructure and thermal conductivity of the composites were systematically studied. The introduction of Cu-O-C covalent bonds and the diffused nickel and silver transition layers at the interface could effectively enhance the interfacial bonding between GO and Cu, accordingly improving its thermal conductivity. Under the optimal process parameters (current density 8 A/dm2, silver ion concentration 4.25 g/L(0.025 M), electrodeposited nickel 25 s), the in-plane thermal conductivity of GO-Cu-GO and GO-Ag-Cu-Ag-GO and GO-Ni-Cu-Ni-GO laminated composite films could reach 572.21 W·m−1·K−1, 652.64 W·m−1·K−1 and 790.36 W·m−1·K−1, respectively. The significant enhancement of thermal performance for the Cu-GO laminated composite films could be attributed to the effective improvement of the interfacial bonding between Cu and GO in the composites by existence of intermediate metal layer.

Frictional performance of C/C–SiC materials at high loads: The role of composition and third-body

Ceramic matrix composites like carbon fiber-reinforced silicon carbon (C/C–SiC) are brake materials for applications at high thermo-mechanical loads. This study investigates the influence of three C/C–SiC pad materials with different compositions on frictional performance. For this purpose, the ceramic pad materials were tested against a steel disk on a dynamometer at brake pressures from 20 to 60 MPa. A large effect due to the different Si and SiC contents of the three pad materials on the frictional behavior was expected. Although the wear rates differed from 40 to 140 mm3/MJ, only marginal differences were found for the coefficient of friction. Hence, additional tests to interrupt and sequence the brake procedure revealed the formation of an intermediate metallic transfer layer from the steel disk on the ceramic pads. The formation and disappearance of this third-body, which was not found in start-complete-stop testing, and the consequences for the frictional properties are discussed.

Multifunctional terahertz metamaterial based onvanadium dioxide and silicon.

This paper proposes a multifunctional metamaterial device operating in the terahertz (THz) band. The metamaterial device can switch functions by using the phase transition properties of vanadium dioxide (V O 2) and the photoconductive effect of silicon. An intermediate metal layer divides the device into the I side and II side. When V O 2 is in the insulating state, the I side can achieve polarization conversion from linear polarization waves to linear polarization waves at 0.408-0.970THz. When V O 2 is in the metal-like state, the I side can perform polarization conversion from linear polarization waves to circular polarization waves at 0.469-1.127THz. When silicon is not excited in the absence of light, the II side can perform polarization conversion from linear polarization waves to linear polarization waves at 0.799-1.336THz. As the light intensity increases, the II side can realize stable broadband absorption at 0.697-1.483THz when silicon is in the conductive state. The device can be applied to wireless communications, electromagnetic stealth, THz modulation, THz sensing, and THz imaging. Moreover, it provides a fresh idea for the design of multifunctional metamaterial devices.

Role of Intermediate Metal and Oxide Layers in Change of Adhesion Properties of TiAl/Al2O3 Interface

Role of Intermediate Metal and Oxide Layers in Change of Adhesion Properties of TiAl/Al2O3 Interface

5G wideband on‐chip dipole antenna for WSN soil moisture monitoring

Recently, soil dielectric constant detection has been used in the irrigation of vastly differing farming conditions. Soil monitoring has seen a push toward fifth generation (5G) telecommunications technology, due to the higher speed and bandwidth required to connect a huge number of sensor nodes simultaneously. A novel architecture for a fully integrated, unequal arms dipole antenna is presented in this article. The proposed on-chip antenna is implemented using UMC180 nm CMOS technology. A dipole radiator is added on the upper metal layer, a ground sheet set at the lower metal layer and a patch layer is added on the intermediate metal layer. This configuration has improved the antenna impedance bandwidth by 38%. In addition, it increased the electrical length of the dipole antenna to reduce the antenna resonant frequency by 10 GHz. The proposed antenna has a total area 1300 × 250 μm, and its wide bandwidth extends from 21 to 40 GHz at reflection coefficient |S11| < –7 dB, which makes it suitable for on-chip wireless sensor network applications in 5G technology. All Simulations are completed by using the Ansys HFSS (high-frequency structure simulator) ver.15 and the simulated results show a good comparison with measurements. To investigate the proposed antenna's performance in different environmental conditions, practical measurements for soil dielectric constant in different compositions with variable moisture ratios are applied. The resulting values are used in antenna simulation and have ultimately proved the antenna's improved capability to sense soil moisture in different conditions.

Синтез, структура и магнитные свойства многослойных наногетероструктур Fe|MgO|Cr|MgO|Fe

Layered nanoheterostructures Fe | MgO | Cr | MgO | Fe is an artificial ferromagnetic material in which the exchange interaction of the magnetic moments of Fe layers through intermediate dielectric and metal layers can lead to magnetic configurations that are not realized in the well-studied Fe | MgO | Fe and Fe | Cr | Fe. In this work, we investigated the correlations of the structural and magnetic properties of layered nanoheterostructures Fe (10 nm) | MgO (1.5 nm) | Cr (t nm) | MgO (1.5 nm) | Fe (7 nm) (thickness t = 0.9 and 1.8 nm). Structural studies performed using X-ray diffractometry and high-resolution reflectometry confirmed the formation of a textured structure and revealed its well-defined layered character with sharp interlayer boundaries.

Development and Optimization of Tin/Flux Mixture for Direct Tinning and Interfacial Bonding in Aluminum/Steel Bimetallic Compound Casting.

Interfacial bonding highly affects the quality of bimetallic bearing materials, which primarily depend upon the surface quality of a solid metal substrate in liquid–solid compound casting. In many cases, an intermediate thin metallic layer is deposited on the solid substrate before depositing the liquid metal, which improves the interfacial bonding of the opposing materials. The present work aims to develop and optimize the tinning process of a solid carbon steel substrate after incorporating flux constituents with the tin powder. Five ratios of tin-to-flux—i.e., 1:1, 1:5, 1:10, 1:15, and 1:20—were used for tinning process of carbon steel solid substrate. Furthermore, the effect of volume ratios of liquid Al-based bearing alloy to solid steel substrate were also varied—i.e., 5:1, 6.5:1 and 8.5:1—to optimize the microstructural and mechanical performance, which were evaluated by interfacial microstructural investigation, bonding area determination, hardness and interfacial strength measurements. It was found that a tin-to-flux ratio of 1:10 offered the optimum performance in AlSn12Si4Cu1/steel bimetallic materials, showing a homogenous and continuous interfacial layer structure, while tinned steels using other percentages showed discontinuous and thin layers, as in 1:5 and 1:15, respectively. Furthermore, bimetallic interfacial bonding area and hardness increased by increasing the volume ratio of liquid Al alloy to solid steel substrate. A complete interface bonding area was achieved by using the volume ratio of liquid Al alloy to solid steel substrate of ≥8.5.

Enabling Efficient Charge Separation for Optoelectronic Conversion via an Energy-Dependent Z-Scheme n-Semiconductor-Metal-p-Semiconductor Schottky Heterojunction.

Achieving good charge separation while maintaining energetic electronic states in heterostructures is a challenge in designing efficient photocatalyst materials. Using first-principles calculations, we propose a Z-scheme Sn-m-Sp (n-semiconductor-metal-p-semiconductor) heterojunction as a viable avenue for achieving broad-spectrum sunlight absorption and, importantly, energy-dependent charge separation. As a proof-of-concept investigation, we investigated two ternary heterostructures, CdS-Au-PdO and SnO2-W-Ag2O, in which the electronic Fermi levels line up by virtue of the presence of an intermediate metal layer. A cascade of work functions in the relative order Wn < Wm < Wp drives electrons flowing from Sn to m and from m to Sp. The inner electric fields established at the Sn-m and m-Sp Schottky junctions selectively guide low-energy photoexcited electrons from Sn (CdS/SnO2) and low-energy holes from Sp (PdO/Ag2O) to the interposing Au or W metal, respectively. Importantly, relatively low Schottky barriers enforce charge separation by constraining high-energy photogenerated charges to the individual semiconductor layers. Operating together, these two mechanisms enable the achievement of highly efficient optoelectronic conversion.

Influence of Cu Thickness and Annealing on the Properties of ZnS/Cu/ZnS Multilayer Films

Zinc sulfide (ZnS), copper (Cu) and ZnS thin films were deposited sequentially on high-borosilicate glass by radio-frequency magnetron sputtering at room temperature, and a ZnS/Cu/ZnS sandwich structure was obtained. Cu thin films with thickness ranging from 4 to 20 nm were used as an intermediate metal layer. The effects of Cu thickness and annealing treatment on the surface morphology and the electrical and optical properties of the ZnS/Cu/ZnS multilayer films were observed. The results show that the surface roughness of the multilayer films was reduced with increasing Cu thickness. The conductivity and transmittance of the multilayer-structure device were regulated by tailoring the Cu thickness, illustrating that the 16-nm-thick Cu film is beneficial for obtaining high conductivity and transmittance performance. The structural properties of the multilayer films annealed at different temperatures were also studied. The annealed multilayers exhibited a cubic zinc blende structure with a highly (111)-textured orientation. The film crystallinity was improved with increasing annealing temperature.

Metallization of Fiber Reinforced Composite by Surface Functionalization and Cold Spray Deposition

The cold spray deposition process has gained interest as a promising technique for producing metallic coatings on polymers and composite materials thank to its low working temperatures. However, poor adhesion of metallic particles on polymeric substrates and the brittle nature of these materials lead to generation of cracks under the impact of the sprayed particles, limiting its application to polymeric matrix composite. The interposition of an intermediate metallic layer over the thermoset composite to be coated has been claimed to improve the adhesion of the sprayed particles and the formation of a stable link between the metal coating and the underlying polymer panel. The present work discusses a methodology that integrates the manufacturing of glass reinforced epoxy panels having functionalized surface and the subsequent production of a dense metallic layer by cold spray. Pure copper and titanium metallic powders, having spherical and irregular shape respectively, were placed on the top of the stack of dry glass fiber fabrics. Resin infusion process was then applied to impregnate the glass fabrics providing the simultaneous functionalization of the composite panel. In order to assess the effectiveness of the produced substrate, and of the proposed procedure, metallic coatings have been finally deposited on manufactured composite panels by means of a low-pressure cold spray facility. Regardless the spraying condition (namely gas temperature, stand-off distance, sprayed particles), copper samples showed a remarkable erosion of functionalized layer after cold spray process with pronounced damages of the composite substrate. On the other hand, effective depositions have been observed on titanium samples under specific combination of process parameters.

Postdeposition UV-Ozone Treatment: An Enabling Technique to Enhance the Direct Adhesion of Gold Thin Films to Oxidized Silicon.

We found that continuous films of gold (Au) on oxidized silicon (SiO2) substrates, upon treatment with ultraviolet (UV)-ozone, exhibit strong adhesion to the SiO2 support. Importantly, the enhancement is independent of micro- or nanostructuring of such nanometer-thick films. Deposition of a second Au layer on top of the pretreated Au layer makes the adhesion stable for at least 5 months in environmental air. Using this treatment method enables us to large-scale fabricate various SiO2-supported Au structures at various thicknesses with dimensions spanning from a few hundreds of nanometers to a few micrometers, without the use of additional adhesion layers. We explain the observed adhesion improvement as polarization-induced increased strength of Auδ−Siδ+ bonds at the Au–SiO2 interface due to the formation of a gold oxide monolayer on the Au surface by the UV-ozone treatment. Our simple and enabling method thus provides opportunities for patterning Au micro/nanostructures on SiO2 substrates without an intermediate metallic adhesion layer, which is critical for biosensing and nanophotonic applications.

Nano-Programmable Logics Based on Double-Layer Anti-Facing Memristors.

The memristor, as theorized by Chua in 1971 (L. Chua, IEEE Trans. Circuit Theory 18, 507 (1971)), is a two-terminal device whose resistance state is based on the history of charge flow brought about as a result of the voltage applied across its terminals. High-density regular fabrics for nanoscale memristors, such as crossbar arrays, are emerging architectures for system-on-chip (SoC) implementation, which provide both simplified structure and improved performance (W. H. Yu, et al., IEEE Trans. VLSI 20, 1012 (2012)). The advantage of using memristors as the switching devices within crossbar arrays is their nanoscale switching capability, which specifically changes their resistance state between high and low. In this paper, we propose a new nano-programmable logic array (PLA) device in the form of an on anti-facing double-layer memristor array. The PLA is composed of an AND plane and an OR plane merged onto the same layer. The AND and OR planes are stacked vertically such that each layer forms a crossbar architecture; thus, a cross section reveals two anti-facing memristors with 5 layers: the bottom metal layer, a memristive layer, the intermediate metal layer, an anti-facing memristive layer, and the top metal layer. The intermediate metal layer provides its output at the AND plane which is the input of the OR plane, and as such, the input and output nodes of the two logic functions are shared. Thus, the proposed architecture reduces the propagation delay of the AND plane by 70% by sharing the OR plane input wires. Additionally, the anti-facing architecture makes it easy to determine appropriate values for the pull-up and pull-down registers of the PLA.

Exceeding 30 % efficiency for an environment-friendly tandem solar cell based on earth-abundant Se/CZTS materials

In this paper, a new Se/CZTSSe tandem solar cell architecture is proposed as a viable approach to reach ultrahigh efficiency values at low fabrication cost. The proposed tandem design consists of a Se-based top cell with Ti intermediate ultra-thin metallic layers (MLs) and a CZTS bottom cell with graded band-gap aspect. The role of the introduced design amendments in achieving the dual-benefit of enhanced optical behavior and reduced recombination losses is investigated by means of an accurate numerical modeling. Moreover, a comprehensive study which involves the impact of design parameters such as the MLs position and the CZTSSe band-gap profile on the device performance is carried out. Moreover, Particle Swarm Optimization (PSO)-based metaheuristic technique is used to boost up the Se/CZTSSe tandem cell efficiency by identifying both the suitable position of the introduced ultrathin MLs and the appropriate CZTSSe band-gap profile. It is found that the adopted optimization approach pinpoints a new path toward achieving over 30% efficiency, not only it provides the possibility to reduce interface recombination effects by optimizing the band offset at the buffer/absorber interfaces but also enables selecting the most favorable design configuration associated with enhanced optical behavior. This makes the optimized Se/CZTSSe tandem solar cell potential alternative for providing high-efficiency and stable tandem solar cell.

Multilayer structure for highly transmissive angle-tolerant color filter

We propose transmissive color filter which can retain the same perceived color over a wide range of incident angle in the visible spectrum. The enhanced transmission is caused by Tamm plasmons (TP) based on multilayer thin film structure which consists of distributed Bragg reflector (DBR) and intermediate metal layer. High transmission of 60%∼70% efficiently improves the utilization of light energy and contributes to enhancing the color purity. In addition, the color filter is able to display distinctive color over the whole visible spectrum by changing the thickness of dielectric and metal layer. Without etching complex nano-patterns, the multilayer structure can be fabricated by depositing films successively with different materials on the substrate. The presented transmissive color filter exhibits the characteristic of high transmission and angle-tolerance. It has great potential for large-scale application, such as liquid crystal display, imaging sensor, and anti-counterfeiting.