Multilayer Arrays Research Articles

Multilayer Crossbar Array of Amorphous Metal-Oxide Semiconductor Thin Films for Neuromorphic Systems

A multilayer crossbar array has been developed using amorphous metal-oxide semiconductor (AOS) thin films and implemented into a neuromorphic system. The multilayer structure can be realized, because the AOS thin films can be deposited by a simple sputtering method without heat treatment, which does not damage the underlying structures. First, Au thin films are deposited by vapor evaporation as electrodes, an amorphous In-Ga-Zn-O (α-IGZO) thin film is deposited by a sputtering method as a conductance change layer, these processes are repeated, and a multilayer crossbar array is completed, where each of the three conductance change layers is sandwiched between the electrodes. Next, the multilayer crossbar array is implemented into a neuromorphic system with modified Hebbian learning, which enables autonomous learning without control circuitry, and an associative memory function is confirmed, which guarantees the possibility of further advanced functions. These results lead to astronomical large-scale integration (LSI) of synaptic elements in neuromorphic systems in the future.

Deep Learning-Based Single-Shot Computational Spectrometer Using Multilayer Thin Films

Computational spectrometers have mobile application potential, such as on-site detection and self-diagnosis, by offering compact size, fast operation time, high resolution, wide working range, and low-cost production. Although these spectrometers have been extensively studied, demonstrations are confined to a few examples of straightforward spectra. This study demonstrates deep learning (DL)-based single-shot computational spectrometer for narrow and broad spectra using a multilayer thin-film filter array. For measuring light intensities, the device was built by attaching the filter array, fabricated using a wafer-level stencil lithography process, to a complementary metal-oxide-semiconductor image sensor. All the intensities were extracted from a monochrome image captured with a single exposure. A DL architecture comprising a dense layer and a U-Net backbone with residual connections was employed for spectrum reconstruction. The measured intensities were fed into the DL architecture for reconstruction as spectra. We reconstructed 323 continuous spectra with an average root mean squared error of 0.0288 in a 500-850 nm wavelength range with 1-nm spacing. Our computational spectrometer achieved a compact size, fast measuring time, high resolution, and wide working range.

A Wideband and High-Gain All-Metallic Perpendicular-Corporate-Fed Multi-Layered Parallel-Plate Slot Array Antenna

An all-metallic multi-layered parallel-plate slot array antenna operated in the 60-GHz band with wide impedance bandwidth and high-gain characteristics is proposed. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\,{\times }\,16$ </tex-math></inline-formula> -slot antenna is composed of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\,{\times }\,2$ </tex-math></inline-formula> -slot subarrays perpendicularly-fed by a hollow waveguide corporate feeding network. The subarray is partitioned into three functional layers including a bottom one for feeding, a mediate one for radiating and a parasitic one atop for bandwidth enhancement. An undesired resonance of a high-order mode introduced with the parasitic layer is eliminated by loading metal grids between the slotted plates. The contribution of the parasitic layer on bandwidth improvement is verified by a measured 19.2% bandwidth of the antenna with reflection below −10 dB. The removal of the dielectric plate loaded in the conventional double-layered counterpart also contributes to the better performance of the array. The all-metallic feature exempts the design from dielectric loss and beneficial for realizing a higher gain. A high aperture efficiency over 90% is realized over a 19.3% bandwidth and an antenna efficiency over 70% is obtained over a 18.5% bandwidth for the fabricated prototype antennas. The measured realized gain is up to 33.2 dB and the antenna efficiency is 87.2% at 62.0 GHz.

A Novel Strategy to Improve Giant Magnetoresistance Effect of Co/Cu Multilayered Nanowires Arrays

A Novel Strategy to Improve Giant Magnetoresistance Effect of Co/Cu Multilayered Nanowires Arrays

The change in the thermal conductivity of a multilayer array of carbon nanotubes during its lateral compression

Numerical simulation of thermal conductivity across a multilayer array of single-walled carbon nanotubes is carried out. The effect of transverse compression of the array on thermal conductivity has been studied. It is shown that the compression of the array can occur uniformly when all the nanotubes of the array are compressed equally, and it can occur inhomogeneously when a part of the nanotubes is strongly compressed, and the other part is weakly compressed. With homogeneous compression, the thermal conductivity of the array increases, but with inhomogeneous compression, it does not change and may even decrease in case of a large number of layers. This effect is especially pronounced for arrays of nanotubes of small diameter (D&amp;lt;2 nm). Keywords: carbon nanotubes, nanotube arrays, transverse compression, heat conductivity.

Изменение теплопроводности многослойного массива углеродных нанотрубок при его поперечном сжатии

Numerical simulation of thermal conductivity across a multilayer array of single-walled carbon nanotubes is carried out. The effect of transverse compression of the array on thermal conductivity has been studied. It is shown that the compression of the array can occur uniformly when all the nanotubes of the array are compressed equally, and it can occur inhomogeneously when a part of the nanotubes is strongly compressed, and the other part is weakly compressed. With homogeneous compression, the thermal conductivity of the array increases, but with inhomogeneous compression, it does not change and may even decrease in case of a large number of layers. This effect is especially pronounced for arrays of nanotubes of small diameter (D &lt; 2 nm)

Enhancement of gain using a multilayer superstrate metasurface cell array with a microstrip patch antenna

This research presents a new idea in the use of wireless communication antennas: it uses a multi-layered array of cells called a superstrate multi-layer metasurface (MTM) and is placed in front of a patch of microstrip antenna to absorb surface waves and prevent them from passing through the insulating material, which reduces the permeability of the insulator and thus improves the Antenna properties, The proposed hexagonal cell with resonators is placed on the flame resistant (FR4) substrate, with a relative permittivity of 4.3 and an area (14×14) mm2 . It was tested when the metasurface layer is 4 mm in front of the patch and the distance between the metasurface layers is 2 mm. The optimum distances were calculated by the sweep parameter, and the improved antenna gain and the input reflection coefficient were obtained together. (S11) has been improved from -31.217 to -38.338 dB and, the gain from 3.28 dB to 6.554 dB.

Structural insights into the evolution of the RAG recombinase.

Adaptive immunity in jawed vertebrates relies on the assembly of antigen receptor genes by the recombination activating gene 1 (RAG1)-RAG2 (collectively RAG) recombinase in a reaction known as V(D)J recombination. Extensive biochemical and structural evidence indicates that RAG and V(D)J recombination evolved from the components of a RAG-like (RAGL) transposable element through a process known as transposon molecular domestication. This Review describes recent advances in our understanding of the functional and structural transitions that occurred during RAG evolution. We use the structures of RAG and RAGL enzymes to trace the evolutionary adaptations that yielded a RAG recombinase with exquisitely regulated cleavage activity and a multilayered array of mechanisms to suppress transposition. We describe how changes in modes of DNA binding, alterations in the dynamics of protein-DNA complexes, single amino acid mutations and a modular design likely enabled RAG family enzymes to survive and spread in the genomes of eukaryotes. These advances highlight the insight that can be gained from viewing evolution of vertebrate immunity through the lens of comparative genome analyses coupled with structural biology and biochemistry.

Real-time detection of soil crack depth by apparent electrical resistivity method

Soil cracks are caused by many factors, which are harmful to the mechanical and hydraulic properties of the soil. At present, most previous studies have focused on the crack morphology of soil surface, and there are few studies on the depth of soil cracks. The traditional methods for detecting the depth of soil cracks are mostly destructive, so the non-destructive measurement of crack depth needs to be further studied. The electrical resistivity method has been widely used in the measurement of soil surface cracks, but its applications in depth measurements are still poorly studied. In this paper, a three-dimensional desiccation crack experiment of soil was carried out in the laboratory. The variation of the anisotropy index (AI) with the crack depth propagation was studied by a multi-layer electrode array. A new method to detect the crack depth was proposed by theoretical and experimental analyses. The validity of this new method in the detection of crack depth is demonstrated by using the method of crack-tip opening angle (CTOA).

Indication of Strongly Correlated Electron Transport and Mott Insulator in Disordered Multilayer Ferritin Structures (DMFS).

Electron tunneling in ferritin and between ferritin cores (a transition metal (iron) oxide storage protein) in disordered arrays has been extensively documented, but the electrical behavior of those structures in circuits with more than two electrodes has not been studied. Tests of devices using a layer-by-layer deposition process for forming multilayer arrays of ferritin that have been previously reported indicate that strongly correlated electron transport is occurring, consistent with models of electron transport in quantum dots. Strongly correlated electrons (electrons that engage in strong electron-electron interactions) have been observed in transition metal oxides and quantum dots and can create unusual material behavior that is difficult to model, such as switching between a low resistance metal state and a high resistance Mott insulator state. This paper reports the results of the effect of various degrees of structural homogeneity on the electrical characteristics of these ferritin arrays. These results demonstrate for the first time that these structures can provide a switching function associated with the circuit that they are contained within, consistent with the observed behavior of strongly correlated electrons and Mott insulators.

Numerical solution for scattering of multilayer noble metal circular aperture arrays nanostructure

Due to its unique properties, metal-dielectric plasmonic structures have been widely applied in many fields, such as light absorption enhancement, surface enhanced spectrum, biosensor, and solar cell. We presented a numerical solution for light scattering from multilayer noble metal circular aperture arrays nanostructure. Using the generalized boundary conditions of surface impedance, the boundary value problem can be transformed into a set of integral equations about current density and magnetic density. Then utilizing the method of moments to solve these integral equations, more accurate reflected, transmitted, and absorbed power expressions can be obtained.

Logics execution in a multi-layers memristor array

Memristor stateful logic based on a two-dimensional (2D) memristor crossbar array (MCBA) has been proved to be an effective approach to break the von Neumann bottleneck. But the three-dimensional (3D) array which has an inherent high storage density is less investigated in logic computation field. In this work, we implemented the whole linearly separable binary Boolean logic functions completely by using the stateful logic circuits configured in a multi-layer memristor crossbar array. This circuit primitive can execute multi-gates parallelly inside layer or the interlayer of 3D MCBA. This work provided a significant reference for the achievement of real processing in memory (PiM) in a high-density array.

Design of GaAs nanowires array based photovoltaic solar cells: Simulations of optical reflectance

We report the optical response of a periodic square array of GaAs nanowires embedded in epoxy as a candidate for photovoltaic solar cells. The simulated system is a multilayer array constituted by alternating layers of epoxy and an effective medium constituted by GaAs nanowires arrays embedded in epoxy. To discuss the optical response, we investigate the reflectance dependence on the number of bilayers considered in the array and the angle of incident light. The GaAs nanowire dielectric function is described in terms of Webb formalism to take into account the confinement energy of the excitons. The effective dielectric function of GaAs nanowires embedded in epoxy is evaluated within the Maxwell–Garnett theory. We evaluate the reflectance for s- and p-polarized light through the transfer matrix formalism for n bilayers. For both s- and p-polarization, we observe an oscillating behavior of the reflectance, similar to that reported in the literature. We have also obtained a feature peaked around 850 nm. While the oscillations can be ascribed to multiple interference from periodic bilayers, the peak at 850 nm can be understood in term of the gap energy in the nanowire dielectric function. Attending to the reflectance dependence on the light incidence angle, we have found that for s-polarized light, the reflectance is higher with increasing angles, in comparison to p-polarized light cases.

Morphogenesis of Iridescent Feathers in Anna's Hummingbird Calypte anna.

Color is a phenotypic trait of utmost importance, particularly in birds, which are known for their diverse color signals and color-producing mechanisms including pigment-based colors, light scattering from nanostructured feather tissues and combinations thereof. Bright iridescent plumage colors of hummingbirds are caused by light scattering by an organized array of flattened, pigment organelles, containing air-filled vesicles, called melanosomes. These hollow platelets are organized in multilayer arrays that contain numerous sharp air/melanin refractive index interfaces, producing brilliant iridescent colors. Despite their ecological significance and potential for inspiration of new optical materials, how platelets form and spatially arrange in nanostructures in growing feathers remains unknown. Here, we tested the hypothesis that melanosome formation and organization occurs mostly through passive self-assembly processes by assembling a developmental time series of growing hummingbird feathers using optical and electron microscopy. We show that hummingbird platelets contain air bubbles or vesicles upon their formation in pigment-producing cells, melanocytes. When melanosomes are transferred to neighboring keratinocytes (the cells shaping barbule structure) they drastically expand in size; and variation in this enlargement appears to be driven by physical constraints caused by the placement of the melanosomes within the barbule plate and their proximity to other melanosomes. As the barbule elongates and narrows, polymerizing feather corneous beta-protein orients melanosomes unilaterally, forcing them into a stacked configuration. These results reveal potentially novel forces driving the self-assembly of the nanostructures producing some of the brightest colors in nature.

Design and Calibration of a Hall Effect System for Measurement of Six-Degree-of-Freedom Motion within a Stacked Column.

This paper presents the design, development and evaluation of a unique non-contact instrumentation system that can accurately measure the interface displacement between two rigid components in six degrees of freedom. The system was developed to allow measurement of the relative displacements between interfaces within a stacked column of brick-like components, with an accuracy of 0.05 mm and 0.1 degrees. The columns comprised up to 14 components, with each component being a scale model of a graphite brick within an Advanced Gas-cooled Reactor core. A set of 585 of these columns makes up the Multi Layer Array, which was designed to investigate the response of the reactor core to seismic inputs, with excitation levels up to 1 g from 0 to 100 Hz. The nature of the application required a compact and robust design capable of accurately recording fully coupled motion in all six degrees of freedom during dynamic testing. The novel design implemented 12 Hall effect sensors with a calibration procedure based on system identification techniques. The measurement uncertainty was ±0.050 mm for displacement and ±0.052 degrees for rotation, and the system can tolerate loss of data from two sensors with the uncertainly increasing to only 0.061 mm in translation and 0.088 degrees in rotation. The system has been deployed in a research programme that has enabled EDF to present seismic safety cases to the Office for Nuclear Regulation, resulting in life extension approvals for several reactors. The measurement system developed could be readily applied to other situations where the imposed level of stress at the interface causes negligible material strain, and accurate non-contact six-degree-of-freedom interface measurement is required.

Bioprocess-Inspired Room-Temperature Synthesis of Enamel-like Fluorapatite/Polymer Nanocomposites Controlled by Magnesium Ions.

Tooth enamel is composed of arrayed fluorapatite (FAP) or hydroxyapatite nanorods modified with Mg-rich amorphous layers. Although it is known that Mg2+ plays an important role in the formation of enamel, there is limited research on the regulatory role of Mg2+ in the synthesis of enamel-like materials. Therefore, we focus on the regulatory behavior of Mg2+ in the fabrication of biomimetic mineralized enamel-like structural materials. In the present study, we adopt a bioprocess-inspired room-temperature mineralization technique to synthesize a multilayered array of enamel-like columnar FAP/polymer nanocomposites controlled by Mg2+ (FPN-M). The results reveal that the presence of Mg2+ induced the compaction of the array and the formation of a unique Mg-rich amorphous-reinforced architecture. Therefore, the FPN-M array exhibits excellent mechanical properties. The hardness (2.42 ± 0.01 GPa) and Young's modulus (81.5 ± 0.6 GPa) of the as-prepared FPN-M array are comparable to those of its biological counterparts; furthermore, the enamel-like FPN-M array is translucent. The hardness and Young's modulus of the synthetic array of FAP/polymer nanocomposites without Mg2+ control (FPN) are 0.51 ± 0.04 and 43.5 ± 1.6 GPa, respectively. The present study demonstrates a reliable bioprocess-inspired room-temperature fabrication technique for the development of advanced high-performance composite materials.

Broadband, ultrahigh efficiency fiber-to-chip coupling via multilayer nanophotonics.

We design, fabricate, and characterize a multilayer nanophotonic structure that couples light from standard optical fiber to an integrated photonics chip with unprecedented efficiency. The structure comprises a multilayer waveguide array tapering into a single waveguide supporting only fundamental TE- and TM-like modes. Measurements reveal a record-setting fiber-to-chip coupling efficiency of ${98.3}\% \;{\pm}\;{0.3}\%$ per facet at a 1575 nm wavelength that remains greater than ${92.8}\% \;{\pm}\;{0.4}\%$ across the 1550-1600 nm wavelength range. This approach is tailorable to any material platform, fiber type, or operating wavelength and represents a significant step forward for the accessibility of integrated photonics.

Zero-Inflated Poisson Distribution of Sedimented Cells in Multi-Layered Microwell Arrays

Open arrays of micro-scale wells (microwells; MW) are a popular platform for trapping biological cells, as they are gentler than other methods and their openness circumvents several problems associated with enclosed alternatives. This paper presents a dual-layered polymeric film featuring an imprinted MW array (MWA) and various complimentary shallower features that streamline both optical microscopy and alignment with an immunobiosensing (IBS) slide. The dual-layered MWA design presented in this paper represents a substantial improvement over our previous designs. The most substantial contribution of this paper lies with its statistical analysis of the trapped cell count datasets obtained from experiments using this refined MWA design. This analysis confirms experimentally that the distribution of cells into a MWA following sedimentation is indeed naturally Poisson distributed. Moreover, this analysis also shows that a zero-inflated Poisson (ZIP) distribution provides a superior fit, by incorporating an additional variable quantifying dataset sparsity. Furthermore, it is shown that maximum likelihood estimators (MLEs) for the parameters of these Poisson fits are superior to method of moments-based alternatives. This paper should prove useful for those seeking to develop a MWA with which to trap cells via sedimentation, and to mathematically describe this trapping process.

Multilayer regular hexagonal prism barium ferrite nanodot arrays on a substrate based on an AAO mask

Herein, the multilayer regular hexagonal barium ferrite nanodot arrays have been prepared by pulsed laser deposition through a porous anodic alumina template. The BaM nanodot arrays displayed a c-axis oriented crystal with a multilayer regular hexagonal structure, and the degree of orientation was improved by the post-annealing. Furthermore, the hysteresis loops showed the annealed nanodot arrays have a high squareness ratio of 0.65 along the easy magnetization direction. The first-order reversal curve diagram confirmed that the nanodots have a small interactive field between the particles. Consequently, this effective approach is potentially applied in self-biased microwave devices.

Tissue regulatory T cells: regulatory chameleons.

The FOXP3+CD4+ regulatory T (Treg) cells located in non-lymphoid tissues differ in phenotype and function from their lymphoid organ counterparts. Tissue Treg cells have distinct transcriptomes, T cell receptor repertoires and growth and survival factor dependencies that arm them to survive and operate in their home tissue. Their functions extend beyond immune surveillance to tissue homeostasis, including regulation of local and systemic metabolism, promotion of tissue repair and regeneration, and control of the proliferation, differentiation and fate of non-lymphoid cell progenitors. Treg cells in diverse tissues share a common FOXP3+CD4+ precursor located within lymphoid organs. This precursor undergoes definitive specialization once in the home tissue, following a multilayered array of common and tissue-distinct transcriptional programmes. Our deepening knowledge of tissue Treg cell biology will inform ongoing attempts to harness Treg cells for precision immunotherapeutics.