Periodic Multilayer Structure Research Articles

Infrared photoresponse of GeSiSn p–i–n photodiodes based on quantum dots, quantum wells, pseudomorphic and relaxed layers

Structural and photoelectric properties of p-i-n photodiodes based on GeSiSn/Si multiple quantum dots (QDs) both on Si and silicon-on-insulator substrates were investigated. Elastic strained state of grown films was demonstrated by x-ray diffractometry. Annealing of p-i-n structures before the mesa fabrication can improve the ideality factor of current-voltage characteristics. The lowest dark current density of p-i-n photodiodes based on QDs at the reverse bias of 1 V reaches the value of 0.8 mA cm-2. The cutoff wavelength shifts to the long-wavelength region with the Sn content increase. Maximum cutoff wavelength value is found to be 2.6μm. Moreover, multilayer periodic structures with GeSiSn/Ge quantum wells and GeSiSn relaxed layers on Ge substrates were obtained. Reciprocal space maps were used to study the strained state of GeSiSn layers. The optimal growth parameters were determined to obtain slightly relaxed GeSiSn layers. Designed p-i-n photodiodes based on these structures demonstrated the minimal dark current density of 0.7 mA cm-2and the cutoff wavelength of about 2μm.

Infrared photoresponse of GeSiSn p-i-n photodiodes based on quantum dots, quantum wells, pseudomorphic and relaxed layers.

Structural and photoelectric properties of p-i-n photodiodes based on GeSiSn/Si multiple quantum dots both on Si and silicon-on-insulator (SOI) substrates were investigated. Elastic strained state of grown films was demonstrated by x-ray diffractometry. Annealing of p-i-n structures before the mesa fabrication can improve the ideality factor of current-voltage characteristics. The lowest dark current density of p-i-n photodiodes based on quantum dots at the reverse bias of 1 V reaches the value of 0.8 mA/cm2. The cutoff wavelength shifts to the long-wavelength region with the Sn content increase. Maximum cutoff wavelength value is found to be 2.6 μm. Moreover, multilayer periodic structures with GeSiSn/Ge quantum wells and GeSiSn relaxed layers on Ge substrates were obtained. Reciprocal space maps were used to study the strained state of GeSiSn layers. The optimal growth parameters were determined to obtain slightly relaxed GeSiSn layers. Designed p-i-n photodiodes based on these structures demonstrated the minimal dark current density of 0.7 mA/cm2 and the cutoff wavelength of about 2μm.

A perfect ultra-wideband solar absorber with a multilayer stacked structure of Ti-SiO2-GaAs: structure and outstanding characteristics.

In this paper, we introduce an entirely new solar absorber design-a multi-layer periodic stacked structure. Through coupling effects, this design has perfect ultra-wideband absorption characteristics. The absorber structure is composed of four absorption units with varying cycle lengths, which are cyclically stacked on the surface of the refractory metal Cr. Each cycle encompasses three-layer nanosheets of Ti-SiO2-GaAs. We verify through finite difference time domain method (FDTD) simulations that the absorber achieves an absorption efficiency of 97.8% within the wavelength range of 280 nm to 3000 nm, with an average efficiency of 96.6% under the AM1.5 standard solar spectrum. The absorber can achieve such a remarkable absorption effect because of surface plasmon resonance (SPR) and Fabry-Pérot resonance effects. At 1500 K, this structure exhibits a thermal radiation efficiency of up to 97.83%. Furthermore, the design is not affected by polarization and it is less affected by the incident angle of the light source. These absorption spectra remain consistent regardless of whether it is in the TE or TM mode. Even when the angle of incidence is increased to 60 degrees, the absorption efficiency remains high. Its unique structure and excellent performance characteristics provide higher solar energy efficiency. These outstanding features enable solar absorbers to have broad application potential in improving solar energy efficiency.

Simultaneous Enhancement of Cooling Performance and Durability of the Polymer Radiative Cooler by a High UV-Reflective Polymer Multilayer Film.

The development of polymer radiative coolers with easy processing, low cost, and high inherent emissivity has significantly promoted the industrialization process of passive daytime radiative cooling. For excellent outdoor durability, however, the traditional strategy of using UV absorbers inevitably weakens the cooling performance of polymer-based coolers. The introduction of a high UV-reflective layer has been proven to be the most effective strategy to eliminate the negative effects of UV absorption and improve the durability of polymer coolers. Here, a polymer multilayer film (PMF) based on an optical interference mechanism is designed, which exhibits an average reflectance of up to 92.3% in the 300-400 nm UV wavebands. Using a TiO2-doped epoxy resin (TiO2-EP) cooler as an example, the solar reflectance of TiO2-EP increases by 5.43% after introducing PMF as a UV reflective layer. Outdoor tests without shading or convection coverage demonstrate that the average cooling temperature of TiO2-EP with PMF is further elevated by approximately 1.1 °C. Additionally, its aging rate decreases significantly, and the solar reflectance is 5.08% higher than that of TiO2-EP without PMF after 120 h of UV aging experiments. Furthermore, PMF obtains a periodic multilayer structure by multilayer coextrusion, which has the advantages of low cost and the ability to be prepared over a large area. PMF is suitable for any type of polymer cooler, providing an efficient method to further promote large-scale application of polymer coolers.

Framework of acoustic analysis and shape optimization for three-dimensional doubly periodic multilayered structures

In this research, a framework of acoustic analysis and shape optimization, based on isogeometric boundary element method (IGA-BEM), is proposed for three-dimensional doubly periodic multilayered structures. The study addresses a gap in the literature by focusing on the shape optimization of such structures, which has not been extensively explored previously. The interface between different acoustic media is an infinite doubly periodic surface, which can be constructed by an open non-uniform rational B-splines. A periodic IGA-BEM is developed for the sound field analysis of the doubly periodic multilayered structure, in which the Ewald method is used to accelerate the calculation of periodic Green function. Furthermore, the shape derivative of the doubly periodic multiple boundaries is derived by imposing boundary perturbation and using the adjoint variable method. The control points of the NURBS surfaces are defined as the shape design variables, and all shape sensitivities can be quickly calculated by discretizing the shape derivative formula. Finally, in according with shape sensitivities, the corresponding shape optimization problem is solved by the method of moving asymptotes, so that the optimized shape design can be obtained. A series of numerical examples validates the accuracy and applicability of the proposed approaches.

Quantization of topological edge mode in a one-dimensional photonic crystal heterostructure

The study of topological phases of matter has seen significant advancements in recent years, largely driven by the discovery and exploration of their distinctive topological edge states. Here, we delve into the edge properties of a one-dimensional periodic multilayer structure. The analysis reveals that this system exhibits characteristics akin to the Su–Schrieffer–Heeger model in optics. The theoretical analysis explores the impact of multiple interfaces on the emergence of a topological edge mode (TEM) within the structure. The proposed heterostructure functions as a general beam splitter. Moreover, when the interface is doubled, the heterostructure exhibits two TEM states, resulting from the quantization of an incoming beam into its two equally orthogonal constituents. As the number of interfaces increases, more quantized TEM states occur within the photonic bandgap. Also, it identifies that the quality factor of the original TEM mode at 382.08 THz frequency linearly increases with respect to the number of interfaces. The outcome suggests potential applications in photonic sensors, optoelectronics, and photonic devices, indicating the heterostructure’s pivotal role in advancing these fields.

Multiscale topology optimization of anisotropic multilayer periodic structures based on the isogeometric analysis method

Multiscale topology optimization of anisotropic multilayer periodic structures based on the isogeometric analysis method

One dimensional multilayer structure for kerosene adulteration detection in petrol and diesel

Abstract We aim to design a multilayer periodic structure to detect the kerosene adulteration in the petrol and diesel fuels on a single processing setup. We built the structure by arranging TiO2 and SiO2 layers periodically in alternate manner with empty space at the middle. The optical response of the designed structure is then theoretically studied using transfer matrix method. Empty space of the design is filled with different kerosene adulterated petrol and diesel samples for inspecting structure response to incident electromagnetic waves. Theoretical calculations affirm that the proposed structure is capable to detect the fuel adulteration efficiently. Critical performance parameters like sensitivity, quality factor, figure of merit and limit of detection are calculated to check the effectiveness of the sensor. We also optimized the sensitivity of sensors design through modifying the defect thickness as well as angle of incidence of electromagnetic waves, and provides poly fit formula. It is observed that the sensitivity of sensor to detect kerosene adulteration in fuels highly depends on defect thickness and light incidence angle. An efficient sensor possessing high quality factor and figure of merit is realized from the designed structure that is capable of detecting 10 − 5 RIU.

Effects of high-temperature annealing on vacancy complexes and luminescence properties in multilayer periodic structures with elastically strained GeSiSn layers

Effects of postgrowth high-temperature annealing on vacancy complexes and photoluminescence (PL) from GeSiSn/Si multiple quantum wells (MQWs) are studied. The series of PL peaks related to the vacancy-tin complexes was observed for as-grown samples including different structures, such as GeSiSn/Si MQWs, multilayer periodic structure with GeSiSn quantum dots (QDs), GeSn cross-structures upon GeSiSn/Si MQWs, and thick GeSiSn layers. The PL band intensity is significantly reduced after annealing at 700 °C corresponding to the reduction in vacancy density, as demonstrated by the positron annihilation spectroscopy (PAS) data. Such annealing also results in the appearance of the PL signal related to the interband optical transitions in GeSiSn/Si MQWs. However, the high temperature could negatively impact the sharpness of heterointerfaces due to Sn diffusion, thus limiting the PL efficiency. To improve the luminescence properties of GeSiSn/Si structures, we proposed a two-stage technique combining both the annealing and subsequent treatment of samples in a hydrogen plasma at 200 °C. The plasma treatment significantly reduces the PL band of vacancy-related defects, whereas annealing at a moderate temperature of ∼600 °C prevents the blurring of heterointerfaces. As a result, we demonstrate an increase in the relative efficiency of interband PL of type II GeSiSn/Si MQW structures emitting in the range of 1.5–2 μm.

X-Ray Calc 3: improved software for simulation and inverse problem solving for X-ray reflectivity.

This work introduces X-Ray Calc (XRC), an open-source software package designed to simulate X-ray reflectivity (XRR) and address the inverse problem of reconstructing film structures on the basis of measured XRR curves. XRC features a user-friendly graphical interface that facilitates interactive simulation and reconstruction. The software employs a recursive approach based on the Fresnel equations to calculate XRR and incorporates specialized tools for modeling periodic multilayer structures. This article presents the latest version of the X-Ray Calc software (XRC3), with notable improvements. These enhancements encompass an automatic fitting capability for XRR curves utilizing a modified flight particle swarm optimization algorithm. A novel cost function was also developed specifically for fitting XRR curves of periodic structures. Furthermore, the overall user experience has been enhanced by developing a new single-window interface.

Structure and mechanical properties of TiCN-ZrCN multilayer coatings

The present study is focused on the design, deposition and characterization of nanoscale multilayer TiCN/ZrCN coatings obtained by cathodic-arc PVD technique. The multilayer coatings with the bilayer period’s thickness of 12 nm, 20 nm and 32 nm were deposited on stainless steel and high-speed steel substrates at temperature of 320°C in a mixture of N2 and CH4 gases. Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy, was employed to investigate the top surface morphology, cross-sectional morphology, bilayer thickness and structure of the coatings. Mechanical properties were investigated via Calotester, Nanoindentation tester, Scratch tester and Tribometer. The SEM/EDS cross-sectional analysis revealed a columnar morphology and well expressed multi-layered periodic structure. All the multilayer samples demonstrated an increase in hardness and well fracture resistance ability in comparison to TiCN and ZrCN monolayer coatings. The highest nanohardness of 41GPa and better wear resistance for the coatings with bilayer period of 12 nm was determined. The results of the study show that a reduction in the thickness of the individual sub-layers has a significant impact on the mechanical properties of the coatings.

ЛЕОНІД МИКОЛАЙОВИЧ ЛИТВИНЕНКО — ВИДАТНИЙ ВЧЕНИЙ І ОРГАНІЗАТОР НАУКИ

This paper is an attempt of paying tribute to the memory of Leonid Mykolayovych Lytvynenko (LML), an outstanding Ukrainian scientist, Full Member of the National Academy of Sciences who worked most fruitfully in the fields of radio science and radio astronomy. Starting of 1985, Dr. Lytvynenko was, over a 30-plus years period, at the head of the Institute of Radio Astronomy, Acad. Sci. of the Ukrainian SSR (currently the National Academy of Sciences of Ukraine) that had been established owing to his vigorous and direct participation in the process. In 1996 LML promoted foundation of a new scientific journal, namely the "Radio Physics and Radio Astronomy", which he devotedly served for, in the Editor-in-Chief capacity, during the 25 years that followed. Dr. L. Lytvynenko was one of the brightest representatives of the school of theoretical radio physics that had developed within the O. Usikov Institute for Radio Physics and Electronics in Kharkiv and further flourished within the Institute of Radio Astronomy. He is known as the founder of a new branch of radio science, specifically theory of electromagnetic wave diffraction and propagation through composite and multilayered periodic structures.

Novel Miniaturized Self-Packaged Filters Based on Metasubstrate in SISL Platform

In this paper, a novel strategy is proposed to design miniaturized self-packaged filter based on the proposed metasubstrate in substrate integrated suspended line (SISL) platform. Multi-layer SISL and periodic metasubstrate structures contribute to the miniaturization and self-packaging of second-and fourth-order quarterwavelength hairpin filters, caused by the higher permittivity. The designed dumbbell-shaped metasubstrate shows a high relative permittivity of 15.4. The proposed FR4-based second/fourth-order filters with a reduced insertion loss of 1.13 dB/1.49 dB only show the miniaturized size of 0.26 λg ×0.19 λg and 0.27 λg ×0.32 λg, respectively. And the circuit areas of the above two designed filters with metasubstrate are reduced by 46% and 34%, compared with the cases without metasubstrate, successively.

Leveraging Symmetry in the Analysis of Mirror-Symmetric Multilayered Periodic Structures With Application to LP-to-CP Converter Design

This communication proves that the analysis of the scattering by a mirror-symmetric multilayered periodic structure can be replaced by the analysis of the scattering by two semi-structures with half the size in which the symmetry plane behaves either as a perfect magnetic conductor (PMC) or as a perfect electric conductor (PEC). The proof is based on the reflection properties of the electric and magnetic fields through PMCs and PECs, and it is valid for arbitrary oblique incidence. As an application of this concept, the spectral domain Method of Moments (SD-MoM) is reformulated to deal with MPSs limited by PMCs and PECs, and it is used in the design of a mirror-symmetric multilayered linear to circular polarization (LP-to-CP) converter. The results obtained with SD-MoM are validated by comparison with commercial software CST. Numerical simulations show that the CPU time required by both SD-MoM and CST in the analysis of half the LP-to-CP converter limited by PMC and PEC is between 30 and 42 per cent smaller than that required by the analysis of the complete LP-to-CP converter, which shows the numerical advantage gained in exploiting the symmetry when it is present.

Near Infrared -Visible Photonic Bandgap in One-Dimensional Periodic Photonic Crystal Structure Composed of Tio2/Te Layers

In this present paper, we consider some features of the states of one-dimensional photonic crystals. Form the numerical results performed by transfer matrix method in periodic multilayer structure made of titanium dioxide and tellurium material, it is found that the structure possesses a photonic band gap it was determined that the structure has a photonic band gap in the borderline visible and infrared spectral region. Our predictions were in good agreement with the photonic bandgap tuning. Our simple model can also predict and explain the effect of incidence angle and wavelength and number of layers on the photonic bandgap. We expect such structures to play an important role in micromechanical tunable optical sensors and filters.

Bandgaps of microwave photonic crystals: Study of quasi-periodic metamaterial multilayers

A lossy double-negative index and air are used to investigate one-dimensional periodic and quasi-periodic multilayered structure using the transfer-matrix method. The transmittance of the lossy double-negative index and air quasi-system has been shown using the Fibonacci, Thue–Morse, double-period, Octonacci and Dedocanacci quasi-sequence. For the periodic structure, which is used here as the refereed structure for the comparison, a bandgaps called zero-n¯ appears near the frequency at which the permittivity and permeability of double-negative material are negative. Apart from this, zero-ϵ and zero-μ bandgaps have been found except for normal incidence along with the Bragg bandgaps.

Near-field radiative heat transfer between multilayer structures composed of different hyperbolic materials

Near-field radiative heat transfer (NFRHT) has drawn significant interest in the recent years, including thermal management and energy harvesting. The NFRHT between single hyperbolic materials (HMs) has been thoroughly investigated. However, the research on the NFRHT between periodic multilayer structures composed of different HMs is rarely discussed. Moreover, the coupling effect of hyperbolic phonon polaritons (HPPs) supported by different HMs is still unclear. In this work, we investigated the NFRHT between multilayer structures composed of hexagonal boron nitride (hBN) and α-phase molybdenum trioxide (α-MoO3), separated by vacuum layers. The influence of the gap distance, the unit-cell number, the thickness of the HMs and thickness of the vacuum layer on the NFRHT are discussed. The numerical results show that the maximal total heat flux (THF) between six-cell multilayer structures is 19 times compared to the THF between hBN films at the gap distance of 50 nm and is 1.46 times compared to the THF between α-MoO3 films at the gap distance of 30 nm. Such enhancement can also be found at other similar gap distances. The vacuum layer promotes the coupling of HPPs supported by different HMs, which can be elucidated by the energy transmission coefficients. This work could benefit the application of near-field thermal radiative devices based on HMs.

Research on biomimetic design and impact characteristics of periodic multilayer helical structures.

Osteons are composed of concentric lamellar structure, the concentric lamellae are composed of periodic thin and thick sub-lamellae, and every 5 sub-lamellae is a cycle, the periodic helix angle of mineralized collagen fibers in two adjacent sub-lamellae is 30°. Four biomimetic models with different fiber helix angles were established and fabricated according to the micro-nano structure of osteon. The effects of the fiber periodic helical structure on impact characteristic and energy dissipation of multi-layer biomimetic composite were investigated. The calculation results indicated that the stress distribution, contact characteristics and fiber failur during impact, and energy dissipation of the composite are affected by the fiber helix angle. The stress concentration of composite materials under external impact can be effectively improved by adjusting the fiber helix angle when the material composition and material performance parameters are same. Compared with the sample30, the maximum stress of sample60 and sample90 increases by 38.1% and 69.8%, respectively. And the fiber failure analysis results shown that the model with a fiber helix angle of 30° has a better resist impact damage. The drop-weight test results shown that the impact damage area of the specimen with 30° helix angle is smallest among the four types of biomimetic specimens. The periodic helical structure of mineralized collagen fibers in osteon can effectively improve the impact resistance of cortical bone. The research results can provide useful guidance for the design and manufacture of high-performance, impact-resistant biomimetic composite materials.

Construction and performance analysis of a solar thermophotovoltaic system targeting on the efficient utilization of AM0 space solar radiation

Solar thermophotovoltaic (STPV) has great potential as efficient power supply source for spacecraft to meet the demand of spacecraft miniaturization. In this work, a novel space STPV system is proposed to achieve the efficient utilization of the AM0 space solar radiation. Metamaterial structures were designed and FDTD method is used to analyze their radiation regulation mechanism. A multi-layer cylindrical periodic structure is used as the absorber which realizes a total absorptance of 0.9283 to AM0 radiation. A cylindrical periodic structure is used as the emitter to reshape the broadband thermal radiation as narrowband to match with the Si/InGaAsSb tandem cell, which realizes a highest TPV efficiency of 51.36%. System performance analysis is conducted and the system presents a highest STPV efficiency of 40.86% and good adaptability under wide range of operating parameters, which reveals its great potential to realize the efficient utilization of AM0 solar radiation for space power supply.

Fast-printed laser-induced-graphene pattern enabling directional thermal manipulation

Thermal metamaterials have recently attracted extensive attention for capable of manipulating heat flux, which makes it a great application potential in the field of electronic devices. However, developing a thermal manipulation device with facilely fabrication remains challenging as according to the theory of transformation thermotics, it not only needs to judiciously design and precisely distribute multiple materials with distinct thermal conductivity (k), but also should strictly match the background material. Herein, a facile fast-printed UV laser process is proposed to fabricate high-resolution laser induced graphene (LIG) patterns with controllable thermal conductivity enabling directional thermal manipulation—two types of thermal meta-devices, thermal cloak and concentrator. Effective anisotropic thermal conductivities are achieved by alternately assembling multilayer LIG films with polyimide (PI) layers. To obtain the optimal design of the LIG based meta-devices, the effects of k of the LIG, width ratio r, the number of layers n, and the overall size on thermal manipulation are theoretically simulated. The film thickness and k of LIG under different laser parameters were explored, and it was found that the film with a suitable laser power and a smaller thickness expansion can achieve a higher k. Besides, the thermal profiles of LIG-based meta-devices are experimentally demonstrated with varying laser powers and scanning speeds. The experiment result shows that the LIG-based multilayer cloak and bilayer cloak exhibit temperature gradients as low as 0.18 and 0.169 K/mm at the center of cloaks, with k of 8.96 and 13.05 W m−1 K−1, respectively. Additionally, a method of sputtering a layer of Cu film on the surface of the LIG based thermal concentrator to improve its thermal conductivity has also been evaluated. More importantly, LIG films feature with a thermal conductivity tunable, high-resolution, cost-effective, rapidly and facilely fabrication method. The fast-printed LIG periodic multilayered structures construct a new thermal metamaterial that provides a viable approach to the thermal manipulation in electronic devices.