Periodic Multilayer Structure Research Articles

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

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

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.

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.

Achievement of low infrared emissivity photonic crystal design on [CdSe/SiO2]N periodic films

By revealing the transmission matrix of multi-layer thin films system, practical route is provided for preparing the photonic crystals in materials selection and structure optimization on the low infrared emissivity requirements of the specific bands. High infrared reflectivity states are derived based on the conventional materials of CdSe (high refractivity) and SiO2 (low refractivity) through constructing periodic multi-layer film structure [CdSe/SiO2]N. Various photonic crystals are designed via changing the central wavelength. The factors of incident angle, period, film thickness, and refractive index on the forbidden band of infrared are calculated to discover the complex influence of the refractive index for low infrared emissivity of the thin films under full operating conditions.

Interface heterogeneity of periodic multilayer mirrors investigated by X-ray fluorescence, scattering spectroscopy, and mathematical methods of statistics

Multilayer interference structures (X-ray mirrors) based on the alternating layers of Mo/Si and W/Si were investigated using laboratory X-ray micro-fluorescence analysis (micro-XFA) and statistical analysis. The physics of interaction processes of primary X-ray radiation scattered on the surface of multilayer periodic structures have been studied. Using the X-ray spectroscopy together with the mathematical methods of statistics made it possible to evaluate a degree of homogeneity and to compare the chemical compositions of different samples of the multilayer mirrors. A correlation between the statistical characteristics of bimodal frequency distribution and the reflectivity properties of X-ray mirrors for the scattered radiation has been revealed. The frequency distributions of mathematical statistics for experimentally collected intensities of the scattered Rh Kα radiation indicate the depth heterogeneity of the studied samples. Used in this work approach gives a new strategy for testing to improve of efficiency of X-ray mirrors based on the multilayer nanoscale structures.

Methods of Coupled Wave Thicknesses and Equivalent Substitutions for the Exact Analytical Solution of the Problems of Synthesis of Multilayer Periodic Structures with Specified Amplitude–Phase Characteristics ($$\pi$$-Structures)

Methods of Coupled Wave Thicknesses and Equivalent Substitutions for the Exact Analytical Solution of the Problems of Synthesis of Multilayer Periodic Structures with Specified Amplitude–Phase Characteristics ($$\pi$$-Structures)

Quantitative investigation on the crack evolution behavior for creep-fatigue test of CrMoV steel welded joint

The artificial interrupted creep-fatigue test was carried out to quantitatively investigate crack initiation and propagation rate of the CrMoV steel welded joint at 520 °C. The evolution of crack and the role of oxide could be clarified clearly by several stages. A crack of 1.6 μm length initiated on the oxide in the first 10 cycles. Then, crack propagated inside the oxide layer with a low rate, forming a periodic multilayer bamboo-like structure. Meanwhile, further oxidation resulted in deepening of oxide notches. Finally, cracks penetrated the oxide with a rate of 50 μm/cycle into the matrix resulting in the rupture.

Analysis of Floquet Waves in Periodic Multilayered Isotropic Media with the Method of Reverberation-Ray Matrix

The in-plane elastic waves in periodically multilayered isotropic structures, which are decoupled from the out-of-plane waves, are represented mainly by the frequency–wavenumber spectra and occasionally by the frequency–phase velocity spectra as well as being studied predominantly for periodic bi-layered media along and perpendicular to the thickness direction in the existing research. This paper investigates their comprehensive dispersion characteristics along arbitrary in-plane directions and in entire (low and high) frequency ranges, including the frequency–wavelength, wavenumber–phase velocity, wavelength–phase velocity spectra, the dispersion surfaces and the slowness curves with fixed frequencies, as well as the frequency–wavenumber and frequency–phase velocity spectra. Specially, the dispersion surfaces and the slowness curves completely reflect the propagation characteristics of in-plane waves along all directions. First, the method of reverberation-ray matrix (MRRM) combined with the Floquet theorem is extended to derive the dispersion equation of in-plane elastic waves in general periodic multilayered isotropic structures by means of the elastodynamic theory of isotropic materials and the state space formalism of layers. The correctness of the derivation and the numerical stability of the method in both low and high frequency ranges, particularly its superiority over the method of the transfer matrix (MTM) within the ranges near the cutoff frequencies, are verified by several numerical examples. From these demonstrations for periodic octal- and bi-layered media, the comprehensive dispersion curves are provided and their general characteristics are summarized. It is found that although the frequencies associated with the dimensionless wavenumber along thickness ql=nπ (n is an integer) are always the demarcation between pass and stop bands in the case of perpendicular incident wave, but this is not always exist in the case of the oblique incident wave due to the coupling between the two modes of in-plane elastic waves. The slowness curves with fixed frequencies of Floquet waves in periodically multilayered isotropic structures, as compared to their counterpart of body waves in infinite isotropic media obtained from the Christoffel equation now have periodicity along the thickness direction, which is consistent to the configuration of the structures. The slowness curves associated with higher frequencies have a smaller minimum positive period and have more propagation modes due to the cutoff properties of these additional modes.

Bio-Alcohol Sensor Based on One-Dimensional Photonic Crystals for Detection of Organic Materials in Wastewater

In this work, we have explored a novel application of one–dimensional (1D) photonic crystals (PCs) as a biomarker for the detection of organic materials in wastewater. The high concentration of organic materials may lead to adverse impact on human life. In order to save human life from these adverse effects, we have investigated the bio-alcohol sensing properties of a 1D multilayer periodic structure (AB)N/C/(AB)N capable of detecting organic materials in wastewater. The proposed structure works on the principle to detect a very small change in the refractive index of the wastewater sample under investigation by means of producing a shift in the position of the defect mode inside the photonic band gap (PBG) of the proposed structure. The transfer matrix method (TMM) has been used to investigate the transmission properties of the proposed design with the help of MATLAB software. We have also studied the effect of changes in the defect layer’s thickness, the volume fraction of the nanocomposite material and the incident angle on the sensitivity of our proposed bio-alcohol sensing design. Our bio-alcohol sensor shows a high sensitivity value of 500 nm/RIU and a low detection limit value of 1 × 10−5 RIU. The figure of merit and quality factor values of our bio-alcohol sensor are 5 × 103 and 5.236 × 103, respectively. The damping rate of the design is .

2D rigorous coupled wave analysis with adaptive spatial resolution for a multilayer periodic structure.

We utilize the 2D modal solution of rigorous coupled wave analysis with adaptive spatial resolution to enhance the reliability of standard RCWA for multilayer gratings with metal-dielectric structures. The conversion relation in modal solutions between the Cartesian system and the transformed system is for the first time established. Based on the proposed conversion relation, the modal solution of the metal-dielectric structure obtained in the transformed system can match the boundary conditions with modal solutions of other different grating layers in the Cartesian system. Numerical results show that even for metal patches in microwave band, the above method can still achieve good convergence and is perfectly suitable for multi-layer structure calculation.

Tuning the structural and optical properties of GeSiSn/Si multiple quantum wells and GeSn nanostructures using annealing and a faceted surface as a substrate

The optical properties of GeSiSn/Si multiple quantum wells (MQWs) and GeSn nanostructures are studied in the range of 1.3–4 µm. An annealing at the temperature of 650 °C leads to the concentration decrease of vacancy complexes and the intensity increase of the radiative recombination proceeding through the interband luminescence. The energy diagram calculation showed that the transitions occur between the heavy hole subband of the GeSiSn solid solution and the silicon X-valley. A several-fold increase in the photoluminescence was observed in structures containing a nanostructured faceted surface with a (113) facet in the lower part of the MQW structure. The analysis of the reciprocal space map of such structures indicates the bending of the (001) flat growth front during the layer deposition at the faceted pit edges within the (113) facet. The GeSn cross-structure and nanoisland array were first obtained using the nanostructured faceted surface on top of the MQW structure. The regularities of the GeSn nanostructure formation on the deposition rate, the layer thickness, as well as the growth temperature, were investigated. The cross-structures on top of the GeSiSn/Si MQW structure are considered promising as plasmonic nanoantennas amplifying the signal from the multilayer periodic structures.

Comparative study of Faraday rotation spectra of periodic and Fibonacci multilayer structures containing graphene sheets

In this paper, the transmission, Faraday rotation, and ellipticity spectra of the multilayered structures with the arrangement of the periodic and fifth-order Fibonacci sequence have been numerically studied in the THz frequency region. The building blocks of the structures are a graphene sheet on the SiC layer (G-SiC), and a SiO2 layer. An external magnetic field is perpendicularly applied to the structures to induce the gyrotropic characteristics of the graphene sheets. The graphene sheets are considered as the thickness-less surfaces, and the 4 by 4 transfer matrix method has been utilized to study the mentioned spectra for TM and TE polarizations. The effects of incident angles have been investigated on the responses of the structures. The results revealed that the Fibonacci structure indicates a high Faraday rotation angle at around 11 THz. This property originates from the particular arrangement of the constituting layers of the Fibonacci structure.