Wide Band Research Articles

Cage-Based 3D Tetrahexagonal Boron Nitride Crystal with Excellent Terahertz Light Absorption.

In recent findings, a new classification of 1D and 2D tetrahexagonal boron nitrides (th-BN) consisting of square and hexagonal rings has been documented. These materials exhibit impressive properties such as the tunable band gap, strong optical absorption, suitable sign-tunable Poisson's ratio, and high ideal strength, making them promising for applications in nano- and opto-electronic industries. Stimulated by these studies, we have designed a cage-based three-dimensional tetrahexagonal boron nitride (3D th-B6N6) structure, which demonstrates excellent thermal, dynamic, and mechanical stability, including exceptional cohesive and formation energies of 6.66 and -0.93 eV per atom. Unlike direct band gap 1D and 2D tetrahexagonal boron nitride semiconductors, the proposed 3D tetrahexagonal boron nitride exhibits an insulating nature, with a wide indirect band gap of 6.175 eV at the HSE06 level. Moreover, in contrast to the unequal chemical bonding and ultraviolet optical absorption observed in the 2D th-BN sheet, all B and N atoms form a fully sp3-hybridized bonded 3D th-B6N6 structure, with excellent terahertz light absorption in the range of 0.3-10 THz. Notably, it also exhibits a Debye temperature of 1304.55 K and substantial phonon inelastic scattering. Our study introduces the BN family with novel properties and potential applications.

Adsorption and evolution of N2 molecules over ZnO monolayer: a combined DFT and kinetic Monte-Carlo insight

A large surface area, wide band gap, and unique bonding property between Zn and O atoms make the hexagonal ZnO monolayer attractive as a gas sensor. In the present work, the adsorption and evolution of nitrogen (N2) molecules over a ZnO monolayer have been studied using two different theoretical methods: van der Waals density functional theory (vdW-DFT) and kinetic Monte-Carlo (kMC) simulation. The adsorption and diffusion (hopping over the surface) energy of a N2 gas molecule has been calculated considering the different sites over the ZnO substrate using the revPBE-vdW functional. Bader charge, electron localization function analysis, density of states and band structure plotting have been used to understand the adsorption mechanism. Lateral repulsive interaction between two N2 molecules limits the maximum packing number of gas molecules within one hexagonal ring. The output of the vdW-DFT calculation has been fed to the kMC code to predict the rate of adsorption, desorption, and diffusion, along with the overall surface coverage at different temperatures and pressures. Finally, the change in the N2 adsorption energy has been predicted with the increase of the ZnO layer number.

Resource learning aware algorithm for route prediction and resources allocation in elastic optical networks with network analytics

We have proposed two algorithms in this paper for dynamic traffic in elastic optical networks (EON). Algorithm1 considers the spatial access blocking probability metric (SABPM) during dynamic operation and route traffic to a path with lower SABPM. Therefore, it considers a path with more contiguous blocks to support heterogeneous bandwidths (BW) and modulation schemes. Algorithm1 keeps a balance of fragmentation on available routes. Algorithm2 makes routing decision for dynamic traffic based on the maximum idle slots as well as minimum SABPM. Therefore, it selects a less fragmented path with more number of available contiguous blocks to support heterogeneous BW. Algorithm2 balances the path utilization and avoids over utilization of congested route. We have evaluated the performance of both algorithms in terms of spatial external fragmentation, contiguity ratio, contiguous aligned spectrum ratio, SABPM, and BW blocking probability (BwBP). Python with seaborn, pandas, and other libraries are used for network analytics. Results show that resource utilization improves with the proposed algorithms. It has been shown that algorithm2 and algorithm1 achieve 27% and 18% traffic gains respectively over the alternate routing.

Application of OVT Domain Processing Technology in 3D Seismic Exploration of Coalbed Methane in Heshun Hengling Block

This study introduces the OVT (Offset Vector Tile) domain processing technology to improve the accuracy of small structure detection in 3D seismic exploration of coalbed methane in the Heshun-Hengling block in China. The OVT technology optimizes wide azimuth seismic data processing through steps such as facet division, five-dimensional regularization, pre-stack time migration, and azimuthal anisotropy correction. The results show that OVT processing retains azimuth information, enhancing the ability to reflect stratum changes with azimuth; azimuthal anisotropy correction improves the resolution of the profile. The profile after OVT processing has a natural waveform, good continuity of the phase axis, and a wide frequency band, meeting the requirements of the “Coalbed Methane Seismic Exploration Specification”. It demonstrates the advantages of OVT technology in imaging complex geological structures, providing a new perspective for seismic exploration.

Small size dual-band coupled-line coupler for WiMAX applications

Abstract In this paper, a symmetric compact dual-band coupled-line coupler is proposed using microstrip transmission lines, circular resonators, and spiral lines for WiMAX applications. The proposed coupler provides two narrow operating bands, high coupling and isolation, and suitable return loss. The primary design consists of two parallel-coupled lines with a flat coupling over a wide frequency band. Then, the bandwidth, return loss, and isolation are optimized by adding circular resonators and spiral lines to achieve a compact size. In this design, the return loss is better than 30–35 dB in the bandwidth 3.4–5.79 GHz. Finally, this structure is fabricated using a Rogers-RT Duroid 5,880 substrate with a thickness of 20 mil, a loss tangent of 0.0009, a dielectric constant of 2.2, and an area of 18.8 × 14 mm2. The results of the measurements are in good agreement with those of the simulation.

Influence of Zinc Ion Concentration on the Structural, Surface Morphology and Optical Properties of Zinc Selenide Thin Films

ZnSe thin films were deposited on nonconducting glass substrates using different Zn[Formula: see text] ion concentrations. The films were deposited at 80[Formula: see text]C for 2.0[Formula: see text]h via photo-assisted chemical bath technique and annealed for 2.0[Formula: see text]h at 250[Formula: see text]C. X-ray diffraction revealed a hexagonal structure with preferred orientation along the (002) plane and the average crystallite size decreased from 10.5[Formula: see text]nm to 6.8[Formula: see text]nm with increased Zn[Formula: see text] ions. Raman spectra were used to confirm ZnSe phonon modes whose intensity increased with Zn[Formula: see text] ion concentrations although with fluctuation. Optical analysis showed higher absorbance and low transmittance in the visible region than near infrared making the thin films good materials for selective absorber surfaces. The band gap increased from 2.52[Formula: see text]eV to 2.78[Formula: see text]eV as the Zn[Formula: see text] ion concentration varied from 0.05% to 0.25%. The presence of the desired elements was confirmed by the EDS. Photoluminescence studies revealed three emission peaks which were all ascribed to defect state levels in ZnSe and all the samples emitted in reddish color according to CIE color chromaticity analysis. The selective absorption, wide band gap and broad emission properties suggest that the material is promising for optoelectronic applications.

Thermal Conversion of Ultrathin Nickel Hydroxide for Wide Band Gap 2D Nickel Oxides.

Wide band gap (WBG) semiconductors (E g > 2.0 eV) are integral to the advancement of next-generation electronics, optoelectronics, and power industries owing to their capability for high-temperature operation, high breakdown voltage, and efficient light emission. Enhanced power efficiency and functional performance can be attained through miniaturization, specifically via the integration of device fabrication into a two-dimensional (2D) structure enabled by WBG 2D semiconductors. However, as an essential subgroup of WBG semiconductors, 2D transition metal oxides (TMOs) remain largely underexplored in terms of physical properties and applications in 2D optoelectronic devices, primarily due to the scarcity of sufficiently large 2D crystals. Thus, our goal is to develop synthesis pathways for 2D TMOs possessing large crystal domains (e.g., >10 μm), expanding the 2D TMO family and providing insights for future engineering of 2D TMOs. Here, we demonstrate the synthesis of WBG 2D nickel oxide (NiO) (E g > 2.7 eV) thermally converted from 2D nickel hydroxide (Ni(OH)2) with a lateral domain size larger than 10 μm. Moreover, the conversion process is investigated using various microscopic techniques, such as atomic force microscopy, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy, providing significant insights into morphology and structural variations under different oxidative conditions. The electronic structure of the converted Ni x O y is further investigated using multiple soft X-ray spectroscopies, such as X-ray absorption and emission spectroscopies.

Design and Analysis of Sierpinski Fractal Antennas for Millimeter‐Wave 5G and Ground‐Based Radio Navigation Applications

ABSTRACTThe paper describes compact fractal antennae combined with ground defected structures (DGS) and substrate integrated waveguide (SIW) techniques for enhancing resonate and multiband behavior concerning bandwidth, gain, and radiation in the desired mm‐wave region. Based on the proposed antennae, multiple good notches over wide bands depict a good radiation pattern. The antennae's ultra wide bandwidths (UWB) are 16, 16, and 11.4 GHz concerning resonant frequencies 26.34, 30.35, 34.5, 36.65 GHz; 25.8, 32.2, 35.3 GHz; 30.22, 37.68 GHz, of concerning antennae ant 1 (FA1), 4 (FA2), and 6 (FA3), respectively. The proposed antenna (FA3) with the SIW technique has a peak gain of 5.9 dBi and a peak front‐to‐back ratio of 20 dB, respectively. The proposed antennas are targeted to cover the practical contribution aspect, including advanced 5G bands support (24–40 GHz), broadband spectrum, frequency agility, low 3 dB beamwidth, interference reduction, and medical application suitability, respectively. The proposed antennae also cover the desired mm wave 5G region with different resonating notches over ultra‐wide bandwidth, such as n257, n258, n259, n260, and n261, and ground‐based radio navigation applications. Results are validated with vector network analyzer, spectrum analyzer, and power sensor in the presence of absorber, respectively.

Hydrothermal Growth Zinc Oxide Nanorods for pH Sensor Application

The aim of this work is to apply synthesized zinc oxide (ZnO) Nanorods using hydrothermal (HTL) growth technique for pH sensor application. The highly crystallite of ZnO Nanorods was obtained by anneal the growth ZnO Nanorods in furnace at 200 °C for 2 hours. Besides that, XRD analysis shows the produced ZnO Nanorods belonged to the (002) plane. Furthermore, Scanning Electron Microscope (SEM) images confirm that the ZnO Nanorods with hexagonal-faceted structural were successfully produced by HTL growth technique. In addition, Ultraviolet–visible (UV-Vis) spectrophotometer analysis shows that the synthesized ZnO belongs to the wide band gap semiconductor material. The growing ZnO Nanorods were then subjected to electrical measurement with various pH levels. The outcome demonstrates that the current rises as the solution changes from acidic to alkaline. Overall, our study shows a relationship between the electrical as well as the structural characteristics of ZnO Nanorods at various pH levels.

An Inductor‐Less Zero‐IF Down‐Conversion Mixer With Low Flicker Noise and High Conversion Gain

ABSTRACTThis paper presents a novel active inductor (AI) to improve the performance of a down‐conversion active mixer in terms of conversion gain (CG) and flicker noise. The proposed AI exhibits negative resistance and partially flat inductance over a wide frequency band of 0.5–4.5 GHz. The effect of inserting the AI between the source of the switching quad of a Gilbert cell mixer is theoretically analyzed. The proposed inductor‐less mixer, designed to operate at a 2.4‐GHz RF input frequency and a 10‐MHz IF output frequency, employs current reuse and self‐forward body bias (SFBB) techniques. The proposed circuit is simulated in Cadence Spectre‐RF using RF‐TSMC 0.18‐μm CMOS technology. Post‐layout simulations demonstrate that the proposed AI significantly reduces flicker noise by over 23 dB at an IF output frequency of 1 kHz and improves the CG by over 16 dB at an RF frequency of 2.4 GHz. The proposed mixer achieves a CG of 37.6 dB and a flicker noise corner frequency of 6 kHz. Additionally, it exhibits a third‐order intermodulation intercept point (IIP3) of −5.2 dBm and a double‐sideband noise figure (DSB‐NF) of 6.1 dB at the IF output frequency of 10 MHz. Operating with a 1.5‐V supply, the proposed mixer consumes 10.6 mW of power.

High-performance cobalt-embedded SiC nanofiber fabric for microwave dissipation

The incorporation of magnetic ingredients is critical for ceramic-based microwave absorbers with high efficiency. However, this task is becoming challenging due to the dispersion and oxidation issues. In this study, metal-organic framework (MOF) ZIF-67 was employed as the precursor of magnetic compounds and combined with a polymer solution to fabricate SiC textiles using the electrospinning technique. The microstructure analysis confirmed the successful introduction of MOF particles within the SiC nanofibers. Further examination of chemical compositions and magnetic properties revealed the encapsulation of magnetic compounds in hybrid SiC textiles. Since the applied fabrication approach ensures a superior dispersion and protection of metal compounds in a ceramic matrix, the microwave absorption of SiC fabric with both dielectric loss and magnetic loss exhibits a high reflection loss of −59.4 dB and a wide effective absorption band of 5.70 GHz. The current fabrication strategy for fabricating microwave absorbers with dual loss mechanisms advances the development of ceramic-based microwave absorption materials.

Vertically oriented low-dimensional perovskites for high-efficiency wide band gap perovskite solar cells

Controlling crystal growth alignment in low-dimensional perovskites (LDPs) for solar cells has been a persistent challenge, especially for low-n LDPs (n < 3, n is the number of octahedral sheets) with wide band gaps (>1.7 eV) impeding charge flow. Here we overcome such transport limits by inducing vertical crystal growth through the addition of chlorine to the precursor solution. In contrast to 3D halide perovskites (APbX3), we find that Cl substitutes I in the equatorial position of the unit cell, inducing a vertical strain in the perovskite octahedra, and is critical for initiating vertical growth. Atomistic modelling demonstrates the thermodynamic stability and miscibility of Cl/I structures indicating the preferential arrangement for Cl-incorporation at I-sites. Vertical alignment persists at the solar cell level, giving rise to a record 9.4% power conversion efficiency with a 1.4 V open circuit voltage, the highest reported for a 2 eV wide band gap device. This study demonstrates an atomic-level understanding of crystal tunability in low-n LDPs and unlocks new device possibilities for smart solar facades and indoor energy generation.

Synthesis, Optical, Electrical, Fluorescence, Dielectric, Thermal, and Mechanical Characterization of 3-Aminopyridine (Scaffold in Drugs) Single Crystal

Objectives: To screen the optical, electrical, fluorescence, dielectric, thermal, and mechanical behavior of the 3-aminopyridine single crystal for its suitability in optoelectronic applications. Methods: A good single crystal of 3-aminopyridine (3-AP) was grown by the slow evaporation method. Findings: The lattice parameters of the grown crystal were determined using a single crystal X-ray diffractometer as, a = 6.184 (4) Å, b = 15.350 (6) Å, c = 5.361 (7) Å and the required functional groups C-N, NH2 bonds of 3-AP were recognized by the FTIR studies. The grown crystal was screened using the UV-Vis-NIR spectrum to understand the transmission and absorption character of the crystal. The various optical constants such as absorption coefficient, optical conductivity, and electrical conductivity of the crystal have been determined from the UV-Vis transmission plot. The lower cut-off wavelength of the 3-AP crystal was observed at 250 nm. The band gap of the grown crystal is found to be 4.5 eV. The emission property of the crystal was studied using fluorescence spectra. Violet, blue, and red emissions are observed from the fluorescence spectra. Thermal screening of the 3-AP crystal was performed using TGA and DTA. The 3-AP crystal remains stable up to 220 ºC and then the crystal begins to decompose up to 260 ºC due to the loss of the -NH2 group of the 3-aminopyridine. The Vickers hardness test revealed the nature of the material as soft type with Meyer’s index (n) of 2. The electronic polarization behavior of the crystal was examined using the dielectric study. Novelty: The lower cut-off wavelength of 250 nm, wide band gap of 4.5 eV, excellent transparency in the entire visible and near-infrared region, violet, blue, and red emission by the material are the distinguishing and mandatory features for optoelectronic applications. These features are good as compared to the 3-AP derivatives reported earlier. Keywords: Unit cell, Absorption, Emission, Conductivity, Strength, Loss

Broadband and parallel multiple-order optical spatial differentiation enabled by Bessel vortex modulated metalens

Optical analog image processing technology is expected to provide an effective solution for high-throughput and real-time data processing with low power consumption. In various operations, optical spatial differential operations are essential in edge extraction, data compression, and feature classification. Unfortunately, existing methods can only perform low-order or selectively perform a particular high-order differential operation. Here, we propose and experimentally demonstrate a Bessel vortex modulated metalens composed of a single complex amplitude metasurface, which can perform multiple-order radial differential operations over a wide band by presetting the order of the corresponding Bessel vortex. This architecture further enables angle multiplexing to create multiple information channels that synchronously perform multi-order spatial differential operations, indicating the superiority of the proposed devices in parallel processing. Our approach may find various applications in artificial intelligence, machine vision, autonomous driving, and advanced biomedical imaging.

Ultraviolet optical properties of CaSrF2 crystal grown by the cone die Czochralski method

Fluoride crystals with extremely wide band gaps are ideal optical materials in the UV wavelength range. Large 4-inch diameter calcium strontium fluoride (Ca0.582Sr0.418F2) single crystal was grown using the Czochralski method with a Cone-shape Die (CD-CZ). The refractive index and relative transmittance of the crystal was evaluated by cutting it into a triangular prism and polished. The direct measurement of the refractive index and relative transmittance was done by using a spectrograph to image the refraction of light as it passes through a dual prism set-up consisting of a SQ prism as reference and either CaF2 or Ca0.582Sr0.418F2 as the material under evaluation. Characterization results showed that Ca0.582Sr0.418F2 has excellent refractive index dispersion and transmittance in the UV region, confirming the applicability of the dual prism with spectrograph setup to measurements of the refractive index and relative transmittance in the UV region.

Growth of YAG:Nd laser crystals by Horizontal Directional Crystallization in Protective Carbon‐Containing Atmosphere

AbstractLaser‐quality yttrium‐aluminum garnet single crystals doped with neodymium (YAG:Nd) of a concentration up to 1 at. % is grown by the method of horizontal directional crystallization from a molybdenum crucible in the protective reducing atmosphere based on argon, СО, and hydrogen. It is found that the content of carbon impurity in the grown crystals does not exceed 5·10−3 wt %, the content of molybdenum being on the level of 1.5·10−3 wt %. The optical quality of the crystals depends on the composition of the growth atmosphere and annealing. It is shown that, besides the bands of neodymium ion absorption, the crystals are characterized by the intense absorption in the UV edge of the spectrum at 370 nm wavelength, and by the wide absorption band with a maximum at 580 nm caused by formation of F and F+‐centers. The absorption at 370 and 580 nm can be eliminated by annealing. The structure perfection of the crystals is characterized by the rocking curve half‐width (β) which value varies within the limits of 10–14 arc. sec for (001) plane. Laser testing demonstrates the parameters comparable with those of YAG:Nd crystals grown by the Czochralski method from iridium crucible.

Vegetation monitoring in mining area using canopy reflectance and landsat8 oli image

The aim of this study is to find out the vegetation monitoring in mining areas which is of great significance in grasping the ecological environment status of mining areas. As the first target of spectral reflection, the vegetation canopy directly affects the results of spectral reception. Leaf Angle Distribution (LAD) is a key canopy structural parameter, which directly determines the amount of solar radiation intercepted by the canopy. Taking the relationship between the effect of leaf inclination angle on vegetation canopy reflectance and NDVI as an entry point, the study monitored and analyzed the vegetation in Dexing mining area, China, from 2013 to 2018 by NDVI, based on which the Copper Stress Vegetation Index (CSVI), which is applicable to the narrow wavelength band of remote sensing imagery, was evaluated whether it could be applied to the wide wavelength band. The results show that the NDVI value of the horizontal distribution is significantly higher than that of other leaf inclination distributions, and the NDVI in the direction of the horizontal distribution is 0.82, while the NDVI in the direction of the hi-straight distribution is 0.75; the NDVI of the mining area decreases gradually with the increase of the area of the mining area, and the correlation coefficients of the two groups of CSVI based on the wide and narrow bands are not large, which is not suitable for the vegetation monitoring by using the Landsat8 OLI imagery. Wide band is less applicable for vegetation monitoring. Bangladesh J. Bot. 53(3): 835-847, 2024 (September) Special

Generating Immunological Memory Against Cancer by Camouflaging Gold-Based Photothermal Nanoparticles in NIR-II Biowindow for Mimicking T-Cells.

Photothermal therapy (PTT) against cancer not only directly ablates tumors but also induces tumor immunogenic cell death (ICD). However, the antitumor immune response elicited by ICD is insufficient to prevent relapse and metastasis because of the immunosuppressive tumor microenvironment (TME). A biomimetic nanoplatform (bmNP) mimicking cytotoxic lymphocytes (CTLs) for combinational photothermal-immunotherapy to effectively regulate the immunosuppressive TME is reported here. The bmNP is constructed by wrapping the T-cell membrane onto a new type of photothermal agents, spherical Au-based PNCs (sAuPNCs). Similar to T-cells, the bmNP enhanced accumulation at the tumor site by targeting the tumor via adhesion proteins on T-cell membrane. The obtained sAuPNCs have a wide absorption band in the second near-infrared (NIR-II) region with a high photothermal conversion efficiency (PCE) up to about 75% and excellent photostability. The bmNP with a smaller size is more superior compete with T-cells to bond with tumor cells via PD-1/PD-L1 interaction to effectively block the PD-1 checkpoint of T-cells for preventing T-cell exhaustion. Furthermore, in vivo studies reveal the immunological memory effect is significantly elicited in mice received bmNPs therapy. Collectively, bmNPs show great potential in photothermal-enhanced immunotherapy.

Comparison of mathematical and experimental studies of the radio technical characteristics of an acousto-optoelectronic spectrum analyzer for RF monitoring devices

Formulation of the problem. To analyze radio frequency monitoring systems and complexes that can operate in a wide frequency band with high performance parameters, devices such as acousto-optical spectrum analyzers (AOS) are used. This class of devices has several types of implementation. The objective of this article is to increase efficiency in the development of acousto-optoelectronic devices in radio frequency monitoring systems. Target. Based on theoretical and experimental studies, it is necessary to determine which version of the acousto-optical spectrum analyzer will ensure the operation of radio frequency monitoring tools with the best values of radio frequency characteristics, such as dynamic range and signal-to-noise ratio. Results. A calculation of the dynamic range of an acousto-optical spectrum analyzer is presented, as well as a comparative analysis of several acousto-optical spectrum analyzers (an acousto-optic spectrum analyzer with time integration and an acousto-optic spectrum analyzer with spatio-temporal integration) to determine the most effective type of device for radio frequency monitoring systems. Practical significance. The use of the selected design of an acousto-optical spectrum analyzer will make it possible to replace other devices and replace less efficient analogues of the device, which will improve the operation of radio frequency monitoring systems and complexes.

Zinc telluride material properties for solar cell application: Absorber layer

Over recent years, Zinc Telluride (ZnTe) has garnered significant interest from researches. This p-type semiconductors boasts a broad band gap, rendering it valuable in various optoelectronic uses like solar cells, LEDs, and laser displays. Given the growing interest in environmentally friendly energy alternatives, exploring the potential of nano-scale semiconducting materials for solar cells is particularly intriguing. ZnTe stands out due to its direct, wide, and adjustable optical band gap, along with its simple doping process, positioning it as a promising candidate for applications in photochemistry. This study aims to consolidate the research conducted by multiple investigators concerning the optical characteristics and electrical attributes of ZnTe thin films. The primary focus is on understanding how deposition methods and doping impacts these properties. The investigation reveals that the diverse doping techniques employed by different researchers have been extensively examined, demonstrating a positive influence of doping on these properties as well. Following the creation of solar cells based on ZnTe, they have emerged as viable and competitive substitutes for silicon solar cells, thanks to their economical nature and stable performance. As a result, there has been notable focus on advancing ZnTe thin film solar cell technology due to their promising capacity to serve as sustainable energy generators.