Showing papers in "AIP Advances in 2021"

Some optical soliton solutions to the perturbed nonlinear Schrödinger equation by modified Khater method

Abstract: This paper investigates the analytical solutions of the perturbed nonlinear Schrodinger equation through the modified Khater method. This method is considered one of the most recent accurate analytical schemes in nonlinear evolution equations where it obtained many distinct forms of solutions of the considered model. The investigated model in this paper is an icon in quantum fields where it describes the wave function or state function of a quantum-mechanical system. The physical characterization of some obtained solutions in our study is explained through sketching them in two- and three-dimensional contour plots. The novelty of our study is clear by showing the matching between our solutions and those that have been constructed in previously published papers.

Diverse novel analytical and semi-analytical wave solutions of the generalized (2+1)-dimensional shallow water waves model

Abstract: This article studies the generalized (2 + 1)-dimensional shallow water equation by applying two recent analytical schemes (the extended simplest equation method and the modified Kudryashov method) for constructing abundant novel solitary wave solutions. These solutions describe the bidirectional propagating water wave surface. Some obtained solutions are sketched in two- and three-dimensional and contour plots for demonstrating the dynamical behavior of these waves along shallow water. The accuracy of the obtained solutions and employed analytical schemes is investigated using the evaluated solutions to calculate the initial condition, and then the well-known variational iterational (VI) method is applied. The VI method is one of the most accurate semi-analytical solutions, and it can be applied for high derivative order. The used schemes’ performance shows their effectiveness and power and their ability to handle many nonlinear evolution equations.

Numerical study of high performance HTL-free CH3NH3SnI3-based perovskite solar cell by SCAPS-1D

Abstract: In this study, a hole transport layer (HTL)-free perovskite solar cell (PSC) structure with CH3NH3SnI3 as an active layer and TiO2 as an electron transport layer (ETL) has been proposed for the first time. The solar cell capacitance simulator in one dimension program has been carried out to design the proposed HTL-free CH3NH3SnI3-based PSC and simulate its performance. The output parameters of the proposed PSC, such as open circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), power conversion efficiency, and quantum efficiency, are evaluated by varying the physical parameters of various layers. The thermal stability of the proposed cell has also been analyzed. The thicknesses of the ETL and the absorber are optimized to be 0.05 and 1.0 µm, respectively. A conversion efficiency of 26.33% along with Voc of 0.98 V, Jsc of 31.93 mA/cm2, and an FF of 84.34% is obtained for the proposed HTL-free CH3NH3SnI3-based PSC. These simulation results would be helpful in fabricating highly efficient and inexpensive PSCs.

Enhanced nonreciprocal radiation in Weyl semimetals by attenuated total reflection

Abstract: Recent studies have suggested that Weyl semimetals were the promising materials to verify Kirchhoff’s law for nonreciprocal materials in experiment. Nevertheless, existing designs based on Weyl semimetals could not achieve perfect nonreciprocal radiation around a wavelength of 10 µm at small angles. Therefore, it is of significant importance to design structures that can realize perfect nonreciprocal radiation at a shorter wavelength and smaller angle. Here, by using attenuated total reflection, we demonstrate that perfect nonreciprocal radiation can be realized at a wavelength of 10 µm at an angle of 30°. The difference between directional emissivity and absorptivity is as large as 0.99, which is the best result until now, as far as we know. The perfect nonreciprocal radiation is attributed to the nonreciprocal guided resonances in the Weyl semimetal film, which is confirmed by the distribution of magnetic field and dispersion relation. Such a design is promising in verifying Kirchhoff’s law for nonreciprocal materials in experiment.

Drop size measurement techniques for sprays: Comparison of image analysis, phase Doppler particle analysis, and laser diffraction

Abstract: Four different methods for measuring droplet size distributions are evaluated: the Image Analysis VisiSizer technique, a stroboscopic imaging method developed in-house, phase Doppler particle analysis (PDPA), and laser diffraction (Malvern Spraytec). We find that the larger the droplets, the bigger the differences between the results obtained by the different methods. The Image Analysis VisiSizer technique yields results that are comparable with those of the stroboscopic imaging method, provided that the raw Visisizer data are used, as the VisiSizer software makes corrections that can skew the results. Our measurements confirm how the limitations of PDPA can influence its outcomes; the presence of air bubbles inside droplets will cause PDPA to mistake them for smaller droplets. The fact that PDPA reports no droplets larger than 1200 μm might be caused by large drops often not being spherical. The results of the laser diffraction technique are influenced by its fitting method to obtain the droplet size distribution and by overestimation of the number of small droplets due to their low velocity and thus higher concentration in the sample volume. Our results emphasize the need for selecting the size measurement technique to fit the physical nature and expected range of droplet parameters.

Nano-layered surface plasmon resonance-based highly sensitive biosensor for virus detection: A theoretical approach to detect SARS-CoV-2

Abstract: The outbreak of the coronavirus disease (COVID-19) pandemic has become a worldwide health catastrophe instigated by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). Countries are battling to slow the spread of this virus by testing and treating patients, along with other measures such as prohibiting large gatherings, maintaining social distance, and frequent, thorough hand washing, as no vaccines or medicines are available that could effectively treat infected people for different types of SARS-CoV-2 variants. However, the testing procedure to detect this virus is lengthy. This study proposes a surface plasmon resonance-based biosensor for fast detection of SARS-CoV-2. The sensor employs a multilayered configuration consisting of TiO2–Ag–MoSe2 graphene with a BK7 prism. Antigen–antibody interaction was considered the principle for this virus detection. Immobilized CR3022 antibody molecules for detecting SARS-CoV-2 antigens (S-glycoprotein) are used for this sensor. It was found that the proposed sensor’s sensitivity (194°/RIU), quality factor (54.0390 RIU−1), and detection accuracy (0.2702) outperformed those of other single and multilayered structures. This study could be used as a theoretical base and primary step in constructing an actual sensor.

Refractive indices of MBE-grown AlxGa(1−x)As ternary alloys in the transparent wavelength region

Abstract: A series of AlxGa(1−x)As ternary alloys were grown by molecular beam epitaxy (MBE) at the technologically relevant composition range, x < 0.45, and characterized using spectroscopic ellipsometry to provide accurate refractive index values in the wavelength region below the bandgap. Particular attention is given to O-band and C-band telecommunication wavelengths around 1.3 µm and 1.55 µm, as well as at 825 nm. MBE gave a very high accuracy for grown layer thicknesses, and the alloys’ precise compositions and bandgap values were confirmed using high-resolution x-ray diffraction and photoluminescence, to improve the refractive index model fitting accuracy. This work is the first systematic study for MBE-grown AlxGa(1−x)As across a wide spectral range. In addition, we employed a very rigorous measurement-fitting procedure, which we present in detail.

Effect of addition of TiO2 nanoparticles on structural and dielectric properties of polystyrene/polyvinyl chloride polymer blend

Abstract: The present study deals with the effect of the addition of pure titanium oxide nanoparticles (TiO2 NPs) prepared by the sol–gel technique on a polystyrene (PS)/polyvinylchloride (PVC) polymer blend of a composition of 50/50 wt. % using the casting method. X-ray diffraction (XRD), high-resolution transmission electron microscopy, field emission scanning electron microscopy, and energy dispersive x-ray analysis confirmed the preparation of TiO2 NPs in semi-spherical shapes, with the average particle size ranging from 7 to 22 nm. The structural, optical, and dielectric properties of the prepared polymer nanocomposite films are restudied using different tools. In addition, the dielectric properties are studied. XRD and Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy confirmed the complexation and interaction between the PS/PVC polymer blend and TiO2 NPs. HRSEM images reveal that TiO2 NPs appeared as white spots inside the spherical domain of PS/PVC matrices. Optical properties such as absorbance, reflection, bandgap energy, refractive index, and optical dielectric (constant and loss) are studied. These results revealed that TiO2 NPs create inter-bands between valence and conduction bands. The addition of TiO2 NPs to the PS/PVC blend improves the electrical conductivity of the PS/PVC blend due to charge carrier buildup and increased polymeric chain segmental mobility inside the polymeric matrices.

Narrowing bandgap and enhanced mechanical and optoelectronic properties of perovskite halides: Effects of metal doping

Abstract: Perovskite halides are the most promising current candidates for the construction of solar cells and other photovoltaic devices. This is the first theoretical approach to explore the effects of Mn-doping on the optoelectronic performance of the lead-free halide CsGeBr3 and the lead-bearing halide CsPbBr3. We have performed the first-principles calculations to investigate the structural, mechanical, electronic, and optical properties of pure and Mn-doped CsGeBr3 and CsPbBr3 perovskite halides in detail. The lattice constants of Mn-doped halides were slightly reduced compared to their pure phases, which is common in materials after doping. The structural stability of both undoped and doped halides was confirmed by their formation enthalpy. Analysis of the mechanical properties revealed the mechanical stability of both undoped and Mn-doped CsGeBr3 and CsPbBr3. The lower values of the bulk modulus suggested potential optoelectronic applications for the halides being studied. Remarkably, the partial substitution of Ge with Mn narrows the bandgap of both Pb-free and Pb halides, enhancing the electron transfer from the valence band to the conduction band, which increased the absorption and conductivity, essential for superior optoelectronic device applications. The combined analysis of mechanical, electronic, and optical properties indicated that the Mn-doped halides, CsGeBr3 and CsPbBr3, are more suitable for the solar cells and optoelectronic applications than undoped CsGeBr3 and CsPbBr3.

New soliton configurations for two different models related to the nonlinear Schrödinger equation through a graded-index waveguide

Abstract: The present paper studies two various models with two different types: the nonlinear Schrodinger equation with power-law nonlinearity and the (3 + 1)-dimensional nonlinear Schrodinger equation. We perform the modified (G′G)-expansion method to find some exact solutions and to construct various types of solitary wave phenomena for each equation. The received aspects contribute to the firm mathematical foundation and might be essential to the soliton waves. As a result, we obtain all the solutions from Wazwaz [Math. Comput. Modell. 43, 178–184 (2016)] and also obtain some new soliton solutions.

Enhanced ductility and optoelectronic properties of environment-friendly CsGeCl3 under pressure

Abstract: Eco-friendly inorganic halide perovskite materials with numerous structural configurations and compositions are now in the leading place of researcher’s attention for outstanding photovoltaic and optoelectronic performance. In the present approach, density functional theory calculations have been performed to explore the structural, mechanical, electronic, and optical properties of perovskite-type CsGeCl3 under various hydrostatic pressures, up to 10 GPa. The result shows that the optical absorption and conductivity are directed toward the low-energy region (red shift) remarkably with increasing pressure. The analysis of mechanical properties certifies that CsGeCl3 has ductile entity and the ductile manner has increasing affinity with applied pressure. The decreasing affinity of the bandgap is also perceived with applied pressure, which notifies that the performance of the optoelectronic device can be tuned and developed under pressure.

Magneto-hydrodynamics (MHD) flow analysis with mixed convection moves through a stretching surface

Abstract: The objective of this work is to analyze the impact of magneto-hydrodynamics flow across a stretching layer in the existing magnetic sector. The classifying boundary layer equations are converted to a set of non-linear equations by taking advantage of similarity structures. The transformed scheme is mathematically resolved by the homotopy analysis method. Results are measured numerically and plotted graphically for velocity and temperature distribution. Furthermore, flow and heat transfer effects for different physical parameters such as the stretching parameter, mixed convection parameter, magnetic parameter, heat generation coefficient, and Prandtl number are analyzed. Some physical effects reveal that an increase in the Hartmann number raises the fluid’s boundary layer that shows the reverse phenomena of Lorentz force because the speed of the free stream transcends the stretching surface. Upon verifying the homology of the current study with some past investigations, a good harmony is revealed. The velocity of the fluid flow was initially considered to be an increasing function of heat generation, buoyancy parameter, and magnetic field strength, but it later revealed as a decreasing function of the Prandtl number.

Accurate sets of solitary solutions for the quadratic–cubic fractional nonlinear Schrödinger equation

Abstract: The analytical and semi-analytical solutions to the quadratic–cubic fractional nonlinear Schrodinger equation are discussed in this research article. The model’s fractional formula is transformed into an integer-order model by using a new fractional operator. The theoretical and computational approaches can now be applied to fractional models, thanks to this transition. The application of two separate computing schemes yields a large number of novel analytical strategies. The obtained solutions secure the original and boundary conditions, which are used to create semi-analytical solutions using the Adomian decomposition process, which is often used to verify the precision of the two computational methods. All the solutions obtained are used to describe the shifts in a physical structure over time in cases where the quantum effect is present, such as wave-particle duality. The precision of all analytical results is tested by re-entering them into the initial model using Mathematica software 12.

Electronic structure and thermoelectric properties of half-Heusler alloys NiTZ

Abstract: We investigated the electronic and thermoelectric properties of half-Heusler alloys NiTZ (T = Sc and Ti; Z = P, As, Sn, and Sb) having an 18 valence electron count. Calculations were performed by means of density functional theory and the Boltzmann transport equation with constant relaxation time approximation, validated by NiTiSn. The chosen half-Heuslers were found to be indirect bandgap semiconductors, and the lattice thermal conductivity was comparable with the state-of-the-art thermoelectric materials. The estimated power factor for NiScP, NiScAs, and NiScSb revealed that their thermoelectric performance can be enhanced by an appropriate doping rate. The value of ZT found for NiScP, NiScAs, and NiScSb is 0.46, 0.35, and 0.29, respectively, at 1200 K.

Metamaterial-based wearable flexible elliptical UWB antenna for WBAN and breast imaging applications

Abstract: This paper presents a metamaterial-based flexible wearable ultra-wideband (UWB) antenna for breast imaging and wireless body area network (WBAN) applications. The wearable antenna is required to be a planar and low-profile structure using flexible materials. The proposed antenna comprises two layers of denim (10 × 10 mm2) and felt (10 × 15 mm2). The antenna was integrated with six metamaterial unit cells using a modified grain rice shape within a split ring resonator to enhance the bandwidth, gain, and directivity and reduce the specific absorption rate value to less than 2 W/kg. The proposed antenna operates within a broad bandwidth range (6.5 GHz–35 GHz) with the maximum gain and directivity of 8.85 dBi and 10 dBi, respectively, and a radiation efficiency of more than 70% over its operating frequency band. The results verified good agreement between the simulation and measurement of the proposed technique in detecting an existing tumor with a diameter of 4 mm from any location inside the breast. The results convincingly proved the capability of the proposed wearable UWB antenna system for both WBAN and breast imaging applications.

Core-shell Fe3O4@ZnO nanoparticles for magnetic hyperthermia and bio-imaging applications

Abstract: Combining two materials having different functional properties has become a current research area for biomedical applications. The progress of nanoplatforms brings new non-invasive imaging and therapeutic tools for cancer treatment. Here, multifunctional magnetic Fe3O4@ZnO core-shell nanoparticles (Fe3O4@ZnO CSNPs) have been developed by using a soft-chemical approach. Fe3O4@ZnO CSNPs is well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), physical properties measurement system (PPMS), and photoluminescence spectroscopy. XRD and XPS analyses confirm the presence of both Fe3O4 and ZnO phases. TEM micrograph reveals that Fe3O4@ZnO CSNPs are spherical in shape and an average size of 10 nm. Fe3O4@ZnO CSNPs conserve the intrinsic superparamagnetic behavior of its constituent Fe3O4 with a magnetization value of ∼ 31.2 emu/g. These CSNPs exhibit good heating efficacy under the applied AC magnetic field (ACMF). Further, they show a significant reduction in viability of human cervical cancer cells (HeLa) under ACMF and good fluoresecent based cellular imaging capability. Therefore, these results suggested that the multifunctional Fe3O4@ZnO CSNPs could be used as a promising material for image-guided magnetic hyperthermia.

Hydrogel: A potential therapeutic material for bone tissue engineering

Abstract: Current surgical treatments and material applications are not ideal for the treatment of orthopedic clinical injuries, such as large bone defects, cartilage defects, and vascular tendon adhesions that occur after repair. With the continuous development of tissue engineering technology, hydrogels have become important medical biomaterials. Hydrogels are three-dimensional hydrophilic network structures composed of cross-linked polymer chains. They are a new kind of polymeric material for the treatment of orthopedic diseases. Hydrogels have good biocompatibility, biodegradability, drug-carrying capacity, and controllable drug release ability and are less toxic than nanoparticle carriers. They have been widely used in wound repair, guided tissue regeneration, bacteriostasis, hemostasis, postoperative adhesion prevention, drug delivery, and 3D printing. These characteristics can be used to develop a variety of treatments for different diseases. This paper focuses on the innovative progress of hydrogels in promoting and improving bone, cartilage, tendon, and soft tissue regeneration in orthopedic clinical applications. Current and prospective applications of hydrogels in the field of orthopedics are discussed herein.

Optical solitons in birefringent fibers with quadratic-cubic nonlinearity using three integration architectures

Abstract: In this work, the nonlinear Schrodinger’s equation is studied for birefringent fibers incorporating four-wave mixing. The improved tanϕ(ξ)2-expansion, first integral, and G′G2-expansion methods are used to extract a novel class of optical solitons in the quadratic-cubic nonlinear medium. The extracted solutions are dark, periodic, singular, and dark-singular, along with other soliton solutions. These solutions are listed with their respective existence criteria. The recommended computational methods here are uncomplicated, outspoken, and consistent and minimize the computational work size, which give it a wide range of applicability. A detailed comparison with the results that already exist is also presented.

Comprehensive characterization and analysis of hexagonal boron nitride on sapphire

Abstract: Hexagonal boron nitride (h-BN) is considered as one of the most promising materials for next-generation quantum technologies. In this paper, we report bulk-like multilayer h-BN epitaxially grown using a carbon-free precursor on c-plane sapphire with a strong emphasis on material characterization and analysis. In particular, structural, morphological, and vibrational properties, and chemical bonding of such van der Waals materials are presented. Between as-grown h-BN and c-plane sapphire, a compressive residual strain induced by both lattice mismatch and thermal expansion mismatch is examined by both theoretical and experimental studies. Atomic force microscopy revealed and scanning electron microscopy supported the presence of wrinkles across the entire surface of the film, likely due to biaxial compressive strain further verified by Raman spectroscopy. Stacking orders in h-BN with a clearly layered structure were confirmed by high resolution transmission electron microscopy, showing that the films have crystallographic homogeneity. Chemical analysis of the as-grown films was done by x-ray photoelectron spectroscopy, which confirmed the formation of stoichiometric h-BN films with excellent uniformity. This wafer-scale chemical vapor deposition-grown layered h-BN with 2D morphology facilitates applications in the fields of quantum- and deep ultraviolet-photonics.

Boundary layer stagnation point flow of the Casson hybrid nanofluid over an unsteady stretching surface

Abstract: This work examines the behavior of hybrid nanofluid flow toward a stagnation point on a stretching surface. Copper and aluminum are considered as the hybrid nanoparticles. The Casson (non-Newtonian) fluid model is considered for hybrid nanofluids applying magnetic effects perpendicular to the surface. The governing equations are reduced to the ordinary differential equations using similarity transformations. The resulting equations are programmed in the Mathematica software using the OHAM-BVPh 2.0 package. The most important results of this investigation are the effects of different physical parameters such as β, M, S, and Pr on the velocity profile, temperature profile, skin friction coefficient, and local Nusselt number. With the escalation of the magnitude of the Prandtl number Pr, the temperature profile slashes down, while with the variation of the Eckert number, the temperature field improves. The key outcomes specify that the hybrid Casson nanofluid has a larger thermal conductivity when equated with traditional fluids. Therefore, the hybrid fluid plays an important role in the enhancement of the heat phenomena. The ratification of our findings is also addressed via tables and attained noteworthy results.

Germanene/2D-AlP van der Waals heterostructure: Tunable structural and electronic properties

Abstract: Developing van der Waals heterostructures (vdWHs) utilizing vertical mounting of diverse two-dimensional (2D) materials is an efficient way of achieving favorable characteristics. Using first-principles calculations, we demonstrated the geometric configurations and electronic properties of germanene/2D-AlP vdWHs. We considered four high symmetric patterns that show a bandgap opening in the heterostructures of 200 meV–460 meV. The incorporation of spin-orbital coupling reduces the bandgap by 20 meV–90 meV. Both direct and indirect bandgaps were found from these high symmetric patterns, depending on the structural patterns. The charge density distribution and the partial density of states confirmed that germanene was the property builder of the heterostructure, in which 2D-AlP could be a decent substrate. The heterostructure bandgap can be widely tuned in the range 0 meV–500 meV by changing the interlayer separation between the two monolayers. The application of strain and external electric fields also significantly tailored the electronic structures of the heterostructures. Intriguingly, an exceptionally high carrier mobility of more than 1.5 × 105 cm2 V−1 s−1 was observed, which outperforms compared to other studies on germanene heterostructures. All these promising properties make the germanene/2D-AlP heterostructure a viable candidate for FETs, strain sensors, nanoelectronics, and spintronic devices.

β-Ga2O3 on Si (001) grown by plasma-assisted MBE with γ-Al2O3 (111) buffer layer: Structural characterization

Abstract: β-Ga2O3 was deposited in thin film form by plasma-assisted molecular beam epitaxy at 670 °C and 630 °C onto a γ-Al2O3 (111) buffer layer grown at 840 °C by e-beam evaporation on a clean Si (001) surface. The β-Ga2O3 film was 66 nm thick, stoichiometric, and strongly textured, as determined by x-ray reflectivity, x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, x-ray diffraction, and transmission electron microscopy, with three basal growth planes (201), (101), and {310}, including one twin variant {310}. The observed basal growth planes correspond to the close-packing planes of the distorted face-centered cubic oxygen sublattice of β-Ga2O3. Local structural ordering can be thought to occur due to a continuation of the oxygen sublattice from the γ-alumina buffer layer into the β-gallia film. Each β-Ga2O3 growth plane further gives rise to 12 symmetry-derived rotational in-plane variants, resulting in a total of 48 domain variants. Atomistic models of possible gallia–alumina interfaces are presented.

A comparative study of hydrostatic pressure treated environmentally friendly perovskites CsXBr3 (X = Ge/Sn) for optoelectronic applications

Abstract: All-inorganic cubic cesium germanium bromide (CsGeBr3) and cesium tin bromide (CsSnBr3) perovskites have attracted much attention because of their outstanding optoelectronic properties that lead to many modern technological applications. During their evolution process, it can be helpful to decipher the pressure dependence of structural, optical, electronic, and mechanical properties of CsXBr3 (X = Ge/Sn) based on ab initio simulations. The lattice parameter and unit cell volume have been decreased by applying pressure. This study reveals that the absorption peak of CsXBr3 (X = Ge/Sn) perovskites is radically changed toward the lower photon energy region with the applied pressure. In addition, the conductivity, reflectivity, and dielectric constant have an increasing tendency under pressure. The study of electronic properties suggested that CsXBr3 (X = Ge/Sn) perovskites have a direct energy bandgap. It is also found through the study of mechanical properties that CsXBr3 (X = Ge/Sn) perovskites are ductile under ambient conditions and their ductility has been significantly improved with pressure. The analysis of bulk modulus, shear modulus, and Young’s modulus reveals that hardness of CsXBr3 (X = Ge/Sn) perovskites has been enhanced under external pressure. These outcomes suggest that pressure has a significant effect on the physical properties of CsXBr3 (X = Ge/Sn) perovskites that might be promising for photonic applications.

Embedded quantum-error correction and controlled-phase gate for molecular spin qubits

Abstract: A scalable architecture for quantum computing requires logical units supporting quantum-error correction. In this respect, magnetic molecules are particularly promising, since they allow one to define logical qubits with embedded quantum-error correction by exploiting multiple energy levels of a single molecule. The single-object nature of this encoding is expected to facilitate the implementation of error correction procedures and logical operations. In this work, we make progress in this direction by showing how two-qubit gates between error-protected units can be realised, by means of easily implementable sequences of electro-magnetic pulses.

Review: Production of nuclear medicine radioisotopes with ultra-intense lasers

Abstract: In the last two decades, there has been a strong research interest in producing radioisotopes with ultra-intense lasers, as an application of laser-driven accelerators in nuclear medicine. Encouraging progress has been obtained in both experiments and simulations. This Review presents the results of several intense studied radioisotopes in detail, i.e., 18F, 11C, 13N, 15O, 99mTc, 64Cu, and 62Cu. As for other less studied radioisotopes, the results are summarized in Sec. II G. The results are listed in Tables I–VII along with laser intensities, maximum ion/photon energies, number of ions/photons per shot, reactions, and laser repetition rates and facilities. For research based on high repetition rate lasers, both single-shot and multi-shot productions are provided for the purpose of comparison. With key technologies implemented in new commissioning ultra-intense lasers, further experiments will definitely help moving this area forward, which will bring the realization of laser-driven radioisotope production closer.

Optically transparent antenna based on carrier-doped three-layer stacked graphene

Abstract: We fabricated an optically transparent monopole antenna using graphene film and investigated the feasibility of the film as an electrode material for antennas. A low sheet resistance (80 Ω/sq) was attained by stacking the graphene films and carrier doping with an ionic liquid. The optical transmittance of the carrier-doped three-layer stacked graphene film was greater than 90%, enabling it to be embedded in highly transparent objects without altering their landscape. Using the monopole antenna structure with a metal ground plane, we measured the reflection and radiation characteristics of the graphene monopole antenna, excluding the contribution from the power feeding components. The radiation efficiency of the graphene monopole antenna, which was measured by the Wheeler cap method, was determined to be 52.5% at 9.8 GHz. Through the measurements of the graphene monopole antenna, we demonstrated that the carrier-doped three-layer stacked graphene film can be used as an electrode material for optically transparent antennas.

Fast homoepitaxial growth of (100) β-Ga2O3 thin films via MOVPE

Abstract: A high growth rate process above 1 µm/h was achieved for Si-doped (100) β-Ga2O3 homoepitaxial films grown via metalorganic vapor phase epitaxy (MOVPE) while maintaining high crystalline perfection up to a film thickness of 3 µm. The main growth parameters were investigated to increase the growth rate and maintain the step-flow growth mode, wherein the enhanced diffusion channel due to the formation of a Ga adlayer was proposed to be the possible growth mechanism. Si doping allowed precise control of the n-type conductivity of the films with electron concentrations ranging from 1.5 × 1017 to 1.5 × 1019 cm−3 and corresponding mobilities from 144 to 21 cm2 V−1 s−1, as revealed by Hall effect measurements at room temperature. Secondary ion mass spectrometry confirmed homogeneous Si doping through the film and a one-to-one correlation between the Si concentration and the electron concentration. Low defect density in the films was determined by x-ray diffraction measurements. The demonstration of a high growth rate process of β-Ga2O3 films with μm level thickness and smooth surface morphology via MOVPE is critical for high power electronics with vertical device architecture.

Ab initio investigation of the physical properties of Tl based chloroperovskites TlXCl3 (X = Ca and Cd)

Abstract: This theoretical study is performed to investigate structural, elastic, and electronic properties as well as optical response to incident photons of thallium based chloroperovskite TlXCl3 (X = Ca and Cd) compounds. Both compounds have a stable crystal structure with optimized lattice constants ranging from 5.40 A to 5.26 A. The elastic parameters such as elastic constants, bulk modulus, anisotropy factor, Poisson’s ratio, and Pugh’s ratio are evaluated. Poisson’s ratio describes the ductile nature of these materials. The band structure and elemental contribution to different states for all the compounds are analyzed. Materials have a wide bandgap with indirect band nature. Optical parameters such as dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, and optical conductivity are studied in the energy range of 0 eV–30 eV. The comparative results suggest that thallium based compounds are important to be used as scintillating materials and stimulate further experimental investigations of such compounds.

Structural and transport properties of highly Ru-deficient SrRu0.7O3 thin films prepared by molecular beam epitaxy: Comparison with stoichiometric SrRuO3

Abstract: We investigate structural and transport properties of highly Ru-deficient SrRu0.7O3 thin films prepared by molecular beam epitaxy on (001) SrTiO3 substrates. To distinguish the influence of the two types of disorders in the films—Ru vacancies within lattices and disorders near the interface—SrRu0.7O3 thin films with various thicknesses (t = 1–60 nm) were prepared. It was found that the influence of the former dominates the electrical and magnetic properties when t ≥ 5–10 nm while that of the latter does when t ≤ 5–10 nm. Structural characterizations revealed that the crystallinity, in terms of the Sr and O sublattices, of SrRu0.7O3 thin films is as high as that of the ultrahigh-quality SrRuO3 ones. The Curie temperature (TC) analysis elucidated that SrRu0.7O3 (TC ≈ 140 K) is a material distinct from SrRuO3 (TC ≈ 150 K). Despite the large Ru deficiency (∼30%), the SrRu0.7O3 films showed metallic conduction when t ≥ 5 nm. In high-field magnetoresistance measurements, the fascinating phenomenon of Weyl fermion transport was not observed for the SrRu0.7O3 thin films irrespective of thickness, which is in contrast to the stoichiometric SrRuO3 films. The (magneto)transport properties suggest that a picture of carrier scattering due to the Ru vacancies is appropriate for SrRu0.7O3 and also that proper stoichiometry control is a prerequisite to utilizing the full potential of SrRuO3 as a magnetic Weyl semimetal and two-dimensional spin-polarized system. Nevertheless, the large tolerance in Ru composition (∼30%) to metallic conduction is advantageous for some practical applications where SrRu1−xO3 is used as an epitaxial conducting layer.