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A new approach was employed in explaining the weak ferromagnetic behavior of conventionally synthesized Zr4+ modified Bi0.8La0.2FeO3. Rietveld refinement of XRD patterns revealed a polar-tonon-polar R3c → Pnma structural transition in Zr4+substituted samples. Magnetic properties were discovered to be remarkably enhanced, with extracted coercivity and remanence as high as 14 kOe and 0.2 emu/g, respectively. More importantly, an answer to the essential question of the magnetic domain state of the samples has been put forward. Our analysis established, nearly without doubt, the presence of grains consisting of a single magnetic domain. Separated ferromagnetic and anti-ferromagnetic components of the total M-H curves helped to reveal an immense effect of the structural transition on the shape of the hysteresis loops. The orthorhombic magnetocrystalline anisotropy of the Pnma phase has been primarily deemed responsible for the high coercivity and remanence of the Zr4+ modified samples. The effect of the grain size and Fe-O-Fe bond angle on the magnetic properties of the samples has also been discussed. Ferroelectricity was found to be absent in Zr-substituted samples because of their non-polar structure. However, the leakage current was reduced by up to two orders of magnitude compared to Bi0.8La0.2FeO3 upon addition of Zr4+. Dielectric measurements conformed to the ferroelectric and leakage current characteristics, and Zr4+ substitution was again found to be beneficial. [ABSTRACT FROM AUTHOR]

We present a new approach to perform beam steering in reflecting type apertures such as reflectarray antennas. The proposed technique exploits macro-scale mechanical movements of parts of the structure to achieve two-dimensional microwave beam steering without using any solid-state devices or phase shifters integrated within the aperture of the antenna. The principles of operation of this microwave beam steering technique are demonstrated in an aperture occupied by ground-plane-backed, sub-wavelength capacitive patches with identical dimensions. We demonstrate that by tilting the ground plane underneath the entire patch array layer, a phase shift gradient can be created over the aperture of the reflectarray that determines the direction of the radiated beam. Changing the direction and slope of this phase shift gradient on the aperture allows for performing beam steering in two dimensions using only one control parameter (i.e., tilt vector of the ground plane). A proof-of-concept prototype of the structure operating at X-band is designed, fabricated, and experimentally characterized. Experiments demonstrate that small mechanical movements of the ground plane (in the order of 0.05λ0) can be used to steer the beam direction in the ±10° in two dimensions. It is also demonstrated that this beam scanning range can be greatly enhanced to ±30° by applying this concept to the same structure when its ground plane is segmented. [ABSTRACT FROM AUTHOR]

Opto-electronic properties of boron phosphide–germanium carbide (BP/GeC), a new van der Walls hetero-bilayer (HBL) with all possible stacking patterns, are studied under the density functional theory originated first-principles. The dynamical and chemical stabilities of the hetero-bilayer are confirmed by phonon spectra and binding energy. Among the dynamically stable HBLs, HBL 1 has the lowest binding energy with the smallest interlayer spacing of about 3.442 Å. Both values and natures (indirect or direct) of the electronic band structure are highly responsive to the stacking patterns. We have found that HBL 1 is indirect, while HBL 2 and HBL 3 become a direct bandgap at the K high symmetry point. All HBLs show type-II band alignment. Both compressive and tensile biaxial strains on the electronic properties of HBLs have been considered. All the HBLs become a direct bandgap for the compressive strain at 4% and 6%. We have also presented the optical property calculations on the HBLs, namely, the complex dielectric function and absorption properties, showing unique optical properties with significant absorption (5 × 105 cm−1 in HBL 2) in the whole solar spectra compared with their comprising monolayers. Moreover, the strain-dependent optical absorption coefficients with varying photon wavelengths are calculated and the maximum value is attained to be about 6.5 × 105 cm−1 in HBL 2 at 4% compressive strain. Consequently, the optoelectronic properties we have explored in our proposed new hetero-bilayer systems can guide the experimental realization of the hetero-bilayers and effective use in the future photovoltaic applications. [ABSTRACT FROM AUTHOR]

A dominant mode of transmission for the respiratory disease COVID-19 is via airborne virus-carrying aerosols. As national lockdowns are lifted and people begin to travel once again, an assessment of the risk associated with different forms of public transportation is required. This paper assesses the risk of transmission in the context of a ride-sharing motorbike taxi—a popular choice of paratransit in South and South-East Asia and Sub-Saharan Africa. Fluid dynamics plays a significant role in understanding the fate of droplets ejected from a susceptible individual during a respiratory event, such as coughing. Numerical simulations are employed here using an Eulerian–Lagrangian approach for particles and the Reynolds-averaged Navier–Stokes method for the background air flow. The driver is assumed to be exhaling virus laden droplets, which are transported toward the passenger by the background flow. A single cough is simulated for particle sizes 1, 10, 50 μ m , with motorbike speeds 1 , 5 , 15 m / s. It has been shown that small and large particles pose different types of risk. Depending on the motorbike speed, large particles may deposit onto the passenger, while smaller particles travel between the riders and may be inhaled by the passenger. To reduce risk of transmission to the passenger, a shield is placed between the riders. The shield not only acts as a barrier to block particles, but also alters the flow field around the riders, pushing particles away from the passenger. The findings of this paper therefore support the addition of a shield potentially making the journey safer. [ABSTRACT FROM AUTHOR]

There is increasing interest in a ferroelectric transistor, mainly using vacuum processed hafnium oxide based materials. We report in this paper a solution processed ZnO thin-film transistor (TFT) with improved ferroelectric performance in Hf0.5Zr0.5O2 (HZO) using a triple layer of ZrOx/HZO/AlOx by spray pyrolysis. The performance enhancement is due to the difference in thermal expansion coefficient between the bottom/top dielectric and HZO layers. Grazing incident x-ray diffraction, current–voltage, capacitance–voltage, polarization–voltage, and anticlockwise hysteresis in transfer curve confirm the excellent ferroelectricity of the triple layer. A memory window as large as ∼3 V, the maximum on/off ratio of 3.5 × 109, the field-effect mobility of 125 cm2/V s, and the subthreshold slope of 0.18 V/decade were obtained from the ZnO TFT with the ZrOx/HZO/AlOx gate insulator, demonstrating the high performance ferroelectric ZnO TFT. This result can open opportunities for ferroelectric oxide TFT for large area electronics on glass, including display. [ABSTRACT FROM AUTHOR]

An experimental study was performed on a 30P30N three-element high-lift airfoil fitted with different types of slat finlets and its noise reduction capabilities were assessed. To develop a better understanding of the noise reduction mechanism, simultaneous measurements of the unsteady surface pressure were taken at various locations at the vicinity of the slat cove and at far-field locations. While there was a small reduction in far-field noise for the fundamental peak, the use of slat finlets showed a substantial reduction in surface pressure fluctuations. The reduction of vortex shedding energy by the slat finlets also resulted in the reduction of nonpropagating hydrodynamic field between the slat and the main-element substantially reducing the near-field pressure spectra. Fourier and wavelet-based analysis along with high-order spectral analysis were provided for further confirmation of the observations and hypothesis. Finally, the wavelet coefficient findings showed spectral peaks as well as amplitudes modulated in time in the baseline case; however, these peaks were substantially reduced for the finlet configuration with larger spacing. [ABSTRACT FROM AUTHOR]

We introduce a new technique for designing wideband circular-polarization selective surfaces (CPSSs) based on anisotropic miniaturized element frequency selective surfaces. The proposed structure is a combination of two linear-to-circular polarization converters sandwiching a linear polarizer. This CPSS consists of a number of metallic layers separated from each other by thin dielectric substrates. The metallic layers are in the form of two-dimensional arrays of subwavelength capacitive patches and inductive wire grids with asymmetric dimensions and a wire grid polarizer with sub-wavelength period. The proposed device is designed to offer a wideband circular-polarization selection capability allowing waves with left-hand circular polarization to pass through while rejecting those having right-hand circular polarization. A synthesis procedure is developed that can be used to design the proposed CPSS based on its desired band of operation. Using this procedure, a prototype of the proposed CPSS operating in the 12-18 GHz is designed. Full-wave electromagnetic simulations are used to predict the response of this structure. These simulation results confirm the validity of the proposed design concept and synthesis procedure and show that proposed CPSS operates within a fractional bandwidth of 40% with a co-polarization transmission discrimination of more than 15 dB. Furthermore, the proposed design is shown to be capable of providing an extremely wide field of view of ±60°. [ABSTRACT FROM AUTHOR]

Using a one dimensional time dependent convection-reaction-diffusion model, the temporal and spatial distributions of species propagating downstream of an atmospheric pressure air surface barrier discharge was studied. It was found that the distribution of negatively charged species is more spatially spread compared to positive ions species, which is attributed to the diffusion of electrons that cool down and attach to background gas molecules, creating different negative ions downstream of the discharge region. Given the widespread use of such discharges in applications involving the remote microbial decontamination of surfaces and liquids, the transport of plasma generated reactive species away from the discharge region was studied by implementing mechanical convection through the discharge region. It was shown that increased convection causes the spatial distribution of species density to become uniform. It was also found that many species have a lower density close to the surface of the discharge as convection prevents their accumulation. While for some species, such as NO2, convection causes a general increase in the density due to a reduced residence time close to the discharge region, where it is rapidly lost through reactions with OH. The impact of the applied power was also investigated, and it was found that the densities of most species, whether charged or neutral, are directly proportional to the applied power. [ABSTRACT FROM AUTHOR]

The combined effects of free-stream inclination (α) and heating [ ϵ = (T w − T ∞) / T ∞ ] on aerodynamic and heat transfer parameters are studied at fixed Reynolds number (Re = 100), Prandtl number (Pr = 0.71), cylinder inclination (ϕ = 0 °), Froude number (Fr = 1.0), and Mach number (M = 0.1) in the large-scale heating regime. For this purpose, a non-Oberbeck–Boussinesq compressible model for thermally perfect gases incorporating volumetric straining as well as transport property variations under large-scale heating is employed. The free-stream inclination (α) is varied in the range [ 0 ° , 90 ° ] while the over-heat ratio (ϵ) is varied in the range of [0, 1]. It is found that at small free-stream inclinations (α ≤ 45 °), increase in heating causes a significant increase in mean drag coefficient, while at large α (α > 45 °), heating has little effect on mean drag coefficient. The mean lift coefficient (CL) increases by increasing ϵ for any value of α except α = 0. At a fixed heating level, the variation of mean CL is very non-monotonic with lower values at α = 45 ° and 90 °. It is found that the increase in flow inclination from 0 ° to 90 ° reduces the sensitivity of Strouhal number (St) to heating. For ϵ ≤ 0.6 , mean Nusselt number exhibits a non-monotonic trend with increase in α and attains a maximum value at α ≅ 40 °. However, for ϵ > 0.6 , heat transfer decreases with increase in α and is maximum for aligned flow (α = 0 °). [ABSTRACT FROM AUTHOR]

The influence of natural convection cells on heat transfer and the evolution of melt interface is studied for low Prandtl number fluid (Pr = 0.025) in phase-change Rayleigh–Benard convection using the lattice Boltzmann method. The thermal lattice Boltzmann model is used to evaluate the effect of Rayleigh number (Ra = 6708, 11 708, and 21 708) and cavity aspect ratio (γ = 0.062 5, 0.125, 0.25, 0.5, and 1) on the onset of convection, number of convection cells, and Nusselt number in the classical Rayleigh–Benard convection. The modified equilibrium distribution function-based thermal lattice Boltzmann model is applied to evaluate the effect of Stefan number (Ste = 0.025, 0.05, and 0.1) in the phase change Rayleigh–Benard convection. Distinct flow configurations depend on the Rayleigh number, aspect ratio, and Stefan number. The number of convection cells follows an inverse relation with the aspect ratio. Nusselt number increases with decreasing cavity aspect ratio and increasing Rayleigh number in the classical Rayleigh–Benard convection. With the variation in the aspect ratio based on the melt layer height during melting of phase change material, the number of convection cells changes resulting in the change in the evolution of the melt interface and convective heat transfer. Melting in a cavity of aspect ratio less than 0.5, the evolution of melt interface remains symmetrical. For an aspect ratio greater than 0.5, the interface evolution becomes unsymmetrical depending on the transition to single convection cell-dominated heat transfer. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate ferroelectricity in high-quality monocrystalline quaternary alloy ScAlGaN. Sc0.2Al0.45Ga0.35N films are grown by plasma-assisted molecular beam epitaxy and exhibit a surface roughness of 0.5 nm, limited by the roughness of the underlying molybdenum template. Polarization-electric field and positive-up-negative-down measurements reveal unambiguous ferroelectric switching with a coercive field of ∼5.5 MV cm−1 at 10 kHz and high remanent polarization of ∼150 μC cm−2. Time-dependent measurements suggest that the polarization reversal behavior adheres to the Kolmogorov–Avrami–Ishibashi model and follows a scheme of domain nucleation and growth. Detailed piezoresponse force microscopy studies further elucidate the evolution of polarity reversal domains in wurtzite nitride ferroelectrics and support the notion that the growth of inversion domains occurs via an in-plane motion of the domain walls. The realization of functional ferroelectric quaternary alloys in the wurtzite nitride family extends beyond being a technical demonstration. The additional degree of bandgap, band alignment, lattice parameter, and piezoelectric constant tunability achievable through quaternary alloys unveils a vast dimension through which wurtzite nitride ferroelectrics can be optimally engineered for a broad variety of high-performance electronic, optoelectronic, and acoustic devices and systems. [ABSTRACT FROM AUTHOR]

The geometric, electronic, and thermodynamic properties of ring-shaped beryllium oxide (BeO)n (n = 3–5) clusters along with changes in these characteristics after doping with transition metals—scandium, titanium, and vanadium—have been investigated based on density functional theory (B3LYP/LanL2DZ) calculations. It has been observed that ring-shaped (BeO)n (n = 3–5) clusters have become more stable and effective due to doping with transition metals, and this stability is better for the bigger clusters. In addition, from the IR spectroscopy analysis, it has been observed that both the pristine and doped clusters are formed naturally as there is no imaginary frequency found in these clusters. From the analysis of electronic properties, it has been found that the bandgap drastically reduces after doping in these clusters and shows semiconductivity. Therefore, these doped clusters could be suitable for different high-tech applications in the semiconductor industries. [ABSTRACT FROM AUTHOR]

Irradiation by laser pulses and a fluctuating surrounding liquid environment can, for example, lead to time-dependent effects in the transport through molecular junctions. From the theoretical point of view, time-dependent theories of quantum transport are still challenging. In one of these existing transport theories, the energy-dependent coupling between molecule and leads is decomposed into Lorentzian functions. This trick has successfully been combined with quantum master approaches, hierarchical formalisms, and non-equilibrium Green's functions. The drawback of this approach is, however, its serious limitation to certain forms of the molecule-lead coupling and to higher temperatures. Tian and Chen [J. Chem. Phys. 137, 204114 (2012)] recently employed a Chebychev expansion to circumvent some of these latter problems. Here, we report on a similar approach also based on the Chebychev expansion but leading to a different set of coupled differential equations using the fact that a derivative of a zeroth-order Bessel function can again be given in terms of Bessel functions. Test calculations show the excellent numerical accuracy and stability of the presented formalism. The time span for which this Chebychev expansion scheme is valid without any restrictions on the form of the spectral density or temperature can be determined a priori. [ABSTRACT FROM AUTHOR]

Thin film transistors (TFTs) with a ferroelectric Hf0.5Zr0.5O2 (HZO) gate insulator (GI) have been reported by using the vacuum process for HZO such as sputtering and atomic layer deposition methods. We report in this paper the ZnO TFT with ferroelectric GI using solution processed AlOx/HZO. AlOx assists in the initiation of ferroelectricity by applying large mechanical stress and provides a sufficient amount of oxygen vacancy to the underlying HZO. X-ray diffraction and capacitance-voltage, polarization-voltage, and anti-clockwise hystereses in the transfer curve confirm the formation of the ferroelectric phase of HZO. The AlOx/HZO TFTs exhibited a field-effect mobility of 140 cm2/V s, an on/off current ratio of 109, and a sub-threshold swing of 0.32 V/decade. The TFT shows a good bias-voltage tunable memory window of ∼4.5 V and memory retention characteristics up to 10 000 s for a programing/erasing voltage of ±10 V with a pulse width of 0.5 s. This work demonstrates the fabrication of ferroelectric HZO TFT using the solution process, and the results can be applied to ferroelectric oxide semiconductor TFT electronics. [ABSTRACT FROM AUTHOR]

Wave propagation models in the time domain have been extensively used in the available literature to study the flow characteristics in blood vessels. Most of the wave propagation models have considered flat or parabolic velocity profile functions to estimate the nonlinear convection and diffusion terms present in the conservation of momentum equation. There are only a few works available on the wave propagation analysis in which the velocity profile is approximated using different polynomial functions. In this study, a computationally efficient nonlinear axisymmetric formulation is presented without a priori assumed velocity profile function across the cross section to model the blood flow. Such a formulation in terms of axial velocity (u), pressure (p), and domain radius (R) facilitates the evolution/development of axial velocity profile as the flow progresses with time. The arterial mechanical behavior is modeled using a linear elastic constitutive relation. Partial differential equations are discretized using the finite element method and the Galerkin time integration technique in space and time domains, respectively. This study finds a phase difference between the shear stress at the wall and the flow rate. The flow characteristics and the velocity profile function are found to be in good agreement with the three-dimensional computational results available in the literature. The detailed investigation of the axial velocity across the cross section reveals neither flat nor parabolic profiles, as previously assumed in the literature. [ABSTRACT FROM AUTHOR]

The spatial instability of inward radial Rayleigh–Bénard–Poiseuille flow was investigated using direct numerical simulations with random and controlled inflow forcing. The simulations were carried out with a higher-order-accurate compact finite difference code in cylindrical coordinates. Inward radial Rayleigh–Bénard–Poiseuille flows can be found, for example, in the collectors of solar chimney power plants. The conditions for the present simulations were chosen such that both steady and unsteady three-dimensional waves are amplified. The spatial growth rates are attenuated significantly in the downstream direction as a result of strong streamwise acceleration. For the oblique waves, the growth rates and wave angles decrease and the phase speeds get larger with increasing frequency. As the oblique waves travel downstream, the phase speeds decrease and the wave angles increase. Overall, steady waves with a wave angle of 90 ° are the most amplified. In general, because of the finite azimuthal extent, only certain azimuthal wavenumbers are possible. As a result, the steady waves appear to merge in the streamwise direction. When the inflow is at an angle such that a spiral flow is formed, one family of oblique waves is favored over the other and the mode shapes of the left- and right-traveling oblique waves are asymmetric with respect to the radius. As the inflow angle increases, this asymmetry is aggravated and the wavenumber of the most amplified disturbances is diminished. [ABSTRACT FROM AUTHOR]

Tunnel junction devices grown monolithically by metal organic chemical vapor deposition were optimized for minimization of the tunnel junction voltage drop. Two device structures were studied: an all-GaN homojunction tunnel junction and a graded InGaN heterojunction-based tunnel junction. This work reports a record-low voltage drop in the graded-InGaN heterojunction based tunnel junction device structure achieving a de-embedded tunnel junction voltage drop of 0.17 V at 100 A/cm2. The experimental data were compared with a theoretical model developed through technology computer-aided design (TCAD) simulations that offer a physics-based approach to understanding the key components of the design space, which lead to a more efficient tunnel junction. [ABSTRACT FROM AUTHOR]

Experiments were conducted to assess the aeroacoustic characteristics of a 30P30N three-element high-lift airfoil fitted with two different types of slat cove fillers in the Aeroacoustic Facility at the University of Bristol. The results are presented for the angle of attack α = 18° at a free-stream velocity of U∞ = 30 m/s, which corresponds to a chord-based Reynolds number of Rec = 7 × 105. Simultaneous measurements of the unsteady surface pressure were carried out at several locations in the vicinity of the slat cove and at the far-field location to gain a deeper understanding of the slat noise generation mechanism. The results were analyzed using a higher-order statistical approach to determine the nature of the broadband hump seen at low frequencies for the 30P30N high-lift airfoil observed in recent studies and also to further understand the tone generation mechanism within the slat cavity. Intermittent events induced by the resonant mechanism between the slat and its trailing edge were investigated in detail. A series of correlation and coherence analysis of the unsteady surface pressure measurements was carried out to identify and isolate the low-frequency hump. A wavelet analysis was performed to investigate the nature of the slat-wing resonant intermittent events in both time and frequency domains. Novel approaches, dynamic mode decomposition, and multi-resolution dynamic mode decomposition were applied to the wavelet coefficient moduli to determine the nature of the noise. [ABSTRACT FROM AUTHOR]

Noise reduction capabilities of slat cusp serration were experimentally assessed and demonstrated for a 30P30N three-element high-lift airfoil fitted with two different types of serrated slat cusps. Aerodynamic characteristics were evaluated with the aid of surface pressure distribution, and insignificant differences were found among all the tested configurations. The unsteady flow characteristics of the slat serrations were examined using near- and far-field measurements to gain a deeper understanding of the noise generation mechanism. Although increased surface pressure fluctuations were demonstrated by the slat serrations, a substantial reduction in the far-field noise was observed. The increase in the near-field energy levels was attributed to the non-propagating hydrodynamic energy field within the slat cove and the main element, whereas the far-field noise reduction was attributed to the elimination of vortex shedding by the slat serration. Further reaffirmation of the observations and hypothesis was provided with higher-order spectral analysis and wavelet analysis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The present work numerically investigates the formation and sustenance of a primary vortex ring (PVR) and counter-rotating vortex rings (CRVRs) in laminar, axisymmetric, continuously blowing compressible jets. The effect of jet Reynolds number (Rej), jet Mach number (Mj), and pressure-ratio ( p j p a ) on these compressible vortex rings and their flow dynamics is explored. The core bow shock is formed in the inviscid core of the transonic/supersonic jets for sustaining the supersonic flow field in the PVR. The embedded shock (ES) and vortex-induced shock (VIS) are also found to sustain the evolving PVR in the supersonic jets. The effect of Mj and p j p a on the circulation and pinch-off of the PVR is also investigated. For over-expanded and perfectly expanded supersonic jets, Kelvin–Helmholtz vortices (KHVs) entrained into the PVR interact with the ES to cause a shock–vortex interaction, which results in the appearance of multiple VISs. It is established that the different events of interaction of KHV with the ES inside the PVR after the pinch-off are a manifestation of two factors: (i) the constraint imposed on the PVR by quasi-time-invariance of circulation around a material curve enclosing the PVR and (ii) the requirement of spatially cyclic property distribution inside the PVR. The shock-shear layer–vortex interaction in under-expanded jets is also investigated using vorticity analysis and oblique shock theory. For under-expanded jets, apart from the Mach-reflection timescale, the CRVR pattern formation is also governed by the initial strength of the slip-stream, which, in turn, is regulated by all three parameters, i.e., Rej, Mj, and p j p a . [ABSTRACT FROM AUTHOR]

Intersubband transition energies and absorption lineshape in staggered InGaN/GaN quantum wells surrounded by GaN barriers are computed as functions of structural parameters such as well width, In concentrations, and the doping level in the well. Schrödinger and Poisson equations are solved self-consistently by taking the free and bound surface charge concentrations into account. Many-body effects, namely, depolarization and excitonic shifts are also included in the calculations. Results for transition energies, oscillator strength, and the absorption lineshape up to nonlinear regime are represented as functions of the parameters mentioned. The well width (total and constituent layers separately) and In concentration dependence of the built-in electric field are exploited to tune the intersubband transition energies. [ABSTRACT FROM AUTHOR]

A variety of methods extracting spatially resolved information of solar cell parameters using luminescence imaging on silicon solar cells have been introduced in the past years. Nearly, all methods base on calibrating the local luminescence intensity to local junction voltage. The different methods, however, use different approaches to calibrate the luminescence images to local junction voltage. The assumptions made by the voltage calibration approaches are fundamental for a correct voltage calibration and hence for a correct extraction of other relevant local solar cell parameters. In this work, we review the different voltage calibration approaches and analyse the validity and the effect of the underlying assumptions carefully using circuit simulation results. We present experimental results of voltage calibrated luminescence images of a multicrystalline silicon solar cell using different voltage calibration approaches. We show the relevance of accurate voltage calibration by performing a sensitivity analysis investigating the sensitivity of local cell parameter results obtained by a method known from literature with respect to changes in the calibration constant. We conclude proposing an approach for voltage calibration which is the C most reasonable trade-off between accuracy and sufficiently low data acquisition times. [ABSTRACT FROM AUTHOR]

A planar array of three one-dimensional elastic waveguides mutually coupled periodically along their length and driven externally is shown theoretically and numerically to support nonseparable superpositions of states. These states are the product of Bloch waves describing the elastic displacement along the waveguides and spatial modes representing the displacement across the array of waveguides. For a system composed of finite length waveguides, the frequency, relative amplitude, and phase of the external drivers can be employed to selectively excite specific groups of discrete product modes. The periodicity of the coupling is used to fold bands enabling superpositions of states that span the complete Hilbert space of product states. We show that we can realize a transformation from one type of nonseparable superposition to another one that is analogous to a nontrivial quantum gate. This transformation is also interpreted as the complex conjugation operator in the space of the complex amplitudes of individual waveguides. [ABSTRACT FROM AUTHOR]

A sidewall activation process was optimized for buried magnesium-doped p-GaN layers yielding a significant reduction in tunnel junction-enabled light emitting diode (LED) forward voltage. This buried activation enabled the realization of cascaded blue LEDs with fully transparent GaN homojunction tunnel junctions. The initial optimization of buried p-GaN activation was performed on PN junctions grown by metal organic chemical vapor deposition (MOCVD) buried under hybrid tunnel junctions grown by MOCVD and molecular beam epitaxy. Next the activation process was implemented in cascaded blue LEDs emitting at 450 nm, which were enabled by fully transparent GaN homojunction tunnel junctions. The tunnel junction-enabled multi-active region blue LEDs were grown monolithically by MOCVD. This work demonstrates a state-of-the-art tunnel junction-enabled cascaded LED utilizing homojunction tunnel junctions which do not contain any heterojunction interface. [ABSTRACT FROM AUTHOR]

Direct numerical simulations of reciprocating pipe flow in a straight pipe with a free-end are presented. The range of amplitudes and frequencies studied span the laminar regime and the beginning of transition toward a conditionally turbulent flow. Two primary results are reported: the measurement of the flow development length and the loss of energy, both due to the presence of the free-end. Two regimes of flow are identified with distinct length scales. For low frequencies, the development length scales with the pipe diameter D. However, for higher frequencies, the development length scales with the Stokes layer thickness δ = 2 ν / ω . The energy loss is studied by calculating the viscous dissipation function, indicating where energy is lost, and allowing the energy lost due to the presence of the free-end to be isolated. While strong vortices are formed and convected from the exit, most of the energy they dissipate is lost within a few pipe diameters of the exit. It is shown that these trends continue even as the amplitude and frequency are increased so that the flow begins to transition from a laminar toward a turbulent state. Two modes of instability are observed in the Stokes layers near the free-end, one short wavelength mode with a wavelength set by the Stokes layer thickness and the other long wavelength mode with a wavelength set by the amplitude of the oscillatory flow. These modes are related to those observed in the fully developed oscillatory flow. [ABSTRACT FROM AUTHOR]

It has been recently demonstrated through experiments that the observed high enhancements in thermal conductivity of nanofluids are due to aggregation of nanoparticles rather than the previously stated mechanism of the Brownian motion-induced micro-convection. In this paper, we use equilibrium molecular dynamics simulations to investigate the role of micro-convection on the thermal conductivity of well-dispersed nanofluids. We show that while the individual terms in the heat current autocorrelation function associated with nanoparticle diffusion achieve significant values, these terms essentially cancel each other if correctly defined average enthalpy expressions are subtracted. Otherwise, erroneous thermal conductivity enhancements will be predicted, which are attributed to Brownian motion-induced micro-convection. Consequently, micro-convection does not contribute noticeably to the thermal conductivity and the predicted thermal conductivity enhancements are consistent with the effective medium theory. [ABSTRACT FROM AUTHOR]

The work presented here was motivated by the need to develop a predictive model for thermodynamic stabilization of binary alloys that is applicable to strongly segregating size-misfit solutes, and that can use available input data for a wide range of solvent-solute combinations. This will serve as a benchmark for selecting solutes and assessing the possible contribution of thermodynamic stabilization for development of high-temperature nanocrystalline alloys. Following a regular solution model that distinguishes the grain boundary and grain interior volume fractions by a transitional interface in a closed system, we include both the chemical and elastic strain energy contributions to the mixing enthalpy ΔHmix using an appropriately scaled linear superposition. The total Gibbs mixing free energy ΔGmix is minimized with respect to simultaneous variations in the grain-boundary volume fraction and the solute contents in the grain boundary and grain interior. The Lagrange multiplier method was used to obtain numerical solutions with the constraint of fixed total solute content. The model predictions are presented using a parametric variation of the required input parameters. Applications are then given for the dependence of the nanocrystalline grain size on temperature and total solute content for selected binary systems where experimental results suggest that thermodynamic stabilization could be effective. [ABSTRACT FROM AUTHOR]

We perform the equilibrium molecular dynamics (EMD) determination of thermal conductivity via the Green-Kubo method for several multi-component systems including gas and liquid mixtures, solid nanoparticle liquid suspension (nanofluids), and a solid alloy. The results are compared against those obtained with the application of the heat source and sink and determination of thermal conductivity from non-equilibrium molecular dynamics (NEMD) and the Fourier's Law. We demonstrate that the proper definition of the heat current in the equilibrium simulations leads to the consistency between the results obtained using the equilibrium and non-equilibrium simulations. In particular, EMD simulations, in agreement with NEMD results, do not predict any significant thermal conductivity enhancement for well-dispersed nanofluids. [ABSTRACT FROM AUTHOR]

Using the variational methods, we have calculated the binding energies of the lowest donor states, 1s and 2p±, in wurtzite InGaN/GaN staggered quantum wells. The binding energies in narrow wells are larger in magnitude than the values in bulk GaN due to the quantum confinement effects. However, the energies decrease sharply in wider wells because of the weakening confinement due to the strong built-in electric field inside the well. The binding energies of donors placed at the opposite edges of the well are quite different as the built-in electric field forms an asymmetric, triangular potential inside the well. The oscillator strength of the possible transitions between the donor states is then computed by modelling them as the states of a two-level atom. A magnetic field applied along the growth direction splits up the degenerate 2p± states. The amount of splitting in the quantum well is found to be small possibly due to the heavy electron effective mass inside the well. The oscillator strength of the transition between the donor states becomes greater with the increasing magnetic field. [ABSTRACT FROM AUTHOR]

Reciprocity is a fundamental principle that follows the time reversal symmetry of physics. However, many practical applications require breaking time reversal symmetry, hence, are called nonreciprocal. This article aims at discussing time reversal symmetry, developing fundamental building block to achieve nonreciprocity leading to robust analytical model to explain electromagnetic rotation upon propagation through a nonreciprocal medium. Detailed mathematical derivation is presented for Faraday and Kerr rotation in the presence of external bias which breaks time reversal symmetry and leads to achieve nonreciprocal system. We validate our proposed model for conventional conditions and we compute the Faraday and Kerr rotation from a reported article using our proposed mathematical model and observed excellent agreement. [ABSTRACT FROM AUTHOR]

Chalcogenide crystals are a unique class of materials very different from semiconductors or metallic alloys. They also have many practical applications, especially in relation to their optical properties. However, the fundamental understanding of their electronic structure and physical properties is rather scattered and incomplete. We present a detailed study using first-principles calculations on the electronic structure, interatomic bonding, and optical and mechanical properties for 32 chalcogenide crystals. They consist of 22 binary (AnBm) and 10 ternary (AnA′Bm) crystals with A = Ag, As, Cu, Ge, Sb, Sn, Cd, Zn; A′ = In, Ge, Sn; and B = S, Se, Te with n = 1, 2, 4 and m = 1, 2, 3, 4, 9. We use the novel concept of total bond order density as a single quantum mechanical metric to characterize the internal cohesion of these crystals and correlate them with the calculated properties, especially the mechanical properties. Based on this large database, we are able to identify some new and conspicuous observations to reach some useful conclusions related to the chemical composition of the chalcogenide compounds and their complex interatomic interactions. Specific examples from crystals and their unique properties in relation to the elements A and A′ and chalcogenide element B (S, Se, and Te) are discussed and highlighted. Finally, generalization of the observed trends and empirical rules can be extended to much larger classes of ternary and quaternary chalcogenide crystals and glasses so far unexplored. [ABSTRACT FROM AUTHOR]

We derive a reaction–advection–diffusion equation based framework for analyzing the movement of wealth in urban environments. Gentrification is a core issue that affects many urban areas, and the dynamics of such are not fully understood. To understand the process using a few physically relevant variables, we develop an approach to model the interplay between local amenities and wealth from existing analyses of factors influencing gentrification. We conduct a linear stability analysis on model parameters that results in spatially homogeneous solutions and determine directions for parameter changes to induce instabilities. From these parameters, we determine quantities that lead to the formation of areas of wealth and amenity concentration in the long term on bounded and unbounded domains. We present a global bifurcation result in two dimensions, leading to the existence and stability of non-constant equilibrium solutions, which represents solutions with wealth and amenity hotspots. Finally, we present a theory for discerning the one-dimensional pattern formation in the transition between stability and instability and verify numerically through a weakly nonlinear analysis. The analysis provides a promising framework for further verification using publicly available geospatial data on the relevant variables. [ABSTRACT FROM AUTHOR]

The creation of multilevel quantum states, qudits, has revolutionized concepts for quantum computing. Classical systems that capture behavior analogous to quantum systems have been demonstrated. In this spirit, we consider a three-level classical analogue of the qudit composed of coupled acoustic waveguides. Here, we demonstrate both the experimental realization of a three-level classical analogue of the qudit and the creation and tuning of nonseparable superpositions of two of these analogues, which are classically "entangled." Measurements of velocities and transmission inform our assignment of these nonseparable states. [ABSTRACT FROM AUTHOR]

Spectral singularities have been extensively studied over the last one and half decades for different non-Hermitian potentials in non-Hermitian quantum mechanics. The nature of spectral singularities has not been studied for the case of quaternionic potential. In the present work, we perform an analytical study on scattering from a quaternionic point interaction represented by a delta function. New features of spectral singularities are observed, which are different than the case of a complex (non-quaternionic) point interaction. The most notable difference is the occurrence of spectral singularity from the lossy point interaction, which is forbidden in the case of standard non-Hermitian quantum mechanics. [ABSTRACT FROM AUTHOR]

The rapid surge in perovskite solar cell efficiency has necessitated the development of viable metrology techniques during device integration, paving the way for commercialization. Ellipsometry is considered the most appropriate technique for fast and accurate thickness measurement for large scale production. However, a precise and well-calibrated model is a prerequisite for this technique. While ellipsometry of individual device layers has been reported in recent perovskite literature, a comprehensive multilayer modeling approach is thus far unavailable. Perovskite optoelectronic devices generally consist of a six-layer film stack with three transparent layers required for optical absorption in the perovskite layer. Spin casted thin films, now common in this line of research, impart their own difficulties into ellipsometric modeling. Roughnesses at each heterointerface, similarities in optical spectra of transparent layers, and anomalous dispersion of perovskite are just a few of such challenges. In this work, we report the process of building an ellipsometry model from scratch for thickness measurement of methylammonium lead iodide (MAPI) perovskite and indium tin oxide (ITO)/hole transport layer (HTL) bilayer thin film stacks on a glass substrate. Three promising representatives of HTLs (CuI, Cu2O, and PEDOT:PSS) were studied. The models were extended to measure the individual layer thicknesses of the MAPI/HTL/ITO film stack on a glass substrate using the models developed for individual layers. Optical constants of all the representative thin films were thus extracted for a wide wavelength range (300 nm–900 nm). [ABSTRACT FROM AUTHOR]

Thermal diffusivity (α) of hydrogenated amorphous carbon (a-C:H) thin-films was characterized using the picosecond thermoreflectance measurement technique in the present study. The samples were fabricated in a plasma enhanced chemical vapor deposition system with varying radio frequency (RF) discharge powers from 15 to 70 W. Chemical bonding properties of the a-C:H films were determined from the Fourier transform infrared spectra and Raman spectroscopy. Results show that α is enhanced from 0.07 to 0.20 mm2 s-1 as the RF power increases. It attributes to the dehydrogenation of film resulting from the bombardment of high-energy ion species that breaks C-H bonds at the lower power regime. Particularly at the highest RF power, however, the increase of α is more influenced by the restructuring of bonding configuration associated with the breaking up of sp2 clusters into smaller ones. [ABSTRACT FROM AUTHOR]

We report our study of a silica-water interface using reactive molecular dynamics. This first-of-its-kind simulation achieves length and time scales required to investigate the detailed chemistry of the system. Our molecular dynamics approach is based on the ReaxFF force field of van Duin et al. [J. Phys. Chem. A 107, 3803 (2003)]. The specific ReaxFF implementation (SERIALREAX) and force fields are first validated on structural properties of pure silica and water systems. Chemical reactions between reactive water and dangling bonds on a freshly cut silica surface are analyzed by studying changing chemical composition at the interface. In our simulations, reactions involving silanol groups reach chemical equilibrium in ∼250 ps. It is observed that water molecules penetrate a silica film through a proton-transfer process we call “hydrogen hopping,” which is similar to the Grotthuss mechanism. In this process, hydrogen atoms pass through the film by associating and dissociating with oxygen atoms within bulk silica, as opposed to diffusion of intact water molecules. The effective diffusion constant for this process, taken to be that of hydrogen atoms within silica, is calculated to be 1.68×10-6 cm2/s. Polarization of water molecules in proximity of the silica surface is also observed. The subsequent alignment of dipoles leads to an electric potential difference of ∼10.5 V between the silica slab and water. [ABSTRACT FROM AUTHOR]

Based on density functional theory calculations including an on-site Hubbard U term, we investigate the effect of substrate-induced strain on the properties of ferrimagnetic hematite-ilmenite solid solutions and heterostructures. While the charge compensation mechanism through formation of a mixed Fe2+, Fe3+-contact layer is unaffected, strain can be used to tune the electronic properties of the system, e.g., by changing the position of impurity levels in the band gap. Straining Fe2O3–FeTiO3 films at the lateral lattice parameters of Al2O3(0001), commonly used as a substrate, is found to be energetically unfavorable as compared to films on Fe2O3(0001) or FeTiO3(0001)-substrates. [ABSTRACT FROM AUTHOR]

We use molecular dynamics (MD) with the reactive interatomic potential ReaxFF to characterize the local strains of epitaxial Si/Ge/Si nanoscale bars as a function of their width and height. While the longitudinal strain (along the bars length) is independent of geometry, surface relaxation leads to transverse strain relaxation in the Ge section. This strain relaxation increases with increasing height of the Ge section and reduction in its width and is complete (i.e., zero transverse strain) for roughly square cross sections of Ge leading to a uniaxial strain state. Such strain state is desirable in some microelectronics applications. From the MD results, which are in excellent agreement with experiments, we derive a simple model to predict lateral strain as a function of geometry for this class of nanobars. [ABSTRACT FROM AUTHOR]

A comparative first principles study has been carried out for EuLiH3 (ELH) and EuTiO3 (ETO) using the generalized gradient approximation +U approach. While ELH exhibits ferromagnetic ground state for all volumes, the magnetic ground state of ETO has the tendency to switch from G-type antiferromagnetic to a ferromagnetic state with change in volume. The marked difference in magnetic behavior and magnitude of the nearest neighbors exchange interaction of both the compounds are shown to be related to the difference in their respective electronic structure near the Fermi level. The Ti 3d states are shown to play predominant role in weakening the strength of the exchange interaction in ETO. [ABSTRACT FROM AUTHOR]

The effect of Sb-doping in the Bi-based double perovskite Ba2TbBi1-xSbxO6(x = 0.0, 0.5) on providing a structural and electronic framework for understanding numerous physical aspects at an atomistic level. We study in detail the undoped and Sb-doped Ba2TbBiO6 double perovskite's structural, elastic, mechanical, electronic, and thermodynamic properties for both cubic and monoclinic phases. Doping alters the spatial group structure and lattice constant of Ba2TbBi1−xSbxO6, causing a change in the Brillouin zone, which alters the band structure and bandgap value. The elastic constants confirmed the ductility of the solids and ensured mechanical stability in both phases. This study reveals that both phases of Ba2TbBi1−xSbxO6 are more mechanically stable, ductile, and machinable than Ba2TbBiO6. The Sb-doped monoclinic phase had greater anisotropy than the cubic phase, despite the fact that both phases were anisotropic. Vickers hardness shows that the monoclinic Ba2TbBi1−xSbxO6(x = 0.0, 0.5) phase is harder than the cubic Ba2TbBi1−xSbxO6(x = 0.0, 0.5) phases. The cubic and monoclinic phases of Ba2TbBi0.5Sb0.5O6 have Debye temperatures of 248.48 and 240.75 K, respectively. After doping, the cubic phase's melting temperature (1529.21 K) grows higher than that of the monoclinic phase (1386.87 K). Doping can make a material more stable by lowering its thermal expansion coefficient. Both doped phases can be used as thermal barrier coatings (TBCs). [ABSTRACT FROM AUTHOR]

The analogy between acoustic modes in nonlinear metamaterials and quantum computing platforms constituted of correlated two-level systems opens new frontiers in information science. We use an inductive procedure to demonstrate scalable initialization of and scalable unitary transformations on superpositions of states of multiple correlated logical phi-bits, classical nonlinear acoustic analog of qubits. A multiple phi-bit state representation as a complex vector in a high-dimensional, exponentially scaling Hilbert space is shown to correspond with the state of logical phi-bits represented in a low-dimensional linearly scaling physical space of an externally driven acoustic metamaterial. Manipulation of the phi-bits in the physical space enables the implementation of a non-trivial multiple phi-bit unitary transformation that scales exponentially. This scalable transformation operates in parallel on the components of the multiple phi-bit complex state vector, requiring only a single physical action on the metamaterial. This work demonstrates that acoustic metamaterials offer a viable path toward achieving massively parallel information processing capabilities that can challenge current quantum computing paradigms. [ABSTRACT FROM AUTHOR]

Employing frequency-dependent dielectric susceptibility we characterize the aging in two supercooled liquids, sorbitol and xylitol, below their calorimetric glass transition temperatures. In addition to the alpha relaxation that tracks the structural dynamics, the susceptibility of both liquids possesses a secondary Johari-Goldstein relaxation at higher frequencies. Following a quench through the glass transition, the susceptibility slowly approaches the equilibrium behavior. For both liquids, the magnitude of the Johari-Goldstein relaxation displays a dependence on the time since the quench, or aging time, that is quantitatively very similar to the age dependence of the alpha peak frequency. The Johari-Goldstein relaxation time remains constant during aging for sorbitol while it decreases slightly with age for xylitol. Hence, one cannot sensibly assign a fictive temperature to the Johari-Goldstein relaxation. This behavior contrasts with that of liquids lacking distinct Johari-Goldstein peaks for which the excess wing of the alpha peak tracks the main part of the peak during aging, enabling the assignment of a single fictive temperature to the entire spectrum. The aging behavior of the Johari-Goldstein relaxation time further calls into question the possibility that the relaxation time possesses stronger temperature dependence in equilibrium than is observed in the out-of-equilibrium state below the glass transition. [ABSTRACT FROM AUTHOR]

The linear and nonlinear changes in the refractive index of a Pöschl-Teller quantum well are studied. The Pöschl-Teller potential can easily become asymmetric by a correct choice of its parameter set. We use this feature to investigate the intensity-dependent refractive index of a GaAs quantum well within the density matrix formalism. Numerical results reveal large values of linear and nonlinear changes in the refractive index. [ABSTRACT FROM AUTHOR]

Luminescence and power-gated spectral holeburning studies have been performed on Eu-doped MgS nanoparticles. These particles are atomically tailored to produce and control the relative concentration of Eu2+ and Eu3+, which is necessary for power-gated holeburning. The spectral holes are permanent at low temperatures. Optical studies show that the electron-phonon coupling is stronger in nanoparticles than in thin films or microparticles of the same material. This is the reason for inherently broader spectral holes in nanoparticles as compared to microparticle or thin-film samples. Temperature broadening of spectral holes in nanoparticles follows a T2.4 behavior, a faster rate than thin films or microparticles. This behavior can be attributed to the glassy nature of the particles produced. [ABSTRACT FROM AUTHOR]

We report the development and testing of new integrated cyberinfrastructure for performing free energy simulations with generalized hybrid quantum mechanical/molecular mechanical (QM/MM) and machine learning potentials (MLPs) in Amber. The Sander molecular dynamics program has been extended to leverage fast, density-functional tight-binding models implemented in the DFTB+ and xTB packages, and an interface to the DeePMD-kit software enables the use of MLPs. The software is integrated through application program interfaces that circumvent the need to perform "system calls" and enable the incorporation of long-range Ewald electrostatics into the external software's self-consistent field procedure. The infrastructure provides access to QM/MM models that may serve as the foundation for QM/MM–ΔMLP potentials, which supplement the semiempirical QM/MM model with a MLP correction trained to reproduce ab initio QM/MM energies and forces. Efficient optimization of minimum free energy pathways is enabled through a new surface-accelerated finite-temperature string method implemented in the FE-ToolKit package. Furthermore, we interfaced Sander with the i-PI software by implementing the socket communication protocol used in the i-PI client–server model. The new interface with i-PI allows for the treatment of nuclear quantum effects with semiempirical QM/MM–ΔMLP models. The modular interoperable software is demonstrated on proton transfer reactions in guanine-thymine mispairs in a B-form deoxyribonucleic acid helix. The current work represents a considerable advance in the development of modular software for performing free energy simulations of chemical reactions that are important in a wide range of applications. [ABSTRACT FROM AUTHOR]

The topological characteristics of waves in elastic structures are determined by the geometric phase of waves and, more specifically, by the Berry phase, as a characterization of the global vibrational behavior of the system. A computational procedure for the numerical determination of the geometrical phase characteristics of a general elastic structure is introduced: the spectral analysis of amplitudes and phases method. Molecular dynamics simulation is employed to computationally generate the band structure, traveling modes' amplitudes and phases, and subsequently the Berry phase associated with each band of periodic superlattices. In an innovative procedure, the phase information is used to selectively excite a particular mode in the band structure. It is shown analytically and numerically, in the case of one-dimensional elastic superlattices composed of various numbers of masses and spring stiffness, how the Berry phase varies as a function of the spatial arrangement of the springs. A symmetry condition on the arrangement of springs is established, which leads to bands with Berry phase taking the values of 0 or π. Finally, it is shown how the Berry phase may vary upon application of unitary operations that mathematically describe transformations of the structural arrangement of masses and springs within the unit cells. [ABSTRACT FROM AUTHOR]

Boron nitride nanoscrolls (BNSs) are open-ended, one-dimensional nanostructures made by the process of rolling boron nitride nanosheets into a scroll-like morphology. BNSs offer a high surface area to volume ratio and possess many unique properties (similar to carbon nanotubes, carbon nanoscrolls, and boron nitride nanotubes) such as high resistance to oxidation, chemical stability, increased lubrication, high-temperature resistance, electrical insulation, the ability to cap molecules inside and at the ends, and a wide bandgap regardless of chirality. Despite these attractive features and properties well suited for applications in biotechnology, energy storage, and electronics, the true potential of boron nitride and BNS as the next "miracle material" is yet to be fully explored. In this critical review, we assess, for the first time, various studies published on the formation and structural and dynamic characteristics of BNS; potential routes for BNS synthesis; and the toxicology of BNS. Finally, the future perspectives of BNS are discussed in view of its unique and exceptional candidacy for many (real-world) applications. [ABSTRACT FROM AUTHOR]