Influence of Ag thickness on the structural,optical, and electrical properties of the SnS/Ag/SnS trilayer films for solar cell application

We fabricated the SnS/Ag/SnS (SAS) trilayer thin films by a sputtering method at 200 $°C$. The structural, optical, and electrical properties of the films were studied by varying the Ag interlayer thickness from 9 to 27 nm. The EDS analysis revealed that all SAS trilayer films showed an increase in the atomic percentage of Ag from 1.87 to 6.18. The X-ray diffraction studies confirmed that SAS films with Ag-18 nm thickness showed a preferred (111) peak of the SnS with improved crystallinity. The optical absorption coefficient of the SAS films increased by a factor of 18 when compared to the SnS films without Ag. Also, the optical band gap decreased from 1.53 to 1.28 eV with Ag thickness. All SAS films exhibited the p-type conductivity with increased hole-concentration from 1.94 $\times$ ${10}^{14}$ to 4.15 $\times$${10}^{18}$cm⁻³ and also the mobility from 1.31 to 81.6 cm². V⁻¹s⁻¹.     

An experimental study of coal particle group combustion in conventional and oxy-fuel atmospheres using multi-parameter optical diagnostics

The present work reports an experimental study of particle group combustion of pulverized bituminous coal in laminar flow conditions using advanced multi-parameter optical diagnostics. Simultaneously conducted high-speed scanning OH-LIF, diffuse backlight-illumination (DBI), and Mie scattering measurements enable analyses of three-dimensional volatile flame structures and soot formation in conventional (i.e., N${}_2$/O${}_2$) and oxy-fuel (i.e., CO${}_2$/O${}_2$) atmospheres with increasing O${}_2$ enrichment. Particle-flame interaction is assessed by calculating instantaneous particle number density (PND), whose uncertainties are estimated by generating synthetic particles in DBI image simulations. Time-resolved particle sequences allow the evaluation of the particle velocity, which indicates a PND dependency and interactions between particles and volatile flames. 3D flame structure reconstruction and soot formation detection are first demonstrated in single-shot visualizations and then extended to analyze effects of O${}_2$ concentration, PND, and inert gas composition statistically. The increasing O${}_2$ concentration significantly reduces local flame extinction and suppresses soot formation in N${}_2$ and CO${}_2$ atmospheres. Volatile flames reveal higher intensities and lower lift-off heights as O${}_2$ concentration increases. In contrast to that, an increased PND leads to earlier flame extinction and stronger soot formation due to the local gas temperature reduction and oxygen depletion. The lift-off height reduces with increasing PND, which is explained by the complex interaction between particle dynamics, heat transfer, and volatile reactions. Slightly stronger soot formation and delayed ignition are observed in CO${}_2$ atmospheres, whereas CO${}_2$ replacement reveals insignificant influences on the flame extinction behavior. Finally, non-flammability is quantified for particle group combustion at varying PNDs in different atmospheres.     

Structures,mobilities, electronic and optical properties of two-dimensional α-phase group-VI binary compounds: α-Se2Te and α-SeTe2

Based on the first-principles calculations, we confirm the geometry and electronic structures of two binary group-VI compounds: monolayer α-Se₂Te and α-SeTe₂. The stabilities are confirmed by the cohesive energies, phonon dispersions, and elastic constants. The mechanical properties, strain-stress relationships, and strain-dependent variations of band gaps and band structures are investigated detailed. Furthermore, the high carrier mobilities (up to $5.4\times {10}^3$ cm² V⁻¹ s⁻¹) and optical absorption coefficients (several 10⁵ cm⁻¹) are also exhibited, demonstrating the great application potentials in optoelectronics.     

Effect of bilayer repeats on magnetic properties of Au-buffered Co/Ni multilayers with perpendicular magnetic anisotropy

The effect of bilayer repeats (N) on the static and dynamic magnetic properties of Co/Ni multilayers was investigated. The effective perpendicular magnetic anisotropy constant of multilayers drops from $1.08\times {10}^6$ erg/cm³ to $0.78\times {10}^6$ erg/cm³ with N increasing from 5 to 11. For Co/Ni multilayers with $N\le 7$, sharp magnetization switching was observed. In contrast, Co/Ni multilayers with $N\ge 9$ have a long tail in the hysteresis loop. Ferromagnetic resonance measurements show that intrinsic Gilbert damping changes from 0.021 to 0.016 with increase in N and is inversely proportional to N. This study provides a deep understanding and effective control of magnetic properties of Co/Ni multilayers for spintronics devices.     

Exchange bias behavior and magnetocaloric effect in Ni2In-type Mn7Sn4 alloy

In this work, the exchange bias behavior and magnetocaloric effect have been studied in Mn₇Sn₄ alloy. The X-ray powder diffraction pattern recorded at room temperature indicates that the sample crystallizes in a single phase with Ni₂In-type hexagonal structure (space group $P{6}_3/\mathit{mmc}$). The maximum magnetic entropy change value across paramagnetic/ferrimagnetic transition is about 3.3 J kg⁻¹ K⁻¹ under the magnetic field change of ${\mu }_0\mathrm{\Delta }H=0\text{-}5\text{T}$. With further cooling, the reentrant spin-glass-like state is obtained below 150 K, for which the exchange bias effect has been observed. The exchange bias field is ∼7.8 mT and ∼6.7 mT at $T=10\text{K}$ when the cooling field is ${\mu }_0{H}_{\mathrm{CF}}=0.1\text{T}$ and 0.5 T, respectively. The magnetic behavior and the origin of exchange bias in Mn₇Sn₄ are discussed.     

Motion and swelling of single coal particles during volatile combustion in a laminar flow reactor

Motion and swelling behavior of single bituminous coal particles during volatile combustion are investigated in a laminar flow reactor using a joint experimental and numerical approach. Three different particle samples with mean diameters of 90, 120, and 160 µm are studied in a conventional N${}_2$/O${}_2$ atmosphere with 20 vol% O${}_2$ mole fraction. Diffuse backlight-illumination (DBI) measurements with high temporal (10 kHz) and spatial ($>$ 19 lp/mm) resolutions, combined with detailed parameter evaluation methods, provide fundamental insights into interactions of particle with flow and flame. The acceleration behavior of different particles is assessed based on the response time following the viscosity drag law. Rotation speed is determined by temporally tracking the orientation angle and shown to strongly correlate with the particle size and the devolatilization process. Simultaneously measured slip velocity and particle diameter enable evaluating time-dependent particle Reynolds numbers $R{e}_{\mathrm{p}}$. The swelling behavior is temporally synchronized with the devolatilization process and reveals a strong dependency on particle diameters. To better understand experimental observations, detailed simulations are first quantitatively validated against experimental ignition delay times and then applied to predict particle temperature histories. Further, the reduction of particle heating rates with increasing diameters is numerically quantified. The maximum swelling ratio decreases from 1.22 to 1.07 as the heating rate increases from approximately 3 $\times$ 10${}^4$ to 8 $\times$ 10${}^4$ K/s.     

Fractional spin-vortex states in F = 2 spinor Bose-Einstein condensates

Stable fractional vortices are numerically generated in the two-dimensional rotating $F=2$ spinor Bose-Einstein condensates. We demonstrate the existence of $\frac{1}{4}$-vortex state or $\frac{1}{2}$-vortex state in the biaxial nematic phase, and $\frac{1}{3}$-vortex state in the cyclic phase. At fast rotation a lattice of fractional vortex in the spin space emerges. Intriguingly, the integral spin-winding of the whole system does not increase with the rotation speed but equals to a simple fraction.     

Monte Carlo simulation of electric conductivity for pure and doping fullerene (C60)

In this paper, we have used Monte Carlo (MC) method to simulate and study the temperature and doping effects on the electric conductivity of fullerene (C60). The results show that the band gap has reduced by the doping and the charge carrier transport is facilitated from valence band to conduction band by the temperature where is touched a 300 K. In this case, the conductivity reached a value of $4\times {10}^{-7}\text{S}{\text{cm}}^{-1}$. The electric conductivity of C60 can increase by the triphenylmethane dye crystal violet (CV) alkali metal to reach $4\times {10}^{-3}\text{S}{\text{cm}}^{-1}$ at 303 K. Our results of MC simulation have a good agreement with those extracted from literature [10], [33].     

Composition law for the Cole-Cole relaxation and ensuing evolution equations

Physically natural assumption says that any relaxation process taking place in the time interval $[t_0,t_2]$, $t_2>t_0\ge 0$ may be represented as a composition of processes taking place during time intervals $[t_0,t_1]$ and $[t_1,t_2]$ where $t_1$ is an arbitrary instant of time such that $t_0\le t_1\le t_2$. For the Debye relaxation such a composition is realized by usual multiplication which claim is not valid any longer for more advanced models of relaxation processes. We investigate the composition law required to be satisfied by the Cole-Cole relaxation and find its explicit form given by an integro-differential relation playing the role of the time evolution equation. The latter leads to differential equations involving fractional derivatives, either of the Caputo or the Riemann-Liouville senses, which are equivalent to the special case of the fractional Fokker-Planck equation satisfied by the Mittag-Leffler function known to describe the Cole-Cole relaxation in the time domain.     

Synthesis and microwave dielectric properties of an electronic ceramic Y2WO6 for wireless communications

Y₂WO₆ ceramics were fabricated via a solid-state reaction method and investigated structure stability, densification, microstructure, and dielectric properties at microwave frequency range. Y₂WO₆ crystallized in a monoclinic structure and stabilized to 1500 ^∘C, beyond which the decomposition of Y₆WO₁₂ occurred. Y₂WO₆ ceramic could be sintered into a compact bulk at 1450 ^∘C, which was characterized by a high relative density ∼ 97.6% and a dense microstructure. The favorable dielectric performances were achieved at 1450 ^∘C with a relative permittivity ${\epsilon }_r\sim 11.4$, a quality factor $Q\times f\sim 42,380$ GHz ($f=8.6$ GHz), and a temperature coefficient of resonant frequency ${\tau }_f\sim -49.0$ ppm/^∘C. The MW properties of Y₂WO₆ suggest that it could be useful candidate material for low-loss dielectric resonators.     

Magneto-transport properties in fcc ytterbium

Electron-hole compensation in a heavy rare-earth, ytterbium (Yb), was investigated by room-temperature galvanomagnetic measurements and a two-band model analysis. Face-centered cubic (fcc) Yb films were prepared by a molecular-beam technique. Transverse magnetoresistance (MR) and Hall resistivity (HR) measurements were performed on the fcc Yb film at room temperature. Transverse MR showed a quadratic behavior under magnetic fields up to ±5 T, whereas the HR had linear characteristics and a positive Hall coefficient. The experimental results are quantitatively explained by a two-band model with nearly identical carrier density ($\sim 1\times {10}^{21}$ cm⁻³) and mobility (∼70–80 cm² V⁻¹ s⁻¹) of electrons and holes. The positive Hall coefficient observed is explained by a slightly greater hole density and/or mobility compared with those of electrons.     

Study of the q-Gaussian distribution with the scale index and calculating entropy by normalized inner scalogram

In this paper, we discuss a method based on wavelet analysis for the study of the q-index of the Gaussian distribution. We derive q-index from the scale index, $i_{\mathit{scale}}$, using the expression; $q\equiv 1+2i_{\mathit{scale}}$ where $i_{\mathit{scale}}$ is a wavelet based tool for measuring the degree of aperiodicity of a dynamical system in the range of $0\le i_{\mathit{scale}}\le 1$. We show that this expression gives consistent results with the numerical approach of q-Gaussian distribution which determines the degree of non-extensivity of a dynamical system in the range of $1<q<3$. We also suggest a new entropy calculation method based on the normalized inner scalogram for studying the chaotic characteristics of nonlinear dynamical systems.