MULTIPLE SCATTERING THEORY OF EFFECTIVE MECHANICAL PROPERTIES OF INHOMOGENEOUS MEDIA

The rate of hydrothermal reaction of SiO_2 and/or A1_2O_3 in the system of CaO-Al_2O_3-SiO_2-H_2O at 200℃ and the factors which influence the reactions are investigated by determining the reaction ratio.The rate of reactions depends on the reactive activities of raw materials, initial composition of mixture and relative activity of SiO_2 and A12O3. The hydrothermal reaction can be accelerated by sodium hydroxide,in the case of silica,which has low activity, this is quite obvious.

Sound Scattering From Rough Bubbly Ocean Surface Based on Modified Sea Surface Acoustic Simulator and Consideration of Various Incident Angles and Sub-surface Bubbles＇ Radii

The aim of the present study is to improve the capabilities and precision of a recently introduced Sea Surface Acoustic Simulator(SSAS) developed based on optimization of the Helmholtz–Kirchhoff–Fresnel(HKF) method. The improved acoustic simulator, hereby known as the Modified SSAS(MSSAS), is capable of determining sound scattering from the sea surface and includes an extended Hall–Novarini model and optimized HKF method. The extended Hall–Novarini model is used for considering the effects of sub-surface bubbles over a wider range of radii of sub-surface bubbles compared to the previous SSAS version. Furthermore, MSSAS has the capability of making a three-dimensional simulation of scattered sound from the rough bubbly sea surface with less error than that of the Critical Sea Tests(CST) experiments. Also, it presents scattered pressure levels from the rough bubbly sea surface based on various incident angles of sound. Wind speed, frequency, incident angle, and pressure level of the sound source are considered as input data, and scattered pressure levels and scattering coefficients are provided. Finally, different parametric studies were conducted on wind speeds, frequencies, and incident angles to indicate that MSSAS is quite capable of simulating sound scattering from the rough bubbly sea surface, according to the scattering mechanisms determined by Ogden and Erskine. Therefore, it is concluded that MSSAS is valid for both scattering mechanisms and the transition region between them that are defined by Ogden and Erskine.

Conduction Properties and Scattering Mechanisms in F-doped Textured Transparent Conducting SnO_2 Films Deposited by APCVD

Transparent conducting F-doped texture SnO2 films with resistivity as low as 5× 10-4 Ω ·cm,with carrier concentrations between 3.5 × 1020 and 7× 1020 cm-3 and Hall mobilities from 15.7 to 20.1 cm2/(V/s) have been prepared by atmosphere pressure chemical vapour deposition (APCVD). These polycrystalline films possess a variable preferred orientation, the polycrystallite sizes and orientations vary with substrate temperature. The substrate temperature and fluorine flow rate dependence of conductivity, Hall mobility and carrier conentration fOr the resultingfilms have been obtained. The temperature dependence of the mobiity and carrier concentrationhave been measured over a temperature range 16～400 K. A systematically theoretical analysis on scattering mechanisms for the highly conductive SnO2 films has been given. Both theoretical analysis and experimental results indicate that for these degenerate, polycrystalline SnO2 ：F films in the low temperature range (below 100 K), ionized impurity scattering is main scattering mechanism. However, when the temperature is higher than 100 K, the lattice vibration scattering becomes dominant. The grain boundary scattering makes a small contribution to limit the mobility of the films.

Hole transport and phonon scattering in epitaxial PbSe films

The combined characterizations of mobility and phonon scattering spectra allow us to probe hole transport process in epitaxial PbSe crystalline films grown by molecular beam epitaxy (MBE). The measurements of Hall effect show p-type con- ductivity of PbSe epitaxial films. At 295 K, the PbSe samples display hole concentrations of (5～8)×1017 cm–3 with mobilities of about 300 cm2/(V·s), and at 77 K the hole mobility is as high as 3×103 cm2/(V·s). Five scattering mechanisms limiting hole mobilities are theoretically analyzed. The calculations and Raman scattering measurements show that, in the temperatures between 200 and 295 K, the scattering of polar optical phonon modes dominates the impact on the observed hole mobility in the epitaxial PbSe films. Raman spectra characterization observed strong optical phonon scatterings at high temperature in the PbSe epitaxial films, which is consistent with the result of the measured hole mobility.

Symmetry-constrained quantum coupling in non-Fermi-liquid transport

Finding the common origin of non-Fermi liquids(NFLs) transport in high-temperature superconductors(HTSCs)has proven to be fundamentally challenging due to the prominence of various collective fluctuations.Here,we propose a comprehensive non-Hermitian Hamiltonian(NHH) for quantum coupling of multiple scattering mechanisms associated with four types of order fluctuations.It predicts that the anticommutation symmetry of the spinor fermions constrains the scattering rate to a unified quadrature scaling,i.e.,Γ=Γ_(1)+√Γ_(Q)^(2)+(μk_(B)T)^(2)+(vμ_(B)B)^(2)+(γ_(E)E)^(2).This scaling yields a comprehensive and accurate description of two widespread NFL behaviors in HTSCs,i.e.,a temperature-scaling crossover between quadratic and linear laws and the quadrature magnetoresistance,validated by several dozens of data sets for broad phase regimes.It reveals that the common origin of these behaviors is the spinor-symmetry-constrained quantum coupling of spin-wave and topological excitations of mesoscopic orders.Finally,we show that this NHH can be easily extended to other complex quantum fluids by specifying the corresponding symmetries.It is concluded that this work uncovers a critical organization principle(i.e.,the spinor symmetry) underlying the NFL transport,thus providing a novel theoretical framework to advance the transport theory of correlated electron systems.

Carrier behavior of Hg Te under high pressure revealed by Hall effect measurement

We investigate the carrier behavior of HgTe under high pressures up to 23 GPa using in situ Hall effect measurements. As the phase transitions from zinc blende to cinnabar, then to rock salt, and finally to Cmcm occur, all the parameters change discontinuously. The conductivity variation under compression is described by the carrier parameters. For the zinc blende phase, both the decrease of carrier concentration and the increase of mobility indicate the overlapped valence band and conduction band separates with pressure. Pressure causes an increase in the hole concentration of HgTe in the cinnabar phase, which leads to the carrier-type inversion and the lowest mobility at 5.6 GPa. In the phase transition process from zinc blende to rock salt, Te atoms are the major ones in atomic movements in the pressure regions of 1.0-1.5 GPa and 1.8-3.1 GPa, whereas Hg atoms are the major ones in the pressure regions of 1.5-1.8 GPa and 3.1-7.7 GPa. The polar optical scattering of the rock salt phase decreases with pressure.

Fang-Howard wave function modelling of electron mobility in AlInGaN/AlN/InGaN/GaN double heterostructures

To study the electron transport properties in InGaN channel-based heterostructures,a revised Fang-Howard wave function is proposed by combining the effect of GaN back barrier.Various scattering mechanisms,such as dislocation impurity(DIS)scattering,polar optical phonon(POP)scattering,piezoelectric field(PE)scattering,interface roughness(IFR)scattering,deformation potential(DP)scattering,alloy disorder(ADO)scattering from InGaN channel layer,and temperature-dependent energy bandgaps are considered in the calculation model.A contrast of AlInGaN/AlN/InGaN/GaN double heterostructure(DH)to the theoretical AlInGaN/AlN/InGaN single heterostructure(SH)is made and analyzed with a full range of barrier alloy composition.The effect of channel alloy composition on InGaN channel-based DH with technologically important Al(In,Ga)N barrier is estimated and optimal indium mole fraction is 0.04 for higher mobility in DH with Al_(0.4)In_(0.07)Ga_(0.53)N barrier.Finally,the temperature-dependent two-dimensional electron gas(2DEG)density and mobility in InGaN channel-based DH with Al_(0.83)In_(0.13)Ga_(0.04)N and Al_(0.4)In_(0.07)Ga_(0.53)N barrier are investigated.Our results are expected to conduce to the practical application of InGaN channel-based heterostructures.

Spin Polarizations of Electron with Rashba Couplings in T-Shaped Devices:A Finite Element Approach

A generalized finite element formulation is proposed for the study of the spin-dependent ballistic transport of electron through the two-dimensional quantum structures with Rashba spin-orbit interactions （SOI）. The transmission coefficient, conductance, the total and local polarization are numerically calculated and discussed as the Rashba eoefficient, the geometric sizes, and incident energy are changed in the T-shaped devices. Some interesting features are found in the proper parameter regime. The polarization has an enhancement as the Rashba coefficient becomes stronger. The polarization valley is rigid in the regime of the conductance plateaus since the local interference among the polarized multi-wave modes. The Rashba interactions coupling to geometry in sizes could form the structure-induced Fano-Rashba resonance. In the wider stub, the localized spin lattice of electron could be produced. The conductance plateaus correspond to weak polarizations. Strong polarizations appear when the stub sizes, incident energy, and the Rashba coupling coefficient are matched. The resonances are formed in a wide Fermi energy segment easily.

Electrical and optical properties of hydrogen plasma treatedβ-Ga_(2)O_(3) thin films

The behavior of H inβ-Ga_(2)O_(3) is of substantial interest because it is a common residual impurity that is present inβ-Ga_(2)O_(3),regardless of the synthesis methods.Herein,we report the influences of H-plasma exposure on the electric and optical properties of the heteroepitaxialβ-Ga_(2)O_(3) thin films grown on sapphire substrates by chemical vapor deposition.The results in-dicate that the H incorporation leads to a significantly increased electrical conductivity,a greatly reduced defect-related photolu-minescence emission,and a slightly enhanced transmittance,while it has little effect on the crystalline quality of theβ-Ga_(2)O_(3) films.The significant changes in the electrical and optical properties ofβ-Ga_(2)O_(3) may originate from the formation of shallow donor states and the passivation of the defects by the incorporated H.Temperature dependent electrical properties of the H-in-corporatedβ-Ga_(2)O_(3) films are also investigated,and the dominant scattering mechanisms at various temperatures are dis-cussed.

GTD MODEL-BASED TIME-SHIFT INVARIANT TARGET IDENTIFICATION USING MATCHING PURSUITS AND LIKELIHOOD RATIO TESTS

In order to improve the identification capability of ultra wide-band radar,this paper in-troduces a step-variant multiresolution approach for the time-shift parameter estimation. Subsequently,combining with the approach,a Geometrical Theory of Diffraction(GTD) model-based time-shift Invariant method to target identification using Matching Pursuits and Likelihood Ratio Test(IMPLRT) is developed. Simulation results using measured scattering signatures of two targets in an ultra wide-band chamber are presented contrasting the performance of the IMPLRT to the Wang's MPLRT technique.

Elevating the comprehensive thermal properties of rare-earth cerates through high-entropy design

In the rapidly evolving aerospace sector,the quest for sophisticated thermal barrier coating(TBC)materials has intensified.These materials are primarily sought for their superior comprehensive thermal characteristics,which include a low thermal conductivity coupled with a high coefficient of thermal expansion(CTE)that synergizes with the substrate.In our study,we adopt a solid-state method to synthesize a series of high-entropy rare-earth cerates:La_(2)Ce_(2)O_(7)(1RC),(La_(1/2)Nd_(1/2))2Ce_(2)O_(7)(2RC),(La_(1/3)Nd_(1/3)Sm_(1/3))_(2)Ce_(2)O_(7)(3RC),(La_(1/4)Nd_(1/4)Sm_(1/4)Eu_(1/4))_(2)Ce_(2)O_(7)(4RC),and(La_(1/5)Nd_(1/5)Sm_(1/5)Eu_(1/5)Gd_(1/5))_(2)Ce_(2)O_(7)(5RC),all sintered at 1,600℃ for 10 h.We thoroughly examine their phase structure,morphology,elemental distribution,and thermal properties.Our in-depth analysis of the phonon scattering mechanisms reveals that 4RC and 5RC exhibit exceptional thermal properties:high CTEs of 13.00×10^(−6) K^(−1) and 12.77×10^(−6) K^(−1) at 1,400℃,and low thermal conductivities of 1.55 W/(m·K)and 1.68 W/(m·K)at 1,000℃,respectively.Compared to other TBC systems,4RC and 5RC stand out for their excellent thermal characteristics.This study significantly contributes to the development of high-entropy oxides for TBC applications.

Advances and prospects in SAR microwave vision three-dimensional imaging

Synthetic Aperture Radar three-dimensional(3D)imaging enables the acquisition of more comprehensive information,making it a recent hotspot in radar imaging.Traditional 3D imaging methods have evolved from 2D and interferometric imaging,combining elevation aperture extension with signal processing techniques.Limitations such as long acquisition or complex system from its imaging mechanism restrict its application.In recent years,rapid development of artificial intelligence has led to a swift advancement in radar,injecting new vitality into SAR 3D imaging.SAR microwave vision 3D imaging theory,which is built upon advanced technologies,has emerged as a new interdisciplinary field for radar imaging.This paper reviews SAR 3D imaging’s history and present situation,and introduces SAR microwave vision.We establish a theoretical framework covering representation models,computational models,processing paradigms and evaluation systems.Additionally,our research progress in this area is discussed,along with future prospects for SAR microwave vision 3D imaging.

Non-Relativistic Phase Shifts for Scattering on Generalized Radial Yukawa Potentials

Non-relativistic phase shifts for a generalized Yukawa potential V(r) =-V_0( e^(-αr)/r)-V_1( e^(-2αr)/r^2) are studied by the amplitude-phase method and by a frequently used analytic method based on a Pekeris-type approximation of power-law potential terms.Small variations of V_1 seem to have marginal effects on the effective potential and on exact phase shifts.However,as pointed out in this study,a Pekeris-type approximation in scattering applications often implies serious distortions of both effective potentials and phase shifts.The Pekeris-type based analytic approximation in this study seems to give low-quality scattering results for this model potential at low energies.

Epitaxial growth of large area ZrS_(2)2D semiconductor films on sapphire for optoelectronics

Recently,group-IVB semiconducting transition metal dichalcogenides(TMDs)of ZrS_(2) have attracted significant research interest due to its layered nature,moderate band gap,and extraordinary physical properties.Most device applications require a deposition of high quality large-area uniform ZrS_(2) single crystalline films,which has not yet been achieved.In this work,for the first time,we demonstrate the epitaxial growth of high quality large-area uniform ZrS_(2) films on c-plane sapphire substrates by chemical vapor deposition.An atomically sharp interface is observed due to the supercell matching between ZrS_(2) and sapphire,and their epitaxial relationship is found to be ZrS_(2)(0001)[1010]||Al_(2)O_(3)(0001)[1120].The epitaxial ZrS_(2) film exhibits n-type semiconductor behavior with a room temperature mobility of 2.4 cm^(2)·V^(−1)·s^(−1),and the optical phonon is the dominant scattering mechanism at room temperature or above.Furthermore,the optoelectronic applications of ZrS_(2) films are demonstrated by fabricating photodetector devices.The ZrS_(2) photodetectors exhibit the excellent comprehensive performance,such as a light on/off ratio of 106 and a specific detectivity of 2.6×10^(12) Jones,which are the highest values compared with the photodetectors based on other group-IVB two-dimensional TMDs.

A physical model of hole mobility for germanium-on-insulator pMOSFETs

A physical model of hole mobility for germanium-on-insulator p MOSFETs is built by analyzing all kinds of scattering mechanisms, and a good agreement of the simulated results with the experimental data is achieved, confirming the validity of this model. The scattering mechanisms involved in this model include acoustic phonon scattering, ionized impurity scattering, surface roughness scattering, coulomb scattering and the scattering caused by Ge film thickness fluctuation. The simulated results show that the coulomb scattering from the interface charges is responsible for the hole mobility degradation in the low-field regime and the surface roughness scattering limits the hole mobility in the high-field regime. In addition, the effects of some factors, e.g. temperature, doping concentration of the channel and the thickness of Ge film, on degradation of the mobility are also discussed using the model, thus obtaining a reasonable range of the relevant parameters.