Consecutive induction melting of nickel-based superalloy in electrode induction gas atomization
The crucible-free electrode induction melting gas atomization (EIGA) technology is an advanced technology for preparing ultra-clean nickel-based superalloy powders. One of the key issues for fabricating powders with high quality and yield is the consecutive induction melting of a superalloy electrode. The coupling of a superalloy electrode and coil, frequency, output power, and heat conduction are investigated to improve the controllable electrode induction melting process. Numerical simulation results show that when the coil frequency is 400 kHz, the output power is 100 kW, superalloy liquid flow with a diameter of about 5 mm is not consecutive. When the coil frequency is reduced to 40 kHz, the output power is 120 kW, superalloy liquid flow is consecutive, and its diameter is about 7 mm.
Determination of the vapor-liquid transition of square-well particles using a novel generalized-canonical-ensemble-based method
The square-well (SW) potential is one of the simplest pair potential models and its phase behavior has been clearly revealed, therefore it has become a benchmark for checking new theories or numerical methods. We introduce the generalized canonical ensemble (GCE) into the isobaric replica exchange Monte Carlo (REMC) algorithm to form a novel isobaric GCE-REMC method, and apply it to the study of vapor-liquid transition of SW particles. It is validated that this method can reproduce the vapor-liquid diagram of SW particles by comparing the estimated vapor-liquid binodals and the critical point with those from the literature. The notable advantage of this method is that the unstable vapor-liquid coexisting states, which cannot be detected using conventional sampling techniques, are accessed with a high sampling efficiency. Besides, the isobaric GCE-REMC method can visit all the possible states, including stable, metastable or unstable states during the phase transition over a wide pressure range, providing an effective pathway to understand complex phase transitions during the nucleation or crystallization process in physical or biological systems.
Solvability of a class of PT-symmetric non-Hermitian Hamiltonians: Bethe ansatz method
Approximate energies and thermal properties of a position-dependent mass charged particle under external magnetic fields
We solve the Schrödinger equation with a position-dependent mass (PDM) charged particle interacted via the superposition of the Morse-plus-Coulomb potentials and is under the influence of external magnetic and Aharonov-Bohm (AB) flux fields. The nonrelativistic bound state energies together with their wave functions are calculated for two spatially-dependent mass distribution functions. We also study the thermal quantities of such a system. Further, the canonical formalism is used to compute various thermodynamic variables for second choosing mass by using the Gibbs formalism. We give plots for energy states as a function of various physical parameters. The behavior of the internal energy, specific heat, and entropy as functions of temperature and mass density parameter in the inverse-square mass case for different values of magnetic field are shown.
Generating EPR-entangled mechanical state via feeding finite-bandwidth squeezed light
Performance analysis of quantum access network using code division multiple access model
Realization of quantum permutation algorithm in high dimensional Hilbert space
Fast generating W state of three superconducting qubits via Lewis-Riesenfeld invariants
Multi-copy entanglement purification with practical spontaneous parametric down conversion sources
Superconducting phase qubits with shadow-evaporated Josephson junctions
Gravitational quasi-normal modes of static R2 Anti-de Sitter black holes
Equilibrium dynamics of the sub-Ohmic spin-boson model under bias
Using the bosonic numerical renormalization group method, we studied the equilibrium dynamical correlation function C(ω) of the spin operator σz for the biased sub-Ohmic spin-boson model. The small-ω behavior C(ω)∝ωs is found to be universal and independent of the bias ε and the coupling strength α (except at the quantum critical point α=αc and ε=0). Our NRG data also show C(ω)∝χ2ωs for a wide range of parameters, including the biased strong coupling regime (ε≠0 and α > αc), supporting the general validity of the Shiba relation. Close to the quantum critical point αc, the dependence of C(ω) on α and ε is understood in terms of the competition between ε and the crossover energy scale ω0* of the unbiased case. C(ω) is stable with respect to ε for ε≪ε*. For ε≫ε*, it is suppressed by ε in the low frequency regime. We establish that ε*∝(ω0*)1/θ holds for all sub-Ohmic regime 0≤s < 1, with θ=2/(3s) for 0 < s≤1/2 and θ=2/(1+s) for 1/2 < s < 1. The variation of C(ω) with α and ε is summarized into a crossover phase diagram on the α-ε plane.
Dynamical correlation functions of the quadratic coupling spin-Boson model
The spin-boson model with quadratic coupling is studied using the bosonic numerical renormalization group method. We focus on the dynamical auto-correlation functions CO(ω), with the operator Ô taken as σx, σz, and X, respectively. In the weak-coupling regime α < αc, these functions show power law ω-dependence in the small frequency limit, with the powers 1+2s, 1+2s, and s, respectively. At the critical point α=αc of the boson-unstable quantum phase transition, the critical exponents yO of these correlation functions are obtained as yσx=yσz=1-2s and yX=-s, respectively. Here s is the bath index and X is the boson displacement operator. Close to the spin flip point, the high frequency peak of Cσx(ω) is broadened significantly and the line shape changes qualitatively, showing enhanced dephasing at the spin flip point.
Attempt to generalize fractional-order electric elements to complex-order ones
Anisotropic total variation minimization approach in in-line phase-contrast tomography and its application to correction of ring artifacts
Visibility enhancement in two-dimensional lensless ghost imaging with true thermal light
We report an experimental demonstration of two-dimensional (2D) lensless ghost imaging with true thermal light. An electrodeless discharge lamp with a higher light intensity than the hollow cathode lamp used before is employed as a light source. The main problem encountered by the 2D lensless ghost imaging with true thermal light is that its coherence time is much shorter than the resolution time of the detection system. To overcome this difficulty we derive a method based on the relationship between the true and measured values of the second-order optical intensity correlation, by which means the visibility of the ghost image can be dramatically enhanced. This method would also be suitable for ghost imaging with natural sunlight.
Theoretical investigation on radiation tolerance of Mn+1AXn phases
Ternary Mn+1AXn phases with layered hexagonal structures, as candidate materials used for next-generation nuclear reactors, have shown great potential in tolerating radiation damage due to their unique combination of ceramic and metallic properties. However, Mn+1AXn materials behave differently in amorphization when exposed to energetic neutron and ion irradiations in experiment. We first analyze the irradiation tolerances of different Mn+1AXn (MAX) phases in terms of electronic structure, including the density of states (DOS) and charge density map. Then a new method based on the Bader analysis with the first-principle calculation is used to estimate the stabilities of MAX phases under irradiation. Our calculations show that the substitution of Cr/V/Ta/Nb by Ti and Si/Ge/Ga by Al can increase the ionicities of the bonds, thus strengthening the radiation tolerance. It is also shown that there is no obvious difference in radiation tolerance between Mn+1ACn and Mn+1ANn due to the similar charge transfer values of C and N atoms. In addition, the improved radiation tolerance from Ti3AlC2 to Ti2AlC (Ti3AlC2 and Ti2AlC have the same chemical elements), can be understood in terms of the increased Al/TiC layer ratio. Criteria based on the quantified charge transfer can be further used to explore other Mn+1AXn phases with respect to their radiation tolerance, playing a critical role in choosing appropriate MAX phases before they are subjected to irradiation in experimental test for future nuclear reactors.
Optical sensors based on the NiPc–CoPc composite films deposited by drop casting and under the action of centrifugal force
Design and characterization of a 3D encapsulation with silicon vias for radio frequency micro-electromechanical system resonator
Co-focus experiment of segmented mirror
Structural optimization of Au-Pd bimetallic nanoparticles with improved particle swarm optimization method
Difference scattering field properties between periodic defect particles and three-dimensional slightly rough optical surface
Based on the practical situation of nondestructive examination, the calculation model of the composite scattering is established by using a three-dimensional half-space finite difference time domain, and the Monte Carlo method is used to solve the problem of the optical surface with roughness in the proposed scheme. Moreover, the defect particles are observed as periodic particles for a more complex situation. In order to obtain the scattering contribution of defects inside the optical surface, a difference radar cross section is added into the model to analyze the selected calculations on the effects of numbers, separation distances, different depths and different materials of defects. The effects of different incident angles are also discussed. The numerical results are analyzed in detail to demonstrate the best position to find the defects in the optical surface by detecting in steps of a fixed degree for the incident angle.
Effect of atmospheric turbulence on entangled orbital angular momentum three-qubit state
Investigation of the nonlinear CPT spectrum of 87Rb and its application for large dynamic magnetic measurement
The coherent population trapping (CPT) phenomenon has found widespread application in quantum precision measurements. Various designs based on the narrow resonant spectrum corresponding to the linear Zeeman effect have been demonstrated to achieve high performance. In this article, the nonlinear Zeeman split of the CPT spectrum of 87Rb in the lin||lin setup is investigated. We observe re-split phenomenon for both magnetic sensitive and magnetic insensitive CPT resonant lines at a large magnetic field. The re-split in the magnetic sensitive lines raises a practical problem to magnetometers worked in the lin||lin setup while the other one shows a good potential for applications in large magnetic field. We propose a design based on the nonlinear split of the magnetic insensitive lines and test its performance. It provides a much larger measurement range compared to the linear one, offering an option for atomic magnetometers where a large dynamic range is preferred.
Enhanced thermal stability of VCSEL array by thermoelectric analysis-based optimization of mesas distribution
The thermal stability of a vertical-cavity surface-emitting laser (VCSEL) array is enhanced by redesigning the mesa arrangement. Based on a thermoelectric coupling three-dimensional (3D) finite-element model, an optimized VCSEL array is designed. The effects of this optimization are studied experimentally. Power density characteristics of VCSEL arrays with different mesa configuration are obtained under different thermal stress in which the optimized device shows improved performance. Optimized device also shows better stability from measured spectra and calculated thermal resistances. The experimental results prove that our simulation model and optimization is instructive for VCSEL array design.
Enhancement of multiple four-wave mixing via cascaded fibers with discrete dispersion decreasing
Cascaded fiber geometry with the dispersion of each fiber decreasing is proposed to enhance the multiple four-wave mixing (FWM) generation. The first fiber with relatively large dispersion initiates and accelerates the expansion of multiple FWM, and the second fiber with small dispersion would allow the phase-matching process (thus the spectrum broadening) to keep going. Numerical and experimental results show that with this geometry not only multiple FWM expansion can be accelerated, but also the efficiency of multiple FWM products can be effectively improved with shorter fibers.
Optical pulse evolution in the presence of a probe light in CW-pumped nonlinear fiber
Wavelength modulation spectroscopy for measurements of gas parameters in combustion field
Generation of femtosecond laser pulses at 263 nm by K3B6O10Cl crystal
The third harmonic generation (THG) of a linear cavity Ti:sapphire regenerative amplifier by use of a K3B6O10Cl (KBOC) crystal is studied for the first time. Output power up to 5.9 mW is obtained at a central wavelength of 263 nm, corresponding to a conversion efficiency of 4.5% to the second harmonic power. Our results show a tremendous potential for nonlinear frequency conversion into the deep ultraviolet range with the new crystal and the output laser power can be further improved.
Design of tunable surface mode waveguide based on photonic crystal composite structure using organic liquid
Adaptive optimization on ultrasonic transmission tomography-based temperature image for biomedical treatment
Hyperthermia has proven to be beneficial to treating superficial malignancies, particularly chest wall recurrences of breast cancer. During hyperthermia, monitoring the time-temperature profiles in the target and surrounding areas is of great significance for the effect of therapy. An ultrasound-based temperature imaging method has advantages over other approaches. When the temperature around the tumor is calculated by using the propagation speed of ultrasound, there always exist overshoot artifacts along the boundary between different tissues. In this paper, we present a new method combined with empirical mode decomposition (EDM), similarity constraint, and continuity constraint to optimize the temperature images. Simulation and phantom experiment results compared with those from our previously proposed method prove that the EMD-based method can build a better temperature field image, which can adaptively yield better temperature images with less computation for assistant medical treatment control.
Density and temperature reconstruction of a flame-induced distorted flow field based on background-oriented schlieren (BOS) technique
Equation of state for warm dense lithium: A first principles investigation
Simulations of the effects of density and temperature profile on SMBI penetration depth based on the HL-2A tokamak configuration
Drift vortices in inhomogeneous collisional dusty magnetoplasma
Generation of high quality ion beams through the stable radiation pressure acceleration of the near critical density target
Modeling and optimization of the multichannel spark discharge
This paper reports a novel analytic model of this multichannel spark discharge, considering the delay time in the breakdown process, the electric transforming of the discharge channel from a capacitor to a resistor induced by the air breakdown, and the varying plasma resistance in the discharge process. The good agreement between the experimental and the simulated results validated the accuracy of this model. Based on this model, the influence of the circuit parameters on the maximum discharge channel number (MDCN) is investigated. Both the input voltage amplitude and the breakdown voltage threshold of each discharge channel play a critical role. With the increase of the input voltage and the decrease of the breakdown voltage, the MCDN increases almost linearly. With the increase of the discharge capacitance, the MDCN first rises and then remains almost constant. With the increase of the circuit inductance, the MDCN increases slowly but decreases quickly when the inductance increases over a certain value. There is an optimal value of the capacitor connected to the discharge channel corresponding to the MDCN. Finally, based on these results, to shorten the discharge time, a modified multichannel discharge circuit is developed and validated by the experiment. With only 6-kV input voltage, 31-channels discharge is achieved. The breakdown voltage of each electrode gap is larger than 3 kV. The modified discharge circuit is certain to be widely used in the PSJA flow control field.
Comparison benchmark between tokamak simulation code and TokSys for Chinese Fusion Engineering Test Reactor vertical displacement control design
Numerical study on the discharge characteristics and nonlinear behaviors of atmospheric pressure coaxial electrode dielectric barrier discharges
Effect of driving frequency on the structure of silicon grown on Ag (111) films by very-high-frequency magnetron sputtering
The effect of driving frequency on the structure of silicon grown on Ag (111) film is investigated, which was prepared by using the very-high-frequency (VHF) (40.68 MHz and 60 MHz) magnetron sputtering. The energy and flux density of the ions impinging on the substrate are also analyzed. It is found that for the 60-MHz VHF magnetron sputtering, the surface of silicon on Ag (111) film exhibits a small cone structure, similar to that of Ag (111) film substrate, indicating a better microstructure continuity. However, for the 40.68-MHz VHF magnetron sputtering, the surface of silicon on Ag (111) film shows a hybrid structure of hollowed-cones and hollowed-particles, which is completely different from that of Ag (111) film. The change of silicon structure is closely related to the differences in the ion energy and flux density controlled by the driving frequency of sputtering.
Serrated magnetic properties in metallic glass by thermal cycle
Fe-based metallic glasses (MGs) with excellent soft magnetic properties are applicable in a wide range of electronic industry. We show that the cryogenic thermal cycle has a sensitive effect on soft magnetic properties of Fe78Si9B13 glassy ribbon. The values of magnetic induction (or magnetic flux density) B and coercivity Hc show fluctuation with increasing number of thermal cycles. This phenomenon is explained as thermal-cycle-induced stochastically structural aging or rejuvenation which randomly fluctuates magnetic anisotropy and, consequently, the magnetic induction and coercivity. Overall, increasing the number of thermal cycles improves the soft magnetic properties of the ribbon. The results could help understand the relationship between relaxation and magnetic property, and the thermal cycle could provide an effective approach to improving performances of metallic glasses in industry.
Label-free tungsten disulfide quantum dots as a fluorescent sensing platform for highly efficient detection of copper (II) ions
A fluorescent probe for the sensitive and selective determination of copper ion (Cu2+) is presented. It is based on the use of tungsten disulfide quantum dots (WS2 QDs) which is independent of the pH of solution and emits strong blue fluorescence. Copper ions could cause aggregation of the WS2 QDs and lead to fluorescence quenching of WS2 QDs. The change of fluorescence intensity is proportional to the concentration of Cu2+, and the limit of detection is 0.4 μM. The fluorescent probe is highly selective for Cu2+ over some potentially interfering ions. These results indicate that WS2 QDs, as a fluorescent sensing platform, can meet the selective requirements for biomedical and environmental application.
Electronic and thermoelectric properties of Mg2GexSn1-x (x=0.25, 0.50, 0.75) solid solutions by first-principles calculations
The electronic structure and thermoelectric (TE) properties of Mg2GexSn1-x (x=0.25, 0.50, 0.75) solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure (SQS) is used to model the solid solutions, which can produce reasonable band gaps with respect to experimental results. The n-type solid solutions have an excellent thermoelectric performance with maximum zT values exceeding 2.0, where the combination of low lattice thermal conductivity and high power factor (PF) plays an important role. These values are higher than those of pure Mg2Sn and Mg2Ge. The p-type solid solutions are inferior to the n-type ones, mainly due to the much lower PF. The maximum zT value of 0.62 is predicted for p-type Mg2Ge0.25Sn0.75 at 800 K. The results suggest that the n-type Mg2GexSn1-x solid solutions are promising mid-temperature TE materials.
Effects of pressure on structural, electronic, and mechanical properties of α, β, and γ uranium
Stability, elastic anisotropy, and electronic properties of Ca2C3
Unraveling the effect of uniaxial strain on thermoelectric properties of Mg2Si: A density functional theory study
In this work, the effect of uniaxial strain on electronic and thermoelectric properties of magnesium silicide using density functional theory (DFT) and Boltzmann transport equations has been studied. We have found that the value of band gap increases with tensile strain and decreases with compressive strain. The variations of electrical conductivity, Seebeck coefficient, electronic thermal conductivity, and power factor with temperatures have been calculated. The Seebeck coefficient and power factor are observed to be modified strongly with strain. The value of power factor is found to be higher in comparison with the unstrained structure at 2% tensile strain. We have also calculated phonon dispersion, phonon density of states, specific heat at constant volume, and lattice thermal conductivity of material under uniaxial strain. The phonon properties and lattice thermal conductivity of Mg2Si under uniaxial strain have been explored first time in this report.
Direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene via van der Pauw geometry
We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope (4P-STM). The gate-tunable conductivity and mobility are extracted from standard van der Pauw resistance measurements where the four STM probes contact the four peripheries of hexagonal graphene flakes, respectively. The high homogeneity of transport properties of the single-crystalline graphene flake is confirmed by comparing the extracted conductivities and mobilities from three setups with different geometry factors. Our studies provide a reliable solution for directly evaluating the entire electrical properties of graphene in a non-invasive way and could be extended to characterizing other two-dimensional materials.
Study of structural and magnetic properties of Fe80P9B11 amorphous alloy by ab initio molecular dynamic simulation
Anisotropic and mutable magnetization in Kondo lattice CeSb2
First-principles investigation of the effects of strain on elastic, thermal, and optical properties of CuGaTe2
Spin-filter effect and spin-polarized optoelectronic properties in annulene-based molecular spintronic devices
Transport properties in monolayer-bilayer-monolayer graphene planar junctions
The transport study of graphene based junctions has become one of the focuses in graphene research. There are two stacking configurations for monolayer-bilayer-monolayer graphene planar junctions. One is the two monolayer graphene contacting the same side of the bilayer graphene, and the other is the two-monolayer graphene contacting the different layers of the bilayer graphene. In this paper, according to the Landauer-Büttiker formula, we study the transport properties of these two configurations. The influences of the local gate potential in each part, the bias potential in bilayer graphene, the disorder and external magnetic field on conductance are obtained. We find the conductances of the two configurations can be manipulated by all of these effects. Especially, one can distinguish the two stacking configurations by introducing the bias potential into the bilayer graphene. The strong disorder and the external magnetic field will make the two stacking configurations indistinguishable in the transport experiment.
Flexible electrically pumped random lasing from ZnO nanowires based on metal-insulator-semiconductor structure
Flexible electrically pumped random laser (RL) based on ZnO nanowires is demonstrated for the first time to our knowledge. The ZnO nanowires each with a length of 5 μm and an average diameter of 180 nm are synthesized on flexible substrate (ITO/PET) by a simple hydrothermal method. No obvious visible defect-related-emission band is observed in the photoluminescence (PL) spectrum, indicating that the ZnO nanowires grown on the flexible ITO/PET substrate have few defects. In order to achieve electrically pumped random lasing with a lower threshold, the metal-insulator-semiconductor (MIS) structure of Au/SiO2/ZnO on ITO/PET substrate is fabricated by low temperature process. With sufficient forward bias, the as-fabricated flexible device exhibits random lasing, and a low threshold current of ~11.5 mA and high luminous intensity are obtained from the ZnO-based random laser. It is believed that this work offers a case study for developing the flexible electrically pumped random lasing from ZnO nanowires.
Tunable charge density wave in TiS3 nanoribbons
Recently, modifications of charge density wave (CDW) in two-dimensional (2D) show intriguing properties in quasi-2D materials such as layered transition metal dichalcogenides (TMDCs). Optical, electrical transport measurements and scanning tunneling microscopy uncover the enormous difference on the many-body states when the thickness is reduced down to monolayer. However, the CDW in quasi-one-dimensional (1D) materials like transition metal trichalcogenides (TMTCs) is yet to be explored in low dimension whose mechanism is likely distinct from their quasi-2D counterparts. Here, we report a systematic study on the CDW properties of titanium trisulfide (TiS3). Two phase transition temperatures were observed to decrease from 53 K (103 K) to 46 K (85 K) for the bulk and <15-nm thick nanoribbon, respectively, which arises from the increased fluctuation effect across the chain in the nanoribbon structure, thereby destroying the CDW coherence. It also suggests a strong anisotropy of CDW states in quasi-1D TMTCs which is different from that in TMDCs. Remarkably, by using back gate of -30 V~70 V in 15-nm device, we can tune the second transition temperature from 110 K (at -30 V) to 93 K (at 70 V) owing to the altered electron concentration. Finally, the optical approach through the impinging of laser beams on the sample surface is exploited to manipulate the CDW transition, where the melting of the CDW states shows a strong dependence on the excitation energy. Our results demonstrate TiS3 as a promising quasi-1D CDW material and open up a new window for the study of collective phases in TMTCs.
Structural, elastic, and vibrational properties of phase H: A first-principles simulation
Transition from tunneling regime to local point contact realized on Ba0.6K0.4Fe2As2 surface Hot!
Using scanning tunneling spectroscopy, we studied the transition from tunneling regime to local point contact on the iron-based superconductor Ba0.6K0.4Fe2As2. By gradually reducing the junction resistance, a series of spectra were obtained with the characteristics evolving from single-particle tunneling into Andreev reflection. The spectra can be well fitted to the modified Blonder-Tinkham-Klapwijk (BTK) model and exhibit significant changes of both spectral broadening and orbital selection due to the formation of point contact. The spatial resolution of the point contact was estimated to be several nanometers, providing a unique way to study the inhomogeneity of unconventional superconductors on such a scale.
Kosterlitz-Thouless transition, spectral property and magnetic moment for a two-dot structure with level difference
By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where the dot energies are kept symmetric to the half-filled level. A Kosterlitz-Thouless (KT) transition between local spin triplet and singlet is found. In the triplet regime, the local spin is partially screened by the conduction leads and spin-1 Kondo effect is realized. While for the singlet, the Kondo peak is strongly suppressed and the magnetic moment decreases to 0 at a definite low temperature. We attribute this KT transition to the breaking of the reflection symmetry, resulting from the difference of the charge occupations of the two dots. To understand this KT transition and related critical phenomena, detailed scenarios are given in the transmission coefficient and the magnetic moment, and an effective Kondo model refers to the Rayleigh-Schrödinger perturbation theory is used.
Effects of Pr substitution on the hydrogenating process and magnetocaloric properties of La1-xPrxFe11.4Si1.6Hy hydrides
Low temperature ferromagnetic properties of CdS and CdTe thin films
The magnetic property in a material is induced by the unpaired electrons. This can occur due to defect states which can enhance the magnetic moment and the spin polarization. In this report, CdS and CdTe thin films are grown on FTO glass substrates by chemical bath deposition and close-spaced sublimation, respectively. The magnetic properties, which are introduced from oxygen states, are found in CdS and CdTe thin films. From the hysteresis loop of magnetic moment it is revealed that CdS and CdTe thin films have different kinds of magnetic moments at different temperatures. The M-H curves indicate that from 100 K to 350 K, CdS and CdTe thin films show paramagnetism and diamagnetism, respectively. A superparamagnetic or a weakly ferromagnetic response is found at 5 K. It is also observed from ZFC/FC curves that magnetic moments decrease with temperature increasing. Spin polarized density functional calculation for spin magnetic moment is also carried out.
Influences of different oxidants on characteristics of La2O3/Al2O3 nanolaminates deposited by atomic layer deposition
A comparative study of two kinds of oxidants (H2O and O3) with the combination of two metal precursors (TMA and La(iPrCp)3) for atomic layer deposition (ALD) La2O3/Al2O3 nanolaminates is carried out. The effects of different oxidants on the physical properties and electrical characteristics of La2O3/Al2O3 nanolaminates are studied. Initial testing results indicate that La2O3/Al2O3 nanolaminates could avoid moisture absorption in the air after thermal annealing. However, moisture absorption occurs in H2O-based La2O3/Al2O3 nanolaminates due to the residue hydroxyl/hydrogen groups during annealing. As a result, roughness enhancement, band offset variation, low dielectric constant and poor electrical characteristics are measured because the properties of H2O-based La2O3/Al2O3 nanolaminates are deteriorated. Addition thermal annealing effects on the properties of O3-based La2O3/Al2O3 nanolaminates indicate that O3 is a more appropriate oxidant to deposit La2O3/Al2O3 nanolaminates for electron devices application.
Improved photovoltaic effects in Mn-doped BiFeO3 ferroelectric thin films through band gap engineering
As a low-bandgap ferroelectric material, BiFeO3 has gained wide attention for the potential photovoltaic applications, since its photovoltaic effect in visible light range was reported in 2009. In the present work, Bi(Fe, Mn)O3 thin films are fabricated by pulsed laser deposition method, and the effects of Mn doping on the microstructure, optical, leakage, ferroelectric and photovoltaic characteristics of Bi(Fe, Mn)O3 thin films are systematically investigated. The x-ray diffraction data indicate that Bi(Fe, Mn)O3 thin films each have a rhombohedrally distorted perovskite structure. From the light absorption results, it follows that the band gap of Bi(Fe, Mn)O3 thin films can be tuned by doping different amounts of Mn content. More importantly, photovoltaic measurement demonstrates that the short-circuit photocurrent density and the open-circuit voltage can both be remarkably improved through doping an appropriate amount of Mn content, leading to the fascinating fact that the maximum power output of ITO/BiFe0.7Mn0.3O3/Nb-STO capacitor is about 175 times higher than that of ITO/BiFeO3/Nb-STO capacitor. The improvement of photovoltaic response in Bi(Fe, Mn)O3 thin film can be reasonably explained as being due to absorbing more visible light through bandgap engineering and maintaining the ferroelectric property at the same time.
Giant low-frequency magnetoelectric torque (MET) effect in polyvinylidene-fluoride (PVDF)-based MET device
Hybrid temperature effect on a quartz crystal microbalance resonator in aqueous solutions
Combined effect of light intensity and temperature on the magnetic resonance linewidth in alkali vapor cell with buffer gas
One of the peculiar phenomenons in non-zero magnetic resonance magnetometer is that, with the increase of the temperature, the magnetic resonance linewidth is narrowed at first instead of broadened due to the increasing collision rate. The magnetometer usually operates at the narrowest linewidth temperature to obtain the best sensitivity. Here, we explain this phenomenon quantitatively considering the nonlinear of the optical pumping in the cell and did experiments to verify this explanation. The magnetic resonance linewidth is measured using one amplitude-modulated pump laser and one continuous probe laser. The field is along the direction orthogonal to the plane of pump and probe beams. We change the temperature from 53℃ to 93℃ and the pumping light from 0.1 mW to 2 mW. The experimental results agree well with the theoretical calculations.
Different angle-resolved polarization configurations of Raman spectroscopy: A case on the basal and edge plane of two-dimensional materials Hot!
Angle-resolved polarized Raman (ARPR) spectroscopy can be utilized to assign the Raman modes based on crystal symmetry and Raman selection rules and also to characterize the crystallographic orientation of anisotropic materials. However, polarized Raman measurements can be implemented by several different configurations and thus lead to different results. In this work, we systematically analyze three typical polarization configurations:1) to change the polarization of the incident laser, 2) to rotate the sample, and 3) to set a half-wave plate in the common optical path of incident laser and scattered Raman signal to simultaneously vary their polarization directions. We provide a general approach of polarization analysis on the Raman intensity under the three polarization configurations and demonstrate that the latter two cases are equivalent to each other. Because the basal plane of highly ordered pyrolytic graphite (HOPG) exhibits isotropic feature and its edge plane is highly anisotropic, HOPG can be treated as a modelling system to study ARPR spectroscopy of two-dimensional materials on their basal and edge planes. Therefore, we verify the ARPR behaviors of HOPG on its basal and edge planes at three different polarization configurations. The orientation direction of HOPG edge plane can be accurately determined by the angle-resolved polarization-dependent G mode intensity without rotating sample, which shows potential application for orientation determination of other anisotropic and vertically standing two-dimensional materials and other materials.
Super scattering phenomenon in active spherical nanoparticles
Localized surface electromagnetic resonances in spherical nanoparticles with gain are investigated by using the Mie theory. Due to the coupling between the gain and resonances, super scattering phenomenon is raised and the total scattering efficiency is increased by over six orders of magnitude. The dual frequency resonance induced by the electric dipole term of the particle is observed. The distributions of electromagnetic field and the Poynting vector around nanoparticles are provided for better understanding different multipole resonances. Finally, the scattering properties of active spherical nanoparticles are investigated when the sizes of nanoparticles are beyond the quasi-static limit. It is noticed that more high-order multipole resonances can be excited with the increase of the radius. Besides, all resonances dominated by multipole magnetic terms can only appear in dielectric materials.
Temperature-dependent photoluminescence of size-tunable ZnAgInSe quaternary quantum dots
Graphene/Mo2C heterostructure directly grown by chemical vapor deposition
Influence of adatom migration on wrinkling morphologies of AlGaN/GaN micro-pyramids grown by selective MOVPE
Different effect of NiMnCo or FeNiCo on the growth of type-IIa large diamonds with Ti/Cu as nitrogen getter
In order to synthesize high-quality type-IIa large diamond, the selection of catalyst is very important, in addition to the nitrogen getter. In this paper, type-IIa large diamonds are grown under high pressure and high temperature (HPHT) by using the temperature gradient method (TGM), with adopting Ti/Cu as the nitrogen getter in Ni70Mn25Co5 (abbreviated as NiMnCo) or Fe55Ni29Co16 (abbreviated FeNiCo) catalyst. The values of nitrogen concentration (Nc) in both synthesized high-quality diamonds are less than 1 ppm, when Ti/Cu (1.6 wt%) is added in the FeNiCo or Ti/Cu (1.8 wt%) is added in the NiMnCo. The difference in solubility of nitrogen between both catalysts at HPHT is the basic reason for the different effect of Ti/Cu on eliminating nitrogen. The nitrogen-removal efficiency of Ti/Cu in the NiMnCo catalyst is less than in the FeNiCo catalyst. Additionally, a high-quality type-IIa large diamond size of 5.0 mm is obtained by reducing the growth rate and keeping the nitrogen concentration of the diamond to be less than 1 ppm, when Ti/Cu (1.6 wt%) is added in the FeNiCo catalyst.
Anomalous temperature dependence of photoluminescence spectra from InAs/GaAs quantum dots grown by formation-dissolution-regrowth method
Magnesium incorporation efficiencies in MgxZn1-xO films on ZnO substrates grown by metalorganic chemical vapor deposition
A low cost composite quasi-solid electrolyte of LATP, TEGDME, and LiTFSI for rechargeable lithium batteries Hot!
The composite quasi solid state electrolytes (CQSE) is firstly synthesized with quasi solid state electrolytes (QSE) and lithium-ion-conducting material Li1.4Al0.4Ti1.6(PO4)3 (LATP), and the QSE consists of[LiG4][TFSI] with fumed silica nanoparticles. Compared with LATP, CQSE greatly improves the interface conductance of solid electrolytes. In addition,it has lower liquid volume relative to QSE. Although the liquid volume fraction of CQSE drops to 60%, its conductivity can also reach 1.39×10-4 s/cm at 20℃. Linear sweep voltammetry (LSV) is conducted on each composite electrolyte. The results show the possibility that CQSE has superior electrochemical stability up to 5.0 V versus Li/Li+1. TG curves also show that composite electrolytes have higher thermal stability. In addition, the performance of Li/QSE/LiMn2O4 cells and Li/CQSE/LiMn2O4 is evaluated and shows good electrochemical characteristics at 60℃.
Synthesis and characterization of NaAlSi2O6 jadeite under 3.5 GPa
Reversal current observed in micro-and submicro-channel flow under non-continuous DC electric field
Correction of failure in antenna array using matrix pencil technique
Helicase activity and substrate specificity of RecQ5β
RecQ5β is an essential DNA helicase in humans, playing important roles in DNA replication, repair, recombination and transcription. The unwinding activity and substrate specificity of RecQ5β is still elusive. Here, we used stopped-flow kinetic method to measure the unwinding and dissociation kinetics of RecQ5β with several kinds of DNA substrates, and found that RecQ5β could well unwind ss/dsDNA, forked DNA and Holiday junction, but was compromised in unwinding blunt DNA and G-quadruplex. Rec5β has the preferred unwinding specificity for certain DNA substrates containing the junction point, which may improve the binding affinity and unwinding activity of RecQ5β. Moreover, from a comparison with the truncated RecQ5β1-467, we discovered that the C-terminal domain might strongly influence the unwinding activity and binding affinity of RecQ5β. These results may shed light on the physiological functions and working mechanisms of RecQ5β helicase.
A damping boundary condition for atomistic-continuum coupling
Cooperative impulsive formation control for networked uncertain Euler-Lagrange systems with communication delays
Dissociation of H2 on Mg-coated B12C6N6
Influence of interface states, conduction band offset, and front contact on the performance of a-SiC: H(n)/c-Si(p) heterojunction solar cells
O3 fast and simple treatment-enhanced p-doped in Spiro-MeOTAD for CH3NH3I vapor-assisted processed CH3NH3PbI3 perovskite solar cells