Improved control for distributed parameter systems with time-dependent spatial domains utilizing mobile sensor—actuator networks
Geometry and thermodynamics of smeared Reissner-Nordström black holes in d-dimensional AdS spacetime
We construct a family of d-dimensional Reissner-Nordström-AdS black holes inspired by noncommutative geometry. The density distribution of the gravitational source is determined by the dimension of space, the minimum length of spacetime l, and other parameters (e.g., n relating to the central matter density). The curvature of the center and some thermodynamic properties of these black holes are investigated. We find that the center of the source is nonsingular for n≥ 0 (under certain conditions it is also nonsingular for -2 ≤ n < 0), and the properties at the event horizon, including the Hawking temperature, entropy, and heat capacity, are regular for n >-2. Due to the presence of l, there is an exponentially small correction to the usual entropy.
Stochastic responses of tumor—immune system with periodic treatment
Invariants-based shortcuts for fast generating Greenberger—Horne—Zeilinger state among three superconducting qubits
As one of the most promising candidates for implementing quantum computers, superconducting qubits (SQs) are adopted for fast generating the Greenberger-Horne-Zeilinger (GHZ) state by using invariants-based shortcuts. Three SQs are separated and connected by two coplanar waveguide resonators (CPWRs) capacitively. The complicated system is skillfully simplified to a three-state system, and a GHZ state among three SQs is fast generated with a very high fidelity and simple driving pulses. Numerical simulations indicate the scheme is insensitive to parameter deviations. Besides, the robustness of the scheme against decoherence is discussed in detail.
Cancelable remote quantum fingerprint templates protection scheme
With the increasing popularity of fingerprint identification technology, its security and privacy have been paid much attention. Only the security and privacy of biological information are insured, the biological technology can be better accepted and used by the public. In this paper, we propose a novel quantum bit (qbit)-based scheme to solve the security and privacy problem existing in the traditional fingerprint identification system. By exploiting the properties of quantum mechanics, our proposed scheme, cancelable remote quantum fingerprint templates protection scheme, can achieve the unconditional security guaranteed in an information-theoretical sense. Moreover, this novel quantum scheme can invalidate most of the attacks aimed at the fingerprint identification system. In addition, the proposed scheme is applicable to the requirement of remote communication with no need to worry about its security and privacy during the transmission. This is an absolute advantage when comparing with other traditional methods. Security analysis shows that the proposed scheme can effectively ensure the communication security and the privacy of users' information for the fingerprint identification.
A high-fidelity memory scheme for quantum data buses
A novel quantum memory scheme is proposed for quantum data buses in scalable quantum computers by using adjustable interaction. Our investigation focuses on a hybrid quantum system including coupled flux qubits and a nitrogen-vacancy center ensemble. In our scheme, the transmission and storage (retrieval) of quantum state are performed in two separated steps, which can be controlled by adjusting the coupling strength between the computing unit and the quantum memory. The scheme can be used not only to reduce the time of quantum state transmission, but also to increase the robustness of the system with respect to detuning caused by magnetic noises. In comparison with the previous memory scheme, about 80% of the transmission time is saved. Moreover, it is exemplified that in our scheme the fidelity could achieve 0.99 even when there exists detuning, while the one in the previous scheme is 0.75.
Determination of the thermal noise limit in test of weak equivalence principle with a rotating torsion pendulum
Stochastic bifurcations of generalized Duffing-van der Pol system with fractional derivative under colored noise
A generalized model of TiOx-based memristive devices andits application for image processing
Memristive technology has been widely explored, due to its distinctive properties, such as nonvolatility, high density, versatility, and CMOS compatibility. For memristive devices, a general compact model is highly favorable for the realization of its circuits and applications. In this paper, we propose a novel memristive model of TiOx-based devices, which considers the negative differential resistance (NDR) behavior. This model is physics-oriented and passes Linn's criteria. It not only exhibits sufficient accuracy (IV characteristics within 1.5% RMS), lower latency (below half the VTEAM model), and preferable generality compared to previous models, but also yields more precise predictions of long-term potentiation/depression (LTP/LTD). Finally, novel methods based on memristive models are proposed for gray sketching and edge detection applications. These methods avoid complex nonlinear functions required by their original counterparts. When the proposed model is utilized in these methods, they achieve increased contrast ratio and accuracy (for gray sketching and edge detection, respectively) compared to the Simmons model. Our results suggest a memristor-based network is a promising candidate to tackle the existing inefficiencies in traditional image processing methods.
Recursion-transform method and potential formulae of the m×n cobweb and fan networks
In this paper, we made a new breakthrough, which proposes a new Recursion-Transform (RT) method with potential parameters to evaluate the nodal potential in arbitrary resistor networks. For the first time, we found the exact potential formulae of arbitrary m×n cobweb and fan networks by the RT method, and the potential formulae of infinite and semi-infinite networks are derived. As applications, a series of interesting corollaries of potential formulae are given by using the general formula, the equivalent resistance formula is deduced by using the potential formula, and we find a new trigonometric identity by comparing two equivalence results with different forms.
ADC border effect and suppression of quantization error in the digital dynamic measurement
Microwave coherent manipulation of cold atoms in optically induced fictitious magnetic traps on an atom chip
We propose a novel on-chip platform for controlling and manipulating cold atoms precisely and coherently. The scheme is achieved by producing optically induced fictitious magnetic traps (OFMTs) with 790 nm (for 87Rb) circularly polarized laser beams and state-dependent potentials simultaneously for two internal atomic states with microwave coplanar waveguides. We carry out numerical calculations and simulations for controlled collisional interactions between OFMTs and addressable single atoms' manipulation on our designed hybrid atom chips. The results show that our proposed platform is feasible and flexible, which has wide applications including collisional dynamics investigation, entanglement generation, and scalable quantum gates implementation.
Elastic strain response in the modified phase-field-crystal model
To understand and develop new nanostructure materials with specific mechanical properties, a good knowledge of the elastic strain response is mandatory. Here we investigate the linear elasticity response in the modified phase-field-crystal (MPFC) model. The results show that two different propagation modes control the elastic interaction length and time, which determine whether the density waves can propagate or not. By quantitatively calculating the strain field, we find that the strain distribution is indeed extremely uniform in case of elasticity. Further, we present a detailed theoretical analysis for the orientation dependence and temperature dependence of shear modulus. The simulation results show that the shear modulus reveals strong anisotropy and the one-mode analysis provides a good guideline for determining elastic shear constants until the system temperature falls below a certain value.
Pressure-induced phase transition of B-type Y2O3
Theoretical study of spin-forbidden cooling transitions of indium hydride using ab initio methods
The feasibility of spin-forbidden cooling of the InH molecule is investigated based on ab initio quantum chemistry calculations. The potential energy curves for the X1Σ0++, a3Π0-, a3Π0+, a3Π1, a3Π2, A1Π1, 13Σ0-+, and 13Σ1+ states of InH are obtained based on multi-reference configuration interaction plus the Davidson corrections method. The calculated spectroscopic constants are in good agreement with the available experimental data. In addition, the influences of the active space and spin-orbit coupling effects on the potential energy curves and spectroscopic constants are also studied. For Re of a3Π0-, a3Π0+, a3Π1, and a3Π2 states, the error from large active space is small. The potential energy curve of the A1Π1 state is not smooth for small active space. The spin-orbit coupling effects have great influences on the potential well depth and equilibrium internuclear distance of the A1Π state. The Franck-Condon factors and radiative lifetimes are obtained on the basis of the transition dipole moments of the a3Π0+→X1Σ0++,a3Π1→X1Σ0++,and A1Π1→X1Σ0++ transitions. Our calculation indicates that the a3Π1(v'=0)→X1Σ0++(v=0) transition provides a highly diagonally distributed Franck– Condon factor and a short radiative lifetime for the a3Π1 state, which can ensure rapid and efficient laser cooling of InH. The proposed laser drives a3Π0+→X1Σ0++ transitions by using three wavelengths.
First-principles study of solute diffusion in Ni3Al
Using first-principles calculations in combination with Wagner-Schottky and kinetic Monte Carlo methods, the diffusion behaviors of solutes via various vacancy-mediated diffusion mechanisms in L12 γ'-Ni3Al were investigated. The formation energies of the point defects and the migration energies for solutes were calculated. Adding alloying elements can decrease the defect-formation energies of Nim Al, increase the defect-formation energies of AlNi, and have little effect on the formation energy of VNi. The migration energies of solutes are related with the site preference and the diffusion mechanism. The diffusion coefficients of Ni, Al, and solutes were calculated, and the concentration of antisite defects plays a crucial role in the elemental diffusion.
Relativistic and distorted wave effects on Xe 4d electron momentum distributions
The relativistic and distorted wave effects are investigated for the electron momentum distributions of Xe 4d electrons. The theoretical results show good agreements with the experimental data measured previously with electron momentum spectroscopy. The distorted wave effect and the relativistic effect are found to play important roles in the low and high momentum regions, respectively.
Effect of grain boundary structures on the behavior of He defects in Ni: An atomistic study
Thermodynamic properties of ZnSe under pressure and with variation in temperature
Lattice stability and the effect of Co and Re on the ideal strength of Ni: First-principles study of uniaxial tensile deformation
Using first-principles density functional calculations, lattice stability of γ-Ni under , , and  uniaxial tensions and the effect of alloying elements Co and Re on the uniaxial tensile behavior of γ-Ni were studied in this paper. With elastic constants and phonon spectra calculations, we examined the mechanical stability and phonon stability of Ni during the uniaxial tensions along the three characteristic directions. The results show that the mechanical stability and phonon stability of a lattice occurs before the maximum stress-strain point under the  and  tension, respectively. The effects of Co and Re on the ideal tensile strength of γ-Ni show a significant directivity: Co and Re have little effect on the stresses in  and  directions, but increases the ideal strength of the system in the weakest uniaxial tensile direction. Moreover, the strengthening effect of Re is significantly better than that of Co. By further analyzing electronic structure, it is found that the effect of alloying elements on the uniaxial tensile behavior of γ-Ni comes from their interactions with host atoms.
First principles study and comparison of vibrational and thermodynamic properties of XBi (X= In, Ga, B, Al)
Isolated attosecond pulse generation with few-cycle two-color counter-rotating circularly polarized laser pulses
Most of the schemes for generating isolated attosecond pulses (IAP) are sensitive to the carrier-envelope phase (CEP) of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized (TC-CRCP) laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower.
Optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis
A model of an optical pumping nuclear magnetic resonance system rotating in a plane parallel to the quantization axis is presented. Different coordinate frames for nuclear spin polarization vector are introduced, and theoretical calculation is conducted to analyze this model. We demonstrate that when the optical pumping nuclear magnetic resonance system rotates in a plane parallel to the quantization axis, it will maintain a steady state with respect to the quantization axis which is independent of rotational speed and direction.
Design of double-layer active frequency-selective surface with PIN diodes for stealth radome
Reduced technique for modeling electromagnetic immunity on braid shielding cable bundles
A linear-to-circular polarization converter based on I-shapedcircular frequency selective surfaces
Orbital angular momentum density and spiral spectra of Lorentz-Gauss vortex beams passing through a single slit
Based on the Hermite-Gaussian expansion of the Lorentz distribution and the complex Gaussian expansion of the aperture function, an analytical expression of the Lorentz-Gauss vortex beam with one topological charge passing through a single slit is derived. By using the obtained analytical expressions, the properties of the Lorentz-Gauss vortex beam passing through a single slit are numerically demonstrated. According to the intensity distribution or the phase distribution of the Lorentz-Gauss vortex beam, one can judge whether the topological charge is positive or negative. The effects of the topological charge and three beam parameters on the orbital angular momentum density as well as the spiral spectra are systematically investigated respectively. The optimal choice for measuring the topological charge of the diffracted Lorentz-Gauss vortex beam is to make the single slit width wider than the waist of the Gaussian part.
Fabrication and characterization of ultra-low noise narrow and wide band Josephson parametric amplifiers Hot!
We have fabricated two types of lumped-element Josephson parameter amplifiers (JPAs) by using a multilayer micro-fabrication process involving wet etching of Al films. The first type is a narrow band JPA which shows typical gain above 14 dB in a bandwidth around 35 MHz. The second type is a wideband JPA which is coupled to an input 50 Ω transmission line via an impedance transformer that changes the impedance from about 15 Ω on the non-linear resonator side to 50 Ω on the input transmission line side. The wideband JPA could operate in a 200 MHz range with a gain higher than 14 dB. The amplifiers were used for superconducting qubit readout. The results showed that the signal to noise ratio and hence the readout fidelity were improved significantly.
Super-resolution and super-sensitivity of entangled squeezed vacuum state using optimal detection strategy
Phase estimation of phase shifts in two arms for an SU(1,1) interferometer with coherent and squeezed vacuum states
Er3+,Yb3+:glass-Co2+:MgAl2O4 diffusion bonded passively Q-switched laser
Retrieval of high-order susceptibilities of nonlinear metamaterials
Structural deformation of nitro group of nitromethane molecule in liquid phase in an intense femtosecond laser field
Odd-even harmonic emission from asymmetric molecules: Identifying the mechanism
We study odd-even high-order harmonic generation (HHG) from oriented asymmetric molecules HeH2+ numerically and analytically. The variational method is used to improve the analytical description of the ground-state wave function for the asymmetric system, with which the ground-state-continuum-state transition dipole is evaluated. The comparison between the odd-even HHG spectra and the improved dipoles allows us to identify and clarify the complex generation mechanism of odd-even harmonics from asymmetric molecules, providing deep insights into the relation between the odd-even HHG and the asymmetric molecular orbital.
Electro-optical properties of high birefringence liquid crystal compounds with isothiocyanate and naphthyl group
Liquid crystal (LC) compound with isothiocyanate and naphthyl group is an attractive high birefringence LC material, and can be used in optical devices. In this paper, the electro-optical properties of a series of this type of LC compounds were investigated. The melting points and enthalpy values of these LC compounds were higher than those of corresponding compounds with the phenyl group. These compounds exhibited high birefringence with a maximum value of 0.66. Fluorine substitution in the molecular almost does not affect the birefringence value. When these LC compounds with the naphthyl group were dissolved in a commercial LC mixture, the electro-optical properties depending on temperature were investigated. In the low-temperature region, LC mixtures with the naphthyl-group LC compounds exhibited higher viscosity than pure commercial LCs. In the high-temperature region, viscosity values very closely approached each other. When response performance was investigated, figure-of-merit (FoM) values were measured. The FoM values of LC mixtures containing LC compounds with naphthyl group were lower than those of reference benzene LCs in the low-temperature region. However, in the high-temperature region, the results were reversed. These isothiocyanate LC compounds with naphthyl group can be applied in special fast-response LC device, particularly the ones used under high-temperature conditions.
Optical and defect properties of S-doped and Al-doped GaSe crystals
A scheme for Sagnac-effect quantum enhancement with Fock state light input
Wideband dispersion removal and mode separation of Lamb waves based on two-component laser interferometer measurement
Ultrasonic Lamb waves are considered as a sensitive and effective tool for nondestructive testing and evaluation of plate-like or pipe-like structures. The nature of multimode and dispersion causes the wave packets to spread, and the modes overlap in both time and frequency domains as they propagate through the structures. By using a two-component laser interferometer technique, in combination with a priori knowledge of the dispersion characteristics and wave structure information of Lamb wave modes, a two-component signal processing technique is presented for implementing dispersion removal and mode separation simultaneously for two modes mixture signals of Lamb waves. The proposed algorithm is first processed and verified using synthetic Lamb wave signals. Then, the two-component displacements test experiment is conducted using different aluminum plate samples. Moreover, we confirm the effectiveness and robustness of this method.
Magneto-elastic dynamics and bifurcation of rotating annular plate
In this paper, magneto-elastic dynamic behavior, bifurcation, and chaos of a rotating annular thin plate with various boundary conditions are investigated. Based on the thin plate theory and the Maxwell equations, the magneto-elastic dynamic equations of rotating annular plate are derived by means of Hamilton's principle. Bessel function as a mode shape function and the Galerkin method are used to achieve the transverse vibration differential equation of the rotating annular plate with different boundary conditions. By numerical analysis, the bifurcation diagrams with magnetic induction, amplitude and frequency of transverse excitation force as the control parameters are respectively plotted under different boundary conditions such as clamped supported sides, simply supported sides, and clamped-one-side combined with simply-another-side. Poincaré maps, time history charts, power spectrum charts, and phase diagrams are obtained under certain conditions, and the influence of the bifurcation parameters on the bifurcation and chaos of the system is discussed. The results show that the motion of the system is a complicated and repeated process from multi-periodic motion to quasi-period motion to chaotic motion, which is accompanied by intermittent chaos, when the bifurcation parameters change. If the amplitude of transverse excitation force is bigger or magnetic induction intensity is smaller or boundary constraints level is lower, the system can be more prone to chaos.
Interaction between infinitely many dislocations and a semi-infinite crack in one-dimensional hexagonal quasicrystal
Tungsten ion source under double-pulse laser ablation system
New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd:YAG laser beams (266+1064 nm) are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laser wavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pulse laser ablation configuration is more potent technique for producing more metal ion source deposition, thin film formation, and activated plasma-facing component material.
Rotation of a single vortex in dusty plasma
Interactions of ion acoustic multi-soliton and rogue wave with Bohm quantum potential in degenerate plasma
Understanding hydrogen plasma processes based on the diagnostic results of 2.45 GHz ECRIS at Peking University
Radiative divertor behavior and physics in Ar seeded plasma on EAST
Initial growth and microstructure feature of Ag films prepared by very-high-frequency magnetron sputtering
The initial growth and microstructure feature of Ag films formation were investigated, which were prepared by using the very-high-frequency (VHF) (60 MHz) magnetron sputtering. Because of the moderate energy and very low flux density of ions impinging on the substrate, the evolutions of initial growth for Ag films formation were well controlled by varying the sputtering power. It was found that the initial growth of Ag films followed the island (Volmer-Weber, VW) growth mode, but before the island nucleation, the adsorption of Ag nanoparticles and the formation of Ag clusters dominated the growth. Therefore, the whole initial stages of Ag films formation included the adsorption of nanoparticles, the formation of clusters, the nucleation by the nanoparticles and clusters simultaneously, the islands formation, and the coalescence of islands.
Synthesis and magnetotransport properties of Bi2Se3 nanowires Hot!
Bi2Se3, as a three-dimensional topological insulator, has attracted worldwide attention for its unique surface states which are protected by time-reversal symmetry. Here we report the synthesis and characterization of high-quality single-crystalline Bi2Se3 nanowires. Bi2Se3 nanowires were synthesized by chemical vapor deposition (CVD) method via gold-catalyzed vapor-liquid-solid (VLS) mechanism. The structure and morphology were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. In magnetotransport measurements, the Aharonov-Bohm (AB) effect was observed in a nanowire-based nanodevice, suggesting the existence of surface states in Bi2Se3 nanowires.
Ionizing radiation effect on single event upset sensitivity of ferroelectric random access memory
Direct measurement and analysis of total ionizing dose effect on 130 nm PD SOI SRAM cell static noise margin
Strain rate and cold rolling dependence of tensile strength and ductility in high nitrogen nickel-free austenitic stainless steel
Theoretical study on the structural, mechanical, electronic properties and QTAIM of CrB4 as a hard material
First-principles investigations on the mechanical, thermal,electronic, and optical properties of the defect perovskites Cs2SnX6 (X= Cl, Br, I)
The mechanical properties, thermal properties, electronic structures, and optical properties of the defect perovskites Cs2SnX6 (X=Cl, Br, I) were investigated by first-principles calculation using PBE and HSE06 hybrid functional. The optic band gaps based on HSE06 are 3.83 eV for Cs2SnCl6, 2.36 eV for Cs2SnBr6, and 0.92 eV for Cs2SnI6, which agree with the experimental results. The Cs2SnCl6, Cs2SnBr6, and Cs2SnI6 are mechanically stable and they are all anisotropic and ductile in nature. Electronic structures calculations show that the conduction band consists mainly of hybridization between the halogen p orbitals and Sn 5s orbitals, whereas the valence band is composed of the halogen p orbitals. Optic properties indicate that these three compounds exhibit good optical absorption in the ultraviolet region, and the absorption spectra red shift with the increase in the number of halogen atoms. The defect perovskites are good candidates for probing the lead-free and high power conversion efficiency of solar cells.
Effect of ballistic electrons on ultrafast thermomechanical responses of a thin metal film
First-principles study of helium clustering at initial stage in ThO2
Voltage-controlled Kosterlitz-Thouless transitions and various kinds of Kondo behaviors in a triple dot device
The transport property and phase transition for a parallel triple dot device are studied by adopting Wilson's numerical renormalization group technique, focusing on the effects of level spacings between neighboring dot sites. By keeping dot 2 at the half-filled level and tuning the level differences, it is demonstrated that the system transits from local spin quadruplet to triplet and doublet sequently, and three kinds of Kondo peaks at the Fermi surface could be found, which are separated by two Kosterlitz-Thouless type quantum phase transitions and correspond to spin-3/2, spin-1, and spin-1/2 Kondo effect, respectively. To obtain a detailed understanding of these problems, the charge occupation, the spin-spin correlation, the transmission coefficient, and the temperature-dependent magnetic moment are shown, and necessary physical arguments are given.
Magnetpolaron effect in two-dimensional anisotropic parabolic quantum dot in a perpendicular magnetic field
Parasitic source resistance at different temperatures for AlGaN/AlN/GaN heterostructure field-effect transistors
Effects of Mn substitution on thermoelectric properties of CuIn1-xMnxTe2
CuIn1-xMnxTe2 samples have been synthesized by a melt-annealing method. The x-ray powder diffraction (XRD) analysis shows that the CuIn1-xMnxTe2 samples crystallize in the chalcopyrite phase. Mn doping can effectively optimize the electrical properties and accordingly improve the power factor. The room temperature electrical conductivity of doped CuInTe2 increases by several orders of magnitude due to substituting In with Mn. In addition, a large reduction in thermal conductivity is achieved through the enhanced phonon scattering via Mn-related point defects and precipitates. Therefore, an enhanced average ZT value up to 0.34 is achieved for sample CuIn0.925Mn0.075Te2, which is 41% higher than that of the pristine CuInTe2.
Ultrafast interlayer photocarrier transfer in graphene-MoSe2 van der Waals heterostructure Hot!
We report the fabrication and photocarrier dynamics in graphene-MoSe2 heterostructures. The samples were fabricated by mechanical exfoliation and manual stacking techniques. Ultrafast laser measurements were performed on the heterostructure and MoSe2 monolayer samples. By comparing the results, we conclude that photocarriers injected in MoSe2 of the heterostructure transfer to graphene on an ultrafast time scale. The carriers in graphene alter the optical absorption coefficient of MoSe2. These results illustrate the potential applications of this material in optoelectronic devices.
Inverted organic solar cells with solvothermal synthesized vanadium-doped TiO2 thin films as efficient electron transport layer
Application of real space Kerker method in simulating gate-all-around nanowire transistors with realistic discrete dopants
Polaron effects in cylindrical GaAs/AlxGa1-xAs core-shell nanowires
Tunneling field effect transistors based on in-plane and vertical layered phosphorus heterostructures
Tunneling field effect transistors (TFETs) based on two-dimensional materials are promising contenders to the traditional metal oxide semiconductor field effect transistor, mainly due to potential applications in low power devices. Here, we investigate the TFETs based on two different integration types: in-plane and vertical heterostructures composed of two kinds of layered phosphorous (β-P and δ-P) by ab initio quantum transport simulations. NDR effects have been observed in both in-plane and vertical heterostructures, and the effects become significant with the highest peak-to-valley ratio (PVR) when the intrinsic region length is near zero. Compared with the in-plane TFET based on β-P and δ-P, better performance with a higher on/off current ratio of ～106 and a steeper subthreshold swing (SS) of ～23 mV/dec is achieved in the vertical TFET. Such differences in the NDR effects, on/off current ratio and SS are attributed to the distinct interaction nature of the β-P and δ-P layers in the in-plane and vertical heterostructures.
Influence of Ni/Mn ratio on magnetostructural transformation and magnetocaloric effect in Ni48-xCo2Mn38+xSn12 (x = 0, 1.0, 1.5, 2.0, and 2.5) ferromagnetic shape memory alloys
An investigation on the magnetostructural transformation and magnetocaloric properties of Ni48-xCo2Mn38+xSn12 (x=0, 1.0, 1.5, 2.0, and 2.5) ferromagnetic shape memory alloys is carried out. With the partial replacement of Ni by Mn in the Ni48Co2Mn38Sn12 alloy, the electron concentration decreases. As a result, the martensitic transformation temperature is decreased into the temperature window between the Curie-temperatures of austenite and martensite. Thus, the samples with x=1.5 and 2.0 exhibit the magnetostructural transformation between the weak-magnetization martensite and ferromagnetic austenite at room temperature. The structural transformation can be induced not only by the temperature, but also by the magnetic field. Accompanied by the magnetic-field-induced magnetostructural transformation, a considerable magnetocaloric effect is observed. With the increase of x, the maximum entropy change decreases, but the effective magnetic cooling capacity increases.
Nonvolatile control of transport and magnetic properties in magnetoelectric heterostructures by electric field
Nonvolatile manipulation of transport and magnetic properties by external electric field is significant for information storage. In this study, we investigate the electric field control of resistance and magnetization in a magnetoelectric heterostructure comprising an electronic phase-separated La0.325Pr0.3Ca0.375MnO3 (LPCMO) thin film and a ferroelectric (011)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) substrate. In a room-temperature poled sample, the metal-to-insulator transition temperature of an LPCMO film increases and the resistance decreases with variation in the effect of the remnant strain. Meanwhile, the increase in the magnetization of the sample is observed as well. This effect would be beneficial for the development of novel storage devices with low power consumption.
Magnetic properties of AlN monolayer doped with group 1A or 2A nonmagnetic element: First-principles study
Large tunable FMR frequency shift by magnetoelectric coupling in oblique-sputtered Fe52.5Co22.5B25.0/PZN-PT multiferroic heterostructure
In this study, we observe a strong inverse magnetoelectric coupling in Fe52.5Co22.5B25.0/PZN-PT multiferroic heterostructure, which produces large electric field (E-field) tunability of microwave magnetic properties. With the increase of the E-field from 0 to 8 kV/cm, the magnetic anisotropy field Heff is dramatically enhanced from 169 to 600 Oe, which further leads to a significant enhancement of ferromagnetic resonance frequency from 4.57 to 8.73 GHz under zero bias magnetic field, and a simultaneous decrease of the damping constant α from 0.021 to 0.0186. These features demonstrate that this multiferroic composite is a promising candidate for fabricating E-field tunable microwave components.
Electronic structure and photoluminescence property of a novel white emission phosphor Na3MgZr(PO4)3:Dy3+ for warm white light emitting diodes
Optical response of tunable terahertz plasmon in a grating-gated graphene transistor
A synthetic semi-empirical physical model of secondary electron yield of metals under E-beam irradiation
Synthesis of diamonds in Fe—C systems using nitrogen and hydrogen co-doped impurities under HPHT
In this study, we investigate the effect of nitrogen and hydrogen impurities on colors, morphologies, impurity structures and synthesis conditions of diamond crystals in Fe-C systems with C3N6H6 additives at pressures in the range 5.0-6.5 GPa and temperatures of 1400-1700 ℃ in detail. Our results reveal that the octahedron diamond nucleation in a Fe-C system is evidently inhibited by co-doped N-H elements, thereby resulting in the increase of minimum pressure and temperature of diamond synthesis by spontaneous nucleation. The octahedron diamond crystals synthesized from a pure Fe-C system are colorless, while they become green in the system with C3N6H6 additive. The surface defects of diamond will deteriorate when the nitrogen and hydrogen atoms simultaneously incorporate in the diamond growth environment in the Fe-C system. We believe that this study will provide some important information and be beneficial for the deep understanding of the crystallization of diamonds from different component systems.
Silicon quantum dots delivered phthalocyanine for fluorescence guided photodynamic therapy of tumor
Imaging-guided cancer therapy provides a simultaneous tumor imaging and treatment, which helps to eliminate the excessive toxicity to the healthy tissues. For this purpose, multifunctional probes capable of both imaging and curing are needed. In this work, we synthesize water-soluble silicon quantum dots (Si QDs) smaller than 5 nm. Such Si QDs are used for delivering the hydrophobic drug phthalocyanine (Pc). The as-prepared Si/Pc nanocomposite particles show efficient transmembrane delivery into cells and feasible biocompatibility. Moreover, these composite particles emit dual-channel fluorescence signals even after cellular internalization and demonstrate robust photostability in the Si channel. More interestingly, the Si/Pc composite particles show efficient photodynamic therapy effects against tumors both in vitro and in vivo.
Crystalline silicon surface passivation investigated by thermal atomic-layer-deposited aluminum oxide
Material microstructures analyzed by using gray level Co-occurrence matrices
The mechanical properties of materials greatly depend on the microstructure morphology. The quantitative characterization of material microstructures is essential for the performance prediction and hence the material design. At present, the quantitative characterization methods mainly rely on the microstructure characterization of shape, size, distribution, and volume fraction, which related to the mechanical properties. These traditional methods have been applied for several decades and the subjectivity of human factors induces unavoidable errors. In this paper, we try to bypass the traditional operations and identify the relationship between the microstructures and the material properties by the texture of image itself directly. The statistical approach is based on gray level Co-occurrence matrix (GLCM), allowing an objective and repeatable study on material microstructures. We first present how to identify GLCM with the optimal parameters, and then apply the method on three systems with different microstructures. The results show that GLCM can reveal the interface information and microstructures complexity with less human impact. Naturally, there is a good correlation between GLCM and the mechanical properties.
Performance enhancement of CMOS terahertz detector by drain current
In this paper, we study the effect of the drain current on terahertz detection for Si metal-oxide semiconductor field-effect transistors (MOSFETs) both theoretically and experimentally. The analytical model, which is based on the small-signal equivalent circuit of MOSFETs, predicts the significant improvement of the voltage responsivity Rv with the bias current. The experiment on antennas integrated with MOSFETs agrees with the analytical model, but the Rv improvement is accompanied first by a decrease, then an increase of the low-noise equivalent power (NEP) with the applied current. We determine the tradeoff between the low-NEP and high-Rv for the current-biased detectors. As the best-case scenario, we obtained an improvement of about six times in Rv without the cost of a higher NEP. We conclude that the current supply scheme can provide high-quality signal amplification in practical CMOS terahertz detection.
Modulation depth of series SQUIDs modified by Josephson junction area
The superconducting quantum interference device (SQUID) amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlOx/Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method. Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlOx/Nb trilayer. In addition, the current-voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.
Improved high-frequency equivalent circuit model based on distributed effects for SiGe HBTs with CBE layout
Impact of Al addition on the formation of Ni germanosilicide layers under different temperature annealing
Intrinsic relationship between photoluminescence and electrical characteristics in modulation Fe-doped AlGaN/GaN HEMTs
Experimental and simulation studies of single-event transient in partially depleted SOI MOSFET
Performance of dual-band short- or mid-wavelength infrared photodetectors based on InGaAsSb bulk materials and InAs/GaSb superlattices
In this paper, we demonstrate bias-selectable dual-band short- or mid-wavelength infrared photodetectors based on In0.24Ga0.76As0.21Sb0.79 bulk materials and InAs/GaSb type-II superlattices with cutoff wavelengths of 2.2 μm and 3.6 μ m, respectively. At 200 K, the short-wave channel exhibits a peak quantum efficiency of 42% and a dark current density of 5.93×10-5 A/cm2 at 500 mV, thereby providing a detectivity of 1.55×1011 cm·Hz1/2/W. The mid-wave channel exhibits a peak quantum efficiency of 31% and a dark current density of 1.22×10-3 A/cm2 at -300 mV, thereby resulting in a detectivity of 2.71×1010 cm·Hz1/2/W. Moreover, we discuss the band alignment and spectral cross-talk of the dual-band n-i-p-p-i-n structure.
Lowering the driving voltage and improving the luminance of blue fluorescent organic light-emitting devices by thermal annealing a hole injection layer of pentacene
We chose pentacene as a hole injection layer (HIL) to fabricate the high performance blue fluorescent organic light-emitting devices (OLEDs). We found that the carrier mobility of the pentacene thin films could be efficiently improved after a critical annealing at temperature 120 °C. Then we performed the tests of scanning electron microscopy, atomic force microscopy, and Kelvin probe to explore the effect of annealing on the pentacene films. The pentacene film exhibited a more crystalline form with better continuities and smoothness after annealing. The optimal device with 120 ℃ annealed pentacene film and n-doped electron transport layer (ETL) presents a low turn-on voltage of 2.6 V and a highest luminance of 134800 cd/m2 at 12 V, which are reduced by 26% and improved by 50% compared with those of the control device.
Gas-sensor property of single-molecule device: F2 adsorbing effect
Spin-dependent transport characteristics of nanostructures based on armchair arsenene nanoribbons
Heat transfer enhancement in MOSFET mounted on different FR4 substrates by thermal transient measurement
Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistance are the critical parameters that determine the thermal management and reliability in electronics cooling. Metal oxide field effect transistor (MOSFET) is an important semiconductor device for light emitting diode-integrated circuit (LED IC) driver application, and thermal management in MOSFET is a major challenge. In this study, investigations on thermal performance of MOSFET are performed for evaluating the junction temperature and thermal resistance. Suitable modifications in FR4 substrates are proposed by introducing thermal vias and copper layer coating to improve the thermal performance of MOSFET. Experiments are conducted using thermal transient tester (T3ster) at 2.0 A input current and ambient temperature varying from 25 ℃to 75 °C. The thermal parameters are measured for three proposed designs: FR4 with circular thermal vias, FR4 with single strip of copper layer and embedded vias, and FR4 with I-shaped copper layer, and compared with that of plain FR4 substrate. From the experimental results, FR4I-shaped shows promising results by 33.71% reduction in junction temperature and 54.19% reduction in thermal resistance. For elevated temperature, the relative increases in junction temperature and thermal resistance are lower for FR4I-shaped than those for other substrates considered. The introduction of thermal vias and copper layer plays a significant role in thermal performance.
Analysis of dynamic features in intersecting pedestrian flows
Collective motion of active particles in environmental noise
We study the collective motion of active particles in environmental noise, where the environmental noise is caused by noise particles randomly diffusing in two-dimensional space. We show that active particles in a noisy environment can self organize into three typical phases: polar liquid, band, and disordered gas states. In our model, the transition between band and disordered gas states is discontinuous. Giant number fluctuation is observed in the polar liquid phase. We also compare our results with the Vicsek model and show that the interaction with noise particles can stabilize the band state to very low noise condition. This band structure could recruit most of the active particles in the system, which greatly enhances the coherence of the system. Our findings of complex collective behaviors in environmental noise help us to understand how individuals modify their self-organization by environmental factors, which may further contribute to improving the design of collective migration and navigation strategies.
Temperature dependence of heat conduction coefficient in nanotube/nanowire networks
Air breakdown induced by the microwave with two mutually orthogonal and heterophase electric field components
Relationship measurement between ac-Stark shift of 40Ca+ clock transition and laser polarization direction
Ac-Stark shift of atom levels is caused by an ac-electromagnetic field. As an electromagnetic wave, laser light does induce ac-Stark shift. It is proved experimentally that if the light is linearly polarized, the dynamic polarizability changes with polarization direction. The polarization direction of the linearly-polarized laser is tuned by 720°, and the ac-Stark shifts of the 4S1/2, m= 1/2→3D5/2, m= 1/2 clock transitions in 40Ca+ are measured in steps of 10°. The frequency shifts change with laser polarization in a periodical manner and have values opposite to each other.