Rectification and electroluminescence of nanostructured GaN/Si heterojunction based on silicon nanoporous pillar array

A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. The average size of nc-Ga N is determined to be ~10 nm. The spectral measurements disclose that the photoluminescence（PL） from GaN/SiNPA is composed of an ultraviolet（UV） band and a broad band spanned from UV to red region, with the feature that the latter band is similar to that of electroluminescence（EL）. The electron transition from the energy levels of conduction band and, or, shallow donors to that of deep acceptors of Ga N is indicated to be responsible for both the broad-band PL and the EL luminescence. A study of the I-V characteristic shows that at a low forward bias, the current across the heterojunction is contact-limited while at a high forward bias it is bulk-limited, which follows the thermionic emission model and space-charge-limited current（SCLC） model, respectively. The bandgap offset analysis indicates that the carrier transport is dominated by electron injection from n-GaN into the p-Si-NPA, and the EL starts to appear only when holes begin to be injected from Si-NPA into GaN with biases higher than a threshold voltage.

Structural,magnetic,and dielectric properties of Ni-Zn ferrite and Bi_(2)O_(3)nanocomposites prepared by the sol-gel method

Ni-Zn ferrite and Bi_(2)O_(3)composites were developed by the sol-gel method.The structural,magnetic,and dielectric properties were studied for all the prepared samples.X-ray diffraction(XRD)was performed to study the crystal structure.The results of field emission scanning electron microscopy(FE-SEM)showed that the addition of Bi_(2)O_(3)can increase the grain size of the Ni-Zn ferrite.Magnetic properties were analyzed by a hysteresis loop test and it was found that the saturation magnetization and coercivity decreased with the increase of Bi_(2)O_(3)ratio.In addition,the dielectric properties of the Ni-Zn ferrite were also improved with the addition of Bi_(2)O_(3).

Design of a multiband terahertz perfect absorber

A thin-flexible multiband terahertz metamaterial absorber （MA） has been investigated. Each unit cell of the MA consists of a simple metal structure, which includes the top metal resonator ring and the bottom metallic ground plane, separated by a thin-flexible dielectric spacer. Finite-difference time domain simulation indicates that this MA can achieve over 99% absorption at frequencies of 1.50 THz, 3.33 THz, and 5.40 THz by properly assembling the sandwiched structure. However, because of its asymmetric structure, the MA is polarization-sensitive and can tune the absorptivity of the second absorption peak by changing the incident polarization angle. The effect of the error of the structural parameters on the absorption efficiency is also carefully analyzed in detail to guide the fabrication. Moreover, the proposed MA exhibits high refractive-index sensing sensitivity, which has potential applications in multi-wavelength sensing in the terahertz region.

Handling Error Propagation in Sequential Data Assimilation Using an Evolutionary Strategy

An evolutionary strategy-based error parameterization method that searches for the most ideal error adjustment factors was developed to obtain better assimilation results. Numerical experiments were designed using some classical nonlinear models （i.e., the Lorenz-63 model and the Lorenz-96 model）. Crossover and mutation error adjustment factors of evolutionary strategy were investigated in four aspects： the initial conditions of the Lorenz model, ensemble sizes, observation covarianee, and the observation intervals. The search for error adjustment factors is usually performed using trial-and-error methods. To solve this difficult problem, a new data assimilation system coupled with genetic algorithms was developed. The method was tested in some simplified model frameworks, and the results are encouraging. The evolutionary strategy- based error handling methods performed robustly under both perfect and imperfect model scenarios in the Lorenz-96 model. However, the application of the methodology to more complex atmospheric or land surface models remains to be tested.

The Partner of f_(4)(2050)in the 1^(3)F_(4) Meson Nonet

The assignment of the 1^(3)F_(4) meson nonet is phenomenologically analyzed in the framework of Regge phenomenology and meson-meson mixing.The mass of the partner of in the 1^(3)F_(4) meson nonet is determined to be 2167±27 MeV.The quarkonia content and the decay properties of the two isoscalar states of the 1^(3)F_(4) meson nonet are presented.The predictions can be tested by the BES-Ⅲ experiment in the near future.

Photon and Elementary Particles Theory

At present, the research of single-photon is a hot topic, it has been widely applied in quantum measurement, quantum entanglement and quantum information. In this paper, we have proposed a new single photon theory, which is the vector potential A rotation at the vertical motion direction of photon, it can produce the microscopic electric field and magnetic field, and they satisfy the Maxwell equations. We have calculated photon spin, momentum, energy, and found there are left-handed and right-handed photon. In addition, we study the multi-photon theory and the dynamics theory between photons interaction. On this basis, we have further given the compound structures of electron, proton, neutron, neutrino, π meson, dark matter with the photon structural theory, and calculated their mass, charge and spin.

Obtaining low energy γ dose with CMOS sensors

A method is established for measuring low energy γ-rays dose by using CMOS sensors without any X-/γ-ray converters. Gamma-ray source of241 Am and152Eu are used to test the system. Based on gray value, an analysis method is proposed to obtain the γ-ray dose. Cumulative dose is determined by correlating the gray value to the dose readings of standard dosimeters. The relationship between gray value and the cumulative dose of γ-rays are trained by using back propagation neural network with BFGS algorithm. After comparison, it shows that BFGS algorithm trainings are suitable for different γ-ray sources under higher error condition. These indicate the feasibility of measuring low energy γ-ray dose by using common CMOS image sensors.

Spectra of charmed and bottom baryons with hyperfine interaction

Up to now, the excited charmed and bottom baryon states have still not been well studied experimentally or theoretically. In this paper, we predict the mass of Ωb, the only L=0 baryon state which has not been observed, to be 6069.2 MeV. The spectra of charmed and bottom baryons with the orbital angular momentum L= 1 are studied in two popular constituent quark models, the Goldstone boson exchange （GBE） model and the one gluon exchange （OGE） hyperfine interaction model. Inserting the latest experimental data from the ＂Review of Particle Physics＂, we find that in the GBE model, there exist some multiplets （∑c（b）, ≡c（b） and Ωc（b）） in which the total spin of the three quarks in their lowest energy states is 3/2, but in the OGE model there is no such phenomenon. This is the most important difference between the GBE and OGE models. These results can be tested in the near future. We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally, not only for the abundance of baryon spectra, but also for determining which hyperfine interaction model best describes nature.

Effect of oxygen pressure on electrical transport properties for(110) oriented La_(2/3)Sr_(1/3)MnO_3 films directly deposited on silicon

La2/3Sr1/3MnO3 films with （110） preferred orientation were deposited on Si （100） substrate without any buffer layer by pulsed laser deposition technique. Effect of oxygen pressure on orientation, surface morphology, and electrical transport properties were investigated. The film deposited at 10 Pa presented （110） preferred orientation with the best crystalline quality, the largest grain size, and the smallest roughness. The （110） oriented film presented higher metal-insulator transition temperature, and the lower resis- tivity than that of the samples without preferred orientation.

Constraints on ultracompact minihalos using neutrino signals from gravitino dark matter decay

Ultracompact dark matter minihalos （UCMHs） would be formed during the early universe if there were large density perturbations. If dark matter can decay into particles described by the standard model, such as neutrinos, these objects would become potential astrophysical sources of emission which could be detected by in- struments such as IceCube. In this paper, we investigate neutrino signals from nearby UCMHs due to gravitino dark matter decay and compare these signals with the back- ground neutrino flux which is mainly from the atmosphere to obtain constraints on the abundance of UCMHs.

Comparison of aerosol characteristics during haze periods over two urban agglomerations in China using CALIPSO observations

Using CALIPSO （cloud-aerosol lidar and infrared pathfinder satellite observation） vertical observation data during haze periods from January 2007 to December 2008, we analyzed differences in aerosol char- acteristics near the surface, as well as in the middle troposphere between the Beijing-Tianjin-Hebei metropolitan region （Area A） and the Yangtze River Delta region （Area B） in China. One significant dif- ference was that haze pollution in Area A was related to local and non-local aerosols, while in Area B it was related to local anthropogenic sources. In all seasons apart from autumn, aerosol pollution in Area A was more severe than in Area B, both near the surface and at higher altitudes, In Area A, non-spherical aerosols were dominant from 0 to 4 km in spring, summer, and winter; while in autumn, there were con- siderably high numbers of non-spherical aerosols below 0.5 km, and near-spherical aerosols from 0.5 to 4 km. In Area B, both near-spherical and non-spherical aerosols were common in all seasons. Moreover, aerosols with attenuated color ratios of 0-0.2 were more common in all seasons in Area A than in Area B, indicating that fine particle pollution in Area A was more serious than in Area B. Finally, relatively large aerosols linked to gravity settling appeared more frequently near the surface in Area A than in Area B.

Masses of heavy-light mesons in Regge phenomenology

The masses of some orbitally and radially excited heavy-light mesons are calculated in Regge phenomenol- ogy. The results are in reasonable agreement with the experimental data and those given in many other theoretical approaches. Based on the calculation, we suggest that the recently observed D（2550）, D（2600） and D（2760） can be assigned as the charmed members of the 21S0, 23S1 and 13D1 multiplets, respectively. D＇1（2700） may be assigned as the charm-strange member of the 23S1 state. The results may be helpful in understanding the nature of current and future experimentally observed heavy-light mesons.

Probing the mass degeneracy of particles with different spins

The spin is an important property of a particle. Although it is unlikely, there is still a possibility that two particles with different spins share similar masses. In this paper, we propose a method to probe this kind of mass degeneracy of particles with different spins. We use the cascade decay B^＋ →X（3872）K^＋, X（3872）→D^＋D^- to illustrate our method. It can be seen that the possible mass degeneracy of X（3872） can lead to interesting behavior in the corresponding cascade decay.

Intrinsic Localized Spin-Wave Modes in an Anisotropic Ferromagnet with Dzyaloshinsky–Moriya Interaction

The existence and properties of intrinsic localized spin-wave modes in a ferromagnetic XXZ spin chain with Dzyaloshinsky–Moriya interaction are investigated analytically in the semiclassical limit. The model Hamiltonian is quantized by introducing the Dyson–Maleev transformation and the coherent state representation is chosen as the basic representation of the system. By making use of the method of multiple scales combined with a quasidiscreteness approximation, the equation of motion for the coherent-state amplitude is reduced to the nonlinear Schr¨odinger equation.It is shown that a bright intrinsic localized spin-wave mode whose eigenfrequency lies below the bottom of the magnon frequency band can exist in the ferromagnetic system. We also show that the system can produce a dark intrinsic localized spin-wave mode, i.e., nonpropagating kink, whose eigenfrequency is below the upper of the magnon frequency band. In addition, we find that the introduction of the Dzyaloshinsky–Moriya interaction changes wave numbers in the Brillouin-zone corresponding to the appearance of intrinsic localized spin-wave modes.

La_2CuBiS_5化合物的电子结构和热电特性研究(英文)

本文采用第一性原理和半经典玻尔兹曼理论相结合的方法研究了La_2CuBiS_5的基本性质.电荷差分密度图显示电子积聚在Bi-S原子之间,这意味着Bi和S之间成共价键.Cu和S之间的电荷差分密度与Bi-S的相似,表明Cu-S之间成共价键.计算表明La_2CuBiS_5的最小热导率非常小,这有利于材料的热电特性.受热激发引起的双极化效应的影响,材料的塞贝克系数在T=800 K时明显下降,n型和p型掺杂对应的最大S^2σ/τ值分别是-1.71×10^(11)和1.837×10^(11)WK^(-2)ms^(-1).沿Γ-Y方向上能带的大的弥散性和较高简并度有利于S_y和σ/τ_y.因此,La_2CuBiS_5展现出各向异性的热电特性,并且沿y方向上的热电特性最佳.