Epitaxial growth of ZnO films on (100) and (001) gamma-LiAlO2 substrates by pulsed laser deposition

Structural and optical properties were investigated for ZnO films grown on (100) and (001) gamma-LiAlO2 (LAO) substrates by pulsed laser deposition method. According XRD results, it is intuitionistic that (100) LAO is suitable for fabricating high quality ZnO film, while (001) LAO is unsuitable. The FWHM of XRD, stress in film and FWHM of UV PL spectra for ZnO films on (100) LAO show a decreasing with increasing substrate temperature from 300 to 600 degrees C. ZnO film fabricated at 600 degrees C has the greatest grain size, the smallest stress (0.47 Gpa) and PL FWHM value (similar to 85 meV). This means that the substrate temperature of 600 degrees C is optimum for ZnO film deposited on (100) LAO. Moreover, it was found that the UV PL spectra intensity of ZnO film is not only related to the grain size and stoichiometric, but also depends on the stress in the film.

Composite substrate LiGaO2(001)/beta-Ga2O3(100) fabricated by vapor transport equilibration

Highly (001) orientation LiGaO2 layers have been successfully fabricated on (100) beta-Ga2O3 surface by vapor transport equilibration (VTE) technique. The temperature is very important for the WE treatment. At low temperature (800 degrees C), LiGaO(2)layers are textured. As the temperature was raised to 1100 C the layer becomes highly oriented in the [100] direction. It shows that the best temperature for WE treatment is 1100 degrees C. This technique is promising to fabricate small lattice mismatch composite substrate of LiGaO2 (001)//beta-Ga2O3 (100) for GaN films. (c) 2006 Elsevier B.V. All rights reserved.

Fabrication of beta-BaB2O4 layers on (001) Sr2+-doped alpha-BaB2O4 by vapor transport equilibration (VTE)

Crystalline beta-BBO layers have been successfully prepared on (0 0 1)-oriented Sr2+-doped alpha-BBO substrates using vapor transport equilibration technique. The layers were characterized by X-ray diffraction, X-ray rocking curve and transmission spectra. The present results manifest that the VTE treatment time and powder ratio are important factors on the preparation of beta-BBO layers. beta-BBO layers with a highly (0 0 l) preferred orientation were obtained according to XRD profiles. The full width at half-maximum of the rocking curve for the layer is as low as about 1000 in., which shows the high crystallinity of the layer. These results reveal the possibility of fabricating beta-BBO (0 0 1) layers on (0 0 1)-oriented Sr2+-doped alpha-BBO substrates by VTE. (C) 2006 Elsevier Ltd. All rights reserved.

青岛市水资源复合系统动力学模拟研究

水资源是人类赖以生存和发展的最重要的物质资源之一，水资源的可持续利用是实现社会经济可持续发展的必要前提。随着人口的增加，社会经济的发展和人民生活水平的提高，青岛市水资源供需矛盾进一步凸显。本文在分析青岛市水资源利用现状的基础上，运行系统动力学方法，研究了青岛市水资源复合系统可持续利用状况，主要结论如下： （1）采用系统动力学Vensim-PLE软件，以水资源供需平衡为核心，建立了青岛市水资源-社会-经济-生态环境复合系统动力学模型，并以青岛市2000~2008年的统计资料作为基础数据检验了模型的有效性。为了提高模拟效果，分析了模型主要参数的敏感度，发现工业供水比例对模拟结果影响最大，生活供水比例、第三产业供水比例、回用水工业供水比例、污水处理投资系数及回用水生态环境供水比例等参数的敏感度依次减小。 （2）运用所建立的系统动力学模型模拟趋势条件下青岛市2009~2030年的水资源利用及需求状况。结果表明，现状趋势方案下青岛市2009~2030年的总需水量快速增加，2020年、2030年的总需水量分别为96190.6万吨、137300万吨；水资源供需差额急速增加，缺水程度越来越大，到2030年缺水程度达到0.5055；随着青岛市污水处理能力的提高，污水回用量增加，从3000万吨左右增加到接近10000万吨；现状趋势条件下2009~2030年青岛市GDP值快速增长，人口承载力逐渐上升，但上升趋势逐渐趋缓。 （3）假设了5种水资源发展方案：现状趋势发展型，提高污水处理投资系数，提高海水淡化产量，调整各行业用水定额，调整产业结构。用建立的系统动力学模型模拟分析了在这5种方案下的青岛市水资源可持续利用能力。综合比较这5种方案的优缺点，提出优化方案。优化方案1：将污水处理投资系数由0.001提高至0.003；从2009年起海水淡

白鱼属鱼类一新种

白鱼属是鲌亚科鱼类中最大的属。有16种和亚种。种类集布于滇东南盘江和金沙江两大水系,少数在滇西北及邻近的四川省部分地区。最近在禄丰县(属红河水系)获白鱼属标本6尾,经鉴定认为是一新种少耙白鱼(Anabarilus paucirastellius sp.nov.)。正模标本:编号86Ⅶ002,全长105mm,体长88mm。采自云南省禄丰县一平浪樟木箐。副模标本:编号86Ⅶ001,86Ⅶ003～006,共5尾,全长85～100mm,体长68～82mm。采集地点同上。新种模式及副模标本分别保存于中国科学院水生生

GaN/GaAs(001)薄膜的MOCVD生长与结构特性分析

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

Co doping enhanced giant magnetocaloric effect in Mn1-xCoxAs films epitaxied on GaAs (001)

A giant magnetocaloric effect was found in series of Mn1-xCoxAs films epitaxied on GaAs (001). The maximum magnetic entropy change caused by a magnetic field of 4 T is as large as 25 J/kg K around room temperature, which is about twice the value of pure MnAs film. The observed small thermal hysteresis is more suitable for practical application. Growing of layered Mn1-xCoxAs films with Co concentration changing gradually may draw layered active magnetic regenerator refrigerators closer to practical application. Our experimental result may provide the possibility for the combination of magnetocaloric effect and microelectronic circuitry.

Magnetic anisotropies of laterally confined structures of epitaxial Fe films on GaAs (001)

We have investigated magnetic properties of laterally confined structures of epitaxial Fe films on GaAs (001). Fe films with different thicknesses were grown by molecular-beam epitaxy and patterned into regular arrays of rectangles with varying aspect ratios. In-plane magnetic anisotropy was observed in all of the patterned Fe films both at 15 and 300 K. We have demonstrated that the coercive fields can be tuned by varying the aspect ratios of the structures. The magnitudes of the corresponding anisotropy constants have been determined and the shape anisotropy constant is found to be enhanced as the aspect ratio is increased.

Structural and electrical properties of (110) ZnO epitaxial thin films on (001) SrTiO3 substrates

(110) oriented ZnO thin films were epitaxially prepared on (001) SrTiO3 single crystal substrates by a pulsed laser deposition method. The evolution of structure, surface morphology, and electrical conductivity of ZnO films was investigated on changing the growth temperature. Two domain configurations with 90 degrees rotation to each other in the film plane were found to exist to reduce the lattice mismatch between the films and substrates. In the measured temperature range between 80 K and 300 K, the electrical conductivity can be perfectly fitted by a formula of a (T) = sigma(0) + aT(b/2). implying that the electron-phonon scattering might have a significant contribution to the conductivity. (C) 2008 Elsevier Ltd. All rights reserved.

Anisotropic exchange splitting of excitons in (001)GaAs/Al0.3Ga0.7As superlattice studied by reflectance difference spectroscopy

Anisotropic exchange splitting (AES) is induced by the joint effects of the electron-hole exchange interaction and the symmetry reduction in quantum wells and quantum dots. A model has been developed to quantitatively obtain the electron-hole exchange energy and the hole-mixing energy of quantum wells and superlattices. In this model, the AES and the degree of polarization can both be obtained from the reflectance difference spectroscopy. Thus the electron-hole exchange energy and the hole-mixing energy can be completely separated and quantitatively deduced. By using this model, a (001)5 nm GaAs/7 nm Al0.3Ga0.7As superlattice sample subjected to [110] uniaxial strains has been investigated in detail. The n=1 heavy-hole (1H1E) exciton can be analyzed by this model. We find that the AES of quantum wells can be linearly tuned by the [110] uniaxial strains. The small uniaxial strains can only influence the hole-mixing interaction of quantum wells, but have almost no contribution to the electron-hole exchange interaction. (c) 2008 American Institute of Physics.

Investigation of GaSb epilayer grown on vicinal GaAs(001) substrate by high resolution x-ray diffraction

GaSb epilayers grown on GaAs(001) vicinal substrate misoriented towards (111) plane were studied using high-resolution x-ray diffraction (HRXRD). The results show that GaSb epilayers exhibit positive crystallographic tilt and the distribution of 60 degrees misfit dislocations (MDs) is imbalanced. The vicinal substrate also leads to the anisotropy of the mosaic structure, i.e. the lateral coherent lengths in [1 (1) over bar0] directions are larger than those in [110] directions. Furthermore, the full-width at half maximum (FWHM) of the off-axis peaks varies with the inclination angle, which is a result of different dislocation densities in the {111} glide planes.

Surface plasmon enhanced ultraviolet emission from ZnO films deposited on Ag/Si(001) by magnetron sputtering

The ZnO films were grown on Ag/Si(001) substrates by sputtering Ag and ZnO targets successively in a pure Ar ambient. A significant enhancement of ZnO ultraviolet emission and a reduction of its full width of half maximum have been observed while introducing a 100 nm Ag interlayer between ZnO film and Si substrate. Furthermore, a complete suppression of the defect related visible emission was also found for the ZnO/Ag/Si sample. This improved optical performance of ZnO is attributed to the resonant coupling between Ag surface plasmon and ultraviolet emission of ZnO. (c) 2007 American Institute of Physics.

Spin precession and electron spin polarization wave in [001]-grown quantum wells

We theoretically study the spatial behaviors of spin precessions modulated by an effective magnetic field in a two-dimensional electron system with spin-orbit interaction. Through analysis of interaction between the spin and the effective magnetic field, we find some laws of spin precession in the system, by which we explain some previous phenomena of spin precession, and predict a controllable electron spin polarization wave in [001]-grown quantum wells. The shape of the wave, like water wave, mostly are ellipse-like or circle-like, and the wavelength is anisotropic in the quantum wells with two unequal coupling strengths of the Rashba and Dresselhaus interactions, and is isotropic in the quantum wells with only one spin orbit interaction.

Strain and magnetic anisotropy of as-grown and annealed Fe films on c(4x4) reconstructed GaAs (001) surface

Fe films with the different thicknesses were grown on c(4x4) reconstructed GaAs (001) surfaces at low temperature by molecular-beam epitaxy. Well-ordered bcc structural Fe epitaxial films are confirmed by x-ray diffraction patterns and high-resolution cross-sectional transmission electron microscopy images. A large lattice expansion perpendicular to the surface in Fe film is observed. In-plane uniaxial magnetic anisotropy is determined by the difference between magnetizing energy along [110] and [110] directions, and the constant of interfacial uniaxial magnetic anisotropy is calculated to be 1.02x10(-4) J m(-2). We also find that magnetic anisotropy is not obviously influenced after in situ annealing, but in-plane strain is completely changed.