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981.
Comparative study of different properties of GaN films grown on(0001) sapphire using high and low temperature AlN interlayers
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Comparative study of high and low temperature AlN
interlayers and their roles in the properties of GaN epilayers
prepared by means of metal organic chemical vapour deposition on
(0001) plane sapphire substrates is carried out by high resolution
x-ray diffraction, photoluminescence and Raman spectroscopy. It is
found that the crystalline quality of GaN epilayers is improved
significantly by using the high temperature AlN interlayers, which
prevent the threading dislocations from extending, especially for
the edge type dislocation. The analysis results based on
photoluminescence and Raman measurements demonstrate that there
exist more compressive stress in GaN epilayers with high temperature
AlN interlayers. The band edge emission energy increases from
3.423~eV to 3.438~eV and the frequency of Raman shift of $E_{2
}$(TO) moves from 571.3~cm$^{ - 1}$ to 572.9~cm$^{ - 1}$ when the
temperature of AlN interlayers increases from 700~$^{\circ}$C to
1050~$^{\circ}$C. It is believed that the temperature of AlN
interlayers effectively determines the size, the density and the
coalescence rate of the islands, and the high temperature AlN
interlayers provide large size and low density islands for GaN
epilayer growth and the threading dislocations are bent and
interactive easily. Due to the threading dislocation reduction in
GaN epilayers with high temperature AlN interlayers, the approaches
of strain relaxation reduce drastically, and thus the compressive
stress in GaN epilayers with high temperature AlN interlayers is
high compared with that in GaN epilayers with low temperature AlN
interlayers. 相似文献
982.
The first order differential matrix equations of the host shell and constrained layer for a sandwich rotational shell are derived based on the thin shell theory.Employing the layer wise principle and first order shear deformation theory, only considering the shearing deformation of the viscoelastic layer, the integrated first order differential matrix equation of a passive constrained layer damping rotational shell is established by combining with the normal equilibrium equation of the viscoelastic layer.A highly precise transfer matrix method is developed by extended homogeneous capacity precision integration technology.The numerical results show that present method is accurate and effective. 相似文献
983.
In this paper, we prove the existence of Hermitian-Einstein metrics for holomorphic vector bundles on a class of complete Kähler manifolds which include Hermitian symmetric spaces of noncompact type without Euclidean factor, strictly pseudoconvex domains with Bergman metrics and the universal cover of Gromov hyperbolic manifolds etc. We also solve the Dirichlet problem at infinity for the Hermitian-Einstein equations on holomorphic vector bundles over strictly pseudoconvex domains.
984.
Zhi’an Ren Guangcan Che Shunlian Jia Hong Chen Yongming Ni Zhongxian Zhao 《中国科学 数学(英文版)》2001,44(9):1205-1208
The effect of Mg and C contents on TC in MgCN3, and structure and superconductivity of MgCNi3-x Co x were studied. It is found that the excess of Mg and C in initial material mixture is favorable to improvement inT c and helps to obtain single-phase samples. For preparing MgCNi3 superconductor, the optimum composition of starting materials is MgC1.45Ni3 with excess of Mg (20 wt.%) of the stoichiometric composition. In gCNi3-x Co x system, a continuous solid solution is formed, lattice parameter decreases slightly andT c decreases obviously with increasingx. A suppression of superconductivity is observed due to the substitution of Co (Mn) for Ni. The suppression effect is smaller for the substitution of Co than that of Mn 相似文献
985.
A simple long-range-order parameterPis defined for describing the process of formation of chains in the electric field direction. The free energy of the system is taken to be the sum of the internal energy, the electrostatic interaction and configuration entropy as a function o P. Calculated results indicate that the critical parameter is a function of electric field, temperature, misfit dielectric coefficients and concentration of particles. 相似文献
986.
The complex separated flows induced by shock wave/boundary layer interaction were studied at hypersonic speed of Mach number 5. The experimental results on hypersonic flow over a set of rectangular cylinders are presented in this paper. The rectangular cylinder mounted on a flat plate worked as a typical model to simulate the obstacle on the vehicle surface. The effects of flow interaction on the aerodynamic characteristics have to be predicted for various geometrical parameters. So the static pressure distributions on the model surface were measured, the complex shock wave system was shown by schlieren photos, and the separated flow patterns around the obstacle were visualized by oil flow technique. All of the results describe the interactive flowfield features including peak pressure levels and their locations as well as separated boundaries associated with influence regions. 相似文献
987.
1 IntroductionLet X be a real Banach space and let Jdenotethe normalized duality mapping from X into2 X* given byJ( x) ={ f*∈ X* :〈x,f*〉 =‖ x‖ 2 , ‖ f*‖ =‖ x‖ } ,where X* is the dual and〈· ,·〉denotes the generalized duality pairing.Clearly,X issmooth if and only if J is a single-valued mapping.An operator T with domain D( T) =K and range R( T) in X iscalled strongly accretive ifthere exists a constant k>0 and for all x,y∈D( T) ,there exists j( x-y)∈ J( x-y) suchthat… 相似文献
988.
根据形状记忆合金的一维热力学本构关系,建立了粘贴预拉伸SMA薄层的复合悬臂粱弯曲变形的模型。分析了在不同温度下,SMA相交恢复力驱动粱而产生的弯曲变形,并进行了实验研究。 相似文献
989.
Tian Weizhi Ni Bangfa Wang Pingsheng Cao Lei Zhang Yangmei 《Accreditation and quality assurance》2001,6(12):488-492
In a series of three papers, the inherent characteristics of relative instrumental neutron activation analysis (INAA) as a
primary ratio method of measurement, the unique functions of parametric INAA as an ideal back-up method of the relative INAA,
and the valuable role of INAA in characterization of sampling behavior of individual elements in certified reference materials
(CRMs) will be discussed. In this paper, the first of the series, the uncertainty evaluation and the traceability of values
measured by neutron activation analysis (NAA), especially instrumental NAA (INAA), will be described to demonstrate the method
at its ”the state-of-the-art” level can meet CCQM criteria for a primary ratio method. The scope and examples will be given.
Received: 19 March 2001 Accepted: 2 October 2001 相似文献
990.