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A statistical approach is used to construct a kinematic theory of x-ray diffraction on a semiconducting superlattice with
a two layer period. This theory takes two types of structural deformations into account: crystal lattice defects caused by
microdefects distributed chaotically over the thickness of the superlattice, and periodicity defects of an additional superlattice
potential owing to random deviations in the thicknesses of the layers of its period from specified values. Numerical simulation
is used to illustrate the effect of structural defects on the development of the diffraction reflection curve. The theory
is used to analyze experimental x-ray diffraction spectra of semiconducting InxGa1−x
As/GaAs superlattices.
Zh. Tekh. Fiz. 69, 44–53 (February 1999) 相似文献
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V. A. Maksimenko V. V. Makarov A. A. Koronovskii A. E. Hramov R. Venckevičius G. Valušis A. G. Balanov F. V. Kusmartsev K. N. Alekseev 《JETP Letters》2016,103(7):465-470
A very simple model describing steady-state electron transport along a quantum superlattice of a finite length taking into account an arbitrary electrical characteristic of the injecting contact is considered. In the singleminiband approximation, exact formulas for the spatial distribution of the electric field in the superlattice are derived for different types of contact. Conditions under which the field is uniform are identified. Analytical expressions for the current–voltage characteristics are obtained. In the context of the developed theory, the possibility of attaining uniform-field conditions in a diode structure with a natural silicon-carbide superlattice is discussed. 相似文献
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《Physics letters. A》1992,170(1):67-69
A theory of high-quality X-ray eigenmodes in a crystal-vacuum superlattice is developed. We show that the superlattice can be used for X-rays as a resonator with the Q-factor ∼ 1010. 相似文献
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L.E. Ramos G.M. Sipahi L.M.R. Scolfaro R. Enderlein J.R. Leite 《Superlattices and Microstructures》1997,22(4):437-442
A microscopic theory is presented for high-field miniband transport in a two-dimensional superlattice. The energy transfer to the lateral electron motion is taken into account as well as scattering on polar optical phonons. Oscillatory current anomalies appear when the optical phonon frequency is a multiple of the Bloch frequency. The current oscillations, which are due to Wannier–Stark localization, are much more pronounced in a two-dimensional than in a three-dimensional system with a superlattice structure in one direction. 相似文献
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We investigate theoretically the feasibility of amplification of terahertz radiation in aligned achiral carbon nanotubes, a zigzag (12,0) and an armchair (10,10) in comparison with a superlattice using a combination of a constant direct current (dc) and a high-frequency alternate current (ac) electric fields. The electric current density expression is derived using the semiclassical Boltzmann transport equation with a constant relaxation time. The electric field is applied along the nanotube axis. Analysis of the current density versus electric field characteristics reveals a negative differential conductivity behavior at high frequency, as well as photon assisted peaks. The photon assisted peaks are about an order of magnitude higher in the carbon nanotubes compared to the superlattice. These strong phenomena in carbon nanotubes can be used to obtain domainless amplification of terahertz radiation at room temperature. 相似文献
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R. N. Kyutt G. N. Mosina M. P. Shcheglov L. M. Sorokin 《Physics of the Solid State》2006,48(8):1577-1583
High-resolution x-ray diffractometry and electron microscopy are used to study the defect structure and relaxation mechanism of elastic stresses in AlGaN/GaN superlattices grown by the MOCVD method on sapphire covered with a preliminarily deposited GaN and AlGaN buffer layer. Based on an analysis of the half-widths of three-crystal scan modes of x-ray reflections measured in different diffraction geometries, the density of different dislocation families is determined. For all the dislocation families, the density is shown to increase with the Al concentration in the solid-solution layers and depend only weakly on the superlattice period. From the electron-microscopic patterns of planar and cross sections, the types of dislocations and their distribution in depth are determined. It is shown that, in addition to high-density vertical edge and screw dislocations, which nucleate in the buffer layer and propagate through the superlattice layers, there are sloped intergrowing dislocations with a large horizontal projection and bent mixed dislocations with a Burgers vector $\left\langle {11\overline 2 3} \right\rangle $ at the interface between individual superlattice layers. The former dislocations form at the interface between the buffer layer and the superlattice and remove misfit stresses between the buffer and the superlattice as a whole, and the latter dislocations favor partial relaxation of stresses between individual superlattice layers. In samples with a high Al concentration (greater than 0.4) in AlGaN layers, there are cracks surrounded by high-density chaotic horizontal dislocations. 相似文献
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The structural and thermodynamic properties of hydrogen dissolved in Nb/Ta superlattices are studied by in-situ x-ray scattering techniques. From the x-ray satellite intensities, it is found that H induces a strain modulation exhibiting a Curie-Weiss temperature dependence. The intensities are analyzed in terms of a mean field model of the modulated lattice gas, yielding quantitative information on the hydrogen-metal and hydrogen-hydrogen interaction energies. Critical behavior associated with a gas-liquid transition is also observed. Hydrogen density fluctuations with wavelengths shorter than a superlattice period are, however, suppressed by the superlattice, which represents a novel manifestation of a coherent phase transition. These experiments provide new and fundamental insight into the role of spacially varying two body interactions in critical phenomena. 相似文献
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Gas-phase synthesis of nitrogen-containing carbon nanotubes and their electronic properties 总被引:1,自引:0,他引:1
A. G. Kudashov A. V. Okotrub N. F. Yudanov A. I. Romanenko L. G. Bulusheva O. G. Abrosimov A. L. Chuvilin E. M. Pazhetov A. I. Boronin 《Physics of the Solid State》2002,44(4):652-655
Nitrogen-containing carbon nanotubes are synthesized using a gas-phase reaction. The synthesis of nitrogen-doped carbon nanotubes from 100 to 500 Å in diameter is accomplished through pyrolysis of acetonitrile (CH3CN) at a temperature of 800°C. Cobalt and nickel metallic particles formed upon thermal decomposition of a mixture of maleate salts are used as catalysts. The materials synthesized are investigated by scanning and transmission electron microscopy. Analysis of the x-ray photoelectron spectra demonstrates that the content of nitrogen atoms in three nonequivalent charge states is approximately equal to 3%. A comparison of the CK α x-ray fluorescence spectrum of the carbon nanotubes synthesized through electric-arc evaporation of graphite and the x-ray fluorescence spectrum of the nitrogen-containing carbon nanotubes prepared by catalytic decomposition of acetonitrile indicates that, in the latter case, the spectrum contains a certain contribution from the sp 3 states of carbon atoms. The temperature dependences of the electrical conductivity for different types of multi-walled carbon nanotubes are compared. The difference observed in the temperature dependences of the electrical conductivity is associated with the presence of additional scattering centers in nitrogen-containing carbon nanotubes. 相似文献
11.
《Surface science》1986,166(1):45-56
A theoretical investigation has been made of surface plasmon polariton modes in truncated superlattices using a local theory with retardation. The modes are characterized by electric fields that decay exponentially away from each interface and that have an envelope that decays exponentially away from the end of the truncated superlattice. A criterion for the existence of the surface models is developed. Numerical results are presented for several illustrative cases. 相似文献
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《Superlattices and Microstructures》1993,13(2):237
We present resonance reflectivity measurements performed on graded GaAs/AlAs superlattices in the transitional region from type I to type II. A theory of exciton states and exciton oscillator strength is developed making allowance for the mixing of Γ1, X1 and X3 electron states in the superlattice. Experimental and theoretical results are compared taking into account effects of superlattice imperfections. 相似文献
13.
介电体超晶格是一种新型的有序微结构材料.它具有通常均质材料所不具有的独特优异性能,展现出重要的应用前景.文章介绍了南京大学研究组关于介电体超晶格研究所取得的进展,如将多个光参量过程集成于一块介电体超晶格之中获得了多波长激光同时输出,研制成超晶格全固态三基色激光器原型,在介电体超晶格中将拉曼散射强度增强到104-105倍,用超晶格研制的器件填补了体波超声器件从几百MHz到几千MHz的空白频段,发现了微波与超晶格振动的强烈耦合以及极化激元(polariton)的激发与传播等. 相似文献
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M. M. Brzhezinskaya E. M. Baitinger V. I. Kormilets 《Journal of Experimental and Theoretical Physics》2000,91(2):393-398
An attempt is made to calculate the energy bands and spectra of the characteristic CK α emission of small-diameter carbon nanotubes. The calculated spectra for the nanotubes are compared with similar spectra for graphite monolayers used as a test object and with known experimental results for nanotubes. It is concluded that the x-ray emission spectra can be used to identify thin carbon nanotubes. A classification of solid-phase carbon is proposed which takes into account the position of carbon nanotubes in the family of allotropic carbon forms. The type of hybridization of the electrons in the carbon atom is used as the criterion for classification. 相似文献
16.
Ting-Chang Chang Wen-Kuan Yeh Yu-Jane Mei Wen-Chung Tsai Chun-Yen Chang Y. F. Chen 《Optical and Quantum Electronics》1996,28(10):1295-1303
Ordered (Ord-SL) and disordered (Dis-SL) Si-SiGe superlattices are grown using ultrahigh vacuum chemical vapour deposition (UHVCVD). The results of cross-sectional transmission electron microscopy (XTEM) and high-resolution double crystal x-ray diffraction (HRXRD) indicate that high quality Si-SiGe superlattices can be achieved. Well-defined band-edge excitonic luminescence is observed for the Si0.86Ge0.14-Si superlattice. Stronger phosoluminescence (PL) is observed for the Si-SiGe disordered superlattice compared with the corresponding Si-SiGe ordered superlattice. Furthermore, PL peak energy of the Dis-SL shifts to lower value with respect to the peak position of the corresponding Ord-SL. The stronger intensity of the no-phonon (NP) peak and the red shift of the PL peak are possibly a result of two probable mechanisms: (i) the tunnelling effect and (ii) the formation of localized states. 相似文献
17.
Trellakis A 《Physical review letters》2003,91(5):056405
A general theoretical approach for the nonperturbative Bloch solution of Schr?dinger's equation in the presence of a constant magnetic field is presented. Using a singular gauge transformation based on a lattice of magnetic flux lines, an equivalent quantum system with a periodic vector potential is obtained. For rational magnetic fields this system forms a magnetic superlattice for which Bloch's theorem then applies. Extensions of the approach to particles with spin and many-body systems and connections to the theory of magnetic translation groups are discussed. 相似文献
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《Solid State Communications》1986,58(11):799-802
The recently developed theory of superlattice lateral surface magnetoplasmon is extended to type II superlattices consisting of alternating two-dimensional planes of electrons and holes. The magnetoplasmon dispersion relation is calculated by transforming the two coupled integral equations for the a.c. potential into a composite matrix equation. This method can be generalized to study charge density collective excitations in an arbitrary multi-component superlattice. 相似文献
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The action of a strong high-frequency electromagnetic field on a lateral semiconductor superlattice is considered based on the quasi-classical electron transport theory in the self-consistent wave formulation. The theory predicts that a lateral superlattice can emit terahertz radiation wave trains, which are associated with periodic excitation of Bloch oscillations in the superlattice arising because of the development of transient processes in it in a variable self-consistent electric field. The conditions necessary for observing Bloch oscillator radiation were found. The spectral composition of radiation transmitted through the superlattice and the energy efficiency of frequency multiplication related to Bloch oscillator excitation were calculated. 相似文献
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用等效介质理论计算了半无限侧向铁磁/铁磁超晶格的推迟模式.且以Co/Ni体系超晶格为例具体计算了该超晶格的表面模式和体模式,展示出一些与磁性/非磁性超晶格不同的有趣性质.侧向磁性/磁性超晶格具有较复杂的推迟模式,这是一种具有高度一般性的体系,在改变构成超晶格的两种铁磁层的厚度的比值、外场时,可以调节两支表面模式的频率以及体模式的频带,这种调节作用是与两种铁磁层的饱和磁化值有关的.当饱和磁化值相差较大时,调制效果是很明显的.当第二种铁磁介质饱和磁化值趋于零时,该体系演变成熟知的磁性/非磁性超晶格.当取麦克斯
关键词:
铁磁/铁磁超晶格
推迟模式
等效介质理论
自旋波谱 相似文献