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81.
A. Saber G. Mattei X. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):393-399
Within the framework of the effective field theory with a probability distribution technique that accounts for the single-site
spin correlations, we examine the critical behavior of the transverse ferromagnetic spin-1 Ising model of an alternating magnetic
superlattice. The critical temperature of the alternating magnetic superlattice has been studied as a function of the interlayer
and intralayer exchange interactions and the strength of the transverse field and the thickness of the finite superlattice.
Received 12 January 2000 and Received in final form 14 September 2000 相似文献
82.
By using the transfer matrix method, within the framework
of the dielectric continuum approximation, uniform forms for the
interface optical (IO) phonon modes as well as the corresponding electron-IO
phonon interaction Hamiltonians in n-layer coupling low-dimensional systems
(including the coupling quantum well (CQW), coupling quantum-well wire
(CQWW), and coupling quantum dot (CQD)) have been presented. Numerical
calculations on the three-layer asymmetrical AlGaAs/GaAs systems are
performed, and the analogous characteristics for limited frequencies of IO phonon in the three types of systems (CQW, CQWW, and CQD) when the
wave-vector and the quantum number approach zero or infinity are analyzed
and specified. 相似文献
83.
Prof. Enrique Rodríguez-Castellón Dr. Daniel Delgado Dr. Ana Dejoz Dr. Isabel Vázquez Dr. Said Agouram Dr. Juan A. Cecilia Dr. Benjamín Solsona Prof. José M. López Nieto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(42):9371-9381
A Nb-containing siliceous porous clay heterostructure (PCH) with Nb contents from 0 to 30 wt %) was prepared from a bentonite and used as support in the preparation of supported NiO catalysts with NiO loading from 15 to 80 wt %. Supports and NiO-containing catalysts were characterised by several physicochemical techniques and tested in the oxidative dehydrogenation (ODH) of ethane. The characterisation studies on Nb-containing supports showed the presence of well-anchored Nb5+ species without the formation of Nb2O5 crystals. High dispersion of nickel oxide with low crystallinity was observed for the Nb-containing PCH supports. In addition, when NiO is supported on these Nb-containing porous clays, it is more effective in the ODH of ethane (ethylene selectivity of ca. 90 %) than NiO supported on the corresponding Nb-free siliceous PCH or on Nb2O5 (ethylene selectivities of ca. 30 and 60 %, respectively). Factors such as the NiO–Nb5+ interaction, the NiO particle size and the properties of surface Nin+ species were shown to determine the catalytic performance. 相似文献
84.
V. N. Strocov X. Wang M. Shi M. Kobayashi J. Krempasky C. Hess T. Schmitt L. Patthey 《Journal of synchrotron radiation》2014,21(1):32-44
Soft‐X‐ray angle‐resolved photoelectron spectroscopy (ARPES) with photon energies around 1 keV combines the momentum space resolution with increasing probing depth. The concepts and technical realisation of the new soft‐X‐ray ARPES endstation at the ADRESS beamline of SLS are described. The experimental geometry of the endstation is characterized by grazing X‐ray incidence on the sample to increase the photoyield and vertical orientation of the measurement plane. The vacuum chambers adopt a radial layout allowing most efficient sample transfer. High accuracy of the angular resolution is ensured by alignment strategies focused on precise matching of the X‐ray beam and optical axis of the analyzer. The high photon flux of up to 1013 photons s?1 (0.01% bandwidth)?1 delivered by the beamline combined with the optimized experimental geometry break through the dramatic loss of the valence band photoexcitation cross section at soft‐X‐ray energies. ARPES images with energy resolution up to a few tens of meV are typically acquired on the time scale of minutes. A few application examples illustrate the power of our advanced soft‐X‐ray ARPES instrumentation to explore the electronic structure of bulk crystals with resolution in three‐dimensional momentum, access buried heterostructures and study elemental composition of the valence states using resonant excitation. 相似文献
85.
L. Ardaravicˇius J. Liberis O. Kiprijanovicˇ A. Matulionis M. Wu H. Morkoç 《固体物理学:研究快报》2011,5(2):65-67
A nanosecond‐pulsed current–voltage technique was applied to study hot‐electron transport along the two‐dimensional electron gas channel confined at a nominally undoped AlInN/AlN/GaN heterointerface. Hot‐electron drift velocity was deduced under the assumptions of uniform longitudinal electric field and field‐independent electron sheet density. At a fixed electric field strength, a resonance‐type non‐monotonous dependence of the velocity on the electron density was found in the investigated range from 1 to When the electric field increased from 20 kV/cm to 80 kV/cm, the peak velocity increased from ~1.1 to cm/s, and the position of the resonance shifted from ~1.1 to ~1.2 respectively. The resonance position correlates with that for the fastest decay of hot phonons known from independent experiment. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
86.
A simple design of one-dimensional omni-directional reflector based on photonic crystal heterostructures structure has been proposed. The proposed structure consists of a periodic array of alternate layers of SiO2 and Te as the materials of low and high refractive indices, respectively. The structure considered here has three stacks of periodic structures having five layers each. The lattice period of successive stack is increased by a certain multiple (say gradual constant, δ) of the lattice period of the just preceding stack. For numerical computation, the method of transfer matrix method (TMM) has been employed. It is found that such a structure has wider reflection bands in comparison to a conventional dielectric PC structure and the width of the omni-directional reflection (ODR) bands can be enlarged by increasing the value of the gradual constant δ. 相似文献
87.
Zhonghao Zhou Jinyang Zhao Yuxiang Du Kang Wang Jie Liang Yongli Yan Yong Sheng Zhao 《Angewandte Chemie (International ed. in English)》2020,59(29):11814-11818
A universal approach is demonstrated for realizing dual‐wavelength lasing in organic core–shell structured microlaser arrays, which show great promise in serving as all‐color laser display panels. By alternately printing hydrophilic and hydrophobic laser dye solutions on preprocessed substrates, precisely patterned core–shell heterostructure arrays were obtained. The spatially separated core and shell independently function as optical resonators to support dual‐wavelength tunable lasing in each heterostructure. Such a general method enables to flexibly control the lasing wavelength of the core–shell microlasers across a wide spectral range by systematically designing the gain media. Using as‐prepared microlaser arrays as display panels, full‐color laser displays were achieved with a color gamut much larger than that of standard RGB space. These results provide insights for design concepts and device construction for novel optoelectronic applications. 相似文献
88.
Yan Wang Sibo Wang Song Lin Zhang Xiong Wen Lou 《Angewandte Chemie (International ed. in English)》2020,59(29):11918-11922
Hierarchical FeCoS2–CoS2 double‐shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO2 reduction under visible light. The synthetic strategy, engaging the two‐step cation‐exchange reactions, precisely integrates two metal sulfides into a double‐shelled tubular heterostructure with both of the shells assembled from ultrathin two‐dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS2–CoS2 hybrid can reduce bulk‐to‐surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO2 adsorption and surface‐dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS2–CoS2 double‐shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO2 reduction, affording a high CO‐generating rate of 28.1 μmol h?1 (per 0.5 mg of catalyst). 相似文献
89.
Summary We show how to compute the optical functions (reflection and transmission) of a semiconductor thin slab, in the vicinity of
nearly degenerate exciton states. Additional boundary conditions are not required in the coherentwave-function approach and
multiple-polariton effects are included since Maxwell equations are satisfied. When the slab thickness is comparable to the
exciton Bohr radius, centre of mass quantization results. When the slab thickness is smaller than the Bohr radius, we obtain,
quantum well polaritons. Numerical examples appropriate to GaAs are given. 相似文献
90.
M. Salvato F. Bobba G. Calabrese C. Cirillo A. M. Cucolo A. De Santis A. Vecchione C. Attanasio 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(1):79-85
Resistivity vs. temperature measurements on
La0.7Ca0.3MnO3/YBa2Cu3O7-δ
/La0.7Ca0.3MnO3 (LCMO/YBCO/LCMO) trilayers with different
YBCO thickness, were performed in external magnetic field H up to 8 T. By
evaluating the activation energy U from the slope of the resistivity
Arrhenius plot, a strong depression of U has been observed when decreasing
the YBCO layer thickness and the absolute U values appear to be reduced with
respect to the values reported in literature in the case of YBCO thin films
and YBCO/insulating multilayers. Moreover, a logarithmic U vs. H dependence is
shown both in the case of thick and thin YBCO layers indicating the
formation of a two dimensional vortex lattice. The experimental data are
discussed considering the strong influence of the ferromagnetic LCMO on the
superconducting YBCO properties which reduces the effective YBCO thickness
more than predicted by the conventional theories. 相似文献