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排序方式: 共有1116条查询结果,搜索用时 15 毫秒
91.
A. Fonseca N.A. Sobolev E. Alves N.D. Zakharov A.A. Tonkikh 《Journal of luminescence》2006,121(2):417-420
In this work we studied the influence of high-energy proton irradiation on the optical and structural properties of an Si/Ge superlattice (SL) with embedded Ge quantum dots (QDs). The presence of QDs in the as-grown samples was established by transmission electron microscopy and photoluminescence (PL). The samples were irradiated with 2.0 MeV protons to fluences in the range 2×1012-2×1014 cm-2. The structural characterization made by X-ray reciprocal space mapping, X-ray reflection and Rutherford backscattering/channelling has shown no changes in the as-grown heterostructure due to the irradiation. In spite of the expected high concentration of nonradiative recombination centres caused by the proton-induced damage, the PL emission from the Ge dots has been observed even for the highest irradiation fluence. The studied QD-in-SL structure has shown an extraordinarily high radiation hardness when compared with previously studied QD heterostructures. 相似文献
92.
93.
A. Chatterjee B. K. Chakrabarti 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(3):399-404
We study here numerically the behavior of an ideal gas like model of markets having
only one non-consumable commodity. We investigate the behavior of the
steady-state distributions of money, commodity and total wealth,
as the dynamics of trading or exchange of money and commodity proceeds,
with local (in time) fluctuations in the price of the commodity.
These distributions are studied in markets with agents having uniform and
random saving factors. The self-organizing features in money distribution
are similar to the cases without any commodity (or with consumable
commodities), while the commodity distribution shows an exponential decay.
The wealth distribution shows interesting behavior: gamma like
distribution for uniform saving propensity and has the same power-law tail,
as that of the money distribution, for
a market with agents having random saving propensity. 相似文献
94.
In the title compound, germanium is penta‐coordinated and adopts a trigonal bipyramidal geometry. The (2‐thienyl)phenyl group and the nitrogen atom each occupy an apical position with a transannular N→Ge bond distances of 2.247(4) and 2.219(4) Å for the two independent molecules. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
95.
Exact solutions for vibrational levels of diatomic molecules via the Morse potential are obtained by means of the asymptotic
iteration method. It is shown that the numerical results for the energy eigenvalues of7Li2 are all in excellent agreement with those obtained before. Without any loss of generality, other states and other diatomic
molecules could be treated in a similar way. 相似文献
96.
The c(4 × 2) structures in (0 0 1) surfaces of Si and Ge have been studied by low-energy electron diffraction (LEED). Using a proper cleaning method for the Si surface, we were able to observe clear c(4 × 2) LEED patterns up to incident energy of ∼400 eV as well as the Ge surface. Extensive experimental intensity-voltage curves allowed us to optimize the asymmetric dimer model up to the eighth layer (including the dimer layer) in depth in the dynamical LEED calculation. Optimized structural parameters are almost the same for the Si and Ge except for the height of the buckled-up atom of the asymmetric dimer. For the Ge surface, the structural parameters are in excellent agreement with those obtained by a previous theoretical calculation. The tilt angle and bond length of the dimer are 18 ± 1 (19 ± 1)° and 2.4 ± 0.1 (2.5 ± 0.1) Å for the Si(0 0 1) (Ge(0 0 1)), respectively. 相似文献
97.
欧阳修是北宋著名的文学家,其多方面的文学成就,在中国古代文学史上占有重要的地位。本文通过对欧阳修台阁名胜记文的分析,探讨它们的分类、特征及其重要地位,并在此基础上进一步研究其对苏轼等人的影响。 相似文献
98.
M. Serpentini A. Souifi M. Abdallah I. Berbezier G. Bremond 《Journal of luminescence》1998,80(1-4):515-518
In this paper, we present a photoluminescence (PL) study of Si/Ge/SiGe/Si structures grown by gas source molecular beam epitaxy on an (1 1 8) undulated surface with various Ge coverage. Nucleation and growth of Ge films is obtained by the Stranski–Krastanov mechanism. The influence of the substrate orientation on the changeover 2D–3D growth mode is investigated. Furthermore, we show the use of growing an SiGe wetting layer to control the uniformity of the Ge island size. The PL signal related to the Ge islands is found to be highly dependent of the power excitation and is observed up to room temperature. 相似文献
99.
Transmission resonances in magnetic-barrier structures 总被引:1,自引:0,他引:1
Y. Guo Z.-Q. Li B.-L. Gu Q. Sun J.-Z. Yu Y. Kawazoe 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):263-270
Quantum transport properties of electrons in simple magnetic-barrier (MB) structures and in finite MB superlattices are investigated
in detail. It is shown that there exists a transition of transmission resonances, i.e., from incomplete transmission resonances in simple MB structures consisting of unidentical blocks, to complete transmission
resonances in comparatively complex MB structures (, n is the number of barriers). In simple unidentical block arrangements in double- and triple-MB structures we can also obtain
complete transmission by properly adjusting parameters of the building blocks according to ky-value (ky is the wave vector in y direction). Strong suppression of the transmission and of the conductance is found in MB superlattices which are periodic
arrangements of two different blocks. The resonance splitting effect in finite MB superlattices is examined. It is confirmed
that the rule (i.e., for n-barrier tunneling the splitting would be (n-1)-fold) obtained in periodic electric superlattices can be extended to periodically arranged MB superlattices of identical
blocks through which electrons with tunnel, and it is no longer proper for electrons with k
y
<0 to tunnel.
Received: 18 August 1997 / Revised: 20 September 1997 / Accepted: 13 October 1997 相似文献
100.
Using the basic ingredient of supersymmetry, a simple alternative approach is developed to perturbation theory in one-dimensional non-relativistic quantum mechanics. The formulae for the energy shifts and wavefunctions do not involve tedious calculations which appear in the available perturbation theories. The model applicable in the same form to both the ground state and excited bound states, unlike the recently introduced supersymmetric perturbation technique which, together with other approaches based on logarithmic perturbation theory, are involved within the more general framework of the present formalism. 相似文献