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排序方式: 共有106条查询结果,搜索用时 18 毫秒
51.
D.A. Magdas D. Maestre A. Cremades L. Gregoratti J. Piqueras 《Superlattices and Microstructures》2009,45(4-5):429-434
In this work sintered thick microcrystalline films as well as micro and nanostructures of In2O3 have been studied. The results obtained by XPS microscopy show that the boundary regions of the microcrystalline films present a higher amount of oxygen, as well as a different O (1s) core level XPS spectrum with respect to the grains. CL images recorded at room temperature show that the emission is preferentially associated with the grain boundaries and the main emission band appeared at 1.9 eV in the recorded CL spectra.Core level and valence band spectromicroscopy measurements of the indium oxide arrows grown at the surface of the sintered InN revealed the incorporation of nitrogen, coming from the starting material. In these structures the N (1s) core level splits into two components, showing a higher amount of nitrogen in the pyramid surface than in the columns of the structures which correlates with an increase of CL intensity. 相似文献
52.
Nanostructures of two transition metal oxides, WO3 and α-Fe2O3, have been grown by a thermal deposition method without a catalyst and characterized by x-ray diffraction, scanning electron microscopy (SEM), high-resolution transmission electron microscopy and cathodoluminescence (CL) in the SEM. WO3 micro and nanorods exhibit CL emission two orders of magnitude higher than CL intensity from the untreated oxide. α-Fe2O3 nanostructures with different morphologies (wires, belts, rods, urchins) were grown at different temperatures on Fe substrates. CL spectra of these nanostructures show emission bands related to charge transfer and ligand field transitions. 相似文献
53.
A photonic vector modulator architecture for generating pure quadrature amplitude modulation (QAM) signals is presented. An electrical quadrature-modulated signal at microwave-millimeter-wave frequencies is generated from its corresponding baseband in-phase (I) and quadrature (Q) components. In the proposed scheme, no electrical devices apart from the electrical tone oscillator are needed in the generation process. In addition, the purity of the generated signal is increased, and the hardware requirements are reduced when compared with previously proposed architectures so a highly compact low-cost architecture can be implemented. A pure 1.25 Gbit/s 4-QAM signal has been experimentally generated at a 42 GHz carrier frequency. 相似文献
54.
Quenching of MgO crystals produces an increase of the photoluminescence emission in the 400 nm region and often the appearance of a shoulder at 470–490 nm previously observed in CL experiments. An emission band at 560 nm which is not related to the F centre band has also been observed. 相似文献
55.
The behaviour of the total energy for a semi-infinite piezoelectricbeam, with uniform or variable cross-section, in dynamical conditionsis investigated. Precisely, we obtain some estimates in termsof the data for the energy of the portion of the body at distancegreater than z from the base and for its norm in L1(0,t) (wheret is an arbitrary positive time). We obtain some estimates whichdepend on the initial data if t z/V (where V is a computablepositive material constant); if t > z/V, by using also theKorn inequality, we show that the bounds depend on all the data.Under mild hypotheses on the initial data we derive the asymptoticbehaviour of the energy as z +. All possible combinations ofboundary conditions are examined and the kind of the estimateis formally the same for all the problems whether the beam isa cylinder or not. 相似文献
56.
Chen D Albuquerque IF Baublis VV Bondar NF Carrigan RA Cooper PS Lisheng D Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Goritchev PA Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Lebedenko VN Li Chengze Li Yunshan Mahon JR McCliment E Morelos A Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Sun CR Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng 《Physical review letters》1992,69(23):3286-3289
57.
Foucher M Albuquerque IF Bondar NF Carrigan R Chen D Li Chengze Cooper PS Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Tang Fukun Golovtsov VL Goritchev PA Gottschalk H Gouffon P Grachev VT Shi Huanzhang Yan Jie Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Luksys M Lebedenko VN Dai Lisheng Mahon JR McCliment E Morelos A Newsom C Lang Pengfei Pommot Maia MC Samsonov VM Zheng Shuchen Smith VJ Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Zhao Wenheng Zhong Yuanyuan 《Physical review letters》1992,68(20):3004-3007
58.
We present the results of valence effective hamiltonian (VEH) band structure calculations on stereoregular block copolymers of poly(thienylene vinylene) and poly(pyrrylene vinylene). We have examined the evolution of the electronic properties as a function of the extension and distribution of the block copolymer sequences. In both cases, the electronic-properties deviate from a linear evolution as a consequence of the localization of both HOCO and LUCO. 相似文献
59.
C. Díaz-Guerra A. Mitric J. Piqueras T. Duffar 《Superlattices and Microstructures》2009,45(4-5):407-412
Cathodoluminescence (CL) in the scanning electron microscope and wavelength dispersive X-ray microanalysis (WDX) have been used to assess the homogeneity of a whole Te-doped InxGa1?xSb ingot grown by the vertical Bridgman method under an alternating magnetic field. In particular, WDX has been used to determine the chemical composition of the ingot along the growth axis and several radial directions, while CL has been used to investigate the effective incorporation of In into the alloy, the nature and distribution of extended defects influencing the luminescence of the material and the shape evolution of the growth interfaces along the growth axis. CL spectroscopy reveals that doping with Te influences the band gap energy of this ternary compound through the Moss–Burstein effect. 相似文献
60.
Yu. Ya. Tomashpol’skii N. V. Sadovskaya C. Diaz-Guerra J. Piqueras C. Opagiste 《Physics of the Solid State》1997,39(3):392-396
The structural changes and the cation and anion compositions of the surface of superconducting YBa2Cu3O7−x
and Tl2Ba2CuO6+x
ceramics after local irradiation for several seconds by an electron probe with an accelerating voltage of 25 kV and a current
exceeding 10−7 A are investigated by secondary-electron emission and by cathodoluminescence and x-ray microanalysis in a scanning electron
microscope. Morphologically altered regions are detected in the irradiation epicenter, where the structure, chemical composition,
and phase composition of the original compound are completely lost. In the intermediate zone between the epicenter and the
periphery a distribution of the secondary emission yield is observed with a complex character that differs for the yttrium
and thallium ceramics, and anomalies appear in the cathodoluminescence spectra. The experimental data are interpreted on the
basis of ideas of oxygen losses under the direct influence of the electron probe and related electronic processes in superconductors.
Fiz. Tverd. Tela (St. Petersburg) 39, 452–456 (March 1997) 相似文献