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We demonstrate the controlled preparation of Er‐ and Eu‐doped GaP‐oxide porous composites. The fabrication procedure entails the use of porous semiconductor templates and the impregnation of rare earth ions from a rare earth salt solution in alcohol and thermal treatment. The composites exhibit strong green and red emission that comes from finely dispersed ErPO4 and EuPO4 oxide submicron phases in the composite. These materials may prove useful in future generations of optoelectronic and photonic devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
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Problems, associated with electrochemical dimensional treatment and chemical deposition as methods of manufacturing nanocomposites based on the AIIIBV semiconductors, are considered by studying indium phosphide (n-InP). The results of manufacturing nanocomposites Cu-n-InP and Ag-n-InP by chemical deposition of copper and silver into pores produced by electrochemical anodic dissolution are described. The metallization kinetics and peculiarities of metal distribution inside nanopores at large values of A are described (A = h/d is a geometrical factor or an aspect ratio, where h and d are the pore’s depth and diameter). It is shown that the degree of the nanopores’ filling is defined by the chemical deposition rate. A relatively high copper deposition rate pertaining to the manufacturing of Cu-n-InP leads to a low throwing power of electrolyte and, as a consequence, to a low level of the pores’ filling. Conversely, the substantially lower rate of the silver chemical deposition from a triethanolamine-containing solution leads to a better uniformness of deposition and to the reaching of conditions conducive to a higher degree of the pores’ filling with metal.  相似文献   
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We propose to assemble negative index materials (NIMs) from dielectric nanotubes with inner and outer surfaces covered by thin metallic films. The focusing properties of flat and concave lenses assembled from metallized titania nanotubes are compared with those of lenses made from nanorods with the refractive index n = –1 by performing numerical calculations using a multiple‐scattering approach. Focusing is proved for both types of lenses, however, the focusing properties of concave lenses are better. The lenses are shown to be tolerant to the introduction of disorder in the arrangement of nanotubes. Moreover, the disorder proves to improve the quality of the focal spot. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
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Results of a complex study of electroabsorption, photoconductivity, and luminescence of two groups of cadmium thiogallate single crystals are presented. The energy positions of levels of deep centres are found. Some assumptions about the characteristics of these levels are made and the scheme for radiative electron transitions in CdGa2S4 single crystals is proposed.  相似文献   
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Self‐organized quasi‐ordered two‐dimensional hexagonal arrays of pores with diameters as low as 70 nm in n‐InP substrates subjected to anodic etching in aqueous solution of NaCl are reported. We show that proper periodic modulation of the applied potential with time allows one to reach 3D nanostructuring of the material. Anodization in salty water proves to be a cost‐effective and environmentally‐friendly tool for spatial nanostructuring of materials and nonlithographic manufacturing of semiconductor nanotemplates for nanofabrication. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
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This work reports measurements with a concave lens based on a photonic crystal (PC) structure, which was designed to have an effective index of refraction neff < 1 or even < 0, and which is intended as a model system for future down‐scaled optical elements based on PCs with an unusual effective index. The dimensions of the model PC were optimized for experiments in the microwave regime around 10 GHz. Calculations for a material with no losses allowed to select the wavelengths for which the lens could be expected to behave as a homogeneous meta‐material with an unusual effective refractive index. The field distribution behind the lens was measured, and good focusing efficiencies for neff < 1 were found for perfect and strongly disturbed PC's in reasonable accordance with the predictions. The (down‐scaled) model system investigated thus can serve as a reference for testing PC‐based optical elements made from materials which so far elude reliable predictions, e.g. doped semiconductors, nanorod assemblies, or meta‐materials with anisotropic behavior. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
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