排序方式: 共有33条查询结果,搜索用时 15 毫秒
1.
Anna Muscará Maria Eloisa Castagna Salvatore Leonardi Salvatore Coffa Liliana Caristia Simona Lorenti 《Journal of luminescence》2006,121(2):293-297
We report on the fabrication and characterization of Si/SiO2 Fabry-Perot microcavities. These structures are used to enhance the external quantum efficiency along the cavity axis and the spectral purity of emission from silicon rich oxide films that are used as active media to fabricate a Si based RCLED (resonant cavity light emitting devices). A new structure to electrically pump the active media in the resonant cavity has been designed. These structures are fabricated by chemical vapour deposition on a silicon substrate. The microcavities are tuned at 850 nm and present a quality factor ranging from 17 to 150 depending on the number of pairs constituting the dielectric mirrors. An enhancement of the electro and photoluminescence (PL) signal of 20 times is achieved for the selected emission wavelength. These cavities are characterized by TEM analysis to evaluate film uniformity, thicknesses and the densification after annealing processes for temperature ranging from 800 to 1100 °C. The electrical properties of the active media are analyzed. The electroluminescence spectral features are compared with PL spectra correlated with the quality factor of the cavities. The photometric diagram shows also a high directionality of the emitted light within a 30° cone from the sample normal. 相似文献
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Snell's law at the boundary between two transversely isotropic media with a vertical axis of symmetry (VTI media) can be solved by setting up a fourth order polynomial for the sine of the reflection/transmission angles. This approach reveals the possible presence of an anomalous postcritical angle for certain transversely isotropic media. There are thus possibly three incident angle regimes for the reflection/refraction of longitudinal or transverse waves incident upon a VTI medium: precritical, postcritical/preanomalous, and postanomalous. The anomalous angle occurs for certain strongly anisotropic media where the required root to the phase velocity equation must be switched in order to obey Snell's law. The reflection/transmission coefficients, polarization directions, and the phase velocity are all affected by both the anisotropy and the incident angle. The incident critical angles are also effected by the anisotropy. 相似文献
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Ferrara SD Nalesso A Castagna F Montisci M Vogliardi S Favretto D 《Rapid communications in mass spectrometry : RCM》2007,21(18):2944-2950
A method was developed to accurately quantify atracurium (a non-depolarizing skeletal muscle relaxant) and its metabolite laudanosine in post-mortem specimens. Analytes were isolated from blood and tissues by liquid/liquid extraction after adding vecuronium as an internal standard. Chromatographic separation was accomplished by gradient elution in a Synergy Max RP 150 x 2.1 mm column. Positive ion electrospray ionization and mass spectrometric analyses were carried out in an ion trap mass spectrometer under collision-induced dissociation conditions. The method proved selective and sensitive, and was validated in post-mortem blood, heart, lung and liver in the range of 1-2000 ng/mL (blood) and 5-5000 ng/g (tissues); the limits of quantification obtained were 1 ng/mL in blood and 5 ng/g in tissues. 相似文献
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Greci L Castagna R Carloni P Stipa P Rizzoli C Righi L Sgarabotto P 《Organic & biomolecular chemistry》2003,1(21):3768-3771
N,N-Dimethyl-p-nitrosoaniline reacts with benzoyl chloride affording a complex salt containing a cation, a hybrid between a nitrenium ion and an iminium ion. The salt reacts with nucleophiles (indoles, indolizines) yielding compounds characterized by a new carbon-nitrogen bond, derived from the nitrenium ion form. According to the type of nucleophile, the reaction, to differing extents, is in competition with an electron transfer process which leads to the formation of the dimer of the nucleophile and of the azoxy corresponding to the N,N-dimethyl-p-nitrosoaniline. In one of the reactions studied, a chlorinated azoxy derivative was also isolated, and its structure was elucidated by X-ray analysis. 相似文献
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Paola Astolfi Patricia Carloni Riccardo Castagna Lucedio Greci Pierluigi Stipa Corrado Rizzoli 《Journal of heterocyclic chemistry》2004,41(6):971-974
1‐Nitroso‐2‐naphthol and 2‐nitroso‐1‐naphthol, both in the isonitroso form, react with benzyl bromides in THF and in the presence of triethylamine affording, in low yields, the corresponding O‐benzyl oximes and 2‐aryl naphthoxazoles in a 1:1 ratio, approximately. The structures of O‐benzyl oximes and naphthoxazoles isolated have been determined by X‐ray analysis. 相似文献
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Porosity variations in saline media containing humidity are induced by temperature gradients. A temperature imposed on a porous
salt sample prepared with some brine and closed to mass transfer leads to significant variations of porosity in few weeks.
Modelling of the experiments permits to understand the processes involved. 相似文献
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Maria Eloisa Castagna Salvatore Coffa Mariantonietta Monaco Liliana Caristia Alberto Messina Rosario Mangano Corrado Bongiorno 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):547
We report on the fabrication and performances of extremely efficient Si-based light sources. The devices consist of MOS structures with erbium (Er) implanted in the thin gate oxide. The devices exhibit strong 1.54 μm electroluminescence (EL) at 300 K with a 10% external quantum efficiency, comparable to that of standard light-emitting diodes using III–V semiconductors. Er excitation is caused by hot electrons impact and oxide wearout limits the reliability of the devices. Much more stable light-emitting MOS devices have been fabricated using Er-doped silicon rich oxide (SRO) films as gate dielectric. These devices show a high stability, with an external quantum efficiency reduced to 1%. In these devices, Er pumping occurs by energy transfer from the Si nanostructures to the rare-earth ions. Finally, we have also fabricated MOS structures with Tb- and Yb-doped SiO2 which show room temperature EL at 540 nm (Tb) and 980 nm (Yb) with an external quantum efficiency of a 10% and 0.1%, respectively. 相似文献