Electronic spectrum of Bi2Sr2CaCu2O8 near the fermi level from results of numerical calculations and ultraviolet (8.43 eV) photoelectron spectroscopy

The structure of the spectrum of the partial density of filled states of Bi₂Sr₂CaCu₂O₈ in the range E _b<4 eV, obtained by ultraviolet (hv=8.43 eV) photoelectron spectroscopy was compared with that calculated by the strong coupling method. The results of the calculations agree with the experimental results in the range of binding energies 1<E _b <4 eV. Analysis of the evolution of the spectra under thermal and phototreatment in ultrahigh vacuum and in oxygen reveals that oxygen atoms from Cu-O planes possess the highest mobility in the lattice and the surface of the single crystal is formed by Bi-O planes. Pis’ma Zh. Tekh. Fiz. 24, 69–74 (February 12, 1998)     

Properties of self-organized SiGe nanostructures formed by ion implantation

Properties of self-organized SiGe quantum dots formed for the first time by ion implantation of Ge ions into Si are studied using Auger electron spectroscopy, atomic-force microscopy, and scanning electron microscopy. It is found that a spatially correlated distribution of Ge atoms is observed in Si layers implanted with Ge ions after subsequent annealing of these layers. As a result, nanometer-sized regions enriched with germanium are formed; germanium concentration in these regions is 10–12% higher than that in the surrounding matrix of the SiGe solid solution. Optical properties of the layers with SiGe quantum dots were studied using Raman scattering and photoluminescence. An intense photoluminescence peak is observed in the wavelength region of 1.54–1.58 μm at room temperature. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 5, 2004, pp. 593–597. Original Russian Text Copyright ? 2004 by Parkhomenko, Belogorokhov, Gerasimenko, Irzhak, Lisachenko.     

Special features of recombination of nonequilibrium charge carriers in porous silicon with different nanostructure morphologies

Photoluminescence of porous silicon with different nanostructure morphologies and silicon monocrystalline wafers used as substrates was studied comparatively. The photoluminescence intensity of mesoporous and nanoporous silicon was established to be related to the excitation intensity by the quadratic and linear dependences, respectively. A model of recombination processes in the semiconductor nanocrystal systems is suggested. The experimental results are in good agreement with the model predictions.     

The effect of adsorption complexes on the electron spectrum and luminescence of porous silicon

Effects of the surface atomic structures on the electron spectrum and luminescent properties of porous silicon (por-Si) were studied by methods of photoluminescence spectroscopy, UV photoelectron spectroscopy, and Fourier-transform IR spectroscopy. An analysis of evolution of the por-Si characteristics in the course of thermal treatment in vacuum revealed a correlation between the photoluminescence spectrum and intensity, on the one hand, and the electron spectrum and surface atomic structure, on the other hand. The thermodesorption of adsorbate from por-Si leads to atomic rearrangements on the sample surface, which is accompanied by changes in the electron structure and, hence, in the luminescent properties of the material.     

Low-pressure chemical and photochemical reactions of oxides of nitrogen on alumina taken as a model substance for mineral dust in relation to air pollution

The interaction of γ-Al₂O₃, taken as a model substance of tropospheric mineral dust, with N₂O, NO and NO₂ has been studied using kinetic and temperature-programmed desorption (TPD) mass-spectrometry in presence and absence of UV irradiation. At low surface coverages (<0.001 ML), adsorption of N₂O and NO₂ is accompanied by dissociation and chemiluminescence, whereas adsorption of NO does not lead to appreciable dissociation. Upon UV irradiation of Al₂O₃ in a flow of N₂O, photoinduced decomposition and desorption of N₂O take place, whereas in a flow of NO, only photoinduced desorption is observed. Dark dissociative adsorption of N₂O and NO and photoinduced N₂O dissociation apparently occur by a mechanism involving electron capture from surface F- and F⁺-centers. Photoinduced desorption of N₂O and NO may be associated with decomposition of complexes of these molecules with Lewis acid sites, V-centers or OH-groups. TPD of N₂O and NO proceeds predominantly without decomposition, while NO₂ partially decomposes to NO and O₂.     

Synthesis of cordierite in a combustion schedule

Translated from Steklo i Keramika, No. 7, pp. 14–17, July, 1989.