Controlled Formation of β-Si3N4 on Native Oxidized Silicon Wafers in Ammonia Flow

Crystallography Reports - The formation of β-Si3N4 for subsequent growth of AlGaN and GaN heterostructures of silicon wafers has been studied. It is established that the native oxide layer...     

Luminescence of molecular silver clusters in oxyfluoride glasses

Luminescence spectra of silver-containing oxyfluoride glasses have been investigated in the excitation spectral range of 360–480 nm. Analysis of the luminescence spectra shows that silver in oxyfluoride glasses that contain no strong reducers and were subjected to heat treatment affecting redox processes exists in the form of neutral atoms and neutral molecular Ag₂, Ag₃, and Ag₄ clusters.     

Luminescent properties of ytterbium-erbium nanostructured lead fluoride silicate glass-ceramics at low temperatures

We have studied the luminescent properties of lead fluoride silicate nanostructured glass-ceramics doped with ytterbium and erbium ions. We have measured luminescence spectra of glass-ceramics in the visible and near-IR ranges at temperatures of 300 and 77 K and under their pumping at a wavelength of 975 nm. We have examined changes in the luminescence spectra of glass-ceramics depending on the time of their secondary thermal treatment, concentration of dopant ions, specimen temperature, and power of excitation radiation.     

Spectral luminescence properties of transparent lead fluoride nanoglassceramics doped with erbium ions

Transparent nanoglassceramics has been synthesized based on lead fluoride silicate glass doped with erbium ions. It is shown that heat treatment of lead fluoride silicate glass leads to the formation of nanoscale (16–40 nm) crystalline phase of lead fluoride. X-ray diffraction analysis and measurement of spectral luminescence properties have revealed that the erbium ions enter the crystalline phase of lead fluoride.     

Transparent ZnO–SnO2 Photocatalytic Nanocoatings Prepared by the Polymer–Salt Method

Optics and Spectroscopy - The structure and properties of transparent ZnO–SnO2 photocatalytic coatings formed on glass surfaces by the polymer–salt method are studied. The physical and...     

Specific features in low-frequency vibrations of nanocrystals in fluorophosphate glassy matrices

A Raman scattering study of low-frequency vibrational spectra of mixed cadmium sulfoselenide nanocrystals in a fluorophosphate glassy matrix is reported. The measurements have revealed a low-frequency feature in the nanocrystal density of states, whose frequency is related to the glass-matrix annealing time and, hence, to the size of the nanocrystals prepared, which is interpreted as a manifestation of the size quantization effect. Besides the line associated with the constraints on the longitudinal acoustic wave in a nanocrystal, a lower-frequency feature assigned to torsional vibrations of a nonspherical nanocrystal has been found. Fiz. Tverd. Tela (St. Petersburg) 41, 1306–1309 (July 1999)     

Photolysis of Diazo Dye in Aqueous Solutions of Metal Nitrates

The photolysis of Chicago Blue Sky diazo dye is studied. It is experimentally shown that the presence of metal nitrates in aqueous solutions changes the photolysis mechanism and sharply increases the photolysis rate.     

The influence of low-temperature silver-ion exchange on the spectral-luminescent properties of fluorophosphate glasses doped with PbSe

Changes in the absorption and luminescence spectra of fluorophosphate glasses doped with PbSe caused by low-temperature Ag⁺–Na⁺ ion exchange are considered. It is found that the silver distribution gradient in a near-surface layer about 16 μm thick leads to two different processes of interaction between metal and semiconductor nanoparticles. PbSe molecular clusters and quantum dots more efficiently grow in deep layers with a low silver concentration. The near-surface glass layers with a high silver concentration exhibit formation of Ag metal nanoparticles, on the surface of which interaction with PbSe molecular clusters leads to the formation of Ag–Se–Pb bonds, which transform into Ag₂Se layers in the process of heat treatment. The appearance of the new phase is confirmed by X-ray diffraction.     

Quantum confinement in CdSxSe1−x spherical nanocrystals in a fluorophosphate glass matrix

Differential (wavelength-modulated) absorption of sulfoselenide solid-solution nanocrystals has been studied in a glassy fluorophosphate matrix near the fundamental absorption edge at 360–620 nm. The observed oscillations in the absorption are attributed to size quantization of electrons and holes under strong quantum-confinement conditions. The sulfur content in the mixed semiconductor has been refined from Raman scattering spectra in CdS_xSe_1?x samples with x=0.30, and the nanocrystal size (R?30 Å) has been derived from low-frequency Raman scattering spectra. These data were used to calculate the energies of electron-hole transitions in nanocrystals of mixed composition, and their subsequent comparison with experiment. The calculations were found to be in a good agreement with the observed experimental absorption spectrum for nanocrystals about 45 Å in size. The applicability of band-structure simulation for a nonspherical nanocrystal grown in a fluorophosphate glass matrix is discussed.