On the origin of 1.5 μm luminescence in porous silicon coated with sol–gel derived erbium-doped Fe2O3 films

Sol–gel derived Fe₂O₃ films containing about 10 wt% of Er₂O₃ were deposited on porous silicon by dipping or by a spin-on technique followed by thermal processing at 1073 K for 15 min. The samples were characterized by means of PL, SEM and X-ray diffraction analyses. They exhibit strong room-temperature luminescence at 1.5 μm related to erbium in the sol–gel derived host. The luminescence intensity increases by a factor of 1000 when the samples are cooled from 300 to 4.2 K. After complete removal of the erbium-doped film by etching and partial etching the porous silicon, the erbium-related luminescence disappears. Following this, luminescence at 1.5 μm originating from optically active dislocations (“D-lines”) in porous silicon was detected. The influence of the conditions of synthesis on luminescence at 1.5 μm is discussed.     

Characteristic features of short-range-order structure of melts of Pb-Tl-Cd(Sn) ternary systems

The paper considers the results of Investigations on the short-range-order structure of Pb-Tl melts and ternary Pb-Tl-Cd(Sn) liquids whose concentrations correspond to the lines of monovariant transformations connecting the Pb-Cd, Tl-Cd, and Pb-Sn, Tl-Sn binary eutectic points, respectively. The parameters of the radial distribution function and the thermodynamic data are analyzed. In the structural respect, Pb-Tl-Cd (Sn) melts have a polystructural structure in which, at temperatures close to the melting point, there are ordered regions with the structure of Pb-Cd(Sn) and Tl-Cd(Sn) binary eutectics and considerably larger microregions with statistical distribution of atoms of each species.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 32–36, May, 1979.     

Magnetic field effect on free and bound excitons in chalcopyrite CuInS<Subscript>2</Subscript>

The effect of a strong magnetic field (induction up to 10 T) on free and bound excitons in CuInS₂ single crystals is studied. A diamagnetic shift to higher energies is observed in the luminescence and reflectance spectra for free-exciton lines A_LPB ≈ 1.5348 eV, A_UPB ≈ 1.5361 eV, and BC ≈ 1.557 eV. The diamagnetic shifts of free-exciton lines A_LPB, A_UPB, and BC provide a basis for estimating the exciton reduced masses = 0.131m₀, = 0.13 4m₀, and μ_BC = 0.111m₀, respectively. Bound-exciton lines in luminescence spectra are split under the influence of the magnetic field. The magnitude of the Zeeman effect (g-factor of the magnetic splitting) is estimated. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 373–377, May–June, 2007.     

Nickel hydroxide obtained by high-temperature two-step synthesis as an effective material for supercapacitor applications

Hybrid supercapacitors with nickel hydroxide electrode are widely used as modern power sources for electrovehicles, ignition of different electric engines, etc. Nickel hydroxide for supercapacitor use must satisfy special features which are quite different from those requested for battery application. The aim of this work is to improve the promising two-stage high-temperature method by altering hydrolysis condition (hot and cold) in order to obtain Ni(OH)₂ with improved electrochemical activity. Ni(OH)₂ samples have been investigated by PXRD, TG, DSC, SEM, TEM, cyclic voltammogramm, and galvanostatic charge-discharge cycling. It has been established from PXRD, TG, and DSC analyses that material obtained by hydrolysis at high temperature is a highly crystalline β-Ni(OH)₂ characterized by high thermal stability. Materials prepared by cold hydrolysis are a highly defective β_bc-Ni(OH)₂, with 6.3 % water content and a lower thermal stability. It has been shown that samples prepared by hot hydrolysis have a high redox reversibility and electrochemical cycling stability, but a lower electrochemical capacity. This suggests that the electrochemical processes are localized in the thin layer at the particle surface. Cyclic voltammograms of samples prepared by cold hydrolysis exhibit gradual activation of the active material, anyhow resulting in higher capacity. By means of the galvanostatic charge-discharge curves at different current densities, the specific capacities of the samples have been calculated. The sample prepared by cold hydrolysis has higher specific capacities than the sample prepared by hot hydrolysis.     

Photoluminescence of gallium arsenide electron-irradiated at 20 K

The processes of defect formation in single crystals of gallium arsenide electron-irradiated at cryogenic temperatures (∼20 K) have been investigated by the luminescence method. It is shown that at such temperatures the primary radiation-induced defects, in particular, intrinsic interstitial atoms, can migrate in a crystal and form complexes with their participation. Institute of Solid-State and Semiconductor Physics of the Academy of Sciences of Belarus, 17, P. Brovka St., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 122–124, January–February, 1997.     

Muscarine research

A mixture of racemates of muscarine and its stereisomers was synthesized by the reaction of 1-hexene-4,5-diol with iodine and subsequent conversion of the resulting 5-iodomethyl-3-hydroxy-2-methyltetrahydrofuran to the corresponding nor-base and methiodide. The presence of all the stereoisomers of muscarine was demonstrated by means of thin-layer chromatography and the IR spectrum. The sulfonium analog was also synthesized.Formerly F. V. Kvasnyuk-Mudryi.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 579–581, May, 1970.     

Structural and optical properties of thin films of Cu(In,Ga)Se<Subscript>2</Subscript> semiconductor compounds

The chemical composition of Cu(In,Ga)Se₂ (CIGS) semiconductor compounds is analyzed by local x-ray spectral microanalysis and scanning Auger electron spectroscopy. X-ray diffraction analysis reveals a difference in the predominant orientation of CIGS films depending on the technological conditions under which they are grown. The chemical composition is found to have a strong effect on the shift in the self-absorption edge of CIGS compounds. It is shown that a change in the relative proportion of Ga and In in CIGS semiconducting compounds leads to a change in the band gap E_g for this material in the 1.05–1.72 eV spectral range at 4.2 K.     

Spectral luminescence properties of nanostructured Ce-Nd-Containing silica gel-glasses

Complex Ce⁴⁺-Nd³⁺ centers were formed in silica gel-glasses. These centers were characterized by weak cross-relaxation quenching of luminescence; an increased luminescence branching ratio in the ⁴F_3/2→⁴I_11/2, ⁴I_13/2 transitions; strong structuring of the analogous spectral bands; and effective intracenter sensitization of luminescence. On reducing the Ce⁴⁺ ions to the triply charged state, the structure of the luminescence bands of Nd³⁺ ions became weaker and the ratio of their intensities approached the value typical of an Nd-containing silica gel-glass.