S. A. Kozyukhin

Physical aging of chalcogenide glasses

Physical aging effects are shown to be typical of chalcogenide glasses with an under- or overconstrained network and to influence their physicochemical properties. The natural physical aging of glasses can be accelerated by gamma irradiation or exposure to light.

A hybrid halobismuthate light-harvesting material with an optical band gap of 1.70 eV

A new organic–inorganic hybrid material (C15H14N4)BiBr5·H2O with an optical band gap of 2.24 eV, having 1-D chains of bromobismuthate anions in its composition, has been obtained from an aqueous solution and characterized. The partial replacement of Br by I resulted in the formation of a thermally stable (<155 °C) black compound (C15H14N4)BiBrI4·H2O with an optical band gap of 1.70 eV, which can be proposed as a promising light-harvesting material for dye-sensitized solid-state solar cells. Further replacement of Br by I results in the formation of red-orange colored (C15H14N4)BiI5 with a band gap of 2.10 eV.

Phase-change-memory materials based on system chalcogenides and their application in phase-change random-access memory

Chalcogenide alloys in the Ge-Sb-Te system are examined from the point of view of their application in nonvolatile phase-change random-access memory (PC RAM). An analysis of the physicochemical properties of crystalline compounds and amorphous films on their basis is carried out.

Electrical Conductivity of Amorphous Films of Chalcogenide Compounds in High Electric Fields

Effect of the electric field’s strength and temperature on the electrical conductivity of amorphous thin films of chalcogenide compounds has been studied. It is demonstrated that, at strengths of the electric field exceeding 104 V cm−1, the current increases exponentially as the voltage is increased. The activation energy of the temperature dependence of the conductivity decreases as the strength of the electric field is increased. A model that satisfactorily describes the experimental data is suggested on the basis of the assumption that the increase in the carrier concentration with the field strength has a dominant effect on the conductivity. The effective carrier’s mobility of ∼10−2 cm2 V−1 s−1 and the activation length of ∼(10–30) nm, which represents the influence of the electric field, are used as characteristic parameters of the model.

Coordination silver polymer with the bridging anion of oxadiazolylacrylic acid: Synthesis, crystal structure, and luminescence properties

Metal complex [AgL] (I) is synthesized by the reaction of AgNO3 with 3-(5-furyl-1,3,4-oxadiazol-2-yl)acrylic acid (HL, C9H6N2O4), and its crystal structure is determined (CIF file CCDC no. 1426528). The crystals are monoclinic, space group P21/n, a = 4.946(1), b = 20.084(1), c = 9.015(1) Å, β = 92.32(1)°, V = 894.482 Å3, ρcalcd = 2.442 g/cm3, Z = 4. In structure I, pairs of centrosymmetric silver atoms are bound by bidentate-bridging oxygen atoms of two anions L into dimeric blocks. The Ag–Ag distance in the dimer is 2.854(1) Å. The coordination sphere of Ag+ contains two oxygen atoms, one silver atom, and one nitrogen atom of the diazolyl fragment of the adjacent anion. The coordination polyhedron of Ag+ is a strongly distorted tetrahedron. The molecular packing of crystal I is built of infinite ribbons (AgL)n extended along the direction [001]. The photoluminescence spectrum of compound I contains intense bands about 550 nm corresponding to the green spectral range and less intense bands at 425 and 485 nm.

Cyclometalated ruthenium complex as a promising sensitizer in dye-sensitized solar cells

Ruthenocycle bis(4,4′-dicarboxy-2,2′-bipyridine)(2-phenylpyridine-2C,N)ruthenium(II) hexafluorophosphate was used as a sensitizer in a dye-sensitized solar cell (DSSC) based on nanocrystalline TiO2, which was applied onto a conducting substrate. Its electrochemical and spectral characteristics were studied. It was found that, when the DSSC was illuminated with visible light of power 35 mW/cm2, the short-circuit current density was 11.6 mA cm−2 and the open-circuit voltage was 0.49 V. The efficiency (η) of DSSC at a fill factor of 45% was 7.1%. Using the method of modulation spectroscopy of photocurrents and photopotentials, the life time and transit time of electrons were found to be 7 and 5 ms, respectively, and the diffusion coefficient of electrons was found to be 10−5 cm2 s−1. Comparing the life and transit times of electron, it was concluded that the photogenerated electrons had time to reach the conducting substrate during their life time.

Coordination molecular compounds of cadmium(II) iodide with dimethylpyridines

The reactions of CdI2 with dimethylpyridines (Me2Py is C7H9N) afford complexes CdI2(2,3-Me2Py)2] (I), [CdI2(2,6-Me2Py) (II), and CdI2(3,5-Me2Py)2 (III). The structures of compounds I and II are determined. The crystals of complex I are orthorhombic, space group Pbca, a = 7.930(1) Å, b = 15.537(1) Å, c = 29.943(1) Å, V = 3689.1(5) Å3, ρcalcd = 2.090 g/cm3, Z = 8. The crystals of complex II are monoclinic, space group C2/c, a = 14.784(1), b = 11.991(1), c = 17.711(1) Å, β = 90.39(1)°, V = 1081.1(2) Å3, ρcalcd = 2.908 g/cm3, Z = 4. The structure of compound I is built of discrete neutral complexes [CdI2(2,3-Me2Py)2]. The Cd polyhedron is a distorted tetrahedron (Cd-I 2.289–2.295, Cd-N 2.708–2.734 Å, angles N(I)CdN(I) 103.1°-114.8°). Polymer chains [CdI2(2,6-Me2Py)]∞ extended along the direction [100] are observed due to the bridging iodine atoms in structure II. The Cd polyhedron is a trigonal bipyramid containing iodine atoms at the axial vertices (Cd-Iaks 3.040 Å) and two iodine atoms and the nitrogen atom of the Me2Py ligand in the equatorial plane Me2Py (Cd-Ieq 2.840 Å, Cd-N 2.309 Å). The compounds in the solid state are photoluminescent.

Photoluminescence and composition of amorphous As2Se3 films modified with Er(thd)3 complex compound

The photoluminescence and composition of amorphous As2Se3 films modified with an Er(thd)3 complex compound have been studied. A band centered at 1.54 μm, characteristic of photoluminescence from Er embedded in amorphous matrices, has been revealed at room temperature. The composition of thin amorphous As2Se3 films modified with an Er(thd)3 complex compound has been examined by methods of nuclear microanalysis: Rutherford backscattering and nuclear resonant reactions. Dependences of the concentrations of Er ions, oxygen, and carbon on the growth conditions of the films are obtained. It is shown that the Er concentration in a thin film varies nonlinearly as the relative concentration of the starting complex compound increases. In addition, the increase in the Er content of a film is accompanied by a simultaneous rise in the content of such light elements as oxygen and carbon. Comparative analysis of the nuclear microanalysis data and IR spectra demonstrates that, in modification of As2Se3 with the Er(thd)3 complex compound by the given method, the nearest environment of Er in the complex compound is partly preserved.

Positronics of radiation-induced effects in chalcogenide glassy semiconductors

Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.

A complex of cadmium(II) iodide with 4-cyanopyridine: Synthesis, crystal structure, and luminescent properties

The complex [CdI2(4-CNPy)2] (I) was obtained by a reaction of CdI2 with 4-cyanopyridine (4-CNPy, C6H4N2) and structurally characterized (CIF file CCDC no. 983377). The crystals of complex I are monoclinic, space group C2, a = 24.698(5) Å, b = 4.127(1) Å, c = 7.597(2) Å, β = 96.05(1)°, V = 770.0(3) Å3, ρcalcd = 2.477 g/cm3, Z = 2. In structure I, iodine atoms serve to unite complex molecules into the polymer chains [CdI2(4-CNPy)2]∞ along the direction [010]. The Cd(1) atom lying on a twofold axis has a slightly distorted octahedral environment made up of four bridging iodine atoms and two nitrogen atoms of two ligands 4-CNPy (Cd-Iav, 2.947(2) and Cd-N(1), 2.410(6) Å). Within each chain, cadmium atoms are spaced apart at 4.13 Å. Complex I exhibits photoluminescence.