Arsenic Chalcogenides Research Articles

Оптические характеристики модифицированных тонких пленок состава AS30S70

The paper reports the results of a comparative study of optical properties of thin films of arsenic chalcogenides of the As–S system taking into account the effect of their modification with molybdenum. An analysis of the experimental optical transmission spectra made it possible to calculate the dispersion curves of the refractive, absorption, and extinction coefficients of the medium, as well as the real and imaginary components of the complex permittivity. The revealed features of the behavior of the obtained spectral dependences are associated with the stereoeffect of a lone electron pair (LEP) in the structure of the arsenic compound under study.

Effect of Pressure on the Temperature Dependence of the Thermal Conductivity of Arsenic Chalcogenide with Different Ordering

Effect of Pressure on the Temperature Dependence of the Thermal Conductivity of Arsenic Chalcogenide with Different Ordering

Prediction of Intrinsic Ferroelectricity and Large Piezoelectricity in Monolayer Arsenic Chalcogenides.

Two-dimensional materials that exhibit spontaneous electric polarization are of notable interest for functional materials. However, despite the prediction of many two-dimensional polar materials, the number of experimentally confirmed two-dimensional ferroelectrics is far less than bulk ferroelectrics. We provide strong evidence that the Pmn21 phase of arsenic chalcogenides As2X3 (X = S, Se, and Te), which include the recently isolated monolayer orpiment, are intrinsic ferroelectrics and demonstrate strong in-plane piezoelectricity. We found the calculated energy barriers for collectively reversing the electric polarization or moving a 180° domain wall are reasonable compared to previously reported ferroelectrics. We propose a high-symmetry structure (with Pmmn space group) that transforms into the ferroelectric Pmn21 phase by a soft B2u phonon mode. By studying other soft modes of the high-symmetry Pmmn structure, we identify several undiscovered metastable polymorphs, including a polar phase (with a P21 space group) with sizable piezoelectricity.

Raman study of laser-induced formation of II–VI nanocrystals in zinc-doped As–S(Se) films

Zn-doped As2Se3 and As2S3 films were prepared by thermal evaporation. Their amorphous structure was confirmed by Raman spectroscopy. Zinc chalcogenide nanocrystals can be formed in the films under laser irradiation due to the photoenhanced diffusion of atoms in the arsenic chalcogenide films, which enables aggregation of Zn and S(Se) atoms in nanocrystals. For As2S3:Zn films, not only ZnS, but also ZnO crystallites can be formed under irradiation with UV laser light due to oxidation of the film surface with abundant zinc atoms.

The solvothermal synthesis and characterization of quaternary arsenic chalcogenides CsTMAsQ3 (TM = Hg, Cd; Q = S, Se) using Cs+ as a structure directing agent: from 1D anionic chains to 2D anionic layers.

Four new quaternary transition metal arsenic chalcogenide Cs–TM–As–Q compounds (TM = Hg, Cd; Q = S, Se) were synthesized using different mixed solvents. A 1,4-diaminobutane(1,4-dab)/water mixed solvent system was used to solvothermally synthesize the selenoarsenates CsTMAsSe3 (TM = Hg (1), Cd (2)). In 1, the eight-membered ring anion chain consists of trigonal-planar [HgSe3] and trigonal-pyramid [AsSe3]. Compound 2 is similar to the eight-membered ring chain anion of compound 1, and [CdAsSe3]− further joins, through μ3-Se and Cd, to form the layer anions [CdAsSe3]−. A 2-diaminopropane (1,2-dap) and water mixed solvent system was used to synthesize two thioarsenates, Cs2TM2As2S6 (TM = Cd (3), Hg (4)). Compounds 3, 4 and 2 are isostructural; the Cd and Hg atoms are four coordinated. Compounds 1–4 utilize Cs+ cations as a structural directing agent. Finally, the structural and optical properties of the novel series of arsenic chalcogenides were characterized.

Cross-relaxation energy transfer between the Er3+ ions in vitreous arsenic chalcogenide

In this paper, we study widely investigated photoluminescent properties of [Formula: see text] compounds in the near-infrared ranges. The increase of the infrared luminescence intensity with increasing [Formula: see text] concentration can be attributed to the cross-relaxation process between the activator ions.

Temperature and Baric Patterns of Changes in the Thermal Conductivity of Composite Materials

Experimental results are presented on the effective thermal conductivity of rocks (sandstone and granite) and polycrystalline arsenic chalcogenides. Measurements are made using an absolute steady-state approach in the temperature range of 273–523 K and at hydrostatic pressures of up to 400 MPa. A power-law temperature dependence of thermal conductivity with a negative exponent is specific to the investigated samples at a fixed pressure. A description of this dependence is proposed. The values used in the equation are calculated from the experimental data.

Radioactive Equilibrium of 119mTe/119Sb Isotopes and Mössbauer Spectra of Impurity 119mSn Atoms in Crystalline and Vitreous Chalcogenide Semiconductors

Information on the valence and coordination states of the daughter 119mSn atoms formed from the parent 119Sb and 119mTe atoms at the cation and anion sites of crystalline lead chalcogenides (PbS, PbTe) and vitreous arsenic chalcogenides (As2S3, As2Te3) is obtained by the method of emission Mossbauer spectroscopy with the parent 119mTe isotope being in a state of mobile radioactive equilibrium with the daughter 119Sb isotope. It is shown that the ratio of different valence and coordination states of tin atoms in crystals and glasses depends on the time of the preparation of Mossbauer sources. The displacement of a part of the daughter 119Sb atoms from positions of parent 119mTe atoms as a result of the decay of the latter is demonstrated.

Network-Forming Nanoclusters in Binary As\u2013S/Se Glasses: From Ab Initio Quantum Chemical Modeling to Experimental Evidences

Network-forming As2(S/Se)m nanoclusters are employed to recognize expected variations in a vicinity of some remarkable compositions in binary As–Se/S glassy systems accepted as signatures of optimally constrained intermediate topological phases in earlier temperature-modulated differential scanning calorimetry experiments. The ab initio quantum chemical calculations performed using the cation-interlinking network cluster approach show similar oscillating character in tendency to local chemical decomposition but obvious step-like behavior in preference to global phase separation on boundary chemical compounds (pure chalcogen and stoichiometric arsenic chalcogenides). The onsets of stability are defined for chalcogen-rich glasses, these being connected with As2Se5 (Z = 2.29) and As2S6 (Z = 2.25) nanoclusters for As–Se and As–S glasses, respectively. The physical aging effects result preferentially from global phase separation in As–S glass system due to high localization of covalent bonding and local demixing on neighboring As2Sem+1 and As2Sem−1 nanoclusters in As–Se system. These nanoclusters well explain the lower limits of reversibility windows in temperature-modulated differential scanning calorimetry, but they cannot be accepted as signatures of topological phase transitions in respect to the rigidity theory.

Adhesion mechanism of destruction of silica-glass surface during the preparation and treatment of optical glassy arsenic Chalcogenides

Adhesion of As–S and As–Se glasses to silica glass is studied by means of the steady detachment method. The results demonstrate that the adhesion strength of the boundary of solid phases increases with the content of chalcogens in the composition of glass. It is found that adhesion of arsenic sulfide glasses with sulfur content over 65% to silica glass exceeds the tensile strength of the silica glass during the process of solidification and annealing of chalcogenide preforms. The adhesion of arsenic chalcogenides to silica glass is determined to be the reason of chalcogenide glass contamination by heterophase inclusions.

The nanostructuring of surfaces and films using interference lithography and chalcogenide photoresist.

The reversible and transient photostimulated structural changes in annealed chalcogenide glass (ChG) layers were used to form interference periodic structures on semiconductor surfaces and metal films. It was shown that negative-action etchants based on amines dissolve illuminated parts of a chalcogenide film, i.e., act as positive etchants. The diffraction gratings and 2-D interference structures on germanium ChGs - more environmentally acceptable compounds than traditionally used arsenic chalcogenides - were recorded, and their characteristics were studied.

Arsenic chalcogenide filled photonic crystal fibers

We prepared hybrid fibers by filling all-silica capillaries and photonic crystal fibers (PCFs) with arsenic chalcogenide glasses. The filling technology is described in detail and a theoretical model for the prediction of the filling length in combination with a simple approximation is presented. The prepared fiber samples are analyzed in terms of optical properties by measuring their transmission spectra which exhibit band-gap guidance and are compared with numerical simulations. Finally, we compare calculations and measurements of thermal stress in such fibers.

Mössbauer studies of two-electron centers with negative correlation energy in crystalline and amorphous semiconductors

The results of the study of donor U −-centers of tin and germanium in lead chalcogenides by Mossbauer emission spectroscopy are discussed. The published data regarding the identification of amphoteric U −-centers of tin in glassy binary arsenic and germanium chalcogenides using Mossbauer emission spectroscopy, and in multicomponent chalcogenide glasses using Mossbauer absorption spectroscopy are considered. Published data concerning the identification of two-atom U −-centers of copper in lattices of semimetal copper oxides by Mossbauer emission spectroscopy are analyzed. The published data on the detection of spatial inhomogeneity of the Bose-Einstein condensate in superconducting semiconductors and semimetal compounds, and on the existence of the correlation between the electron density in lattice sites and the superconducting transition temperature are presented. The principal possibility of using Mossbauer U −-centers as a tool for studying the Bose-Einstein condensation of electron pairs during the superconducting phase transition in semiconductors and semimetals is considered.

Optical and transport properties and electronic structure of nickel doped arsenic chalcogenides

The electronic structure of monoclinic As 2X 3 (X = S, Se) is investigated using full potential linearized augmented plane wave method in the framework of density functional theory. From energy bands and the density of states it is seen that the lone pair p-states of sulfur/selenium contribute closest to Fermi energy level. Introduction of transition metal impurities such as Nickel modifies the semiconducting gap in As 2S 3 and As 2Se 3. The crystal field splits the Ni 3d bands with t 2g electrons in the valence band and e g electrons in conduction band. We compute optical properties like the complex dielectric functions, refractive indices, absorption coefficient, reflectance, etc. The low symmetry chalcogenides exhibit optical dichroism. On doping, As 2S 3 and As 2Se 3 show additional losses in the IR regions, which indicates allowed interband transitions due to available 3d-states in the valence and conduction bands. A narrow transparent window in the visible region is available in Ni 0.5As 1.5Se 3 crystals. Important transport properties such as Seebeck and Hall coefficients, and carrier concentration are computed. It is seen that these high resistivity chalcogenides are n-type semiconductors.

Impurity centers of tin in glassy arsenic chalcogenides

119Sn atoms produced by radioactive decay of 119Sb impurity atoms in the structure of AsxS1 − x and AsxSe1 − x glasses are stabilized in the form of Sn2+ and Sn4+ ions at arsenic sites and correspond to ionized states of the amphoteric two-electron center with negative correlation energy (Sn2+ is an ionized acceptor, and Sn4+ is an ionized donor), whereas the neutral state of the Sn3+ center is unstable. The fraction of Sn4+ states increases with chalcogen content in glass. 119Sn atoms produced by radioactive decay of 119mTe impurity atoms in the structure of AsxS1 − x and AsxSe1 − x glasses are stabilized at chalcogen sites (they are electrically inactive) and arsenic sites, and the fraction of arsenic atoms decreases with the chalcogen content in glass.

Investigation of electronic properties of crystalline arsenic chalcogenides: Theory and experiment

The electronic structure of crystalline As 2S 3 and As 2Se 3 has been calculated in this paper. We present the energy bands, density of states (DOS) and the Compton profiles using the linear combination of atomic orbitals (LCAO) scheme based on the density functional theory (DFT). From the calculated total and partial density of states it is seen that the lone-pair p-states of sulphur/selenium contribute closest to the Fermi energy level. To interpret the theoretical data on the Compton line shape, we have measured the Compton profiles on a 100 mCi 241Am spectrometer. It is seen that the density functional theory within generalised gradient approximation gives a slightly better agreement with the experimental momentum densities. The nature of chemical bonding in arsenic chalcogenides is studied using Mulliken's population analysis and the experimentally measured equal-valence-electron-density profiles; As 2S 3 is found to be more ionic compared to As 2Se 3.

Recent advances in preparation of high-purity glasses based on arsenic chalcogenides for fiber optics

The processes of production of high-purity glasses based on arsenic chalcogenides and optical fibers with low optical losses in the middle IR have been analyzed. Physical–chemical, technological and methodological factors determining the degree of purity of glasses and the level of optical losses in optical fibers are considered. Dominant factors, rational actions and approaches optimizing the manifestation of these factors in glasses formed by arsenic chalcogenides are discussed. Vitreous As 2S 3 is produced with the content of hydroxyl groups not more than 1 ppb wt, of hydrogen in the form of SH-groups — 75 ppb mol, of silicon — 0.2 ppm wt. From this glass a multi-mode optical fiber was manufactured with optical losses of 12 and 14 dB/km at 3.0 and 4.8 μm, respectively, which is the best result published in literature for chalcogenide glass optical fibers.

Enhancement of the output emission efficiency of thin-film photoluminescence composite structures based on PbSe

The opportunity to increase the output emission efficiency of PbSe-based photoluminescence structures by depositing an antireflection layer is analyzed. A model of a three-layer thin film where the central layer is formed of a composite medium is proposed to calculate the reflectance spectra of the system. In von Bruggeman’s approximation of the effective medium theory, the effective permittivity of the composite layer is calculated. The model proposed in the study is used to calculate the thickness of the arsenic chalcogenide (AsS4) antireflection layer. The optimal AsS4 layer thickness determined experimentally is close to the results of calculation, and the corresponding gain in the output photoluminescence efficiency is as high as 60%.

Boson peak in low‐frequency Raman spectra of AsxS100‐x glasses: nanocluster contribution

AbstractThe origin of the Boson peak was investigated using Raman spectroscopy and ab initio calculations. Low frequency Raman active vibrational modes of different branchy‐, ring‐ and cage‐like AsmSn nanoclusters were calculated and compared to experimentally determined Raman spectra of AsxS100‐x glasses with different compositon. A good correlation was found between the spectral features and the calculated Raman modes. The possible structural nature of the Boson peak in arsenic chalcogenides is proposed and discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The influence of amorphization on the local environment of atoms in arsenic chalcogenides

The influence of amorphization on the symmetry of the local environment of chalcogen atoms in the As2S3, As2Se3, and As2Te3 compounds is investigated using Mossbauer emission spectroscopy. In the 129Te(129I) Mossbauer emission spectra of crystalline As2Te3, three states of threefold-coordinated tellurium atoms appear to be indistinguishable. The transformation of the As2Te3 crystalline compound into the vitreous state results in the lowering of the local symmetry of threefold-coordinated states of the tellurium atoms and the formation of twofold-coordinated states of the tellurium atoms in chains of the type-As-Te-Te-As-. Two states of twofold-coordinated chalcogen (X) atoms in chains of the type-As-X-As-in the structure of the As2S3 and As2Se3 crystalline compounds manifest themselves in the form of a broadening of the Mossbauer spectra. The transformation of the As2S3 and As2Se3 crystalline compounds into the vitreous state is not accompanied by a change in the local symmetry of twofold-coordinated chalcogen atoms in chains of the type-As-X-As-; however, the structure of the glass in this case is characterized by the formation of twofold-coordinated states of sulfur and selenium atoms in chains of the type-As-X-X-As-. The fraction of twofold-coordinated chalcogen atoms increases upon changing over from As2 X 3to AsX.