Composition modulation in the GaxIni-xPyAs1-y - InP heterostructure during spinodal decomposition under the conditions of internal energy resonance

The Cahn-Hilliard concepts are generalized and used to the description of the spinodal decomposition of A3B5 quaternary semiconductor solid solutions, when the mixing of components occurs simultaneously in the metallic and metalloid sublattices of the sphalerite structure. The resulting system of differential equations for material decomposition was used to describe the effect of composition modulation observed in the synthesis of GaxIn1-xPyAs1-y - InP heterostructures. Numerical simulation of the spinodal decomposition of the GaxIm-xPyAsuy solid solution is carried out. The intervals of the thermodynamic parameters of the technological process of the synthesis of structures, in which the effect of modulation of the composition should be manifested, are found.

High-pressure behavior of disodered kesterite-type Cu2ZnSnS4

We have investigated the high-pressure structural and vibrational behavior of the disordered kesterite-type Cu2ZnSnS4 compound at ambient temperature. Our experimental and theoretical investigations have revealed a clear structural transition to a GeSb-type phase close to 15 GPa, a tetragonally distorted variant of the NaCl-type phase. The latter transformation is accompanied by a cationic coordination increase from fourfold to sixfold with respect to the sulfur anions. In addition, a change in the compressibility rate was detected at about 8 GPa within the pressure stability range of the disordered kesterite-type phase. Upon decompression, a disordered zinc blende/sphalerite structure is recovered. We discuss our findings in close conjunction with our recent high-pressure work on the ordered Cu2ZnSnS4 modification.

A re-interpretation of the structure of the silver borate, Ag16B4O10, in the light of the extended Zintl–Klemm concept

The borate Ag16B4O10 was synthesized at high temperature and at elevated oxygen pressures [Kovalevskiy et al. (2020). Chem. Sci. 11, 962–969]. Its structure consists of [B4O10]8− polyanions (isostructural to P4O10) embedded in an Ag matrix. According to the standard valences Ag+, B3+ and O2−, the formula has an excess of eight e− which the above authors proposed were located, pairwise, in four Ag4 tetrahedra within the silver substructure. That conclusion was based on the semiconducting and diamagnetic properties, as well as the very small `attractors' of the Electron Localization Function (ELF) found at the centre of these Ag4 tetrahedra. However, a large overlap of the projected density of states (DOS) of silver and oxygen indicated possible dispersion interactions between both atomic species. In this article, an alternative description is proposed based on the extended Zintl–Klemm concept. The anion [B4O10]8− can be formulated as Ψ-[N4O10] P4O10, if it is assumed that the eight e− are transferred to the four B atoms, so converting them into Ψ-N, this then makes sense of its similarity with P4O10, [N4(CH2)6], adamantane and tetraisopropyladamantane. When the Ag atoms connect to the O atoms, they arrange as the H atoms do in hexamethylenetetramine (HMTA). If the two lone pairs of each of the bridging O atoms in Ψ-[N4O10] are equated to the C—H bonds in HMTA, then, this same equivalence exists between the C—H bonds and the O—Ag bonds in the compound Ag16B4O10. The 24 Ag atoms surrounding each [B4O10]8− group prolong the sphalerite structure of the borate anion by means of Ag—O bonds which also fit the sphalerite structure formed of AgO. The eight excess electrons might then be distributed between the Ag and the O atoms, so making sense of the mixing of the Ag and O states. The Ag atoms bonded to the O atoms of the [B4O10]8− groups form a coat that interconnects the borate anions through Ag—O bonds. To establish the validity of this new proposal, the study needs to be extended to the compound Ag3B5O9.

Атомная структура и энергия когезии изолированных кластеров SiC

The first-principle calculations of the atomic and electronic structures and cohesion energy of fullerene-like Si60C60 clusters have been carried out. A model of two-layer fullerene-like Si12C12@Si48C48 cluster with mixed sp2/sp3 bonds has been built for the first time. Ab initio calculations are performed in terms of the electron density functional and the hybrid B3LYP functional theory. The stability and the energy gap width of the clusters are estimated in the dependence on its geometry. It is shown that cohesion energy of two-layer fullerene-like Si12C12@Si48C48 cluster exceeds the cohesion energy of the other fullerene-like clusters with the same number of atoms, but is inferior to the SiC cluster with sphalerite structure. The relaxation of two-layer cluster is shift on outward the surface layer occurs.

Structural and Optical Characterization of ZnS Ultrathin Films Prepared by Low-Temperature ALD from Diethylzinc and 1.5-Pentanedithiol after Various Annealing Treatments

The structural and optical evolution of the ZnS thin films prepared by atomic layer deposition (ALD) from the diethylzinc (DEZ) and 1,5-pentanedithiol (PDT) as zinc and sulfur precursors was studied. A deposited ZnS layer (of about 60 nm) is amorphous, with a significant S excess. After annealing, the stoichiometry improved for annealing temperatures ≥400 °C and annealing time ≥2 h, and 1:1 stoichiometry was obtained when annealed at 500 °C for 4 h. ZnS crystallized into small crystallites (1–7 nm) with cubic sphalerite structure, which remained stable under the applied annealing conditions. The size of the crystallites (D) tended to decrease with annealing temperature, in agreement with the EDS data (decreased content of both S and Zn with annealing temperature); the D for samples annealed at 600 °C (for the time ≤2 h) was always the smallest. Both reflectivity and ellipsometric spectra showed characteristics typical for quantum confinement (distinct dips/peaks in UV spectral region). It can thus be concluded that the amorphous ZnS layer obtained at a relatively low temperature (150 °C) from organic S precursor transformed into the layers built of small ZnS nanocrystals of cubic structure after annealing at a temperature range of 300–600 °C under Ar atmosphere.

Photoluminescence properties and threshold effect of ZnS:Ag nanoparticles synthesized by a hydrothermal process

Ag-doped ZnS nanoparticles were prepared by hydrothermal synthesis from the raw powders of thiourea, zinc acetate and silver nitrate. The effects of Ag[Formula: see text] on the structural, morphological, composition, elemental analysis and luminescence properties were investigated. The results showed that the powders were all found in the cubic sphalerite structure with an average particle size of approximately 40 nm. In addition, various Ag[Formula: see text] doping concentrations (0, 0.5, 1, 3, 4, 7 and 10 at.%) were selected to study the optical properties of the ZnS nanoparticles. It was found that the photoluminescence (PL) spectra excited by 325 nm and X-ray showed a peak at 490 nm for all samples and exhibited concentration quenching behavior. The PL results also indicate that the most favorable silver doping concentration for emission is 3 at.%. These results suggested that ZnS:Ag (3 at.%) nanoparticles were promising candidate materials for certain areas, such as screen displays, scintillators and lasers.

The growth, structure and luminescence properties of ZnSe1-xSx materials

ZnSe1-xSxcrystals with a higher content of selenium or sulfur ions adopt, respectively, a wurtzite or sphalerite structure. Luminescent properties of ZnSe1-xSxcrystals are determined by ternary VZnZniOSecomplexes for crystals with a cubic (sphalerite) lattice, and by sulfur vacancies VSfor crystals with a hexagonal (wurtzite) lattice. Light output of ZnSe1-xSxcrystals increases with increasing the sulfur content up tox= 0.3 and reaches the value of light output observed for ‘classic scintillator’ ZnSe(Te). At the same time, the ZnSe1-xSxbulk crystals possess better thermal stability at the same energy of emitted photons (hν~ 2 eV) as compared to that of the ZnSe(Te) crystals.

Study on Non-Selective Photocatalytic Degradation of Organic Dyes in Presence of Hollow CdS Nanospheres

In this study, template method was applied to synthesize CdS hollow nanospheres via sonochemical method. The morphology, size of the nanospheres and crystal structure of the synthesized hollow CdS were characterized. The results showed that the hollow CdS nanospheres formed have pure cubic sphalerite structure and exhibit good monodispersity and size uniformity. The photocatalytic activity of the samples was evaluated by the decoloration of Rhodamine B (RhB), Methylene Blue (MB) and Methyl Orange (MO) aqueous solution under UV-vis light irradiation. The results indicated the hollow CdS had a good photocatalytic activity and show little selectivity of attack and are able to oxidize various organic pollutants. Moreover, the results of hydroxyl radical (•OH) detection using fluorescent probe method was in accordance with the RhB decolorization efficiency, which the •OH is likely to be the main active species responsible for dye degradation.

Effect of Different Thicknesses of ZnS Thin Films on its Optical and Structural Properties

ZnS films have been deposited on glass by chemical bath deposition (CBD). The optical and structural properties were analyzed by UV-VIS spectrophotometer and X-ray diffraction (XRD). The results showed that different sides of glass substrate have different thicknesses of the ZnS thin films, which can affect the optical and structural properties of ZnS thin films. The ZnS films of the side of glass substrates back to the solution center are thicker than that of the other side, and the ZnS films from ZnSO4 are thicker than that from Zn (NO3)2. The transmittances lower with the thicknesses of ZnS films increasing. The band gaps exhibit blue response with the thicknesses of ZnS films increasing. From the sides of glass substrates back to the solution center, the (111) reflection of the sphalerite structure can be observed at about 2θ=29.1°, while from the other side toward the solution center showed no significant peak.