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Graphene-like ZnX (X=O, S, Se, Te) structures are studied using the DFT+U method to address in detail the questions regarding the dynamical stability and also their utility in optoelectronic devices. The layer modulus, the Young's modulus, the shear modulus, and the Poisson coefficient demonstrate the stability of all ZnX in the presence of the Hubbard parameter U. Cohesion energy calculations show ZnO to be the most stable one and ZnSe to be the least stable one among the four systems. The presence of a direct bandgap in all the systems makes them suitable for use in optoelectronic devices. The gap values range between 2.13 eV in ZnTe and 3.50 eV in ZnO. U values tend to increase the bandgap in all the systems. This increase is seen to be as high as 100% in ZnO. A detailed study of the band structure and partial density of states is carried out. The electronic, optical, and thermoelectric properties of the ZnX monolayers are exhibited. The superior limit of the figure of merit increases with temperature and the highest value is found to be of the order of 0.6 in ZnO at 900 ° C. Overall, the inclusion of the Hubbard parameter demonstrates better stability and also its importance in technological applications. [ABSTRACT FROM AUTHOR]

Developing an efficient photocathode system from earth abundant materials is essential for effectual Photoelectrochemical (PEC) water splitting. Charge transfer between heterojunctions is important in fabricating a novel photocathode, keeping cost-effectiveness, abundance, and PEC performance in mind. The p-type narrow band gap photocathode, CuO (Eg = 1.5 eV) synthesized by hydrothermal method, was decorated with Sb2S3 Nanospheres (NSs) by adopting a facile chemical bath deposition (CBD) procedure to fabricate CuO/Sb2S3 NSs heterojunction. Fabricated heterojunction showed better PEC performance contrary to bare CuO, improvement in photocurrent density CuO/Sb2S3 NSs (J = −1 mA cm−2) than CuO (J = −0.3 mA cm−2) photoelectrode at 0 VRHE in 0.5 M Na2SO4 (pH 6.85) is due to enhanced charge carrier generation/separation. The photostability of CuO/Sb2S3 remains intact for 2.5 h with no degradation in photocurrent density. Sb2S3 works as a sensitizer, diminishing the recombination rate of the e−/h+ in CuO/Sb2S3 NSs. UV–Visible and photoluminescence(PL) emission spectra results suggested CuO/Sb2S3 enhanced absorption spectrum and reduced rate of recombination. Electrochemical impedance spectroscopy studies show less charge transfer resistance for CuO/Sb2S3 NSs than CuO. This finding will pave new path in developing novel photocathodic material configurations and heterojunction with Cu-based binary oxides/chalcogenides for solar harvesting.

The first alkaline-earth metal thioborate–thiophosphate Ba3(BS3)(PS4) was designed from Ba3(BO3)(PO4) by S–O substitution and fabricated experimentally. The [BS3] pseudo-layers formed in the structure contribute to the strong optical anisotropy and a large birefringence of ∼0.11 at 1064 nm. The results enrich the structural and chemical diversity of chalcogenides. [ABSTRACT FROM AUTHOR]

Rongalite whose chemical structure was discovered in 1905, is an inexpensive, easily assessable, and copious industrial product, which has significantly been used for a long time in rubber, dye, and veterinary industries. Moreover, it has also been used as an antidote against several heavy metals poisoning, in addition to its applications in the photographic developer and veterinary medicines. Gratifyingly, Rongalite has also shown its uses as the fungicidal, bactericidal and antioxidant in pharmaceutical formulation. Besides, it has also been used in material sciences, and also as a viable cosmetic hair‐dye‐color removers. Interestingly, in past decade, it has shown its high‐impact in the arena of synthetic organic chemistry serving as SO22− equivalent, C1 synthon donor, reducing agent/radical initiator or proton source ‐ to assemble diverse intricate organic molecules under operationally simple yet efficient conditions. However, the services of multiple features of Rongalite in synthetic chemistry are still at the research stage, and needs to be sophisticated to a higher level in many years to come. Considering the synthetic importance of this valued reagent, this review article presents the advancement made in the field of Rongalite chemistry in the past three years. This review article will update the researchers working in this arena about the advancement of Rongalite in the synthetic organic transformations as well as it will help readers wishing to deal with this easy‐to handle and eco‐friendly low‐cost commodity chemical. This review article updating the rongalite chemistry will be useful to the chemical community in general and synthetic chemists in particular. [ABSTRACT FROM AUTHOR]

The most promising candidates for solar cells and optoelectronic devices are the transition metals dichalcogenides. Here, we employed the well‐known density functional theory to examine the structural, optoelectronic, and elastic characteristics of novel binary chalcogenides. A direct band gap for ZrX2 and an indirect band gap for PtX2 materials were both confirmed by the band structure features. The valence and conduction band regions are formed by the interaction of the A‐d and X‐p bands. Both the formation energy and the cohesive energies are calculated. The phonon dispersion plots confirmed the stability of the structures. Furthermore, the significant optical constants are computed and explained for possible employment in the optoelectronic application. Our computed band gaps and refractive index were found to be inversely associated. The vital elastic properties are also calculated to discuss the mechanical stability of these materials. The greater bulk modulus and Young's modulus for ZrS2 as compared to the studied chalcogenides suggest this material to be harder and more compressible. The B/G values, confirm all the studied dichalcogenides to be ductile. The most ductile of these materials was ZrSe2 with a predicted B/G value of 7.65. The present work could primarily aid in the creation of diverse and potentially useful semiconducting devices and their applications. [ABSTRACT FROM AUTHOR]

The review describes the possibilities of the synthesis of organochalcogen compounds of different classes using elemental chalcogens or available organic dichalcogenides and hydrazine, which converts chalcogens and dichalcogenides into a reactive form of chalcogenide anions. The key features of reactions that occur in a hydrazine hydrate medium are considered. [ABSTRACT FROM AUTHOR]

Noncentrosymmetric ternary and quaternary chalcogenides are studied as promising nonlinear optical (NLO) materials in the mid‐infrared region. Here, we report the synthesis of a new material BaCu2SiS4 in the AIIBI2MIVQ4 family (A=divalent metal; B=monovalent metal; M=tetrel, Q=chalcogen), and discuss its crystal structure, thermal stability, optical behavior, and electronic structure. BaCu2SiS4 crystallizes in the noncentrosymmetric chiral space group P3221 with lattice parameters a=6.1440(3) Å, c=15.3542(8) Å, V=501.95(6) Å3, Z=3. The structure features helical channels formed by corner‐sharing [CuS4] and [SiS4] tetrahedral units. Synthesis was carried out in a molten salt flux, as opposed to a traditional solid‐state route from elements, to minimize the formation of a competing ternary phase, Ba2SiS4. BaCu2SiS4 is a semiconductor with an experimentally‐determined direct bandgap of ~2.2 eV. The material exhibits second harmonic generation (SHG) activity, confirming the noncentrosymmetric nature of the structure. Analysis of reported AIIBI2MIVQ4 crystal structures pointed out a correlation among potential structure types and the radii of the constituent elements. Total energy calculations were carried out to explore the relative stability of several reported crystal structures in this family of compounds. [ABSTRACT FROM AUTHOR]

Chalcogenide glasses are unquestionably one of the most popular materials known for their phase change property. Phase change materials (PCM) have a key role in the field of photonics, memory devices, imaging, etc. With an aim to study the worth of ternary Sb10Se90-xGex (x = 0, 19, 21, 23, 25, 27) and quaternary Sb10Se65Ge25-yIny (y = 0, 3, 6, 9, 12, 15) chalcogenide systems as PCM, the composition variation and effect of dopants on the thermal properties of two systems has been probed. The thermal stability of two glass systems has been investigated using criteria such as the S parameter, fragility index, and rate constants at glass transition and crystallization temperatures. The mechanism of the phase change phenomenon occurring in the glasses has been studied using the Avrami index. [ABSTRACT FROM AUTHOR]

The performance prerequisites for nonlinear optical (NLO) crystals encompass a substantial second‐harmonic generation (SHG), a considerable laser induced damage threshold, and a moderate degree of birefringence. Nevertheless, the presence of particular anions may result in deficiencies within certain properties. The utilization of mixed anionic groups has emerged as an effective strategy to achieve a balance among numerous performance parameters of NLO crystals, particularly in terms of SHG responses and bandgaps. Compared with other heteroanionic compounds, adduct‐type compounds feature more concise structures with specific properties. Herein, we aim to provide an overview of the recent advancements in adduct‐type NLO crystals, focusing on their structures and properties. Furthermore, we analyze the coordination chemistry and disadvantages involved in adducts, and discuss the current synthesis methods as well as future directions for further exploration. [ABSTRACT FROM AUTHOR]

A series of phosphorus and selenium peri-substituted acenaphthene species with the phosphino group oxidized by O, S, and Se has been isolated and fully characterized, including by single-crystal X-ray diffraction. The P(V) and Se(II) systems showed fluxional behavior in solution due to the presence of two major rotamers, as evidenced with solution NMR spectroscopy. Using Variable-Temperature NMR (VT NMR) and supported by DFT (Density Functional Theory) calculations and solid-state NMR, the major rotamers in the solid and in solution were identified. All compounds showed a loss of the through-space JPSe coupling observed in the unoxidized P(III) and Se(II) systems due to the sequestration of the lone pair of the phosphine, which has been previously identified as the major contributor to the coupling pathway. [ABSTRACT FROM AUTHOR]

Benefiting from excellent optoelectronic properties and facile fabrication, Sb2Se3‐based semiconductor devices have drawn great attention in the last decade; in particular, Sb2Se3‐based solar cells and photodetectors have demonstrated decent performance metrics. However, the current research on Sb2Se3 devices is mainly focused on material and device processing and optimization, and few studies have been conducted on charge transport, which is limiting the further development of Sb2Se3‐based devices. To address this issue, post‐treatment techniques are introduced and their influence on the charge carrier dynamics of Sb2Se3 thin films is fully investigated. The charge carrier mobility of evaporated Sb2Se3 thin films is increased by an order of magnitude from 0.02 to 0.4 cm2 V−1 s−1 after the Se post‐treatment. Based on the optimized Sb2Se3 thin films, ultra‐fast photodiodes are further developed and a record‐fast response of 37 ns is achieved. Prototypical devices also demonstrated great potential for high‐speed photodetection in practical applications. [ABSTRACT FROM AUTHOR]

Context: In the present work, the cubic phase of the chalcogenide materials, i.e., A2MoSe4 (A =Li, K) is examined to explore the structural, optoelectronic, magnetic, mechanical, vibrational, and thermodynamic properties. The lattice parameters for Li2MoSe4 are found to be a= 7.62 Å with lattice angles of α=β=γ=90° whereas for K2MoSe4, a= 8.43 Å, and α=β=γ=90°. These materials are categorized as semiconductors because Li2MoSe4 and K2MoSe4 exhibit direct energy band gap worth 1.32 eV and 1.61 eV, respectively through HSE06 functional. The optical analysis has declared them efficient materials for optoelectronic applications because both materials are found to be effective absorbers of ultraviolet radiations. These materials are noticed to be brittle while possessing anisotropic behavior for various mechanical applications. The vibrational properties are explored to check the thermal stability of the materials. On the basis of thermodynamics and heat capacity response, Li2MoSe4 is more stable than K2MoSe4. The results of our study lay the groundwork for future research on the physical characteristics of ternary transition metal chalcogenides (TMC). Methods: These physical properties are explored for the first time while using a first-principles approach based on density functional theory (DFT) in the framework of Cambridge Serial Total Energy Package (CASTEP) by Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) functional. However, GGA+U and HSE06 are also employed to improve electronic properties. Kramers–Kronig relations are used to evaluate the dielectric function with a smearing value of 0.5 eV. Voigt-Reuss-Hill approximation is used for seeking the elastic response of these materials. The thermodynamic response is sought by harmonic approximation. The density functional perturbation theory (DFPT) approach is used for investigating atomic vibrations. [ABSTRACT FROM AUTHOR]

Context: This research focused on the theoretical investigation of transition metal carbonyls [M(CO)4] coordinated with terminal germanium chalcogenides complexes [M(CO)3GeX], where M represents Ni, Pd, and Pt and X represents O, S, Se, and Te labeled 1–15. While the notable complexes M(CO)4 (where M = Ni, Pd, Pt) numbered 1, 6, and 11 are of significance, substituting one of the CO ligands in 1, 6, and 11 with a GeX ligand (where X = O, S, Se, or Te) result in substituted complexes (2–5, 7–10, and 11–15). Substituting of the CO ligand slightly alters these bond angles. Specifically, the ∠CMC bond angles for [Ni] complexes range from 111.9° to 112.2°, for [Pd] complexes from 111.4° to 111.7°, and for [Pt] complexes from 112.4° to 112.8°. These findings indicate a minor deviation from the tetrahedral geometry due to the influence of the new GeX ligand. Similarly, there is a slight change in the geometry of the metal complexes, where the ∠GeMC angles for [Ni] complexes are between 106.7° and 106.9°, for [Pd] complexes between 107.2° and 107.5°, and for [Pt] complexes between 105.9° and 106.4°. Comparing among the substituted GeX complexes, those containing GeTe exhibit a higher natural bond orbital (NBO) contribution from the Ge atom compared to the M atom. Consequently, based on the above observations, it can be inferred that GeX acts as an effective sigma donor in contrast to carbonyl compounds. Results of energy decomposition analysis (EDA) for the M–CO bond in 1, 6, and 11 and for the M–GeX bond in the other [M(CO)3(GeX)] complexes where M = Ni, Pd and Pt. The percentage contribution of ΔEelstat and ΔEorb shows a relatively identical behavior for all ligands in case of each metal complexes. Methods: Density functional theory (DFT) calculations were conducted using the B3LYP/gen/6-31G*/LanL2DZ level of theory to examine transition metal carbonyls [M(CO)4] coordinated with terminal germanium chalcogenides complexes [M(CO)3GeX], where M represents Ni, Pd, and Pt, and X represents O, S, Se, and Te labeled 1–15 utilized through the use of Gaussian 09W and GaussView 6.0.16 software packages. Post-processing computational code such as multi-wave function was employed for results analysis and visualization. [ABSTRACT FROM AUTHOR]

Phase change materials, which show different electrical characteristics across the phase transitions, have attracted considerable research attention for their potential electronic device applications. Materials with metal‐to‐insulator or charge density wave (CDW) transitions such as VO2 and 1T‐TaS2 have demonstrated voltage oscillations due to their robust bi‐state resistive switching behavior with some basic neuronal characteristics. BaTiS3 is a small bandgap ternary chalcogenide that has recently reported the emergence of CDW order below 245 K. Here, the discovery of DC voltage / current‐induced reversible threshold switching in BaTiS3 devices between a CDW phase and a room temperature semiconducting phase is reported. The resistive switching behavior is consistent with a Joule heating scheme and sustained voltage oscillations with a frequency of up to 1 kHz are demonstrated by leveraging the CDW phase transition and the associated negative differential resistance. Strategies of reducing channel sizes and improving thermal management may further improve the device's performance. The findings establish BaTiS3 as a promising CDW material for future electronic device applications, especially for energy‐efficient neuromorphic computing. [ABSTRACT FROM AUTHOR]

Exploring and developing new functional inorganic chalcogenides with unique structures is always one of the most important missions in solid-state chemistry, especially those with molecular structures. Herein, a novel quaternary thioarsenate, Cs2CdAsSe5, is found to be based on an unprecedented molecular (poly)chalcogenide cluster architecture, which has never been discovered in inorganic chalcogenide systems. This rare windmill-like [Cd4As8Se16(Se2)2]8− cluster is made of four [CdSe4] and [As(V)Se4] tetrahedra via corner-sharing Se atoms and Se–Se bonds. Specifically, Cs2CdAsSe5 exhibits a remarkable photocurrent response and a large computationally predicted birefringence, and the origin of the optoelectronic performance and optical anisotropy is confirmed by detailed theoretical investigation. [ABSTRACT FROM AUTHOR]

A copper‐mediated C(sp2)−H chalcogenation of heterocycles with readily available dichalcogenide, benzeneselenol and thiol is described. This protocol demonstrates scalability, good chemo‐ and regio‐selectivity, as well as broad functional group tolerance, which overall provides an accessible method to valuable aryl chalcogenides. The chalcogenated picolinamide products could be further transformed into selenoxanthones and thioxanthone scaffolds through intramolecular cyclization via a semi‐one pot process. [ABSTRACT FROM AUTHOR]

Optoelectronic technologies are based on families of semiconductor alloys. It is rare that a new semiconductor alloy family is developed to the point where epitaxial growth is possible; since the 1950s, this has happened approximately once per decade. Herein, this work demonstrates epitaxial thin film growth of semiconducting chalcogenide perovskite alloys in the Ba‐Zr‐S‐Se system by gas‐source molecular beam epitaxy (MBE). This work stabilizes the full range y = 0 − 3 of compositions BaZrS(3‐y)Sey in the perovskite structure. The resulting films are environmentally stable and the direct band gap (Eg) varies strongly with Se content, as predicted by theory, with Eg = 1.9 − 1.5 eV for y = 0 − 3. This creates possibilities for visible and near‐infrared (VIS–NIR) optoelectronics, solid‐state lighting, and solar cells using chalcogenide perovskites. [ABSTRACT FROM AUTHOR]

Herein, elastic, optical, and thermoelectric properties of zinc chalcogenides with 2D square lattice and hexagonal phases [s‐ and h‐ZnX (X = GrVI)] are reported. The s‐ZnX and h‐ZnX structures are achieved to be dynamically stable, according to the phonon dispersion studies. All s‐ and h‐ZnX compounds are found to be semiconductor, with direct and indirect bandgaps ranging from 0.81 to 2.77 eV under PBE and 1.70 to 4.15 eV by HSE06 calculations. The effective mass, mobility, and relaxation time of electron and hole carriers in the band structures of s‐ and h‐ZnX are investigated to gain a better insight of these materials. In addition to the phonon dispersion analysis, their mechanical stability in terms of elastic properties is evaluated, and the resulting elastic parameters validate their mechanical stability. The optical properties of s‐ and h‐ZnX are inspected in the occurrence of field polarizations across parallel and perpendicular directions. At room temperature, s‐ZnTe compound has an optimum figure of merit (ZT) value, indicating it as the superlative thermoelectric material in the entire series. These compounds may also be explored in ultraviolet lasers, solar cells, electronic image displays, high‐density optical memory, photodetectors, and solid‐state laser devices. [ABSTRACT FROM AUTHOR]

Cu-based chalcogenide materials have attracted a great deal of attention due to their promising optoelectronic properties. The density functional theory (DFT) framework is used in order to estimate the optical and electronic properties of XCu2GeQ4 (X = Ba, Sr and Q = S, Se). We report the optical and electronic properties of Cu-based chalcogenides in this study, which have narrow and direct bandgap materials. The calculated energy bandgap of quaternary chalcogenide materials decreases in the following sequence: SrCu2GeS4 (0.697 eV), BaCu2GeS4 (0.667 eV), BaCu2GeSe4 (0.378 eV), and SrCu2GeSe4 (0.195 eV). This reduction in energy bandgaps shows significant effect of changing dopants on electronic and consequently optical properties of XCu2GeQ4 (X = Ba, Sr and Q = S, Se). The optical characteristics of these materials are investigated in order to explore their potential for optoelectronic applications. However, other materials are emerging as contenders for solar cells, which operate from UV to infrared regions. Initially in infrared region, we can note a redshift in the maximum absorption of incident photons from ε 2 (ω) plots in the following sequence: BaCu2GeS4 (1.52 eV), SrCu2GeS4 (1.50 eV), BaCu2GeSe4 (1.30 eV), and SrCu2GeSe4 (0.93 eV). The approximated values of reflectivity, R(ω) are plotted against incident photon energy from 0 to14 eV. Thus, the reflectivity is approximately below 50% before E ≈ 12.0 eV and then increased to 70% reflection at ~ 13.0 eV. Based on calculated thermoelectric properties, these chalcogenides are promising thermoelectric materials. The ZT values of XCu2GeQ4 (X = Ba, Sr and Q = S, Se) decreased in the following sequence: SrCu2GeSe4 (2.6), BaCu2GeSe4 (1.85), SrCu2GeS4 (1.01) and BaCu2GeS4 (0.94). Hence, we believe our findings propose promising materials for anti-reflecting coating layers in optoelectronic technology. [ABSTRACT FROM AUTHOR]

Halide ions have emerged as important surface active species that regulate the growth of nanomaterials and concomitant physicochemical properties. However, there are very few reports concerning anion exchange of halide ions for the growth and conversion of nanocrystals or nanoclusters. Herein, we present the transformations of silver(I) chalcogenide clusters induced by doping halide ions, which are particularly of interest because of individual pathways controlled by ion species and amounts. Based on the cluster transformation, we further developed a luminescence turn-on sensor with high selectivity, detecting Cl− and Br−. This work opens a new way of understanding the growth of clusters and developing their luminescence sensing applications. [ABSTRACT FROM AUTHOR]

Interlayer sliding modulation in van der Waals (vdW) layered materials opens opportunities to seek tunable applications for photonics and optoelectronics at the nanoscale. In this work, focusing on ternary chalcogenides, dozens of typical vdW layered materials with the formula of A2MZ4 (A, M = metal cation; Z = S/Se) were systematically classified and studied to illustrate the interlayer sliding modulation performance on nonlinear optical (NLO) effect and underlying mechanism. Based on first-principles analysis, the screened Cd2GeSe4 exhibits large second harmonic generation (SHG) deviation (>36 times between high- and low-SHG states) under sliding among all studied materials. This phenomenon arises from the polarization modulation induced by the vdW interlayer charge redistribution of two tetrahedral primitives in the ternary edge-sharing tetrahedral structures. Our findings present a strategy to substantially modulate NLO properties by altering the interlayer charge coupling which is commonly thought to be very weak in vdW layered materials. [ABSTRACT FROM AUTHOR]

The growing demand for energy, as well as the impact on the environment as a result of human activity, has prompted a renewed focus on the development of cleaner alternative fuels. Because of its pure combustion products, hydrogen gas is being used as an alternative in the development of sustainable energy sources. A simple hydrothermal technique was used to prepare copper nickel tin sulphide (CNTS) decorated graphitic carbon nitride (gCN). CNTS-gCN samples were further prepared on different concentrations of gCN that varies from CNTS-gCN(10 mg–50mg) and analyzed under various characterization for its structural, morphological, and electrochemical properties. Field Emission Scanning Electron Microscopy (FESEM), Raman and HR-TEM (High Resolution- Transmitting Electron Microscopy) techniques were used to examine the morphology and surface structure of CNTS-gCN. Owing to its exclusive electrocatalytic property as low charge transfer resistance and high electrochemically active surface area, the composite material reveals a superior catalytic stability for the production of hydrogen energy. The hierarchical flower like structures were still maintained even after the addition of g-CN at different loading concentrations (10–50) respectively. The objective of this research is to prepare a new electrocatalyst based on CNTS with an increased HER activity. [Display omitted] • Copper nickle tin sulphide (CNTS) decorated with gCN exhibits hierarchical structure. • Morphological, structural, catalytic properties were akin with gCN concentrations. • gCN plays vital role in influencing the morphologies of copper nickel tin sulphides. • Excellent HER activity and enhanced synergism were shown by CNTS-gCN (10–50). [ABSTRACT FROM AUTHOR]

Carbon nanomaterials have wide applications in sensors, batteries, electromagnetic shielding, and mechanical reinforcement. Here, carbon nanofiber (CNF)-reinforced Ge 25 Sb 10 S 65 chalcogenide glassy composites with excellent mechanical and electrical properties were obtained. These glassy composites maintained the amorphous properties of glass. Thermodynamic parameters, microscopic morphology, and structural characteristics were further studied. Benefiting from the remarkable high strength and conductivity of CNFs, as well as the great interface connection between CNFs and glass, the electrical and mechanical properties of glassy composites were greatly enhanced. The Vickers hardness improved by 36% (from 200 kg/mm2 to 272 kg/mm2), the tensile modulus increased from 45.9 GPa to 57 GPa, and the shear modulus increased from 22.2 GPa to 23.7 GPa when the CNF concentration increased from 0 wt% to 3.0 wt%. Furthermore, DC conductivity was raised by several orders of magnitude compared with bulk glass at 293 K (from 4.55 × 10−10 S/cm to 3.15 × 10−4 S/cm) owing to the formation of a continuous conductive network. Thus, these CNF-reinforced glassy composites provide a new way for realizing multifunctional composites. [ABSTRACT FROM AUTHOR]

Terahertz third-harmonic generation in topological insulators based on bismuth and antimony chalcogenides has been experimentally investigated. It has been found that the third-harmonic conversion efficiency is inversely proportional to the electron Fermi energy; among the materials under study, antimony telluride has the highest conversion efficiency. [ABSTRACT FROM AUTHOR]

In this work, we report the ternary Cu-based chalcogenide, Cu2TiTe3, as a promising thermoelectric material in middle-temperature range. The bonding interaction between Te p and Ti d states is observed in the Ti–Te octahedron, which drives the side bands up converging with Γ band, yielding a high valence band degeneracy of 5. A high electronic quality factor of 2.2 μW cm−1 K−2 and a decent power factor of 7.5 μW cm−1 K−2 at 300 K are achieved for Cu2TiTe3. Likewise, Cu2TiTe3 demonstrates low lattice thermal conductivity throughout the measured temperature range, which is attributed to the low frequency vibration related to the global motion of Ti–Te–Cu clusters. Finally, a maximum figure-of-merit of 0.38 was obtained for Cu2TiTe3 at 600 K. [ABSTRACT FROM AUTHOR]

In this work, we report the ternary Cu-based chalcogenide, Cu2TiTe3, as a promising thermoelectric material in middle-temperature range. The bonding interaction between Te p and Ti d states is observed in the Ti–Te octahedron, which drives the side bands up converging with Γ band, yielding a high valence band degeneracy of 5. A high electronic quality factor of 2.2 μW cm−1 K−2 and a decent power factor of 7.5 μW cm−1 K−2 at 300 K are achieved for Cu2TiTe3. Likewise, Cu2TiTe3 demonstrates low lattice thermal conductivity throughout the measured temperature range, which is attributed to the low frequency vibration related to the global motion of Ti–Te–Cu clusters. Finally, a maximum figure-of-merit of 0.38 was obtained for Cu2TiTe3 at 600 K. [ABSTRACT FROM AUTHOR]

Two new alkaline metal thioboratephosphates, RbB3P2S10 and CsB3P2S10, have been designed and fabricated by the flux method. The two compounds are composed of alkali metal polyhedral and [B6P4S20] T3-supertetrahedral units, and crystallize in I41/a and R3¯c space groups, respectively. The results enrich the chemical diversity of chalcogenides, and give insights for the exploration of new functional materials in thioboratephosphates. [ABSTRACT FROM AUTHOR]

The development of multifunctional devices could represent a significant advancement in meeting the need for nano and micro technologies. Therefore, we have developed a Ag/Sb2Se3/FTO-based multifunction device having nanostructures, which works as an ultraviolet (UV) photodetector and a switching device. Our theory suggests how oxygen formation leads to detection in the UV range rather than detection in the infrared range, which is the natural detection range of Sb2Se3. The m–s–m photodetector device is based on the photoconductive phenomenon, and ultrafast transient absorption spectroscopy has been extensively used to investigate the charge carrier dynamics of Sb2Se3 films of 500 nm. At two distinct excitations, 375 nm UV and 532 nm visible light, and a pulse energy of 1 J per pulse, the effect of annealing on the charge carrier relaxation of the films was investigated. The kinetics of the hot charge carrier's decay and recombination were studied for both as-grown and annealed films. The proposed theory is analyzed with the help of X-ray photoelectron spectroscopy and density functional theory studies. The device shows external quantum efficiency values of 2.9 and 1.3 at 375 and 386 nm, respectively. The rise time to fall time ratio was 0.29/0.30 s at 375 nm irradiation at 2 V bias at a power density of 32 mW/cm2. The same device shows bipolar resistive switching, in which resistance shifts from a high resistance state to a low resistance state in a voltage sweep from −1 to 0 V and then 0 to 1 V. The result of the switching phenomenon is reasonably justified by the electrochemical metallization phenomenon. An outstanding accomplishment in electronic devices is combining two different features on a single device. [ABSTRACT FROM AUTHOR]

Chalcogenide based nano‐films have attracted considerable attention as a new type of semiconductor material in the fields of optical waveguides, laser devices, and solar cells. However, it remains challenging to use them effectively in a variety of fields, mainly due to their intricate fabrication procedures and limited electrical characteristics. In this study, zinc selenide (ZnSe) is doped with molybdenum (Mo) and gallium (Ga). The heterodimensional structured chalcogenide semiconductor nano‐film is obtained by pulsed laser deposition (PLD). The results of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirm that the structure of the nano‐film is compact and the composition is uniformly distributed. The transmittance of all samples is close to 100% in the 400–2000 nm range shown. The P/N type of the film can be controlled by changing the preparation conditions. All the results indicate that the novel heterodimensional structured chalcogenide semiconductor nano‐film in this study has a simple and efficient preparation method, controllable composition, and unique optical/electrical properties. These properties can be used in integrated circuits and photovoltaic power generation. [ABSTRACT FROM AUTHOR]

Infrared detection technology plays an important role in remote sensing, imaging, monitoring, and other fields. So far, most infrared photodetectors are based on InGaAs and HgCdTe materials, which are limited by high fabrication costs, complex production processes, and poor compatibility with silicon-based readout integrated circuits. This hinders the wider application of infrared detection technology. Therefore, reducing the cost of high-performance photodetectors is a research focus. Colloidal quantum dot photodetectors have the advantages of solution processing, low cost, and good compatibility with silicon-based substrates. In this paper, we summarize the recent development of infrared photodetectors based on mainstream lead chalcogenide colloidal quantum dots. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides are studied due to the possibility of creating nanoscale semiconductor devices, as well as fundamental issues of magnetic ordering. We researched the crystal structure and magnetic properties of niobium dichalcogenide Mn0.30NbS2. The results of the X-ray study showed the possible existence of an intermediate 2 3 a0·2 3 a0 structure between the "basic" superstructures. Also, two local maximums were found in the temperature dependence of the dynamic magnetic susceptibility. These features can indirectly confirm the presence of a transition superstructure and reflect the two-step nature of the magnetic ordering. [ABSTRACT FROM AUTHOR]

Pathogenic microbes are a major concern in hospitals and other healthcare facilities because they affect the proper performance of medical devices, surgical devices, etc. Due to the antimicrobial resistance or multidrug resistance, combatting these microbial infections has grown to be a significant research area in science and medicine as well as a critical health concern. Antibiotic resistance is where microbes acquire and innately exhibit resistance to antimicrobial agents. Therefore, the development of materials with promising antimicrobial strategy is a necessity. Amongst other available antimicrobial agents, metal oxide and chalcogenide-based materials have shown to be promising antimicrobial agents due to their inherent antimicrobial activity as well as their ability to kill and inhibit the growth of microbes effectively. Moreover, other features including the superior efficacy, low toxicity, tunable structure, and band gap energy has makes metal oxides (i.e. TiO2, ZnO, SnO2 and CeO2 in particular) and chalcogenides (Ag2S, MoS2, and CuS) promising candidates for antimicrobial applications as illustrated by examples discussed in this review. [ABSTRACT FROM AUTHOR]

The integration of artificial intelligence systems into daily applications like speech recognition and autonomous driving rapidly increases the amount of data generated and processed. However, satisfying the hardware requirements with the conventional von Neumann architecture remains challenging due to the von Neumann bottleneck. Therefore, new architectures inspired by the working principles of the human brain are developed, and they are called neuromorphic computing. The key principles of neuromorphic computing are in-memory computing to reduce data shuffling and parallelization to decrease computation time. One promising framework for neuromorphic computing is phase-change photonics. By switching to the optical domain, parallelization is inherently possible by wavelength division multiplexing, and high modulation speeds can be deployed. Non-volatile phase-change materials are used to perform multiplications and non-linear operations in an energetically efficient manner. Here, we present two prototypes of neuromorphic photonic computation units based on chalcogenide phase-change materials. First is a neuromorphic hardware accelerator designed to carry out matrix vector multiplication in convolutional neural networks. Due to the neuromorphic architecture, this prototype can already operate at tera-multiply-accumulate per second speeds. Second is an all-optical spiking neuron, which can serve as a building block for large-scale artificial neural networks. Here, the whole computation is carried out in the optical domain, and the device only needs an electrical interface for data input and readout. [ABSTRACT FROM AUTHOR]

We study the role of equi-biaxial strains on the electronic structure in pnictogen chalcogenides Bi2Se3, Bi2Te3, and As2Te3. Bi2Se3 and Bi2Te3 are topological insulators, and As2Te3 is an insulator with a relatively small bandgap. Based on the results of density functional theory calculations including van der Waals corrections, we demonstrate that a topological insulator (TI) state in As2Te3 can be induced by an epitaxial (in-plane) tensile misfit strain of 1%. Furthermore, we find overall that the effect of the misfit on the bandgap is larger for As2Te3 than for Bi2Se3 and Bi2Te3. We attribute this to a complex interplay between the misfit strain, spin–orbit coupling, and the relaxation of surface atomic layers. Our findings indicate that As2Te3 is more suitable than Bi2Se3 and Bi2Te3 for potential applications of strain-induced switching of TIs. [ABSTRACT FROM AUTHOR]

We model electrical conductivity in metastable amorphous Ge2Sb2Te5 (GST) using independent contributions from temperature and electric field to simulate phase change memory devices and ovonic threshold switches. 3D, 2D-rotational, and 2D finite element simulations of pillar cells capture threshold switching and show filamentary conduction in the on-state. The model can be tuned to capture switching fields from ∼5 to 40 MV/m at room temperature using the temperature dependent electrical conductivity measured for metastable amorphous GST; lower and higher fields are obtainable using different temperature dependent electrical conductivities. We use a 2D fixed out-of-plane-depth simulation to simulate an ovonic threshold switch in series with a Ge2Sb2Te5 phase change memory cell to emulate a crossbar memory element. The simulation reproduces the pre-switching current and voltage characteristics found experimentally for the switch + memory cell, the isolated switch, and the isolated memory cell. [ABSTRACT FROM AUTHOR]

We examined the estimation of thermal conductivity through molecular dynamics simulations for a superionic conductor, α-Ag2Se, using the interatomic potential based on an artificial neural network (ANN potential). The training data were created using the existing empirical potential of Ag2Se to help find suitable computational and training requirements for the ANN potential, with the intent to apply them to first-principles calculations. The thermal conductivities calculated using different definitions of heat flux were compared, and the effect of explicit long-range Coulomb interaction on the conductivities was investigated. We clarified that using a rigorous heat flux formula for the ANN potential, even for highly ionic α-Ag2Se, the resulting thermal conductivity was reasonably consistent with the reference value without explicitly considering Coulomb interaction. It was found that ANN training including the virial term played an important role in reducing the dependency of thermal conductivity on the initial values of the weight parameters of the ANN. [ABSTRACT FROM AUTHOR]

Thermoelectric (TE) materials play a crucial role in converting energy between heat and electricity, essentially for environmentally friendly renewable energy conversion technologies aimed at addressing the global energy crisis. Significant advances in TE performance have been achieved over the past decades in various TE materials through key approaches, such as nanostructuring, band engineering, and high-entropy engineering. Among them, the design of high-entropy materials has recently emerged as a forefront strategy to achieve significantly low thermal conductivity, attributed to severe lattice distortion and microstructure effects, thereby enhancing the materials’ figure of merit (zT). This review reveals the progress of high-entropy TE materials developed in the past decade. It discusses high-entropy-driven structural stabilization to maintain favorable electrical transport properties, achieving low lattice thermal conductivity, and the impact of high entropy on mechanical properties. Furthermore, the review explores the theoretical development of high-entropy TE material and discusses potential strategies for future advancements in this field through interactions among experimental and theoretical studies.

The global demand for radio frequency (RF) modules and components has grown exponentially in recent decades. RF switches are the essential unit in RF front-end and reconfigurable systems leading to the rapid development of novel and advanced switch technology. Germanium telluride (GeTe), as one of the Chalcogenide phase-change materials, has been applied as an RF switch due to its low insertion loss, high isolation, fast switching speed, and low power consumption in recent years. In this review, an in-depth exploration of GeTe film characterization is presented, followed by a comparison of the device structure of directly heated and indirectly heated RF phase-change switches (RFPCSs). Focusing on the prototypical structure of indirectly heated RFPCSs as the reference, the intrinsic properties of each material layer and the rationale behind the material selection is analyzed. Furthermore, the design size of each material layer of the device and its subsequent RF performance are summarized. Finally, we cast our gaze toward the promising future prospects of RFPCS technology.

Tin-based chalcogenides have a lot of potential as thermoelectric materials due to their ultralow thermal conductivity. Therefore, most reports on doped SnS focus on its power factor as the other condition for a high thermoelectric figure of merit (ZT). Here, we use the Boltzmann transport formalism to calculate both the power factor and the thermal conductivity for SnS, SnSe, and SnS x Se 1 − x and compare it with experimental measurements. Our theoretical model, based on a relaxation-time formalism, is in very good agreement with the reported values. We conclude that, while impurity scattering plays a major role in electron transport and, therefore, largely determines the power factor, alloy scattering is crucial for phonon transport. Specifically, alloying reduces the thermal conductivity of SnSe 0.70 S 0.30 by a factor of ∼ 1.3 compared to SnSe and by a factor of ∼ 2 compared to SnS. This leads to ∼ 65 % and ∼ 33 % enhancements of ZT for p-type and n-type doping, respectively, at 800 K with respect to SnSe. [ABSTRACT FROM AUTHOR]