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Janus Group-Ⅲ Chalcogenide Monolayers and Derivative Type-Ⅱ Heterojunctions as Water Splitting Photocatalysts with Strong Visible Light Absorbance
摘要： Search for two-dimensional (2D) water splitting photocatalysts is crucial to solve energy crises and environmental problems. In this research, we study the electronic and photocatalytic properties of single-layer Ga2X1X2 (Ga2SeTe, Ga2STe and Ga2SSe) and newly proposed α-Ga2S3/Ga2SSe-A, α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C van der Walls heterojunctions using first-principles calculations. Theoretical results indicate Ga2X1X2 monolayers present suitable band edges. 2D α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C belong to type-Ⅱ heterojunctions, and under biaxial strains embody suitable band edges. Comparisons of the valence band maximum (VBM) charge and electric dipole of α-Ga2S3/Ga2SSe-A and α-Ga2S3/Ga2SSe-B demonstrate it is possible to achieve suitable band edges for water splitting by switching electric dipoles. Especially, the three Ga2X1X2 monolayers, α-Ga2S3/Ga2SSe-B and α-Ga2S3/Ga2SSe-C heterojunctions absorb a large amount of visible light, promising they are photocatalysts for water splitting. More importantly, we find the optical absorption coefficients of 2D monolayers and heterojunctions in previous calculations are several times underestimated because the effective volume is not taken into consideration. To obtain reliable absorption coefficients, the real and imaginary parts of dielectric function must be renormalized.
关键词： visible light absorbance,van der Waals heterojunctions,two-dimensional (2D) materials,Janus group-Ⅲ chalcogenide monolayers,water splitting photocatalysts,first-principles calculations
更新于2025-09-10 09:29:36
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Reversible Polarization Recording in As2S3–Se Multilayer Nanostructures
摘要： Polarization holographic recording of diffraction gratings and their subsequent erasure have been investigated on As2S3–Se multilayer nanostructures. The work investigates how preexposure to actinic laser radiation up to complete photoinduced changes in the optical properties affects the formation of diffraction gratings in the studied structure. It is shown that the preexposure of an As2S3–Se multilayer nanostructure (MNS) leads to photobleaching, and the maximum achievable diffraction efficiency (DE) of 35% does not change; however, the required exposure value is increased. It is also shown that exposure using one laser beam results in complete erasure of the diffraction grating recorded up to the maximum. Seven recording–erasure cycles show that the kinetics of the increase in diffraction efficiency and its maximum value do not change, which indicates that the As2S3–Se multilayer structure is capable of reversible holographic recording under orthogonal circular polarization. Study of the gratings recorded with an atomic-force microscope shows that the main factor determining the diffraction efficiency value is modulation of the relief, the depth of which is greater than 200 nm.
关键词： reversible holographic recording,chalcogenide multilayer nanostructures,diffraction efficiency,direct surface relief formation
更新于2025-09-10 09:29:36
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Study of the optical properties of amorphous As–Se–S thin films
摘要： This study investigates the effects of substitution of selenium by sulfur on the optical constants of amorphous (a-)As20Se80 ? xSx films (x = 0, 4, 8, 12, 16, and 20 at%), where the coordination number for both Se and S is the same. The absorption coefficient, α, and the index of refraction, n, were derived using the transmission spectra in a wide range of wavelengths from 400 to 2500 nm. This revealed that the index of refraction for the a-As20Se80 ? xSx system decreases with increase in sulfur content throughout the range under study. The effective coordination number of As has been determined based on the refractive index dispersion analysis. A decreasing in Nc from 4.022 to 3.752 with increase content of sulfur from 0 to 20 at% has been recorded. In addition, the optical bandgap, Eg, of the a-As20Se80 ? xSx thin films increases with increase in S content which can be explicated in terms of the chemical bond approach.
关键词： optical bandgap,refractive index,amorphous As–Se–S thin films,chalcogenide glasses,optical properties
更新于2025-09-10 09:29:36
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Study of dielectric relaxation and thermally activated a.c. conduction in multicomponent Ge10-xSe60Te30Inx (0 ≤ x ≤ 6) chalcogenide glasses using CBH model
摘要： Amorphous Ge10-xSe60Te30Inx (0 ≤ x ≤ 6) chalcogenide glasses were prepared by melt quench technique. Surface morphology with the chemical composition of the prepared glass was examined using SEM and EDS analysis respectively. Dielectric properties and a.c. conductivity of the multicomponent Ge10-xSe60Te30Inx (0 ≤ x ≤ 6) chalcogenide glasses have been examined in the frequency range 100Hz to 1MHz and temperature range 303 to 328K. It was noticed that dielectric constant and dielectric loss decreases with the increase of frequency and increases with the increase of temperatures. Frequency and temperature dependence of dielectric constant was explained by orientational polarization. The variation of dielectric loss with frequency and temperature was explained by conduction loss and theory of single polaron hopping of charge carriers suggested by Elliot and Shimakawa for chalcogenide glasses. The experimental results show that a.c. conductivity follows the power law where s<1 and value of s decreases with the increase of temperature. The present findings of a.c. conductivity and variation of s with temperatures are reasonably well interpreted in terms of CBH model.
关键词： a c conductivity,dielectric relaxation,Chalcogenide glasses,CBH model,activation energy.
更新于2025-09-10 09:29:36
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Time Domain Modeling of Multimode Selenide-Chalcogenide Glass Fiber Based Mid Infrared Spontaneous Emission Sources
摘要： We develop time domain models of selenide-chalcogenide glass fiber based MIR spontaneous emission sources. The modeling parameters used are derived from experimentally obtained data. The models are based on the rate equations’ approach to simulate the distribution of ions between the relevant energy levels. The optical power distribution within the fiber is calculated by solving a set of partial differential equations using specially developed finite difference schemes that allow for a direct inclusion of the step discontinuities appearing at the fiber facets. The results obtained allow for a thorough analysis of luminescence from lanthanide ion doped chalcogenide fibers.
关键词： mid infrared photonics,chalcogenide glass fibers,numerical modelling
更新于2025-09-10 09:29:36
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Electronic transport properties of (Se80Te20)100?xZnx (2?≤?x?≤?6) chalcogenide alloys
摘要： The bulk chalcogenide (Se80Te20)100-xZnx (2≤x≤6) alloys are prepared using melt quenching technique and electronic transport properties are studied in the frequency range 50 Hz–500 KHz and temperature range 400-520 K. The sharp peaks observed in X-ray diffraction pattern indicate the polycrystalline nature of prepared compositions. The measured dielectric properties and a.c. conductivity reveal the significant influence of Zn doping on the properties of the Se-Te matrix. The a.c. conductivity obeys Jonscher power law as ~ w s (s<1). To describe the conduction mechanism, the experimental results are analyzed in the framework of various theoretical models. The correlated barrier hopping (CBH) model successfully describe the observed frequency, temperature and composition response of ac conductivity.
关键词： a.c. conductivity,electronic transport properties,Chalcogenide alloys,dielectric constant,dielectric loss,X-Ray diffraction
更新于2025-09-09 09:28:46
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[Micro/Nano Technologies] Micro and Nano Fabrication Technology Volume 1 || Precision Molding of Microstructures on Chalcogenide Glass for Infrared Optics
摘要： Chalcogenide glass (ChG), as an alternative material in place of single-crystal germanium, is increasingly used in thermal imaging, night vision, and infrared guidance systems, etc., and microstructure array on the infrared component is widely used in micro-optical systems owing to their excellent formability through precision glass molding (PGM), which can achieve low cost and high efficiency compared with other microstructural manufacturing technologies. To describe the thermomechanical properties of ChG, the viscoelastic constitutive of ChG is modeled and used in finite element simulation to study the influence of process parameters on the forming stress. The processing parameters are studied to reduce the occurrence of microdimples and optimize the molding conditions. Finally, microstructure arrays are molded using spherical ChG preform and the optimal molding materials are identified.
关键词： Microdimples,Finite element simulation,Precision glass molding,Microstructure array,Chalcogenide glass
更新于2025-09-09 09:28:46
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New Candidate Multicomponent Chalcogenide Glasses for Supercontinuum Generation
摘要： Broadband supercontinuum (SC) generation requires host material attributes defined by both optical and physical properties and the material’s manufacturability. We review and define the trade-offs in these attributes as applied to fiber or planar film applications based on homogeneous glass property data, and provide a series of examples of how one might optimize such attributes through material compositional and morphology design. As an example, we highlight the role of varying composition, microstructure, and linear/nonlinear optical properties, such as transmittance, refractive index, and the multiphoton absorption coefficient, for a series of novel multicomponent chalcogenide glasses within a model GeSe2-As2Se3-PbSe (GAP-Se) system. We report key optical property variation as a function of composition and form, and discuss how such glasses, suitable for both fiber and planar film processing, could lend themselves as candidates for use in SC generation. We demonstrate the impact of starting glass composition and morphology and illustrate how tailoring composition and form (bulk versus film) leads to significant variation in linear, nonlinear, and dispersive optical property behavior within this system that enables design options that are attractive to optimization of desirable SC performance, based on optical composites.
关键词： photonics,infrared optical materials,chalcogenide glass science,supercontinuum generation,nonlinear optics
更新于2025-09-09 09:28:46
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Effect of Te Proportion on the Properties of Ge25Sb10Se65-Te Chalcogenide Glasses
摘要： The effect of Te proportion on the physical, thermal and optical properties of Ge-Sb-Se glasses was the goal of this study. In this regards, four different glasses of Ge25Sb10Se65-xTex (x=5,10,15,20) were prepared by conventional melt quenching technique in quartz ampoule. The produced samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR spectroscopy), Vickers hardness tester, Differential scanning calorimetry (DSC) and Thermal mechanical analysis (TMA). Based on the obtained results, we known that the overall transmittance of the samples is about 55%. For physical properties, as the Te content increases from 5% to 20%, the glass density increases from 4.52 g·cm-3 to 4.78 g·cm-3 and the Vickers hardness value is improved from 172 kg·mm-2 to 198 kg·mm-2. With respect to the thermal properties, the glass transition temperature is 551.45 K-514.56 K and the difference of Tx-Tg is more than 110 K, where Tx is the initial crystallization temperature, and Tg is the glass transition temperature. While the thermal expansion coefficient varies little, from 1.87×10-5 to 1.82×10-5. In addition, the Tg value achieved by DSC is higher than that of TMA, which gives out a reference for the measurement of characteristic temperature.
关键词： thermal properties,transmittance,characteristic temperature,Chalcogenide glasses
更新于2025-09-09 09:28:46
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The structure of near stoichiometric Ge-Ga-Sb-S glasses: A reverse Monte Carlo study
摘要： The structure of Ge22Ga3Sb10S65 and Ge15Ga10Sb10S65 glasses was investigated by neutron diffraction (ND), X-ray diffraction (XRD), and extended X-ray absorption fine structure (EXAFS) measurements at the Ge, Ga and Sb K-edges. Experimental data sets were fitted simultaneously in the framework of the reverse Monte Carlo (RMC) simulation technique. Short range order parameters were determined from the obtained large-scale configurations. It was found that the coordination numbers of Ge, Sb and S are around the values predicted by the Mott-rule (4, 3 and 2, respectively). The Ga atoms have on average 4 nearest neighbors. The structure of these stoichiometric glasses can be described by the chemically ordered network model: Ge-S, Ga-S and Sb-S bonds are the most important. Long Sb-S distances (0.3–0.4 ? higher than the usual covalent bond lengths) are observed, suggesting that Sb atoms can be found in various local environments.
关键词： RMC,Structure,Ge-Ga-Sb-S,Diffraction,Chalcogenide glasses,EXAFS
更新于2025-09-09 09:28:46