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Direct Observation of Structural Evolution of Metal Chalcogenide in Electrocatalytic Water Oxidation
摘要： As one of the most remarkable oxygen evolution reaction (OER) electrocatalysts, metal chalcogenides have been intensively reported due to their high OER activities during the past few decades. It has been reported that electron-chemical conversion of metal chalcogenides into oxides/hydroxides would take place after OER. However, the transition mechanism of such unstable structures, as well as the real active sites and catalytic activity during OER for these electrocatalysts, has not been understood yet, which urgently needs a direct observation for the electrocatalytic water oxidation process, especially at nano or even angstrom scale. In this research, by employing advanced Cs-corrected transmission electron microscopy (TEM), a step by step oxidational evolution of amorphous electrocatalyst CoSx into crystallized CoOOH in OER has been in situ captured: irreversible conversion of CoSx to crystallized CoOOH is initiated on the surface of electrocatalysts with a morphology change via Co(OH)2 intermediate during OER measurement, where CoOOH is confirmed as the real active species. Besides, this transition process has also been confirmed by multiple applications of X-ray photoelectron spectroscopy (XPS), in situ Fourier-transform infrared spectroscopy (FTIR) and other ex situ technologies. Moreover, based on this discovery, a high-efficiency electrocatalyst of a nitrogen-doped graphene foam (NGF) coated by CoSx has been explored through a thorough structure transformation of CoOOH. We believe this in situ and in-depth observation of structural evolution in OER measurement can provide insights into the fundamental understanding of the mechanism for OER catalysts, thus enabling the more rational design of low-cost and high-efficient electrocatalysts for water splitting.
关键词： structural evolution,XPS,in situ TEM,water oxidation,cobalt chalcogenide
更新于2025-11-14 15:27:09
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Enhancing light absorption by colloidal metal chalcogenide quantum dots <i>via</i> chalcogenol(ate) surface ligands
摘要： Chemical species at the surface (ligands) of colloidal inorganic semiconductor nanocrystals (QDs) markedly impact the optoelectronic properties of the resulting systems. Here, post-synthesis surface chemistry modification of colloidal metal chalcogenide QDs is demonstrated to induce both broadband absorption enhancement and band gap reduction. A comprehensive library of chalcogenol(ate) ligands is exploited to infer the role of surface chemistry on the QD optical absorption: the ligand chalcogenol(ate) binding group mainly determines the narrowing of the optical band gap, which is attributed to the np occupied orbital contribution to the valence band edge, and mediates the absorption enhancement, which is related to the π-conjugation of the ligand pendant moiety, with further contribution from electron donor substituents. These findings point to a description of colloidal QDs that may conceive ligands as part of the overall QD electronic structure, beyond models derived from analogies with core/shell heterostructures, which consider ligands as mere perturbation to the core properties. The enhanced light absorption achieved via surface chemistry modification may be exploited for QD-based applications in which an efficient light-harvesting initiates charge carrier separation or redox processes.
关键词： colloidal metal chalcogenide quantum dots,light absorption,optoelectronic properties,surface ligands,band gap reduction
更新于2025-10-22 19:40:53
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An optically-gated transistor comprised of amorphous M+Ge2Se3 (M=Cu, Sn) for accessing and continuously programming a memristor
摘要： We demonstrate that a device comprised of sputtered amorphous chalcogenide Ge2Se3/M+Ge2Se3 (M = Sn or Cu) alternating layers, functions as an optically-gated transistor (OGT) and can be used as an access transistor for a memristor memory element. This transistor has only two electrically connected terminals (source and drain), with the gate being optically controlled, thus allowing the transistor to operate only in the presence of light (385 – 1200 nm). The switching speed of the OGTs is less than 15 μs. The OGT is demonstrated in series with a Ge2Se3+W memristor, where we show that by altering the light intensity on the OGT gate, the memristor can be programmed to a continuous range of non-volatile memory states using the saturation current of the OGT as a programming compliance current. By having a continuous range of non-volatile states, one memory cell can potentially achieve 2n levels. This high density, combined with optical programmability, enables hybrid electronic/photonic memory.
关键词： access transistor,chalcogenide,resistive RAM,optoelectronic,selector,amorphous,memristor
更新于2025-09-23 15:23:52
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Viscosity of chalcogenide glass-formers
摘要： Chalcogenide glass-formers are being used in a remarkable range of various optoelectronic, photonics, photoconducting, sensing and memory device applications. The knowledge of viscosity is essential for the processing of any glass-forming material, in particular for the fabrication of precise optical elements, which is the main application field of chalcogenide glasses. This work presents an extensive collection of all available viscosity data for chalcogenides, including the measurement methods. The Mauro–Yue–Ellison–Gupta–Allan (MYEGA), Arrhenius and VFT equations are used to fit the temperature dependences of viscosity. The viscosity glass transition temperatures, fragilities and apparent activation energies are calculated from these fits. Consequently, these parameters are discussed with regard to the compositional evolution of the respective chalcogenide systems.
关键词： glass transition,chalcogenide,viscous flow,fragility,Viscosity
更新于2025-09-23 15:23:52
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Experimental and numerical investigation to rationalize both near-infrared and mid-infrared spontaneous emission in?Pr3+ doped selenide-chalcogenide fiber
摘要： This contribution reports on detailed experimental and numerical investigations of both near-infrared (NIR) and mid-infrared (MIR) photoluminescence obtained in praseodymium trivalent ion doped chalcogenide-selenide glass fiber. The experimental analysis allows for the identification of the radiative transitions within the praseodymium ion energy level structure to account for the photoluminescent behavior. Numerical analysis is carried out using the rate equations' approach to calculate the level populations. The numerical analysis provides further insight into the nature of the radiative transitions in the Pr3+ ion doped chalcogenide-selenide glass and allows for the identification of the electronic transitions, which contribute to the observed photoluminescence. The numerical results agree well with the experimental results.
关键词： chalcogenide glass fibers,optical fiber modelling,lanthanide doped fibers
更新于2025-09-23 15:22:29
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Optical and electrical properties of thermally evaporated Se90Sb10 thin film
摘要： Chalcogenide Se90Sb10 thin ?lms are deposited by thermal evaporation from the bulk alloy. X-ray di?raction examination for the annealed ?lms shows the amorphous-crystalline transformation. This is bene?cial for optical disk data storage technology. The crystallinity is improved by increasing the annealing temperature. The ?lms annealed at relatively low temperatures exhibit highly transparence reaching to about 90% at incident light of wavelength of 900 nm. The as-prepared and annealed Se90Sb10 ?lms reveal an indirect allowed optical transition. The annealed ?lm at 473 K has an optical band gap of 1.676 eV which is suitable value for solar cell as photovoltaic application. Both the indirect optical energy band gap (Eg) and the oscillator energy (Eo) decrease whereas the oscillator strength (Ed) increases with increasing the annealing temperature. The annealing increases the conductivity and decreases the activation energy for conduction resulting in enhancement of ?lm properties for adapting to solar cells.
关键词： Electrical conductivity,Chalcogenide,Optical constants,Thin ?lms
更新于2025-09-23 15:21:21
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Controlling Fano resonances in multilayer dielectric gratings towards optical bistable devices
摘要： The spectral properties of Fano resonance generated in multilayer dielectric gratings (MDGs) are reported and numerically investigated in this paper. We examine the MDG consisting of numerous identically alternative chalcogenide glass (As2S3) and silica (SiO2) multilayers with several grating widths inscribed through the structure, emphasizing quality (Q) and asymmetric (q) factors. Manipulation of Fano lineshape and its linear characteristics can be achieved by tailoring the layers’ amount and grating widths so that the proposed structure can be applicable for several optical applications. Moreover, we demonstrate the switching/bistability behaviors of the MDG at Fano resonance which provide a significant switching intensity reduction compared to the established Lorentzian resonant structures.
关键词： Fano resonance,silica,optical bistable devices,chalcogenide glass,multilayer dielectric gratings
更新于2025-09-23 15:21:21
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A monolithic on-chip magneto-optical isolator with 3 dB insertion loss and 40 dB isolation ratio
摘要： On-chip optical isolators constitute an essential building block for photonic integrated circuits (PICs). Here we experimentally demonstrated a magneto-optical isolator monolithically integrated on silicon featuring 3 dB insertion loss and 40 dB isolation ratio, both of which represent significant improvements over state-of-the-art. The isolator is also fully passive and operates under a simple unidirectional magnetization scheme. Such superior performance is enabled through a three-way combination of a strip-loaded waveguide design, a compositionally optimized chalcogenide glass as the light guiding medium, and low-loss taper structures created via gray-scale lithographic processing. The device represents an important step towards a practical solution for on-chip isolation in PICs.
关键词： Integrated optics devices,Magneto-optical materials,Chalcogenide glass,Resonators,Grayscale-lithography,Isolators
更新于2025-09-23 15:21:21
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Sputter-Deposited-MoS2 nMISFETs with Top-Gate and Al2O3 Passivation under Low Thermal Budget for Large Area Integration
摘要： We have fabricated large area integrated top-gate nMISFETs with sputter-deposited-MoS2 film having n-type operation. A sputtering method enables us to form a large-area MoS2 thin film followed by H2S annealing to compensate sulfur vacancies. Two passivation films of ALD-Al2O3 enhance the process endurance of MoS2 channel. Therefore, we demonstrate TiN-top-gate nMISFET, which is a substantial first step to realize industrial chip-level LSIs with MoS2-channel FETs.
关键词： Top gate,MISFET,Transition metal di-chalcogenide,Sputtering,Passivation,Molybdenum disulfide,Large area integration
更新于2025-09-23 15:21:21
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As2Se3-Ge11.5As24Se64.5 based mid-infrared dual nano-slot optical waveguide with huge and wavelength tunable dispersion
摘要： An As2Se3-Ge11.5As24Se64.5 based dual nano-slot waveguide with huge chromatic dispersion at mid-infrared is proposed. The large chromatic dispersion at the target wavelength is achieved induced by resonance interaction. The characteristics of dispersion are investigated by employing the FDTD method. The simulation results indicate that by optimizing the geometrical parameters, the maximum dispersion of -3.48×105 ps·nm-1·km-1 over a full width at FWHM of 2 nm at 3000 nm has been attained. A flat and ultra-large dispersion of -3.48×105 ps·nm-1·km-1 from 2980 to 3010 nm is achieved by cascading the dual-slot waveguides. The relative dispersion magnitude fluctuation is less than 1.85%.
关键词： chalcogenide waveguide,chromatic dispersion,dual-slot waveguide,mid-infrared
更新于2025-09-23 15:21:01