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A hydrothermally synthesized MoS <sub/>2(1a??x)</sub> Se <sub/>2x</sub> alloy with deep-shallow level conversion for enhanced performance of photodetectors
摘要： Photoelectric detectors based on binary transition metal chalcogenides have attracted widespread attention in recent years. However, due to the high-temperature synthesis of binary TMD, high-density deep-level defect states may be generated, leading to poor responsiveness or a long response time. Besides, the addition of an alloy will change the DLDSs from deep to shallow energy levels caused by S vacancies. In this paper, MoS2(1?x)Se2x nanostructures were synthesized by a hydrothermal method, and a novel type of photodetector was fabricated by using the synthesized material as a light sensitive material. The MoSSe-based photodetector not only has a high photocurrent, but also exhibits a wide spectral response in the range of 405 nm to 808 nm. At the same time, it can achieve a responsivity of 1.753 mA W?1 under 660 nm laser irradiation of 1.75 mW mm?2. Therefore, this work can be considered as a method of constructing a new type of photodetector with a simple process and low cost.
关键词： MoS2(1?x)Se2x,photoelectric detectors,photodetector,transition metal chalcogenides,hydrothermal synthesis
更新于2025-09-23 15:21:01
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Strained bubbles in van der Waals heterostructures as local emitters of photoluminescence with adjustable wavelength
摘要： The possibility to tailor photoluminescence (PL) of monolayer transition metal dichalcogenides (TMDCs) using external factors such as strain, doping and external environment is of significant interest for optoelectronic applications. Strain in particular can be exploited as a means to continuously vary the bandgap. Micrometer-scale strain gradients were proposed for creating ‘artificial atoms’ that can utilize the so-called exciton funneling effect and work, for example, as exciton condensers. Here we describe room-temperature PL emitters that naturally occur whenever monolayer TMDC is deposited on an atomically flat substrate. These are hydrocarbon-filled bubbles which provide predictable, localized PL from well-separated submicron areas. Their emission energy is determined by the built-in strain controlled only by the substrate material, such that both the maximum strain and the strain profile are universal for all bubbles on a given substrate, i.e., independent of the bubble size. We show that for bubbles formed by monolayer MoS2, PL can be tuned between 1.72 to 1.81 eV by choosing bulk PtSe2, WS2, MoS2 or graphite as a substrate and its intensity is strongly enhanced by the funneling effect. Strong substrate-dependent quenching of the PL in areas of good contact between MoS2 and the substrate ensures localization of the luminescence to bubbles only; by employing optical reflectivity measurements we identify the mechanisms responsible for the quenching. Given the variety of available monolayer TMDCs and atomically flat substrates and the ease of creating such bubbles, our findings open a venue for making and studying the discussed light-emitting ‘artificial atoms’ that could be used in applications.
关键词： photoluminescence,exciton funneling,monolayer transition metal chalcogenides,excitons,strain engineering
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE 13th Nanotechnology Materials and Devices Conference (NMDC) - Portland, OR, USA (2018.10.14-2018.10.17)] 2018 IEEE 13th Nanotechnology Materials and Devices Conference (NMDC) - Magnetic Characterization of Cobalt Selenide and Nickel Selenide Thin Films
摘要： Transition metal dichalcogenides (TMDCs) are a family of materials whose crystalline structure consists of a layer of transition metal atoms sandwiched between 2 layers of chalcogenide atoms. Some of these materials can be grown in 2D hexagonal phase and show tunability of their electrical and magnetic properties based on layer thickness. One aspect of these materials that has received little attention is their magnetic properties. Hence, we have investigated magnetic properties of CoSe and NiSe their heterostructure. The reason for choosing these intrinsically ferromagnetic transition metal atoms based TMCs was to examine how reduction from the bulk to 2D films would influence the magnetic activity of these samples. In order to produce large area films, we have employed atomic layer deposition (ALD) for growth of uniform, few layer-thick films. First the composition and crystal structure of these films are characterized, and then their magnetic properties analyzed. We have found that thin films of both these materials show mostly paramagnetic behavior.
关键词： cobalt selenide,magnetic properties,Transition metal chalcogenides,thin film,nickel selenide
更新于2025-09-19 17:15:36
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Comparative Study of the Structure, Composition, and Electrocatalytic Performance of Hydrogen Evolution in MoSx~2+?′/Mo and MoSx~3+?′ Films Obtained by Pulsed Laser Deposition
摘要： Systematic and in-depth studies of the structure, composition, and efficiency of hydrogen evolution reactions (HERs) on MoSx films, obtained by means of on- and off-axis pulsed laser deposition (PLD) from a MoS2 target, have been performed. The use of on-axis PLD (a standard configuration of PLD) in a buffer of Ar gas, with an optimal pressure, has allowed for the formation of porous hybrid films that consist of Mo particles which support a thin MoSx~2+δ (δ of ~0.7) film. The HER performance of MoSx~2+δ/Mo films increases with increased loading and reaches the highest value at a loading of ~240 μg/cm2. For off-axis PLD, the substrate was located along the axis of expansion of the laser plume and the film was formed via the deposition of the atomic component of the plume, which was scattered on Ar molecules. This made it possible to obtain homogeneous MoSx~3+δ (δ~0.8–1.1) films. The HER performances of these films reached saturation at a loading value of ~163 μg/cm2. The MoSx~3+δ films possessed higher catalytic activities in terms of the turnover frequency of their HERs. However, to achieve the current density of 10 mA/cm2, the lowest over voltages were ?162 mV and ?150 mV for the films obtained by off- and on-axis PLD, respectively. Measurements of electrochemical characteristics indicated that the differences in the achievable HER performances of these films could be caused by their unique morphological properties.
关键词： nanocatalysts,buffer gas,pulsed laser deposition,transition metal chalcogenides,hydrogen evolution reaction
更新于2025-09-19 17:13:59
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Pulsed Laser Deposition of Nanostructured MoS3/np-Mo//WO3?y Hybrid Catalyst for Enhanced (Photo) Electrochemical Hydrogen Evolution
摘要： Pulsed laser ablation of MoS2 and WO3 targets at appropriate pressures of background gas (Ar, air) were used for the preparation of new hybrid nanostructured catalytic ?lms for hydrogen production in an acid solution. The ?lms consisted of a nanostructured WO3?y underlayer that was covered with composite MoS3/np-Mo nanocatalyst. The use of dry air with pressures of 40 and 80 Pa allowed the formation of porous WO3?y ?lms with cauli?ower- and web-like morphology, respectively. The ablation of the MoS2 target in Ar gas at a pressure of 16 Pa resulted in the formation of amorphous MoS3 ?lms and spherical Mo nanoparticles. The hybrid MoS3/np-Mo//WO3?y ?lms deposited on transparent conducting substrates possessed the enhanced (photo)electrocatalytic performance in comparison with that of any pristine one (MoS3/np-Mo or WO3?y ?lms) with the same loading. Modeling by the kinetic Monte Carlo method indicated that the change in morphology of the deposited WO3?y ?lms could be caused by the transition of ballistic deposition to di?usion limited aggregation of structural units (atoms/clusters) under background gas pressure growth. The factors and mechanisms contributing to the enhancement of the electrocatalytic activity of hybrid nanostructured ?lms and facilitating the e?ective photo-activation of hydrogen evolution in these ?lms are considered.
关键词： pulsed laser deposition,tungsten oxides,transition metal chalcogenides,nanocatalysts,hydrogen evolution reaction,background gas
更新于2025-09-16 10:30:52
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Low temperature phase-controlled synthesis of titanium di- and tri-sulfide by atomic layer deposition
摘要： Phase-controlled synthesis of two-dimensional (2D) transition metal chalcogenides (TMCs) at low temperature with a precise thickness control has to date been rarely reported. Here, we report on a process for the phase-controlled synthesis of TiS2 (metallic) and TiS3 (semiconducting) nano-layers by atomic layer deposition (ALD) with precise thickness control. The phase-control has been obtained by carefully tuning the deposition temperature and co-reactant composition during ALD. In all cases, characteristic self-limiting ALD growth behavior with a growth per cycle (GPC) of ~0.16 nm per cycle was observed. TiS2 was prepared at 100 °C using H2S gas as co-reactant, and was also observed using H2S plasma as co-reactant at growth temperatures between 150 and 200 °C. TiS3 was only synthesized at 100 °C using H2S plasma as co-reactant. The S2 species in the H2S plasma, as observed by optical emission spectroscopy, has been speculated to lead to the formation of the TiS3 phase at low temperature. The control between synthesis of TiS2 and TiS3 was elucidated by Raman spectroscopy, X-ray photoelectron spectroscopy, high-resolution electron microscopy, and Rutherford back scattering studies. Electrical transport measurements showed the low resistive nature of ALD grown 2D-TiS2 (1T-phase). Post-deposition annealing of the TiS3 layers at 400 °C in a sulfur-rich atmosphere improved the crystallinity of the film and yielded photoluminescence at ~0.9 eV, indicating the semiconducting (direct bandgap) nature of TiS3. The current study opens up a new ALD-based synthesis route for controlled, scalable growth of transition metal di- and tri-chalcogenides at low temperatures.
关键词： phase-controlled synthesis,low temperature,titanium sulfide,transition metal chalcogenides,atomic layer deposition
更新于2025-09-11 14:15:04
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Cu-Fe-Se Ternary Nanosheet-Based Drug Delivery Carrier for Multimodal Imaging and Combined Chemo-photothermal Therapy of Cancer
摘要： Ternary transition-metal chalcogenide nanosheets have shown great potential in diverse applications owing to their intrinsically amazing properties with broad tunable window. Direct preparation of water-soluble and biocompatible ternary chalcogenide nanosheets for theranostic application remains a challenge. In this article, we prepared Cu-Fe-Se nanosheets (CFS NSs) in an aqueous solution under ambient conditions by sequential coprecipitation method. They were functionalized with anticancer drug doxorubin (CFS@DOX) through electrostatic interactions, and labeled with radioactive isotope 99mTc through surface coordination effect. The resulting nanosheets have a size of 70 nm and a thickness of 5 nm, and can be well dispersed in water, PBS, 10% FBS, and 0.9% NaCl with an excellent colloidal stability. They also exhibit a high photothermal conversion efficiency of 78.9% for in vitro and in vivo photoacoustic imaging and photothermal therapy. The isotope-labelled nanosheets (99mTc-CFS NSs) were used for single photon emission computed tomography/computed tomography (SPECT/CT) imaging, and quantification of their blood circulation time (~4.7 h) and biodistributions in major organs, which follow an order of liver > bladder > lung > spleen > heart > kidney. The DOX functionalized nanosheets (CFS@DOX) were used for chemotherapy of cancer and exhibited excellent anti-cancer efficacy. Our research shows the great promise of ternary metal chalcogenide nanosheets for combined imaging and therapy of cancer.
关键词： radiolabeling,2D ternary nanosheets,transition metal chalcogenides,multimodal imaging,chemotherapy,photothermal therapy
更新于2025-09-11 14:15:04
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Single Crystal Growth and Characterization of the Chalcopyrite Semiconductor CuInTe2 for Photoelectrochemical Solar Fuel Production
摘要： Transition metal chalcogenides are a promising family of materials for applications as photocathodes in photoelectrochemical (PEC) H2 generation. A long-standing challenge for chalcopyrite semiconductors is characterizing their electronic structure—both experimentally and theoretically—due to their relatively high energy bandgaps and spin orbit coupling (SOC), respectively. In this work, we present single crystals of CuInTe2, whose relatively small optically measured bandgap of 0.9 ± 0.03 eV enables electronic structure characterization by angle-resolved photoelectron spectroscopy (ARPES) in conjunction with first-principle calculations incorporating SOC. ARPES measurements reveal bands that are steeply dispersed in energy with a band velocity of 2.5-5.4 x 105 m/s, almost 50% of the extremely conductive material graphene. Additionally, CuInTe2 single crystals are fabricated into electrodes to experimentally determine the valence band edge energy and confirm the thermodynamic suitability of CuInTe2 for water redox chemistry. The electronic structure characterization and band edge position presented in this work provide kinetic and thermodynamic factors that support CuInTe2 as a strong candidate for water reduction.
关键词： photoelectrochemical H2 generation,electronic structure,spin orbit coupling,chalcopyrite semiconductors,band velocity,valence band edge energy,Transition metal chalcogenides,angle-resolved photoelectron spectroscopy,water redox chemistry,CuInTe2
更新于2025-09-10 09:29:36