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Electrochemical properties of PEDOT: PSS /V2O5 hybrid fiber based supercapacitors
摘要： Binary conducting polymer (CP)/transition metal oxides (TMOs) fiber-based supercapacitors (FSCs) are considered to possess good electrochemical performance and cyclic stability compared with unitary ones since TMOs within FSCs can prevent the structure damage of CP during charge/discharge cycles to some extent. In this study, the CP/TMOs hybrid fibers are made by directly injecting the solution into capillary. Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate /30 wt% vanadium pentoxide (PEDOT: PSS/30 wt% V2O5) fiber-based electrode has good electrochemical performance and cyclic stability (cycle retention: 94.02% after 4000 cycles at 0.1 mA/cm2). The energy density of the PEDOT: PSS/30 wt% V2O5 fiber in gel electrolyte is 1.37 μWh/cm2 at power density of 20 μW/cm2, which is much lower than the one in organic electrolyte (21.46 μWh/cm2 at power densities of 162.5 μW/cm2). Therefore, the method developed in this work induces good electrochemical performance for hybrid FSCs and promotes scalable fabrication of FSCs.
关键词： transition metal oxides,supercapacitor,Conducting polymers,electrochemical performance,hybrid fiber
更新于2025-09-23 15:23:52
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Effects of Proton Radiation-Induced Defects on Optoelectronic Properties of MoS2
摘要： We report on photoluminescence spectroscopy and transmission electron microscope imaging of suspended and substrate-supported flakes of the 2D semiconductor MoS2 before and after exposure to 100 keV proton radiation with fluences of 6x1013, 6x1014, and 6×1015 p/cm2 and subsequent annealing. An indirect-to-direct band gap transition is observed, which is preserved after annealing. This transition is accompanied by an unexpected increase in photoluminescence intensity after radiation exposure of multi-layer samples, which is attributed to higher radiative efficiency of the direct gap transition.
关键词： surface wettability,Transition metal di-chalcalgenide,proton radiation,semiconductor nanostructures
更新于2025-09-23 15:23:52
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MoS <sub/>2</sub> thin films from a (N <i> <sup>t</sup></i> Bu) <sub/>2</sub> (NMe <sub/>2</sub> ) <sub/>2</sub> Mo and 1-propanethiol atomic layer deposition process
摘要： Potential commercial applications for transition metal dichalcogenide (TMD) semiconductors such as MoS2 rely on unique material properties that are only accessible at monolayer to few-layer thickness regimes. Therefore, production methods that lend themselves to the scalable and controllable formation of TMD films on surfaces are desirable for high volume manufacturing of devices based on these materials. The authors have developed a new thermal atomic layer deposition process using bis(tert-butylimido)-bis(dimethylamido)molybdenum and 1-propanethiol to produce MoS2-containing amorphous films. They observe a self-limiting reaction behavior with respect to both the Mo and S precursors at a substrate temperature of 350 °C. Film thickness scales linearly with precursor cycling, with growth per cycle values of ≈0.1 nm/cycle. As-deposited films are smooth and contain nitrogen and carbon impurities attributed to poor ligand elimination from the Mo source. Upon high-temperature annealing, a large portion of the impurities are removed, and the authors obtain few-layer crystalline 2H-MoS2 films.
关键词： atomic layer deposition,MoS2,thin films,transition metal dichalcogenides,annealing,precursors
更新于2025-09-23 15:23:52
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Understanding Spatiotemporal Photocarrier Dynamics in Monolayer and Bulk MoTe <sub/>2</sub> for Optimized Optoelectronic Devices
摘要： Semiconducting molybdenum ditelluride has emerged as a promising transition-metal dichalcogenide with a number of novel properties. In particular, its bandgap in infrared range makes it an attractive candidate for ultrathin and high-performance infrared optoelectronic applications. Dynamical properties of photocarriers play a key role in determining performance of such devices. We report an experimental study on spatiotemporal dynamics of photocarriers in both monolayer and bulk MoTe2. Transient absorption measurement in reflection geometry revealed ultrafast thermalization and relaxation processes of photocarriers and lifetimes of about 60 and 80 ps in monolayer and bulk MoTe2, respectively. By spatially resolved transient absorption measurements on monolayer, we obtained an exciton diffusion coefficient of 20 ± 10 cm2 s?1, a mean free time of 200 fs, a mean free path of 20 nm, and a diffusion length of 350 nm. The corresponding values for the bulk sample are 40 ± 10 cm2 s?1, 400 fs, 40 nm, and 570 nm, respectively. These results provide fundamental information for understanding and optimizing performance of MoTe2-based optoelectronic devices.
关键词： two-dimensional material,exciton,transient absorption,molybdenum ditelluride,transition-metal dichalcogenide,diffusion,photocarrier dynamics
更新于2025-09-23 15:23:52
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Interface Engineering of Au(111) for the Growth of 1T′-MoSe <sub/>2</sub>
摘要： Phase-controlled synthesis of two-dimensional transition metal dichalcogenides (TMDCs) is of great interest due to the distinct properties of the different phases. However, it is challenging to prepare metallic phase of group-VI TMDCs due to their metastability. At the monolayer level, interface engineering can be used to stabilize the metastable phase. Here, we demonstrate the selective growth of either single-layer 1H or 1T’-MoSe2 on Au(111) by molecular beam epitaxy; the two phases can be unambiguously distinguished using scanning tunnelling microscopy and spectroscopy. While the growth of 1H-MoSe2 is favourable on pristine Au(111), the growth of 1T’-MoSe2 is promoted by the pre-deposition of Se on Au(111). The selective growth of 1T’-MoSe2 phase on Se-pretreated Au(111) is attributed to Mo intercalation-induced stabilization of the 1T’ phase, which is supported by density functional theory calculations. In addition, 1T’ twin boundaries and 1H-1T’ heterojunctions were observed and found to exhibit enhanced tunnelling conductivity. The substrate pre-treatment approach for phase-controlled epitaxy should be applicable to other group-VI TMDCs grown on Au (111).
关键词： phase control,heterojunction,scanning tunnelling microscopy/spectroscopy,interface engineering,transition metal dichalcogenides,MoSe2
更新于2025-09-23 15:23:52
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Current-Induced Torques with Dresselhaus Symmetry Due to Resistance Anisotropy in 2D Materials
摘要： We report measurements of current-induced torques in heterostructures of Permalloy (Py) with TaTe2, a transition-metal dichalcogenide (TMD) material possessing low crystal symmetry, and observe a torque component with Dresselhaus symmetry. We suggest that the dominant mechanism for this Dresselhaus component is not a spin-orbit torque, but rather the Oersted field arising from a component of current that flows perpendicular to the applied voltage due to resistance anisotropy within the TaTe2. This type of transverse current is not present in wires made from a single uniform layer of a material with resistance anisotropy, but will result whenever a material with resistance anisotropy is integrated into a heterostructure with materials having different resistivities, thereby producing a spatially non-uniform pattern of current flow. This effect will therefore influence measurements in a wide variety of heterostructures incorporating 2D TMD materials and other materials with low crystal symmetries.
关键词： van der Waals materials,spin-orbit torque,crystal symmetry,transition metal dichalcogenides,2D materials,spin-torque
更新于2025-09-23 15:23:52
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Monolayer transition metal dichalcogenides in strong magnetic fields: Validating the Wannier model using a microscopic calculation
摘要： Using an equation of motion (EOM) approach, we calculate excitonic properties of monolayer transition metal dichalcogenides perturbed by an external magnetic field. We compare our findings to the widely used Wannier model for excitons in two-dimensional materials and to recent experimental results. We find good agreement between the calculated excitonic transition energies and the experimental results. In addition, we find that the exciton energies calculated using the EOM approach are slightly lower than the ones calculated using the Wannier model. Finally, we also show that the effect of the dielectric environment on the magnetoexciton transition energy is minimal due to counteracting changes in the exciton energy and the exchange self-energy correction.
关键词： monolayer transition metal dichalcogenides,magnetic field,Wannier model,excitons,magnetoexcitons,equation of motion
更新于2025-09-23 15:23:52
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Room temperature spin Hall effect in graphene/MoS <sub/>2</sub> van der Waals heterostructures
摘要： Graphene is an excellent material for long distance spin transport but allows little spin manipulation. Transition metal dichalcogenides imprint their strong spin-orbit coupling into graphene via proximity effect, and it has been predicted that efficient spin-to-charge conversion due to spin Hall and Rashba-Edelstein effects could be achieved. Here, by combining Hall probes with ferromagnetic electrodes, we unambiguously demonstrate experimentally spin Hall effect in graphene induced by MoS2 proximity and for varying temperature up to room temperature. The fact that spin transport and spin Hall effect occur in different parts of the same material gives rise to a hitherto unreported efficiency for the spin-to-charge voltage output. Remarkably for a single graphene/MoS2 heterostructure-based device, we evidence a superimposed spin-to-charge current conversion that can be indistinguishably associated with either the proximity-induced Rashba-Edelstein effect in graphene or the spin Hall effect in MoS2. By comparing our results to theoretical calculations, the latter scenario is found the most plausible one. Our findings pave the way towards the combination of spin information transport and spin-to-charge conversion in two-dimensional materials, opening exciting opportunities in a variety of future spintronic applications.
关键词： Spin Hall effect,Spin-orbit proximity,Rashba-Edelstein effect,Graphene,Transition metal dichalcogenides
更新于2025-09-23 15:22:29
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van der Waals Epitaxy of High-Mobility Polymorphic Structure of Mo <sub/>6</sub> Te <sub/>6</sub> Nanoplates/MoTe <sub/>2</sub> Atomic Layers with Low Schottky Barrier Height
摘要： High contact resistance between two-dimensional (2D) transition metal dichalcogenides (TMDs) and metal electrodes is a practical barrier for applications of 2D TMDs to conventional devices. A promising solution to this is polymorphic integration of 1T′-phase semi-metallic and 2H-phase semiconducting TMD crystals, which can lower the Schottky barrier of the TMDs. Here, we demonstrate the van der Waals epitaxy of density-controlled single isolated 1T′-Mo6Te6 nanoplates on 2H-MoTe2 atomic layers by using metal-organic chemical vapor deposition. Importantly, in situ grown 1T′-Mo6Te6 nanoplates significantly reduce the contact resistance of the 2H-MoTe2 atomic layers, providing a record high mobility of 1,139 cm2/Vs for Pd/1T′-Mo6Te6/2H-MoTe2 back-gated field-effect transistors (FETs), along with a low Schottky barrier height (q?b) of 8.7 meV. These results lead to the possibility of ameliorating the high contact resistance faced by other TMDs, and furthermore, offer polymorphic structures for realizing higher mobility TMD devices.
关键词： 1T′-2H polymorphs,MOCVD,transition metal dichalcogenides,Mo6Te6,MoTe2
更新于2025-09-23 15:22:29
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Probing the Domain Architecture in 2D α-Mo <sub/>2</sub> C via Polarized Raman Spectroscopy
摘要： MXenes are emerging 2D materials with intriguing properties such as excellent stability and high conductivity. Here, a systematic study on the Raman spectra of 2D α-Mo2C (molybdenum carbide), a promising member in MXene family, is conducted. Six experimentally observed Raman modes from ultrathin α-Mo2C crystal are first assigned with the assistance of phonon dispersion calculated from density functional theory. Angle-resolved polarized Raman spectroscopy indicates the anisotropy of α-Mo2C in the b–c plane. Raman spectroscopy is further used to study the unique domain structures of 2D α-Mo2C crystals grown by chemical vapor deposition. A Raman mapping investigation suggests that most of the α-Mo2C flakes contain multiple domains and the c-axes of neighboring domains tend to form a 60° or 120° angle, due to the weak Mo–C bonds in this interstitial carbide and the low formation energy of the carbon chains along three equivalent directions. This study demonstrates that polarized Raman spectroscopy is a powerful and effective way to characterize the domain structures in α-Mo2C, which will facilitate the further exploration of the domain-structure-related properties and potential applications of α-Mo2C.
关键词： α-Mo2C,in-plane anisotropy,2D crystals,transition metal carbides,Raman spectroscopy
更新于2025-09-23 15:22:29