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Trapped charge modulation at the MoS2/SiO2 interface by lateral electric field in MoS2 field-effect transistors
摘要： Controlling trapped charges at the interface between a two-dimensional (2D) material and SiO2 is crucial for the stable electrical characteristics in field-effect transistors (FETs). Typically, gate-source bias has been used to modulate the charge trapping process with a narrow dielectric layer with a high gate electric field. Here, we observed that charge trapping can also be affected by the lateral drain-source voltage (VDS) in the FET structure, as well as by the gate-source bias. Through multiple VDS sweeps with increasing measurement VDS range, we demonstrated that the charge trapping process could be modulated by the range of the applied lateral electric field. Moreover, we inserted hexagonal boron nitride (h-BN) layer between the MoS2 and SiO2 layer to explore the charge trapping behavior when a better interface is formed. This study provides a deeper understanding of controlling the electrical characteristics with interface-trapped carriers and lateral electrical fields in 2D materials-based transistors.
关键词： charge trapping,high electric fields,MoS2,field-effect transistors
更新于2025-09-23 15:23:52
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Constructing 3D sub-micrometer CoO octahedrons packed with layered MoS2 shell for boosting photocatalytic overall water splitting activity
摘要： A 3D architectures of CoO@MoS2 composite photocatalyst was prepared by coating MoS2 onto the (1 1 1) facts of sub-micrometer CoO octahedrons via a facile solvothermal method. The CoO@MoS2 composites show a significantly improved photocatalytic activity for overall water splitting. At an optimal ratio of 3 wt% MoS2, CoO@MoS2-3% composite can split pure water with the stoichiometric ratio production of H2 and O2 under visible light irradiation, meanwhile, presents the highest H2 production evolution (1.07 μmol/h), which is almost four times than that of pure CoO (0.26 μmol/h). Moreover, the CoO@MoS2 composite still remains good stability after three successive cyclings (over 72 h). The enhanced photocatalytic activity and stability can be attributed that the layered MoS2 shell not only promoted the photo-induced charge transfer at the interface of CoO due to the sufficient contact area between CoO and MoS2, but also protected the exposed the (1 1 1) facts of CoO from devastation. Our work offers more insights into the development of a simple synthesis of well-shaped 3D-based composite photocatalysts towards the energy- and environmental-related applications.
关键词： CoO octahedrons,MoS2,Overall water splitting,Core-shell,Visible light
更新于2025-09-23 15:23:52
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Enhanced photo-catalytic performance by effective electron-hole separation for MoS2 inlaying in g-C3N4 hetero-junction
摘要： The MoS2/g-C3N4 heterojunction composite (marked as MoS2/g-C3N4-H) was successfully prepared via calcining the melamine coated MoS2 nano-sphere, where the thin g-C3N4 nano-sheets were tightly grown on the surface of MoS2 nano-sphere to form MoS2 inlaying in g-C3N4 heterostructure. The detailed charge transfer mechanism was discussed by combining theoretical calculation and experiments, in which the intrinsic cause of photo-generated charge separation and transfer was determined as the directional built-in electric field driven by different Fermi levels of MoS2 and g-C3N4. Comparatively, the enhanced photo-catalytic performance and stability of the sample were assessed by degrading the Rhodamine (RhB) and reducing the Dichromate (Cr6+) solutions under the irradiation of the simulated sunlight, which could be attributed to the widened spectral absorption range and improved electron-hole separation rate. Based on above results, the photo-catalytic mechanism involving redox reactions was also clearly proposed.
关键词： MoS2,Built-in electric field,Photocatalyst,Heterojunction,g-C3N4
更新于2025-09-23 15:23:52
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Preliminary characterization of the thickness of bulk MoS2 layer by the colour
摘要： We propose a method to preliminarily determine the thicknesses of bulk MoS2 layers based on their colours. The re?ectance spectra of thin-layer and bulk MoS2 on three substrates were calculated by using the ?nite-di?erence time-domain technique; then, based on chromaticity theory, the corresponding colour coordinates were obtained. By comparing the colours of the experimental sample and the corresponding structure, whose re?ection spectrum was calculated, the thicknesses of bulk MoS2 layers were determined preliminarily, which laid the foundation for the accurate measurement of the thickness, subsequently, through methods based on atomic force microscopy, Raman spectroscopy, and other linear and nonlinear optical processes.
关键词： Re?ection spectra,Colour coordinates,Preliminary characterization,Bulk MoS2 layer
更新于2025-09-23 15:23:52
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Dense Electron-Hole Plasma Formation and Ultra-Long Charge Lifetime in Monolayer MoS <sub/>2</sub> via Material Tuning
摘要： Many-body interactions in photoexcited semiconductors can bring about strongly-interacting electronic states, culminating in the fully-ionized matter of electron-hole plasma (EHP) and electron-hole liquid (EHL). These exotic phases exhibit unique electronic properties, such as metallic conductivity and metastable high photoexcitation density, which can be the basis for future transformative applications. However, the cryogenic condition required for its formation has limited the study of dense plasma phases to a purely academic pursuit in a restricted parameter space. This paradigm can potentially change with the recent experimental observation of these phases in atomically thin MoS2 and MoTe2 at room temperature. A fundamental understanding of EHP and EHL dynamics is critical for developing novel applications on this versatile layered platform. In this work, we studied the formation and dissipation of EHP in monolayer MoS2. Unlike previous results in bulk semiconductors, our results reveal that electro-mechanical material changes in monolayer MoS2 during photoexcitation play a significant role in dense EHP formation. Within the free-standing geometry, photoexcitation is accompanied by an unconstrained thermal expansion, resulting in a direct-to-indirect gap electronic transition at a critical lattice spacing and fluence. This dramatic altering of the material’s energetic landscape extends carrier lifetimes by 2 orders of magnitude and allows the density required for EHP formation. The result is a stable dense plasma state that’s sustained with modest optical photoexcitation. Our findings pave the way for novel applications based on dense plasma states in 2D semiconductors.
关键词： 2D materials,Dense Electron-Hole Plasma,Bandgap Renormalization,MoS2,Transition Metal Dichalcogenides,Direct to Indirect Bandgap Transition
更新于2025-09-23 15:23:52
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(Bz) <sub/><i>n</i> </sub> and (VBz) <sub/><i>n</i> </sub> covalent functionalized MoS <sub/>2</sub> monolayer: electronic and transport properties
摘要： Inspired by Benzene (Bz) derivatives dramatically enhancing MoS2 monolayer electronic properties (ACS Nano. 2015, 9, 6018–6030), we have investigated electronic and transport properties of (Bz)n/MoS2 and (VBz)n/MoS2, which are designed by grafting (Bz)n and (VBz)n arrays onto 2D monolayer MoS2 (ML-MoS2), respectively, using density functional theory (DFT) and non-equilibrium Green’s function (NEGF) methods. ML-MoS2 provides a perfect substrate for grafting (Bz)n and (VBz)n arrays upon its surface as a result of stable covalent binding energy with -3.841 eV and -1.953 eV for (Bz)n/MoS2 and (VBz)n/MoS2 respectively. From the electronic properties, we can find that grafting (Bz)n onto the ML-MoS2 surface turns ML-MoS2 from typical semiconductor to metallic properties because four wide bands coupled by (Bz)n and MoS2 in (Bz)n/MoS2 show better delocalization in heterointerface, resulting to these bands across the Fermi level (Ef). Furthermore, the introduction of metal V. Transport properties of ML-MoS2, (Bz)n/MoS2 or (VBz)n/MoS2 for two-probe devices are all studied in zigzag and armchair direction. The ferromagnetic (VBz)n/MoS2 shows a spin polarized transport characteristic, spin-down state gives a higher conductivity than spin-up state. By comparison the zigzag direction is the preferential pathway for electron transport. Finally this work suggests that the novel (VBz)n nanowire grafted on MoS2 should have potential application in low-dimensional magnetic nanoelectronic devices.
关键词： (Bz)n/MoS2,(VBz)n/MoS2,covalent functionalized,electronic property,transport property
更新于2025-09-23 15:22:29
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Electronic structure and magnetic behaviors of exfoliated MoS<sub>2</sub> nanosheets
摘要： The correlation of electronic structure and magnetic behaviors of layered molybdenum disulfide (MoS2) nanosheets, mechanically exfoliated from pristine hexagonal crystal (2H-MoS2) have been studied. Raman spectra show the energy difference (ΔE) between two Raman peaks A1g and E12g was about 20.2 cm-1, indicating the formation of mono-/bi-layered MoS2 nanosheets as obtained after mechanical exfoliation from pristine 2H-MoS2. The absence of the reflection peak (002) in X-ray diffraction patterns confirms the formation of few-layered and mono-/bi-layered MoS2 nanosheets. Mo LII-edge and S K-edge X-ray absorption near edge structure spectra of mono-/bi-layered MoS2 nanosheets show the splitting of different peaks that cause a noticeable change in their band structure. Magnetic M-H hysteresis loops measurement clearly demonstrates the increase of room temperature ferromagnetism from pristine to mono-/bi-layer MoS2, due to the existence of defects (“S”- vacancies or defects at the grain boundaries region) and the increase of DOS. UPS (He-I) measurements show the valence band maximum position increased from 1.11 eV (pristine MoS2) to 1.57 eV (mono-/bi-layered MoS2 nanosheets), whereas the surface work function (Ф) reduced from 4.85 eV (pristine MoS2) to 4.47 eV (mono-/bi-layered MoS2 nanosheets). UPS (He-II) valence band density of states (DOS) of S 3p - derived states near Fermi level (Ef). Mo 3d and S 2p XPS core level peaks shifted to higher energy with the reduction of the number of layers in exfoliated MoS2. As the number of layers decreased, valence band spectra, as well as VB-PES spectra of mono-/bi-layered MoS2 nanosheets, exhibits an enhanced DOS with reduced thickness.
关键词： UPS,VB-PES,XANES,Exfoliated MoS2-nanosheets,XPS,RT-FM
更新于2025-09-23 15:22:29
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Preparation of MoS <sub/>2</sub> @ZnO heterostructure with enhanced photocatalytic activity
摘要： In order to effectively solve environmental problems induced by organic pollutants, the MoS2@ZnO heterostructure is successfully fabricated via a two-step hydrothermal method, in which the MoS2 nanosheets grew on the surface of ZnO nanorods. The synthetic heterostructure is demonstrated to possess excellent photocatalytic activity in the degradation of methylene blue (MB) under ultraviolet (UV) and visible light irradiation. The corresponding photodegradation rate constant of MoS2@ZnO heterostructure reaches up to 0.02075 min-1 and 0.00916 min-1, which are higher than that of pure ZnO (0.00514 min-1 and 0.00048 min-1) under the same reaction conditions. Obviously, compared with pure ZnO, the photocatalytic activity of the MoS2@ZnO heterostructure has been significantly improved. This could be attributed to the increased specific surface area of photocatalyst and the formation of heterostructure between ZnO and MoS2 after loading the MoS2 on the surface of ZnO nanorods. Which help to provide more reaction sites for the adsorption of pollutant and improve the separation efficiency of photogenerated electron-hole pairs.
关键词： MoS2,composite materials,ZnO,photocatalytic activity,heterostructure
更新于2025-09-23 15:22:29
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Monolayer MoS? Strained to 1.3% With a Microelectromechanical System
摘要： We report on a modified transfer technique for atomically thin materials integrated into microelectromechanical systems (MEMS) for studying strain physics and creating strain-based devices. Our method tolerates the non-planar structures and fragility of MEMS while still providing precise positioning and crack-free transfer of flakes. Furthermore, our method used the transfer polymer to anchor the 2D crystal to the MEMS, which reduces the fabrication time and increases the yield, and allowed us to exploit the strong mechanical coupling between the 2D crystal and polymer to strain the atomically thin system. We successfully strained single atomic layers of molybdenum disulfide (MoS2) with MEMS devices for the first time and achieved greater than 1.3% strain, marking a major milestone for incorporating 2D materials with MEMS. We used the established strain response of MoS2 Raman and photoluminescence spectra to deduce the strain in our crystals and provide a consistency check. We found good comparison between our experiment and the literature.
关键词： photoluminescence,Raman,strain,monolayer MoS2,MEMS
更新于2025-09-23 15:22:29
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MoS2/silicon-on-insulator Heterojunction Field-Effect-Transistor for High-performance Photodetection
摘要： In this letter, we demonstrate a novel junction field effect transistor (JFET) by transferring MoS2 onto silicon-on-insulator (SOI) substrate to control the thin Si channel. By combining high light absorption coefficient in MoS2 with high internal gain in thin Si channel, the device can be used for photodetection and achieve high responsivity up to ~1.78×104 A/W, high detectivity over 3×1013 Jones, and short response time down to 1.44 ms. Furthermore, unlike conventional SOI photodetector which is only sensitive to UV light, the response spectrum of our proposed device peaks in visible/near-infrared region, which is interesting for imaging and optical communication applications.
关键词： SOI,High photoresponsivity,Van der Waals heterojunction,MoS2,Junction field effect transistor
更新于2025-09-23 15:22:29