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Lateral interfaces of transition metal dichalcogenides: A stable tunable one-dimensional physics platform
摘要： We study in-plane lateral heterostructures of commensurate transition-metal dichalcogenides, such as MoS2-WS2 and MoSe2-WSe2, and find interfacial and edge states that are highly localized to these regions of the heterostructure. These are one-dimensional (1D) in nature, lying within the band gap of the bulk structure and exhibiting complex orbital and spin structure. We describe such heteroribbons with a three-orbital tight-binding model that uses first principles and experimental parameters as input, allowing us to model realistic systems. Analytical modeling for the 1D interfacial bands results in long-range hoppings due to the hybridization along the interface, with strong spin-orbit couplings. We further explore the Ruderman-Kittel-Kasuya-Yosida indirect interaction between magnetic impurities located at the interface. The unusual features of the interface states result in effective long-range exchange noncollinear interactions between impurities. These results suggest that transition-metal dichalcogenide interfaces could serve as stable, tunable 1D platform with unique properties for possible use in exploring Majorana fermions, plasma excitations, and spintronics applications.
关键词： spin-orbit coupling,interface states,transition metal dichalcogenides,RKKY interaction,tight-binding model,lateral heterostructures
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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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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Doping of Monolayer Transition Metal Dichalcogenides via Physisorption of Aromatic Solvent Molecules
摘要： Two-dimensional (2D) transition metal dichalcogenides (TMDs) recently emerged as novel materials displaying a wide variety of physico-chemical properties that render them unique scaffolds for high-performance (opto)electronics. The controlled physisorption of molecules on the TMD surface is a viable approach to tune their optical and electronic properties. Solvents, made of small aromatic molecules, are frequently employed for the cleaning of the 2D materials or as 'dispersant' for their chemical functionalization with larger (macro)molecules, without considering their potential key effect in locally modifying the characteristics of 2D materials. In this work, we demonstrate how the electronic and optical properties of mechanically exfoliated monolayer of MoS2 and WSe2 are modified when physically interacting with small aromatic molecules of common solvents. Low-temperature photoluminescence (PL) spectra recorded at 78 K revealed that physisorbed benzene derivatives could modulate the charge carrier density in monolayer TMDs, hence affecting the switching between neutral exciton and trion (charged exciton). By combining experimental evidences with DFT calculations, we confirm that charge transfer doping on TMDs depends not only on difference in chemical potential between molecules and 2D materials, but also on the thermodynamic stability of physisorption. Our results provide unambiguous evidence of the great potential of optical and electrical tuning of monolayer MoS2 and WSe2 by physisorption of small aromatic solvent molecules, which is highly relevant both for fundamental studies and more device applied purposes.
关键词： transition metal dichalcogenides,aromatic molecules,Density Functional Theory,doping,photoluminescence
更新于2025-09-23 15:22:29
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A roadmap for electronic grade 2D materials
摘要： Since their modern debut in 2004, 2-dimensional (2D) materials continue to exhibit scientific and industrial promise, providing a broad materials platform for scientific investigation, and development of nano- and atomic-scale devices. A significant focus of the last decade’s research in this field has been 2D semiconductors, whose electronic properties can be tuned through manipulation of dimensionality, substrate engineering, strain, and doping (Mak et al 2010 Phys. Rev. Lett. 105 136805; Zhang et al 2017 Sci. Rep. 7 16938; Conley et al 2013 Nano Lett. 13 3626–30; Li et al 2016 Adv. Mater. 28 8240–7; Rhodes et al 2017 Nano Lett. 17 1616–22; Gong et al 2014 Nano Lett. 14 442–9; Suh et al 2014 Nano Lett. 14 6976–82; Yoshida et al 2015 Sci. Rep. 5 14808). Molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) have dominated recent interest for potential integration in electronic technologies, due to their intrinsic and tunable properties, atomic-scale thicknesses, and relative ease of stacking to create new and custom structures. However, to go ‘beyond the bench’, advances in large-scale, 2D layer synthesis and engineering must lead to ‘exfoliation-quality’ 2D layers at the wafer scale. This roadmap aims to address this grand challenge by identifying key technology drivers where 2D layers can have an impact, and to discuss synthesis and layer engineering for the realization of electronic-grade, 2D materials. We focus on three fundamental areas of research that must be heavily pursued in both experiment and computation to achieve high-quality materials for electronic and optoelectronic applications.
关键词： transition metal dichalcogenides,2D materials,grand challenges,technology drivers,2D electronics,synthesis,roadmap
更新于2025-09-23 15:22:29
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S-Type Negative Differential Resistance in Semiconducting Transition-Metal Dichalcogenides
摘要： Current-controlled (also known as “S-type”) negative differential resistance (NDR) is of crucial importance to many emerging applications including neuromorphic computing and high-density memristors integration. However, the experimental realization of S-type NDR based on conventional mechanisms poses demanding requirements on materials, which greatly limits their potential applications. Here, it is experimentally identified that semiconducting transition-metal dichalcogenides (TMDs) can host a bipolar S-type NDR devices. Theoretical simulations indicate that the origin of the NDR in these devices arises from a thermal feedback mechanism. Furthermore, the potential applications of TMD-based S-type NDR device in signal processing and neuromorphic electronics are demonstrated.
关键词： transition-metal dichalcogenides,signal processing,negative differential resistance,self-oscillating circuits,neuron spikes
更新于2025-09-23 15:22:29