- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Removing Defects in WSe <sub/>2</sub> via Surface Oxidation and Etching to Improve Solar Conversion Performance
摘要： Layered metal dichalcogenide materials (MX2) have great potential for solar energy conversion. However, as-grown MX2 materials often contain edge and terrace defects that degrade semiconducting properties and hinder their solar performance. Herein, we demonstrate a simple approach to removing surface defects and improving the solar performance by using UV-generated ozone to oxidize the surface of WSe2 nanoplates and single crystals, followed by a simple soak in aqueous solutions to remove the oxide. Structural characterizations reveal that defective edges and basal plane defect sites are selectively oxidized and subsequently etched, and the ratio of the non-stoichiometric WSex species is reduced. After this treatment, p-type WSe2 single crystals show increased electron accumulation on the surface and significantly enhanced photoelectrochemical solar conversion efficiency. These results and insights will be useful in the improvement and utilization of layered MX2 materials based on both Se and S for solar energy conversion and other device applications.
关键词： surface defects,oxidation,layered metal dichalcogenide,WSe2,UV-generated ozone,etching,solar conversion
更新于2025-09-10 09:29:36
-
Engineering the Palladium–WSe <sub/>2</sub> Interface Chemistry for Field Effect Transistors with High Performance Hole Contacts
摘要： Palladium has been widely employed as a hole contact to WSe2 and has enabled, at times, the highest WSe2 transistor performance. However, there are orders of magnitude variation across the literature in Pd–WSe2 contact resistance and ION/IOFF ratios with no true understanding of how to consistently achieve high–performance contacts. In this work, WSe2 transistors with impressive ION/IOFF ratios of 106 and Pd–WSe2 Schottky diodes with near–zero variability are demonstrated utilizing Ohmic–like Pd contacts through deliberate control of the interface chemistry. The increased concentration of a PdSex intermetallic is correlated with an Ohmic band alignment and concomitant defect passivation, which further reduces the contact resistance, variability, and barrier height inhomogeneity. The lowest contact resistance occurs when a 60 minute post metallization anneal at 400 °C in forming gas (FG) is performed. X-ray photoelectron spectroscopy indicates this FG anneal produces 3× the concentration of PdSex and an Ohmic band alignment, in contrast to that detected after annealing in ultra–high vacuum, during which a 0.2 eV hole Schottky barrier forms. Raman spectroscopy and scanning transmission electron microscopy highlight the necessity of the fabrication step to achieve high–performance contacts as no PdSex forms and WSe2 is unperturbed by room temperature Pd deposition. However, at least one WSe2 layer is consumed by the necessary interface reactions that form PdSex requiring strategic exploitation of a sacrificial WSe2 layer during device fabrication. The interface chemistry and structural properties are correlated with Pd–WSe2 diode and transistor performance and the recommended processing steps are provided to enable reliable high–performance contact formation.
关键词： annealing,palladium,WSe2,interface chemistry,X-ray photoelectron spectroscopy,transistor,metal contact
更新于2025-09-09 09:28:46
-
Modulation of the electronic properties of two-dimensional MoTe2/WSe2 heterostructure by electrical field
摘要： The structure and electronic properties of two-dimensional MoTe2/WSe2 van der Waals heterostructure under external electric field have been investigated by first-principles calculation. The interlayer distance between MoTe2 and WSe2 is 3.613? and the binding energy per unit is ?0.183eV, which indicated that MoTe2 is bound to WSe2 via van der Waals interaction. The interlayer distance can be modified by external electric field and the band gap of MoTe2/WSe2 heterostructure continuously decreases with increasing external electric field, eventually a transition from semiconductor to metal is observed, particularly, the band alignment of the MoTe2/WSe2 heterostructure can be effectively tuned from intrinsic type-II to type-I. Applying external electric field along +z direction and ?z direction has different effects on the band gap due to the intrinsic spontaneous polarization in MoTe2/WSe2 heterostructure. Our study indicates that the external electric field can significantly tune the band offsets and modify the band alignment between MoTe2 and WSe2. The present study would be helpful for application of such transition-metal dichalcogenides heterostructures in nano- and optoelectronics.
关键词： band gap,MoTe2/WSe2 heterostructure,external electric field,Density of States
更新于2025-09-09 09:28:46
-
Ultimate limit in size and performance of WSe2 vertical diodes
摘要： Precise doping-profile engineering in van der Waals heterostructures is a key element to promote optimal device performance in various electrical and optical applications with two-dimensional layered materials. Here, we report tungsten diselenide- (WSe2) based pure vertical diodes with atomically defined p-, i- and n-channel regions. Externally modulated p- and n-doped layers are respectively formed on the bottom and the top facets of WSe2 single crystals by direct evaporations of high and low work-function metals platinum and gadolinium, thus forming atomically sharp p–i–n heterojunctions in the homogeneous WSe2 layers. As the number of layers increases, charge transport through the vertical WSe2 p–i–n heterojunctions is characterized by a series of quantum tunneling events; direct tunneling, Fowler–Nordheim tunneling, and Schottky emission tunneling. With optimally selected WSe2 thickness, our vertical heterojunctions show superb diode characteristics of an unprecedentedly high current density and low turn-on voltages while maintaining good current rectification.
关键词： current rectification,WSe2,van der Waals heterostructures,quantum tunneling,vertical diodes
更新于2025-09-04 15:30:14
-
Entanglement of single-photons and chiral phonons in atomically thin WSe2
摘要： Quantum entanglement is a fundamental phenomenon that, on the one hand, reveals deep connections between quantum mechanics, gravity and spacetime1,2, and on the other hand, has practical applications as a key resource in quantum information processing3. Although it is routinely achieved in photon–atom ensembles4, entanglement involving solid-state5–7 or macroscopic objects8 remains challenging albeit promising for both fundamental physics and technological applications. Here, we report entanglement between collective, chiral vibrations in a two-dimensional WSe2 host—chiral phonons (CPs)—and single-photons emitted from quantum dots9–13 (QDs) present in it. CPs that carry angular momentum were recently observed in WSe2 and are a distinguishing feature of the underlying honeycomb lattice14,15. The entanglement results from a ‘which-way’ scattering process, involving an optical excitation in a QD and doubly-degenerate CPs, which takes place via two indistinguishable paths. Our unveiling of entanglement involving a macroscopic, collective excitation together with strong interactions between CPs and QDs in two-dimensional materials opens up ways for phonon-driven entanglement of QDs and engineering chiral or non-reciprocal interactions at the single-photon level.
关键词： chiral phonons,WSe2,two-dimensional materials,quantum dots,Quantum entanglement
更新于2025-09-04 15:30:14
-
Electric field mediated large valley splitting in the van der Waals heterostructure WSe <sub/>2</sub> /CrI <sub/>3</sub>
摘要： In contrast to commonly used means such as the magnetic field, here an electric field is used to achieve a large valley splitting in the van der Waals (vdW) heterostructure WSe2/CrI3. CrI3 contributes to the spin moment. The electric field pushes the valence bands of Cr atoms close to those of the W atoms associated with pseudospin so that they can interact through the exchange interaction. The opposite helicities of pseudospin at the K and K′ points realize a valley splitting as large as 10.5 meV under an electric field of 0.1 V ??1. The underlying physics stems from the interlayer charge transfer, where the spin conservation plays a role.
关键词： van der Waals heterostructure,WSe2/CrI3,electric field,pseudospin,valley splitting
更新于2025-09-04 15:30:14
-
Atomic scale depletion region at one dimensional MoSe <sub/>2</sub> -WSe <sub/>2</sub> heterointerface
摘要： Lateral heterojunctions based on two dimensional (2D) transition metal dichalcogenides (TMDCs) potentially realize monolayer devices exploiting 2D electronic structures and the functions introduced by the presence of 1D heterointerfaces. Electronic structures of a lateral MoSe2-WSe2 junction have been unveiled using scanning tunneling microscopy and spectroscopy. A smooth and narrow depletion region exists despite a defect-rich heterointerface deviating from the preferred zigzag orientations of the TMDC lattice. From the characteristics of the depletion region, a high carrier concentration and high internal electric fields are inferred, offering to benefit designs of lateral TMDC devices.
关键词： depletion region,MoSe2-WSe2,heterointerface,scanning tunneling microscopy,scanning tunneling spectroscopy,TMDCs
更新于2025-09-04 15:30:14
-
[Springer Theses] Properties of Synthetic Two-Dimensional Materials and Heterostructures || Properties of Atomically Thin WSe2 Grown Via Metal-Organic Chemical Vapor Deposition
摘要： Two-dimensional tungsten diselenide (WSe2) is of interest for the next-generation electronic and optoelectronic devices due to its bandgap of 1.65 eV and also its excellent transport properties. However, technologies based on 2D WSe2 cannot be realized without a scalable synthesis process. The first part of this chapter focuses on the scalable synthesis for large-area, mono, and few-layer WSe2 via metal organic chemical vapor deposition (MOCVD) using tungsten hexacarbonyl (W(CO)6) and dimethylselenium ((CH3)2Se). In addition to the excellent scalability of production, this technique allows for the precise control of vapor-phase chemistry, which is not obtainable though the physical vapor reaction using powder precursors. Growth parameters such as temperature, pressure, Se to W ratio, and selection of the substrates for the growth play important roles on the resultant structure. With optimized conditions, domain size >8 μm is yielded.
关键词： electronic devices,WSe2,epitaxial growth,MOCVD,two-dimensional materials
更新于2025-09-04 15:30:14