- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Coupled plasmona??phonon modes in monolayer MoS <sub/>2</sub>
摘要： We present a theoretical study of the plasmon–phonon coupling in a suspended monolayer MoS2 and a MoS2 substrate system using a diagrammatic self-consistent field theory. The four coupled plasmon–phonon modes and the four plasmon-surface phonon modes are observed due to the spin–orbit and electron-optic phonon interactions. The two of coupled plasmon–phonon and plasmon-surface phonon modes are optic-like and the other two are acoustic-like. The plasmon are strongly coupled with the optic-phonon in MoS2 and the surface optic-phonon in the substrates as the electron density or wave-vector increases. The strong plasmon–phonon coupling shows that the optoelectronic properties of monolayer MoS2 are evidently modulated by electron–phonon interactions. The hybrid plasmon–phonon polaritons can be achieved by strong light-mater interactions. This study is relevant to the application of MoS2 as novel plasmonic and nanophotonic devices.
关键词： plasmon–phonon coupling,plasmon,two dimensional materials
更新于2025-09-23 15:19:57
-
Gate Tunable Symmetric Bipolar Junction Transistor Fabricated via Femtosecond Laser Processing
摘要： Two-dimensional (2D) bipolar junction transistor (BJT) with van der Waals heterostructures plays an important role in the development of future nanoelectronics. Herein, a convenient method is introduced for fabricating a symmetric bipolar junction transistor (SBJT) constructed with black phosphorus and MoS2 with femtosecond laser processing. This SBJT exhibits good bidirectional current amplification thanks to its symmetric structure. Next, we place a top gate on one side of the SBJT to change the difference in the major carrier concentration between the emitter and collector in order to further investigate the effect of electrostatic doping on the device’s performance. The SBJT can also act as a gate tunable phototransistor with good photodetectivity and photocurrent gain of β ~ 21. Scanning photocurrent images are used to determine the mechanism governing photocurrent amplification in the phototransistor. These results promote the development of the applications of multifunctional nanoelectronics based on 2D materials.
关键词： Femtosecond laser processing,Phototransistor,Two-dimensional materials,Bipolar junction transistor,Gate tunable
更新于2025-09-23 15:19:57
-
Digital holography for non-invasive quantitative imaging of two-dimensional materials
摘要： Digital holography has found applications in many walks of life, from medicine to metrology, due to its ability to measure complex fields. Here, we use the power of digital holography to quantitatively image two-dimensional Transition Metal Dichalcogenides (TMDs) such as MoS2 and WS2 placed on a SiO2/Si substrate and determine their complex refractive indices or layer thicknesses. By considering the different refractive indices of the TMDs as they are thinned down from bulk to monolayers and by holographically capturing both the amplitude and the phase of reflected light, single atomic layers of TMDs, about 0.7 nm thick, can be resolved. Using holography, we also predict the number of layers contained within a thick TMD flake, which shows agreement with results obtained using Atomic Force Microscopy (AFM). A Bland–Altman analysis was performed to compare our experimental results with the standard AFM measurements, yielding a limit of agreement <5 nm for samples with thicknesses ranging from 15 to 60 nm. Our technique is non-contact, non-invasive, does not require scanning, and produces a field of view of a few hundred micrometers by a few hundred micrometers in a single capture. To further our study, we also perform simulations to demonstrate how the thickness of the SiO2 layer and the laser wavelength are critical in optimizing the amplitude and phase response of a two-dimensional material. These simulations can be used as a roadmap to determine the ideal wavelength and SiO2 layer thickness that should be used to accurately determine the refractive index or thickness of any given sample.
关键词： digital holography,Atomic Force Microscopy,layer thicknesses,Bland–Altman analysis,Transition Metal Dichalcogenides,two-dimensional materials,complex refractive indices
更新于2025-09-23 15:19:57
-
Influence of the support on stabilizing local defects in strained monolayer oxide films
摘要： Two-dimensional materials with a honeycomb lattice, such as graphene and hexagonal boron nitride, often contain local defects in which the hexagonal elements are replaced by four, five, seven, and eight-membered rings. An example is the Stone-Wales (S-W) defect, where a bond rotation causes four hexagons to be transformed into a cluster of two pentagons and two heptagons. A further series of similar defects incorporating divacancies results in larger structures of non-hexagonal elements. In this paper, we use scanning tunneling microscopy (STM) and density functional theory (DFT) modeling to investigate the structure and energetics of S-W and divacancy defects in a honeycomb (2 × 2) Ti2O3 monolayer grown on an Au(111) substrate. The epitaxial rumpled Ti2O3 monolayer is pseudomorphic and in a state of elastic compression. As a consequence, divacancy defects, which induce tension in freestanding films, relieve the compression in the epitaxial Ti2O3 monolayer and therefore have significantly lower energies when compared with their freestanding counterparts. We find that at the divacancy defect sites there is a local reduction of the charge transfer between the film and the substrate, the rumpling is reduced, and the film has an increased separation from the substrate. Our results demonstrate the capacity of the substrate to significantly influence the energetics, and hence favor vacancy-type defects, in compressively strained 2D materials. This approach could be applied more broadly, for example to tensile monolayers, where vacancy-type defects would be rare and interstitial-type defects might be favored.
关键词： elastic strain,local structural defects,monolayers,scanning tunneling microscopy (STM),density functional theory (DFT),two-dimensional materials,ultrathin oxide films
更新于2025-09-19 17:15:36
-
[IEEE 2018 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Hong Kong, China (2018.11.5-2018.11.9)] 2018 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Surface Plasmon Polaritons Scattering by Strong Magnetic field in Two-dimensional Material
摘要： Scattering effect of surface plasmon polaritons in two-dimensional material based devices by magnetic fields are analytically studied within the framework of wave optics and plasma model. The theoretical explanation of magnetic scattering and related formulae are provided by considering plasmonic mechanics and solving the equation of motion of electron gas directly. Calculation results illustrating magnetic scattering phenomena are also given by applying an approximation to the first order.
关键词： two-dimensional materials,magnetic fields scattering,analytic methods,surface plasmon polaritons
更新于2025-09-19 17:15:36
-
Eighteen functional monolayer metal oxides: wide bandgap semiconductors with superior oxidation resistance and ultrahigh carrier mobility
摘要： Layered metal oxides have emerged as an up-and-comer in the family of two-dimensional materials due to their natural abundance, intrinsic bandgap, and chemical inertness. Based on first-principles calculations, we systematically investigated the atomic structures, energetic stability, and electronic properties of 18 monolayer metal oxides. All these monolayer metal oxides are predicted to be energetically favorable with negative formation energies in the range of -4.27 to -0.47 eV per atom, suggesting good experimental feasibility for synthesis of these monolayer metal oxides. Monolayer metal oxides exhibit superior oxidation resistance, and possess modest to wide bandgaps (1.22–6.48 eV) and high carrier mobility (especially up to 8540 cm2 V?1 s?1 for the InO monolayer), thereby rendering these low-dimensional materials promising candidates for carrier transport. Also, a pronounced in-plane anisotropy for the carrier mobility with a longitudinal/horizontal ratio as large as 115 is revealed for the monolayer metal oxides. These 2D metal oxides exhibit notable absorption in the ultraviolet range with the absorption coefficient >10? cm?1. The combined novel properties of these monolayer metal oxides offer a wide range of opportunities for advanced electronic and optoelectronic applications.
关键词： two-dimensional materials,optoelectronics,monolayer metal oxides,bandgap,carrier mobility,oxidation resistance
更新于2025-09-19 17:15:36
-
Fluorescence and Raman Enhancement Effect Caused by a Chemical Mechanism in Metal-Tetraphenylporphyrin on 2D Layered Materials
摘要： Two-dimensional (2D) layered materials exhibiting a flat surface have been strong candidates for studies investigating both the fundamental Raman enhancement in these materials and their practical applications. Here, we explore the Raman and the fluorescence enhancement effects of metal-tetraphenylporphyrin (TPP) molecules on graphene and MoSe2. We attribute the enhancement behaviors to the charge transfer interaction between the 2D materials and the adsorbates. The enhancement factors for the two flat substrates are dissimilar due to the charge transfer ability resulting from the electronic structures. The charge transfer interaction can be explained by the adsorption probability based on Langmuir's model.
关键词： Fluorescence enhancement,Raman enhancement,Two-dimensional materials
更新于2025-09-19 17:15:36
-
Thickness-controlled synthesis of CoX2 (X = S, Se, Te) single crystalline 2D layers with linear magnetoresistance and high conductivity.
摘要： Two-dimensional (2D) materials especially transition metal dichalcogenides (TMDs) have drawn intensive interests owing to their plentiful properties. Some TMDs with magnetic elements (Fe, Co, Ni, etc.) are reported to be magnetic theoretically and experimentally, which undoubtedly provide a promising platform to design functional devices and study physical mechanisms. Nevertheless, plenty of the theoretical TMDs remain unrealized experimentally. In addition, the governable synthesis of these kinds of TMDs with desired thickness and high crystallinity poses a tricky challenge. Here, we report a controlled preparation of CoX2 (X = S, Se, Te) nanosheets through chemical vapor deposition (CVD). The thickness, lateral scale and shape of the crystals show great dependence with temperature and the thickness can be controlled from monolayer to tens of nanometers. Magneto-transport characterization and Density Function Theory (DFT) simulation indicate CoSe2 and CoTe2 are metallic. Besides, unsaturated and linear magnetoresistance have been observed even up to 9 Tesla. The conductivity of CoSe2 and CoTe2 can reach 5 × 106 and 1.8 × 106 S/m respectively, which is pretty high and even comparable with silver. These cobalt-based TMDs show great potential to work as 2D conductors and also provide a promising platform for investigating their magnetic properties.
关键词： Transition metal dichalcogenides,Magnetoresistance,Conductivity,Two-dimensional materials,Chemical vapor deposition
更新于2025-09-19 17:13:59
-
Plasmonic Metasurfaces Situated on Ultra-thin Carbon Nanomembranes
摘要： During the last decade, optical metasurfaces consisting of designed nanoresonators arranged in a planar fashion were successfully demonstrated to allow for the realization of a large variety of flat optical components. However, in common implementations of metasurfaces and metasurface-based devices, their flat nature is thwarted by the presence of a substrate of macroscopic thickness, which is needed to mechanically support the individual nanoresonators. Here, we demonstrate that Carbon Nanomembranes (CNMs) having nanoscale thickness can be used as a basis for arranging array of plasmonic nano-resonators into a metamembrane, allowing for the realization of genuinely flat optical devices. CNMs belong to the family of two-dimensional materials, and their thickness, mechanical, chemical, and electrical properties can be tailored by the choice of the molecular precursors used for their fabrication. We experimentally fabricate gold split-ring-resonator (SRR) metasurfaces on top of a free-standing CNM, which has a thickness of only about 1 nm and shows negligible interaction with the incident light field. For optical characterization of the fabricated SRR CNM metasurfaces, we perform linear-optical transmittance spectroscopy, revealing the typical resonance structure of an SRR metasurface. Furthermore, numerical calculations assuming free-standing SRR arrays are in excellent agreement with corresponding experimental transmittance spectra. We believe that our scheme offers a versatile solution for the realization of ultrathin, ultra lightweight metadevices, and may initiate various future research directions and applications including complex sensor technologies, conformal coating of complex topographies with functional metasurfaces, fast prototyping of multilayer metasurfaces, and studying the optical properties of effectively free-standing nanoparticles without the need for levitation schemes.
关键词： carbon nanomembranes,two-dimensional materials,nanoplasmonics,flat-optics,metasurfaces
更新于2025-09-19 17:13:59
-
Waveguide-integrated van der Waals heterostructure photodetector at telecom wavelengths with high speed and high responsivity
摘要： Intensive efforts have been devoted to the exploration of new optoelectronic devices based on two-dimensional transition-metal dichalcogenides (TMDCs) owing to their strong light–matter interaction and distinctive material properties. In particular, photodetectors featuring both high-speed and high-responsivity performance are of great interest for a vast number of applications such as high-data-rate interconnects operated at standardized telecom wavelengths. Yet, the intrinsically small carrier mobilities of TMDCs become a bottleneck for high-speed application use. Here, we present high-performance vertical van der Waals heterostructure-based photodetectors integrated on a silicon photonics platform. Our vertical MoTe2–graphene heterostructure design minimizes the carrier transit path length in TMDCs and enables a record-high measured bandwidth of at least 24 GHz under a moderate bias voltage of –3 V. Applying a higher bias or employing thinner MoTe2 flakes boosts the bandwidth even to 50 GHz. Simultaneously, our device reaches a high external responsivity of 0.2 A W–1 for incident light at 1,300 nm, benefiting from the integrated waveguide design. Our studies shed light on performance trade-offs and present design guidelines for fast and efficient devices. The combination of two-dimensional heterostructures and integrated guided-wave nano photonics defines an attractive platform to realize high-performance optoelectronic devices, such as photodetectors, light-emitting devices and electro-optic modulators.
关键词： transition-metal dichalcogenides,photodetectors,silicon photonics,van der Waals heterostructures,two-dimensional materials
更新于2025-09-19 17:13:59