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Switchable and dual-wavelength ultrafast fibre lasers with an MoTe <sub/>2</sub> -based saturable absorber
摘要： Based on monolayer MoTe2 film, we have proposed a mode-locked fibre laser delivering single-wavelength and dual-wavelength solitons at the telecommunication band. The saturable absorber (SA) is synthesized by coating monolayer MoTe2 film on the pinhole of fibre pigtail. The experimental results show that our soliton lasers can work at the single- and dual-wavelength states, respectively, by appropriately adjusting the polarization controller. The proposed laser can work stably at the mode-locking state for several hours, indicating that monolayer MoTe2 film is an excellent SA material for ultrafast optics.
关键词： ultrafast fibre laser,two dimensional materials,Saturable absorber
更新于2025-09-19 17:13:59
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Plasmonic Pt Superstructures with Boosted Near‐Infrared Absorption and Photothermal Conversion Efficiency in the Second Biowindow for Cancer Therapy
摘要： Defects are commonly found in two-dimensional (2D) transition-metal dichalcogenide (TMD) materials. Such defects usually dictate the optical and electrical properties of TMDs. It is thus important to develop techniques to characterize the defects directly with good spatial resolution, specificity, and throughput. Herein, we demonstrate that Kelvin probe force microscopy (KPFM) is a versatile technique for this task. It is able to unveil defect heterogeneity of 2D materials with a spatial resolution of 10 nm and energy sensitivity better than 10 meV. KPFM mappings of monolayer WS2 exhibit interesting work function variances that are associated with defects distribution. This finding is verified by aberration-corrected scanning transmission electron microscopy and density functional theory calculations. In particular, a strong correlation among the work function, electrical and optical responses to the defects is revealed. Our findings demonstrate the potential of KPFM as an effective tool for exploring the intrinsic defects in TMDs.
关键词： transition-metal dichalcogenides,density functional theory,defects,Kelvin probe force microscopy,scanning transmission electron microscopy,work function,two-dimensional materials
更新于2025-09-19 17:13:59
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Plasmonically enabled two-dimensional material-based optoelectronic devices
摘要： Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, black phosphorus and hexagonal boron nitride, have been intensively investigated as building blocks for optoelectronic devices in the past few years. Very recently, significant efforts have been devoted to the improvement of the optoelectronic performances of 2D materials, which are restricted by their intrinsically low light absorption due to the ultrathin thickness. Making use of the plasmonic effects of metal nanostructures as well as intrinsic plasmon excitation in graphene has been shown to be one of the promising strategies. In this minireview, recent progresses in 2D material-based optoelectronics enabled by the plasmonic effects are highlighted. A perspective on more possibilities in plasmon-assisted 2D material-based optoelectronic applications will also be provided.
关键词： Transition metal dichalcogenides,Plasmonic effects,Two-dimensional materials,Black phosphorus,Hexagonal boron nitride,Graphene,Optoelectronic devices
更新于2025-09-19 17:13:59
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Surface-Controlled Crystal Alignment of Naphthyl End-Capped Oligothiophene on Graphene: Thin-Film Growth Studied by <i>In Situ</i> X-ray Diffraction
摘要： We report on the microstructure, morphology, and growth of 5,5′-bis(naphth-2-yl)-2,2′-bithiophene (NaT2) thin films deposited on graphene, characterized by grazing-incidence X-ray diffraction (GIXRD) and complemented by atomic force microscopy (AFM) measurements. NaT2 is deposited on two types of graphene surfaces: custom-made samples where CVD-grown graphene layers are transferred onto a Si/SiO2 substrate by us and common commercially transferred CVD graphene on Si/SiO2. Pristine Si/SiO2 substrates are used as a reference. The NaT2 crystal structure and orientation depend strongly on the underlying surface, with the molecules predominantly lying-down on the graphene surface (face-on orientation) and standing nearly out-of-plane (edge-on orientation) on the Si/SiO2 reference surface. Post growth GIXRD and AFM measurements reveal that the crystalline structure and grain morphology differ depending on whether there is polymer residue left on the graphene surface. In situ GIXRD measurements show that the thickness dependence of the intensity of the (111) reflection from the crystalline edge-on phase does not intersect zero at the beginning of the deposition process, suggesting that an initial wetting layer, corresponding to 1-2 molecular layers, is formed at the surface-film interface. By contrast, the (111) reflection intensity from the crystalline face-on phase grows at a constant rate as a function of film thickness during the entire deposition.
关键词： surface-controlled alignment,molecular orientation,conjugated oligomers,GIXRD,small π-conjugated molecules,two-dimensional materials
更新于2025-09-19 17:13:59
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Controlled polymer crystal/two-dimensional material heterostructures for high-performance photoelectronic applications
摘要： Controlled polymer crystal/two-dimensional material heterostructures for high-performance photoelectronic applications
关键词： epitaxy,epitaxial interaction,semiconducting polymer,graphene,crystal interaction,transition-metal dichalcogenide,ferroelectric polymer,two-dimensional materials
更新于2025-09-19 17:13:59
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Visible to Near-Infrared Photodetector Based on Graphene-MoTe2-Graphere Heterostructure
摘要： Graphene and transition metal dichalcogenides (TMDs) are widely investigated two dimensional materials in recent years. As a member of the TMDs family, MoTe2 possesses a suitable bandgap of ~1.0 eV for near infrared (NIR) photodetection. Here we stacked the MoTe2 flake with two graphene flakes of high carrier mobility to form a graphene-MoTe2-graphene heterostructure. It exhibits high photo-response to a broad spectrum range from 500 nm to 1300 nm. The photoresponsivity was calculated to be 1.6 A/W for the 750 nm light under 2 V/0 V drain-source/gate bias, and 154 mA/W for the 1100 nm light under 0.5 V/60 V drain-source/gate bias. Besides, the polarity of the photocurrent under zero Vds can be efficiently tuned by the back gate voltage to satisfy different applications. Finally, we fabricated a vertical graphene-MoTe2-graphene heterostructure photodetector which showed improved photoresponsivity of 3.3 A/W toward visible light.
关键词： photodetector,graphene,TMDs,van der Waals heterostructure,two-dimensional materials
更新于2025-09-19 17:13:59
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Junctions between two-dimensional plasmonic waveguides in the presence of retardation
摘要： Plasmons in two-dimensional (2D) waveguides are traditionally analysed within the electrostatic approximation, which assumes that the plasmon phase velocity is much smaller than the velocity of light. However, novel effects have recently been demonstrated for plasmons whose velocity is comparable to the velocity of light. In this retardation regime, electrostatic models are inaccurate. For a junction between two plasmonic waveguides, we present an analytical and a numerical model both valid in the retardation regime and compare them to an electrostatic model. We quantify the re?ected and transmitted powers and the radiation loss in several scenarios. We found that power is radiated from a junction at the expense of the power of the re?ected plasmon, but retardation has little effect on the phases of the re?ected and transmitted plasmons. The radiation loss is typically below several percent when the plasmon velocities are ?ve or more times below the light velocity. However, radiation still persists for slower plasmon velocities for a junction between a 2D waveguide and a perfectly conducting sheet. As a result, retardation is expected to degrade the quality factors of plasmonic resonators without affecting their eigenfrequencies.
关键词： waveguide junctions,plasmonic waveguides,two-dimensional materials,plasmon
更新于2025-09-19 17:13:59
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Epitaxial growth and characterization of high quality Bi<sub>2</sub>O<sub>2</sub>Se thin films on SrTiO<sub>3</sub> substrates by pulsed laser deposition
摘要： Recently, Bi2O2Se is discovered as a promising two-dimensional (2D) semiconductor for next generation electronics, due to its moderate bandgap size, high electron mobility and pronounced ambient stability. Meanwhile, it has been predicted that high quality Bi2O2Se-related heterostructures may possess exotic physical phenomena, such as piezoelectricity and topological superconductivity. Herein, we report the first successful heteroepitaxial growth of Bi2O2Se films on SrTiO3 substrates via pulsed laser deposition (PLD) method. Films obtained under optimal conditions show an epitaxial growth with the c axis perpendicular to the film surface and the a and b axes parallel to the substrate. The growth mode transition to three dimensional (3D) island is observed as prolonging deposition time of films. The maximum value of electron mobility reaches 160 cm2/V-1s-1 at room temperature in a 70 nm-thick film. The thickness dependent mobility provides evidence that interface-scattering is likely to be the limiting factor for the relatively low electron mobility at low temperature, implying that the interface engineering as an effective method to tune the low temperature electron mobility. Our work suggests the epitaxial Bi2O2Se films grown by PLD are promising for both fundamental study and practical applications.
关键词： Bi2O2Se,pulsed laser deposition,heterostructure,high mobility,two-dimensional materials
更新于2025-09-16 10:30:52
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Recent advances in carbon quantum dot (CQD)-based two dimensional materials for photocatalytic applications
摘要： CQDs are a new class of carbon material with ultrafine sizes and readily tunable optical properties, which make them extremely intriguing. CQDs have gained widespread attention due to their potential and versatility, and they can be applied in many different fields. One of their many applications is photocatalysis, which has garnered incessant research interest in recent years. State-of-the-art technology utilizes sustainable solar energy, which is both clean and virtually inexhaustible. To date, the photocatalytic performance of CQDs in their raw form is still far from ideal. Nevertheless, they can be substantially enhanced through several modification techniques. In this review, strategies to improve the photocatalytic performance of CQDs, such as size-tuning, surface passivation and functionalization, and elemental doping, are extensively discussed. The review also covers the latest advances in the use of CQDs in photocatalysis to address both environmental and energy-related issues. Particular emphasis is placed on the formation of 0D/2D heterojunction nanocomposites with several 2D materials, such as graphene, graphitic carbon nitride, metal oxides and metallates, metal oxyhalides, transition metal oxides and chalcogenides. The hybridization routes to binary nanocomposites, and their photocatalytic application to carbon dioxide reduction, hydrogen production, and dye and pollutant degradation, are thoroughly reviewed in this paper.
关键词： Two-dimensional materials,Photocatalysis,Energy generation,Carbon quantum dots,Environmental remediation,Heterojunction nanocomposites
更新于2025-09-16 10:30:52
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High Sensitivity Hybrid PbS CQD-TMDC Photodetectors up to 2 μm
摘要： Recent approaches to develop infrared photodetectors characterized by high sensitivities, broadband spectral coverage, easy integration with silicon electronics, and low cost have been based on hybrid structures of transition metal dichalcogenides (TMDCs) and PbS colloidal quantum dots (CQDs). However, to date, such photodetectors have been reported with high sensitivity up to 1.5 μm. Here we extend the spectral coverage of this technology toward 2 μm, demonstrating for the ?rst time compelling performance with responsivities 1400 A/W at 1.8 μm with 1 V bias and detectivities as high as 1012 Jones at room temperature. To do this, we studied two TMDC materials as a carrier transport layer, tungsten disul?de (WS2), and molybdenum disul?de (MoS2) and demonstrate that WS2-based hybrid photodetectors outperform those of MoS2 due to a more adequate band alignment that favors carrier transfer from the CQDs.
关键词： quantum dots,tungsten sul?de,infrared photodetectors,lead sul?de,molybdenum sul?de,two-dimensional materials
更新于2025-09-16 10:30:52