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Substrate Temperature Dependence of the Properties of Single-layer MoS2 Film deposited by Using Pulsed Laser Deposition
摘要： Single-layer MoS2 ?lms were deposited on sapphire substrates by using pulsed laser deposition. The substrate temperature dependence of the structural, optical and photoluminescence properties of single-layer MoS2 ?lms was investigated. An increased substrate temperature improved the surface morphology and the crystal quality of the MoS2 ?lms. Moreover, the absorption and the photoluminescence properties of the MoS2 ?lms were enhanced. In addition, the mechanism underlying the e?ect of substrate temperature on the properties of single-layer MoS2 ?lms is discussed.
关键词： Optical properties,Substrate temperature,Crystal quality,Single-layer MoS2 ?lm,Photoluminescence properties
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Composite Material Antiresonant Fibre Optical Modulator with >3DB Depth
摘要： Anti-resonant fibres (ARFs) are of significant interest for state of the art photonic technologies. Mode guidance is largely confined to the air core, demonstrating very low optical losses [1]. Furthermore, their internal structure offers a large surface area and is thus ideal as a deposition template for the addition of novel functional materials which would be able to alter their waveguide properties. We have previously demonstrated that the deposition of thin silicon layers onto the inner regions of an ARF results in strong light-matter interaction [2]. In this work, we utilise this interaction to externally control the optical properties of the composite material ARF (CM-ARF). Here, 2D layers of MoS2 were deposited on the inner (cladding) regions of the ARF as shown in Fig. 1(a). MoS2 is a Transition Metal Dichalcogenide (TMDC) 2D material that exhibits many optoelectronic phenomena such as the electro-absorptive effect [3]. Although there are already a number of examples in which TMDCs are incorporated into optical fibre systems to exploit the third order optical nonlinearity of the material to create saturable absorbers [4], this requires large amounts of power to be absorbed by the film, which is usually placed on the end face of a fibre. In contrast, here we show clear modulation at very low power.
关键词： Electro-absorptive effect,MoS2,Composite material ARF,Anti-resonant fibres,Optical modulation
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Excitonic Effects in Single Layer MoS <sub/>2</sub> Probed by Broadband Two-Dimensional Electronic Spectroscopy
摘要： Atomically thin Transition-metal dichalcogenides (TMDs) have come into the spotlight in optoelectronics thanks to their outstanding physical properties. In single-layer (1L) TMDs strong quantum confinement effects cause a weak screening of Coulomb, so that the excitons created by photo-excitation have large binding energy, up to several hundred meVs. While the steady-state properties of TMDCs have been studied in detail by linear optical techniques, the recent application of time-resolved nonlinear spectroscopy (mainly ultrafast pump-probe) has enabled the study of excited-state dynamics on femtosecond timescales opening up questions about the mechanisms of exciton relaxations and exciton-exciton interactions. Among TMDs, the spectrum of 1L MoS2 is characterized by two peaks of excitonic nature in the visible spectral region (1.9 eV and 2.05 eV), the so-called A and B excitons. They arise from optical transitions between the spin?orbit split top valence band and the bottom conduction band, around K and K’. Here we use two-dimensional electronic spectroscopy (2DES) to track the sub-ps excitonic interactions within 1L MoS2. We report 2DES measurements obtained on a chemical vapor deposition grown 1L MoS2 sample, at 77K, using sub 20-fs broadband pulses. Thanks to its unique combination of high temporal and spectral resolution, 2DES provides a series of excitation/detection correlation energy maps at different delays T, simultaneously covering the A and B excitons.
关键词： excitonic effects,MoS2,Transition-metal dichalcogenides,two-dimensional electronic spectroscopy
更新于2025-09-12 10:27:22
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Integration of MoS <sub/>2</sub> with InAlAs/InGaAs Heterojunction for Dual Color Detection in Both Visible and Near‐Infrared Bands
摘要： At present, dual-channel or even multi-channel recording is a developing trend in the field of photodetection, which is widely applied in environment protection, security, and space science and technology. This paper proposes a novel MoS2/InAlAs/InGaAs n–i–n heterojunction phototransistor by integrating multi-layered MoS2 with InGaAs-based high electron mobility transistors (InGaAs-HEMTs). Due to the internal photocurrent amplification in the InGaAs channels with a narrow energy bandgap of 0.79 eV, this device exhibits high photoresponsivity (R) of over 8 × 105 A W–1 under near-infrared illumination of 1550 nm at 500 pW. Furthermore, with the combination of the photoconductance effect in the vertical MoS2/InAlAs/InGaAs n–i–n heterojunction and the photogating effect in the lateral phototransistor, this device possesses a unique characteristic under visible illumination that its photoresponsivity can be tuned by the top gate electrode from 6 × 105 A W–1 to -4 × 105 A W–1 by gate voltage. This may lead to a new application as an optically controlled electronic inverter, which needs further study in depth. This MoS2/InAlAs/InGaAs phototransistor builds up a new bridge between 2D materials and conventional ternary compounded semiconductor devices.
关键词： MoS2/InAlAs/InGaAs van der Waals heterojunction,gate-tunable negative/positive responsivity,dual-band photodetection,2D electron gas
更新于2025-09-11 14:15:04
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Controlled Synthesis of Ni‐doped MoS2 Hybrid Electrode for Synergistically Enhanced Water‐Splitting Process
摘要： The development of high-efficiency, low cost, and earth abundant electrocatalysts for overall water splitting remains challengeable. In this work, we present the nickel (Ni) modified MoS2 hybrid catalysts grown on carbon cloth (Ni-Mo-S@CC) through a one-step hydrothermal treatment. The optimized Ni-Mo-S@CC catalyst shows excellent HER activity with low overpotentials of 168 mV at a current density of 10 mA cm?2 in 1.0 M KOH, which is lower than those of Ni-Mo-S@CC (1:1), Ni-Mo-S@CC (3:1) and pure MoS2. Significantly, the Ni-Mo-S@CC hybrid catalyst also displays outstanding OER activity with a low overpotential of 320 mV at a current density of 10 mA cm?2, and the remarkable long-term stability for 30 hours at a constant current density of 10 mA cm-2. Experimental and theoretical analysis based on density functional theory demonstrate that the excellent electrocatalytic performance is mainly attributed to remarkable conductivity, abundant active sites and synergistic effect of Ni-doped MoS2. This work sheds light on a unique strategy to design high performance and stable electrocatalysts for water splitting electrolyzers.
关键词： MoS2,nanocomposite,electrocatalysis,doping,water splitting
更新于2025-09-11 14:15:04
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MoS <sub/>2</sub> Quantum Dots Modified Black Ti <sup>3+</sup> –TiO <sub/>2</sub> /g‐C <sub/>3</sub> N <sub/>4</sub> Hollow Nanosphere Heterojunction toward Photocatalytic Hydrogen Production Enhancement
摘要： The MoS2 quantum dots (QDs) modified black Ti3+–TiO2/g-C3N4 hollow nanosphere heterojunction is synthesized via the continuous chemical template deposition and sculpture–reduction processes. The results of structural characterizations imply that the Ti3+–TiO2/g-C3N4/MoS2 QDs hollow nanosphere heterojunction is prepared successfully. The photocatalytic hydrogen evolution reaction (HER) of the B-TiO2/g-C3N4/MoS2 QDs (≈1524.37 μmol g?1 h?1) exhibits an enhancement of ≈33 folds compared with the normal TiO2. Furthermore, the process of photocatalysis and the mechanism of photocatalytic HER enhancement are explored, which can be ascribed to the HER activity sites of MoS2 QDs, Ti3+/Ov ions in the Ti3+–TiO2, and hollow nanosphere heterojunction, which are proved by electrochemical measurements.
关键词： MoS2 quantum dots,photocatalytic hydrogen production,heterojunction,black Ti3+–TiO2
更新于2025-09-11 14:15:04
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MoS2 hybrid heterostructure thin film decorated with CdTe quantum dots for room temperature NO2 gas sensor
摘要： MoS2 hybrid heterostructure thin film decorated with CdTe quantum dots for room temperature NO2 gas sensor
关键词： Hybrid heterostructure,Sputtering,NO2 gas sensor,CdTe/MoS2 thin film
更新于2025-09-11 14:15:04
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Reversible PL Tuning by Defect Passivation via Laser Irradiation on Aged Monolayer MoS2
摘要： Atomically thin (1L) MoS2 emerged as a direct band gap semiconductor with potential optical applications. The photoluminescence (PL) of 1L-MoS2 degrades due to aging related defect formation. The passivation of these defects leads to substantial improvement in optical properties. Here we report the enhancement of PL on aged 1L-MoS2 by laser treatment. Using photoluminescence and Raman spectroscopy in a controlled gas environment, we show the enhancement is associated with efficient adsorption of oxygen on existing sulfur vacancies preceded by removal of adsorbates from the sample’s surface. Oxygen adsorption depletes negative charges, resulting in suppression of trions and improved neutral exciton recombination. The result is a 6-8 fold increase in PL emission. The laser treatment in this work does not cause any measurable damage to the sample as verified by Raman spectroscopy, which is important for practical applications. Surprisingly, the observed PL enhancement is reversible by both vacuum and ultrafast femtosecond excitation. While the former approach allows switching a designed micro pattern on the sample ON and OFF, the latte provides a controllable mean for accurate PL tuning, which is highly desirable for optoelectronic and gas sensing applications.
关键词： Raman,Exciton,Laser Annealing,Oxygen,Photoluminescence,Reversible Defect passivation,MoS2
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Direct Laser Synthesis of Two-Dimensional Transition Metal Dichalcogenides
摘要： The emergence of nanomaterials with their often superior mechanical, electronic and optical properties compared with bulk form demands a robust technology that can synthesize, modify and pattern scalably and cost effectively. This can be fulfilled via laser processing protocols which produce such materials with both high precision and excellent spatial controllability [1]. Direct laser synthesis of nanomaterials such as graphene and nano-structured metal oxides have been explored thoroughly for a wide range of applications [2,3]. However, to date, there are only a few reports associated with the laser processing of two-dimensional transition metal dichalcogenides (2D-TMDCs) [4]. These mainly utilize laser radiation for thinning TMDC films through sublimation down to a single molecular thickness [1]. However, this top-down approach is not practical for large- area and scalable production. In addition, further processing steps such as lithographic patterning are then required for discrete device fabrication. Here we present a novel method for the local synthesis and patterning of two-dimensional MoS2 and WS2 layers. The synthesis of these materials is achieved by spatially selective, visible laser irradiation of suitable precursors coated on the surface of planar substrates under ambient, room temperature conditions. The non- exposed precursor regions are then completely removed in a single step, revealing the synthesised 2D-TMDCs. This method can produce micro-patterned films with lateral dimensions that approach the diffraction limit of the focused laser beam. An example of such laser synthesised MoS2 tracks can be seen in the optical microscopy image of Figure 1(a) where it clearly shows a well-defined micro-pattern without any precursor residue. Using this method, we have achieved local synthesis of of MoS2 and WS2 with thickness down to three molecular layers for MoS2 and monolayer WS2 on various glass and crystalline substrates. The quality and thickness of the resulting films can be tuned by modifying the precursor chemistry and laser parameters. Different microprobe and spectroscopic spectroscopy, photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS) have been used to assess the quality and thickness of the deposited MoS2 and WS2 structures. Finally, we have demonstrated the electronic functionality of our films by fabricating a thin film transistor (TFT). The transfer characteristics (source-drain current vs gate voltage) of such a TFT using a laser-synthesised MoS2 channel is shown in Figure 1(b).
关键词： Two-Dimensional Transition Metal Dichalcogenides,WS2,MoS2,Direct Laser Synthesis,Thin Film Transistor
更新于2025-09-11 14:15:04
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High-speed heterojunction photodiodes made of single- or multiple-layer MoS2 directly-grown on Si quantum dots
摘要： Recently, chemical vapor deposition-grown molybdenum disulfide (MoS2) has been actively employed for MoS2/Si-wafer heterojunction (HJT) photodetectors due to the attractive optoelectronic properties. However, the MoS2/Si HJT is not so advantageous in that it exhibits low photoresponse due to the low light absorption despite the simple device structure. In addition, there is a limitation in achieving high-quality MoS2 films due to the defects at the MoS2/Si interface developed during the transfer of the MoS2 films to the target substrate, resulting from the restriction of the direct growth on the Si wafer. Here, we first report successful direct growth of single- and multi-layer MoS2 films on Si quantum dots (SQDs) multilayers (MLs) embedded SiO2 (SQDs:SiO2 MLs) substrates. The multilayer MoS2/SQDs HTJ photodiodes show response speed of rise time: ~60 ns/fall time: ~756 ns, highest than ever achieved, and detectivity of 6.1 x 10^13 cm Hz^1/2 W^-1. This excellent performance can be attributed to well formation of the HJT at the MoS2/SQDs:SiO2 interface by the direct growth, resulting in the reduction of the defects, thereby facilitating the carrier transport, and high light absorptivity of the SQDs:SiO2 MLs.
关键词： MoS2,Heterojunction,Photodiode,Si quantum dot,Response speed,Direct growth
更新于2025-09-11 14:15:04