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Photoresponse of wafer-scale palladium diselenide films prepared by selenization method
摘要： Palladium diselenide (PdSe2) films exhibit a high charge carrier mobility and sensitivity in photodetection. In this work, wafer-scale PdSe2 thin films with controllable thickness have been synthesized by the selenization of Pd films. A PdSe2-based photodetector can detect a broad wavelength ranging from 420 nm to 1200 nm. The responsivity and detectivity can reach 1.96 × 103 A W-1 and 1.72 × 1010 W / Hz1/2 at VSD = 3 V, respectively. The figure of merit of the photodetection are comparable to the mechanically exfoliated PdSe2 based photodetector. This work demonstrated that selenization is a facile method to synthesize PdSe2 films in large scale and the films are promising for broadband photodetection.
关键词： palladium diselenide,field effect transistors,two-dimensional layered material,photodetection
更新于2025-09-16 10:30:52
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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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[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) - Experimental Realization of Two-Dimensional PT-Symmetric Graphene: Bulk Properties and Edge States
摘要： The condition of real eigenvalue spectra in quantum mechanics is usually met by requiring operators to be Hermitian. This perception was challenged in 1988 by Carl M. Bender and Stefan Boettcher, who showed that parity-time (PT) symmetric Hamiltonians can have real spectra as well [1]. In photonics this concept was adopted by designing gain and loss structures for electromagnetic waves [2]. While numerous hallmark features [2] could be verified, experiments remained limited to one-dimensional settings. In this work we overcome this limitation and demonstrate a two-dimensional PT-symmetric system of photonic waveguides. We use this structure to study the interplay between a PT-phase transition and the emergence of topological edge states.
关键词： photonic waveguides,PT-symmetry,two-dimensional systems,topological edge states
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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A pre-solution mixing precursor method for improving the crystallization quality of perovskite films and electroluminescence performance of perovskite light-emitting diodes
摘要： Quasi-two-dimensional (Q-2D) perovskites are one kind of efficient luminescent material with fast energy transfer and radiative decay of excitons due to the energy cascade formed by the mixed perovskite phase. However, the existence of monolayer or bilayer nanosheets in the Q-2D perovskite film results in poor charge transport, high trap density and rough film surface because of the high ratio of ligands, which leads to poor performance of Q-2D perovskite light-emitting diodes (PeLEDs). Herein, we proposed a new strategy of a pre-solution mixing (PSM) precursor to inhibit the formation of ultrathin perovskite nanosheets, which significantly enhanced the charge carrier mobility, reduced the concentration of defects and improved the film morphology. The PeLEDs based on the PSM precursor achieved the maximum luminescence of 7832.1 cd m?2 (～218% enhancement) and the peak current efficiency of 6.0 cd A?1 (～131% enhancement). By introducing mixed cations in the PeLED, the maximum brightness of 14 211.0 cd m?2 and current efficiency of 14.6 cd A?1 were realized, demonstrating the generality of our PSM method for the preparation of high performance PeLEDs.
关键词： charge transport,pre-solution mixing,Quasi-two-dimensional perovskites,film morphology,light-emitting diodes
更新于2025-09-16 10:30:52
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Graphene Photonics || Electronic Properties
摘要： The ?ow of free charge carriers, i.e., electrons in the conduction band or holes in the valence band, in a semiconductor that is subject to an electric ?eld is accelerated by the electric field but is hindered by scattering events. In a semiconductor, free carriers accelerate in the presence of an electric field. The randomly distributed scattering centers, such as impurities and defects, act as a counter force that decelerates and de?ects the carriers. When the steady state is eventually reached under a constant electric field, a constant ?ow of carriers is achieved. In graphene, by contrast, charge carriers on the Dirac cone have a constant speed and do not accelerate or decelerate in response to the electric field or the scattering centers; instead, the effect of the electric field is rather to align the motion of carriers to the direction of the electric field, and the scattering centers act as a source to disturb this alignment process. This process is well captured by the Boltzmann transport equation, which has successfully described many statistical behaviors of carriers in metals and semiconductors. The purpose of this chapter is to describe the electronic properties of graphene, starting from the Boltzmann transport equation.
关键词： Boltzmann transport equation,charge carriers,electric field,electronic properties,conductivity,scattering events,graphene,two-dimensional material
更新于2025-09-16 10:30:52
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Light-controlled two-dimensional TiO <sub/>2</sub> plate micromotors
摘要： In this work, UV light-controlled two-dimensional (2D) TiO2 plate micromotors are demonstrated for the first time. The 2D TiO2 micromotors are produced by the well-known anodic oxidation method in combination with a cracking and separation process. When the motor is placed in H2O2 aqueous solution under UV irradiation, oxygen bubbles are generated in the holes of the TiO2 membrane. The 2D micromotor thus moves upon O2 bubbles under its own weight. In contrast to bubble-propelled micromotors, which require an addition of surfactants to chemical fuels, the 2D micromotor is capable of moving in aqueous H2O2 solution without surfactants. Moreover, speed of the 2D TiO2 micromotor can be controlled by the intensity of the UV light. Such surfactant-free micromotors and their facile fabrication hold considerable promise for diverse practical applications in the biomedical and energy fields, for example, and in new materials.
关键词： two-dimensional TiO2 plate micromotors,UV light-controlled,anodic oxidation method,energy fields,surfactant-free,biomedical applications
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Two-Dimensional Mixed Lead-Tin Halide Perovskites for Visble Light-Emitting Diodes
摘要： Lead halide perovskites as a new generation of outstanding semiconductor materials have attracted considerable attention. The excellent optical properties and emission qualities makes this kind of materials suitable for light emitting diodes (LED). However, the toxicity of lead limits large-scale industrial production. Here, we report the gradual reduction of lead content in two-dimensional perovskites by substituting lead with non-toxic tin for preparation of two-dimensional perovskites light-emitting diodes (PeLEDs) with different tin-lead ratios. Among these devices, the lead-free PeLEDs exhibits electroluminescence at 615 nm with peak luminance of 117 cd/m2 and maximum external quantum efficiency (EQE) of 0.18%.
关键词： Mixed lead-tin halide perovskites,light-emitting diodes,two-dimensional
更新于2025-09-16 10:30:52
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Speckle reduction by employing two green lasers and two-dimensional vibration of lenses
摘要： A method of speckle reduction suitable for use in a laser projector was proposed in the paper. Speckle contrast ratio (SCR) reduction was achieved by combining wavelength diversity and angular diversity methods. First, wavelength diversity was demonstrated by the use of two green laser sources (a 520 nm laser diode (LD) and a 532 nm diode-pumped solid-state (DPSS) laser) at a power ratio of 4:1. Second, angular diversity was achieved via the vibration of two lenses in two orthogonal directions placed directly after the laser source. The vibrating lenses are small and do not require changes to the beam path of the laser source, allowing for more compact projector designs. The frequency of vibration of these lenses was optimized to minimize the SCR in the output image. A SCR of less than 4% was achieved without the use of optical diffusers, which significantly reduces optical losses. Optical transmission could be further increased with the optimization of optical coatings on the lenses. This result shows great promise for applications such as laser pico-projectors within the realm of heads-up displays (HUDs) and mobile devices.
关键词： two-dimensional vibration of lenses,speckle reduction,mini-/pico-projectors
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