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- 摘要
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- 实验方案
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Phasea??Controlled Synthesis of Monolayer W <sub/>1a??</sub><i> <sub/>x</sub></i> Re <i> <sub/>x</sub></i> S <sub/>2</sub> Alloy with Improved Photoresponse Performance
摘要： Tuning bandgap and phases in the ternary 2D transition metal dichalcogenides (TMDs) alloys has opened up unexpected opportunities to engineer optoelectronic properties and explore potential applications. In this work, a salt-assisted chemical deposition vapor (CVD) growth strategy is reported for the creation of high-quality monolayer W1?xRexS2 alloys to fulfill a readily phase control from 1H to DT by changing the ratio of Re and W precursors. The structures and chemical compositions of doping alloys are confirmed by combining atomic resolution scanning transmission electron microscopy-annular dark field imaging with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy, matching well with the calculated results. The field-effect transistors (FETs) devices fabricated based on 1H-W0.9Re0.1S2 monolayer exhibit a n-type semiconducting behavior with the mobility of 0.4 cm2 V?1 s?1. More importantly, the FETs show high-performance responsivity with a value of 17 μA W?1 in air, which is superior to that of monolayer CVD-grown WS2. This work paves the way toward synthesizing monolayer ternary alloys with controlled phases for potential optoelectronic applications.
关键词： W1?xRexS2 alloys,phase transition,ternary TMDs,chemical vapor deposition,photoresponsivity
更新于2025-09-23 15:19:57
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CVD preparation of vertical graphene nanowalls/VO2 (B) composite films with superior thermal sensitivity in uncooled infrared detector
摘要： Vanadium dioxide with superior thermal sensitivity is one of the most preferred materials used in microbolometer, and the B phase of VO2 is particularly prominent. However, conventional VO2 (B) undergoes low temperature-coefficient of resistance (TCR) values and large resistances. In this paper, simple controllable composite films of vertical graphene nanowalls/VO2 (B) (i.e., VGNWs/VO2 (B)) with a suitable square resistance (12.98 k?) and a better temperature-coefficient of resistance (TCR) (-3.2 %/K) were prepared via low pressure chemical vapor deposition. The VGNWs can provide a fast channel for electron transport and enhance the conductivity of VO2 (B). This preparation method can provide a low cost, facile and simple pathway for the design and fabrication of high performance VO2 (B) thin films with superior electrical properties for its application in uncooled infrared detectors.
关键词： Chemical vapor deposition,VO2 (B) films,Vertical graphene nanowalls,Uncooled infrared detectors
更新于2025-09-23 15:19:57
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Characterization of Epitaxial ?2-(Al,Ga,In)2O3-Based Films and Applications as UV Photodetectors
摘要： Epitaxial ?lms of b-(AlxGa1?x)2O3, b-Ga2O3, and b-(InxGa1?x)2O3 were grown on (001) sapphire substrates via metalorganic chemical vapor deposition (MOCVD). The compositions of the ?lms as determined from energy dispersive x-ray analysis (EDX) and x-ray photoelectron spectroscopy (XPS) results were XAl = 0.57 ± 0.05 and 0.76 ± 0.05 and XIn = 0.12 ± 0.05 and 0.21 ± 0.05. The optical bandgap was found to correspondingly vary between 6.0 ± 0.2 and 3.9 ± 0.1 eV, as a function of composition via XPS and UV–visible spectroscopy (UV–Vis). X-ray diffraction, scanning electron microscopy, and atomic force microscopy revealed the ?lms to be highly-oriented with nanocrystalline domains. Schottky- and MSM-based solar-blind UV photodetectors were fabricated on the ?lms and showed responsivities at 20 V varying from > 104 A/W for the Ga2O3 devices, > 103 A/W for the (AlxGa1?x)2O3 devices and > 102 A/W for the (InxGa1?x)2O3 devices. Modest shifts in wavelength selectivity corresponding with the changes in composition/bandgap were also measured. Time response measurements on Schottky and MSM detectors reveal rise and dwell times on the order of a minute, indicating the presence of photoconductive gain. Noise-equivalent powers were in the fW–pW regime with speci?c detectivities (D?) between 1010 and 1012 Jones. Scanning photocurrent maps display large photocurrent generation at the Schottky interface in the case of a b-Ga2O3 Schottky detector, whereas for an b-(InxGa1?x)2O3 MSM detector the photocurrent generation occurs in the device channel and at the Schottky interface.
关键词： b-(AlxGa1?x)2O3,b-(InxGa1?x)2O3,b-Ga2O3,Metalorganic chemical vapor deposition
更新于2025-09-23 15:19:57
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Growth mechanism of porous 3Ca??SiC films prepared via laser chemical vapor deposition
摘要： Porous SiC film is an excellent electrode material for robust micro-supercapacitors used in extremely harsh environments. In one of our previous studies, porous 3C–SiC film with high areal capacitance and high deposition rate was prepared via laser chemical vapor deposition (LCVD). However, it is still urgent to explore the formation mechanism of porous structures using LCVD. In this study, the microstructure of the porous cubic SiC film prepared via LCVD was analyzed in detail using scanning and transmission electron microscopy techniques. The growth mechanism of the deposits has been proposed according to the “growth competing theory” and “shadow effect theory.”
关键词： Growth mechanism,Porous 3C–SiC film,Microstructure,Laser chemical vapor deposition (LCVD)
更新于2025-09-23 15:19:57
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Eye safe emission in Tm3+/Ho3+ and Yb3+/Tm3+ co-doped optical fibers fabricated using MCVD-CDS system
摘要： The RE-co-doped silica optical fibers emitting in the eye-safe spectral range are still attractive for new applications like LIDAR, pollution monitoring, navigation, and free-space optical communication. High gain and beam quality of fiber sources based on large mode area (LMA) active fibers can be fabricated by the well-known Modified Chemical Vapor Deposition (MCVD) technology improved by the chelate doping system. Considering silica matrix, the most interesting co-dopants in the region above 1400 nm are thulium and holmium. In the paper Tm3t/Ho3t and Yb3t/Tm3t co-doped silica optical fibers (refractive index and rare earth distribution profile, luminescence) are presented. Their respective emission spectra has been measured over the range 1550–2150 nm for Tm3t/Ho3t (exc. at 796 nm) and 1600–2100 nm for Yb3t/Tm3t (exc. at 976 nm). A wide luminescent spectrum has been recorded from RE co-doping of silica glass during the MCVD process and we were able to achieve the appropriate and uniform concentration for getting the conditions of energy transfer. The fabrication and characterization of Tm3t/Ho3t and Yb3t/Tm3t co-doped optical fibres are presented. The analysis of luminescence spectrum changes vs. fibre length has shown that there is Amplified Spontaneous Emission (ASE) at 1960 nm in Yb3t/Tm3t co-doped optical fibre. The possibilities of obtaining novel constructions of RE co-doped optical fibers for eye-safe emission region will be also shown.
关键词： Modified chemical vapor deposition (MCVD),Optical fibers,Lanthanides,Eye-safe emission
更新于2025-09-23 15:19:57
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Sustained and Controlled Release of Volatile Precursors for Chemical Vapor Deposition of Graphene at Atmospheric Pressure
摘要： Precursors and catalysts play vital roles in chemical reactions. Considerable efforts have been devoted to the investigation of catalysts for graphene growth by chemical vapor deposition in recent years. However, the research on precursors has been hardly accomplished because of the lack of innovation in controllable feeding method. Herein, we present a novel sustained and controlled release approach, and develop a convenient, safe, and potentially scalable feeding system with the assistance of matrix materials and a simple portable feeder. As a result, a highly volatile liquid precursor can be accurately fed to grow large-area, uniform graphene films with optimal properties. This feeding approach will further benefit the synthesis of other two-dimensional materials from various precursors.
关键词： controlled release,chemical vapor deposition,graphene,carbon source
更新于2025-09-23 15:19:57
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Effects of alkali and transition metal-doped TiO <sub/>2</sub> hole blocking layers on the perovskite solar cells obtained by a two-step sequential deposition method in air and under vacuum
摘要： Planar perovskite solar cells (PPSCs) have received great attention in recent years due to their intriguing properties, which make them a good choice for photovoltaic applications. In this work, the effect of alkali and transition metal-doped TiO2 (cesium-doped TiO2 (Cs-TiO2) and yttrium-doped TiO2 (Y-TiO2)) compact layers on the optical, structural and the photovoltaic performance of the PPSCs have been investigated. The perovskite layer syntheses were carried out by depositing a lead iodide (PbI2) layer via spin-coating; converting PbI2 into methyl ammonium iodide (CH3NH3PbI3) by chemical vapor deposition (CVD) and spin-coating at 60 min and 60 s conversion times respectively. The as-deposited PPSCs were studied layer-by-layer using an X-ray diffractometer, scanning electron microscope, and UV-vis diffuse reflectance, transmittance and absorbance. The power conversion efficiency for stable processed perovskite solar cells were 3.61% and 12.89% for air and vacuum processed, respectively.
关键词： TiO2 doping,Chemical vapor deposition,Perovskite solar cells,Spin-coating,Photovoltaic performance
更新于2025-09-23 15:19:57
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Self-powered ultra-broadband and flexible photodetectors based on the bismuth films by vapor deposition
摘要： Bismuth (Bi), as a topological semi-metallic material, has received widespread attention on account of its fascinating properties. Here, Bi films were successfully grown through a direct and facile vapor deposition method on 300 nm SiO2/Si (SiO2) and polyimide (PI) substrates. The Bi films were utilized further to fabricate rigid and flexible photodetectors. The rigid photodetector based on Bi/SiO2 show fast, highly stable, self-powered, and ultra-broadband photoresponses. The flexible Bi/PI photodetector exhibits durability and reproducibility in photoresponse behaviors under bending with various curvature radius and after hundreds of bending cycles. Our results demonstrated that the Bi films by vapor deposition have great application potentials in next generation of optoelectronic devices.
关键词： flexible,vapor deposition,ultra-broadband,self-powered,photodetector,Bi films
更新于2025-09-23 15:19:57
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Rational Control of WSe<sub>2</sub> Layer Number via Hydrogen-Controlled Chemical Vapor Deposition
摘要： Transition metal dichalcogenides are a promising family of materials for electronics and optoelectronics, in part due to their range of bandgaps that can be modulated by layer number. Here, we show that WSe2 can be selectively grown with one, two, or three layers, as regulated by a one-step hydrogen-controlled chemical vapor deposition (H-CVD) process involving cyclical pulses of H2 flow. The physical and vibrational properties of the resulting mono-, bi-, and tri-layer WSe2 films are characterized by atomic force microscopy and Raman spectroscopy. Modifying the H-CVD process to include more than three H2 pulses results in thicker WSe2 films, however the thickness of these films is not well controlled and feature small, bulk-like pyramidal islands. Transmission electron microscopy analysis reveals that most of these islands exhibit a spiral structure and appear to be grown via screw-dislocation-driven growth, similar to other works. Therefore, the H-CVD process is demonstrated to be a powerful tool for controlling the layer thickness of WSe2, but its practicality is limited to the few-layer regime.
关键词： Chemical vapor deposition,Transition metal dichalcogenides,Screw-dislocation-driven growth
更新于2025-09-23 15:19:57
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Growth of monolayer and bilayer MoS2 through the solution precursor for high-performance photodetectors
摘要： Various studies suggest that the performances of TMDs are largely thickness dependent. In this paper, we develop a chemical vapor deposition method to synthesis monolayer and bilayer MoS2 flakes with a solution precursor. The MoS2 phototransistors were prepared to investigate their optoelectronic performance. The MoS2 photodetectors exhibit high detectivity of 2.44×1011 and a fast response/recovery time of 97 ms/291 ms. The photoresponsivity of bilayer MoS2 flakes was found up to 7160 A W?1. Our research will pave a pathway to control the layer numbers of other TMDs nanostructures, expand the application of high performance 2D materials.
关键词： Fast response/recovery time,Chemical vapor deposition,H8MoN2O4,Liquid precursor,Control of the layer numbers,High detectivity
更新于2025-09-23 15:19:57