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Fabricating GaN-based LEDs on (?2 0 1) <i>β</i> -Ga <sub/>2</sub> O <sub/>3</sub> substrate via non-continuous/continuous growth between low-temperature undoped-GaN and high-temperature undoped-GaN in atmospheric pressure metal-organic chemical vapor deposition
摘要： This study demonstrates two approaches to the growth of GaN-based LEDs on (?2 0 1)-oriented β-Ga2O3 single crystal substrates using metal-organic CVD under atmospheric pressure. One approach induces non-continuous growth between low-temperature undoped-GaN (u-GaN) and high-temperature u-GaN, whereas the other approach induces continuous growth. We observed the following reduction in the FWHM of X-ray diffraction rocking curves: GaN (0 0 2) on (?2 0 1) β-Ga2O3 substrate (from 464 to 342 arcsec) and GaN (1 0 2) (from 886 to 493 arcsec). An LED with six pairs of InGaN/GaN multiple quantum wells was successfully fabricated on the (?2 0 1) β-Ga2O3 single crystal substrate.
关键词： metal-organic chemical vapor deposition,X-ray diffraction,β-Ga2O3 substrate,non-continuous/continuous growth,GaN-based LEDs
更新于2025-09-11 14:15:04
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High-Power Large-Energy Rectangular Mode-Locked Er-Doped Fiber Laser Based on High-Damage-Threshold MoS <sub/>2</sub> Saturable Absorber
摘要： In our work, based on chemical vapor deposition method and a newly designed glass–material–glass sandwich structure, MoS2 saturable absorber (SA) with a damage threshold of higher than 0.26 J/cm2 was fabricated and employed for demonstrating high-power, large-energy rectangular mode-locked Er-doped laser operation. Stable mode-locked operation with maximum output power of 122.77 mW and largest pulse energy of 130.49 nJ were successively achieved along with power scaling process. In comparison with previous works, our results show remarkable breakthroughs both in the aspects of average output power and pulse energy. Our experimental design and results will open a new avenue for generating high-power, large-energy mode-locked ?ber lasers based on two-dimensional materials as SAs.
关键词： Chemical vapor deposition,new-designed glass-material-glass sandwich structure,high-power mode-locked ?ber laser
更新于2025-09-11 14:15:04
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Properties of Arsenic–Doped ZnTe Thin Films as a Back Contact for CdTe Solar Cells
摘要： As-doped polycrystalline ZnTe layers grown by metalorganic chemical vapor deposition (MOCVD) have been investigated as a back contact for CdTe solar cells. While undoped ZnTe ?lms were essentially insulating, the doped layers showed signi?cant rise in conductivity with increasing As concentration. High p-type carrier densities up 4.5 × 1018 cm?3 was measured by the Hall-e?ect in heavily doped ZnTe:As ?lms, displaying electrical properties comparable to epitaxial ZnTe single crystalline thin ?lms in the literature. Device incorporation with as-deposited ZnTe:As yielded lower photovoltaic (PV) performance compared to reference devices, due to losses in the open-circuit potential (VOC) and ?ll factor (FF) related to reducing p-type doping density (NA) in the absorber layer. Some minor recovery observed in absorber doping following a Cl-free post–ZnTe:As deposition anneal in hydrogen at 420 ?C contributed to a slight improvement in VOC and NA, highlighting the signi?cance of back contact activation. A mild CdCl2 activation process on the ZnTe:As back contact layer via a sacri?cial CdS cap layer has been assessed to suppress Zn losses, which occur in the case of standard CdCl2 anneal treatments (CHT) via formation of volatile ZnCl2. The CdS sacri?cial cap was e?ective in minimising the Zn loss. Compared to untreated and non-capped, mild CHT processed ZnTe:As back contacted devices, mild CHT with a CdS barrier showed the highest recovery in absorber doping and an ~10 mV gain in VOC, with the best cell e?ciency approaching the baseline devices.
关键词： solar cells,CdTe,metalorganic chemical vapor deposition (MOCVD),ZnTe:As back contact,thin ?lms
更新于2025-09-11 14:15:04
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Lateral cavity enabled Fabry-Perot microlasers from all-inorganic perovskites
摘要： Microlasers play an important role in the development of photonics and optoelectronics. As the rising star in the semiconductor family, all-inorganic lead halide perovskites (ILHPs) have been recognized as promising optical gain and lasing media. However, until now, achieving duplicable and single-mode microlasers remains a taunting challenge. Herein, we fabricated rectangular-shaped ILHP microsheets by the chemical vapor deposition method. The single-crystalline nature and the atomically smooth surfaces of the sample enable the achievement of lateral-cavity Fabry–P(cid:2)erot (F-P) microlasers. Speci?cally, the lasing characteristics including the wavelength, mode spacing, and Q-factors can be well-reproduced along the axial direction of the individual microsheet. By regulating the width of the ILHP microsheet, the desirable single-longitudinal mode F-P microlaser was eventually achieved. Our results provide an enabling coherent light source for optics-related applications.
关键词： microlasers,all-inorganic lead halide perovskites,Fabry–P(cid:2)erot,single-mode lasing,chemical vapor deposition
更新于2025-09-11 14:15:04
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Regrowth and catalytic etching of individual single-walled carbon nanotubes studied by isotope labeling and growth interruption
摘要： To realize the efficient growth of single-walled carbon nanotubes (SWCNTs), the growth mechanism behind catalyst activity and growth rates needs to be elucidated at the single nanotube level. In this study, we synthesized SWCNTs with growth interruption, where only Ar, Ar/H2, or Ar/H2/H2O was introduced during a pause in the supply of a carbon source, in order to examine the effects of additive molecules in a chemical vapor deposition process. This interrupted growth was performed in combination with an isotope labeling technique to show the time evolution of individual SWCNT growth. While the introduction of Ar during the growth interruption tended to terminate SWCNT growth, the introduction of Ar/H2 resulted in the regrowth of SWCNTs once ethanol was reintroduced. When interrupted with Ar/H2/H2O, SWCNTs were etched catalytically while sliding themselves in the reverse direction of growth and, then, regrew. Raman analysis revealed that the chirality of SWCNTs was preserved even after etching and regrowth. The growth rates of SWCNTs were unchanged before and after the interruption in the case of Ar/H2, but they were increased by a factor of ~1.7 in the case of Ar/H2/H2O. These results provide effective means to maintain the catalyst activity and to enhance growth rates.
关键词： Isotope labeling,Catalytic etching,Single-walled carbon nanotubes,Growth interruption,Chemical vapor deposition
更新于2025-09-11 14:15:04
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N- and S-codoped graphene hollow nanoballs as an efficient Pt-free electrocatalyst for dye-sensitized solar cells
摘要： We synthesize heteroatoms-doped graphene hollow nanoballs (GHBs) on flexible carbon cloth (CC) substrates via chemical vapor deposition (CVD) reaction to be used as an efficient non-noble electrocatalyst in dye-sensitized solar cells (DSSCs). The as-synthesized heteroatoms-doped GHBs/CC, including nitrogen-doped GHBs, sulfur-doped GHBs, and nitrogen and sulfur-codoped GHBs (denoted by N-GHBs/CC, S-GHBs/CC and N,S-GHBs/CC, respectively), are used as an efficient counter electrode (CE) in DSSCs. Unlike planar graphene sheets, the highly curved GHBs can avoid self-assembly restacking to provide high surface areas for electrocatalytic reactions. In addition, the heteroatomic incorporation in GHBs can reduce the charge-transfer resistance to enhance the electrocatalytic activity. Among these doped GHB samples, N,S-GHBs show the best catalytic performance due to the synergistic effect from both electronic and geometric changes, caused by the N- and S-dopings, respectively. The DSSC with a N,S-GHB CE exhibits the power conversion efficiency of 9.02%, comparable to that (8.90%) of a Pt-based counterpart.
关键词： Dye-sensitized solar cell,Heteroatom-doping,Graphene hollow ball,Chemical vapor deposition,Pt-free counter electrode
更新于2025-09-11 14:15:04
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Self-formed PbI <sub/>2</sub> -DMSO adduct for highly efficient and stable perovskite solar cells
摘要： Currently, chemical vapor deposition (CVD) has attracted widespread attention for preparing high efficiency and large-scale perovskite solar cells (PSCs). The surface morphology and crystallinity of precursor lead iodide (PbI2) films play a critical role in the subsequent CVD process. Here, we use a self-formed PbI2-dimethyl sulfoxide adduct in precursor PbI2 for fabricating a high quality perovskite film. The results show that a larger grain size and excessive PbI2 in the perovskite film effectively suppress carrier recombination, which is helpful to improve the device stability and efficiency. It is noted that the device maintained an excellent stability with almost the same efficiency after 1000 h (in a dry N2 glovebox, 25 (cid:2)C). Finally, the PSC by using the CVD method exhibits a high power conversion efficiency of 17.9% with a bandgap of 1.60 eV, an open voltage (VOC) of 1140 mV, a short-circuit current density (JSC) of 20.1 mA/cm2, and a fill factor of 78%. This method provides guidance for preparing large-area solar cells or applications in tandem solar cells.
关键词： stability,perovskite solar cells,PbI2-DMSO adduct,chemical vapor deposition,efficiency
更新于2025-09-11 14:15:04
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Recent progress in the controlled synthesis of 2D metallic transition metal dichalcogenides
摘要： Two-dimensional (2D) metallic transition metal dichalcogenides (MTMDCs), the complement of 2D semiconducting TMDCs, have attracted extensive attentions in recent years because of their versatile properties such as superconductivity, charge density wave, and magnetism. To promote the investigations of their fantastic properties and broad applications, the preparation of large-area, high-quality, and thickness-tunable 2D MTMDCs has become a very urgent topic and great efforts have been made. This topical review therefore focuses on the introduction of the recent achievements for the controllable syntheses of 2D MTMDCs (VS2, VSe2, TaS2, TaSe2, NbS2, NbSe2, etc.). To begin with, some earlier developed routes such as chemical vapor transport, mechanical/chemical exfoliation, as well as molecular beam epitaxy methods are briefly introduced. Secondly, the scalable chemical vapor deposition methods involved with two sorts of metal-based feedstocks, including transition metal chlorides and transition metal oxidations mixed with alkali halides, are discussed separately. Finally, challenges for the syntheses of high-quality 2D MTMDCs are discussed and the future research directions in the related fields are proposed.
关键词： chemical vapor deposition,metallic transition metal dichalcogenides,synthesis,two dimensional
更新于2025-09-11 14:15:04
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Quantum Multibody Interactions in Halide-Assisted Vapor-Synthesized Monolayer WSe <sub/>2</sub> and Its Integration in a High Responsivity Photodetector with Low-Interface Trap Density
摘要： Among the two-dimensional (2D) transitional-metal dichalcogenides, monolayer (1L) tungsten diselenide (WSe2) has recently attracted a great deal of interest because of its direct band gap and tunable charge transport behavior, making it attractive for a variety of electronic and optoelectronic applications. Controlled and efficient synthesis of 1L WSe2 using chemical vapor deposition (CVD) is often challenging because of the high temperatures required to generate a steady flux of tungsten atoms in the vapor phase from the oxide precursors. Here, the use of halide-assisted low-pressure CVD with NaCl helps to reduce the growth temperature to ～750 °C, which is lower than the typical temperatures needed with conventional CVD for realizing 1L WSe2. Moreover, we experimentally probed the quantum multibody interactions in 1L WSe2 ascribed to excitons, trions, and other localized states by analyzing the temperature-dependent photoluminescence spectra, where such multibody interactions govern the intrinsic electronic and optoelectronic properties of 1L WSe2 for device platforms. The role of the metal?2D semiconductor interface is also critical to realize high-performance devices. In this study, a 1L WSe2-based photodetector was fabricated using Al contacts, which shows a high photoresponsivity, and the interface-state density Dit of the Al/WSe2 junction was computed to be the lowest reported to date ～3.45 × 1012 cm?2 eV?1. Our work demonstrates the tremendous potential of WSe2 to open avenues for state-of-the-art electronic, optoelectronic, and quantum-optoelectronic devices using scalable synthesis routes.
关键词： transitional-metal dichalcogenides,photodetector,tungsten diselenide (WSe2),two-dimensional (2D) materials,quantum multibody interactions,interface-state density,chemical vapor deposition (CVD)
更新于2025-09-11 14:15:04
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Nucleation promoted synthesis of large-area ReS<sub>2</sub> film for high-speed photodetectors
摘要： Rhenium disulfide (ReS2) is a transition metal dichalcogenide with a layer-independent direct bandgap. Notably, the weak interlayer coupling owing to its T-phase structure enables multi-layer ReS2 to behave similarly to decoupled monolayers. This inherent characteristic makes continuous multi-layer ReS2 film a unique platform for large-area electronic applications. To date, the bulk of work on ReS2 has been conducted using mechanically exfoliated samples or small size flakes (< 1mm2) with no potential for large-scale electronics. A chemical vapor deposition (CVD) synthesis of a large area, continuous ReS2 film directly on a SiO2 substrate is also known to be more challenging compared with that of other 2D materials, such as MoS2 and WS2. This is partly due to its tendency to grow into discrete dendritic structures. In this study, a large-area (> 1 cm2), continuous multilayer ReS2 film is directly synthesized on a SiO2 substrate without any transfer process. The polycrystalline ReS2 film synthesized by this method exhibits one of the fastest photoresponse speeds (0.03 s rise time and 0.025 s decay time) among the reported CVD films. The responsivity Rλ was also the highest among large-area CVD films. The synthesis method for a continuous multilayer ReS2 film is amenable to large-scale integration and will pave the way for practical optoelectronic applications based on 2D layered materials.
关键词： Photodetector,Large-area synthesis,Metal chalcogenides,Chemical vapor deposition,Two-dimensional material,Nucleation promotor
更新于2025-09-11 14:15:04