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- 摘要
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- 实验方案
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Strong Quantum Confinement Effects in Nanometer Devices with Graphene Directly Grown on Insulator by Catalyst-free Chemical Vapor Deposition
摘要： Background: The understanding of electrical properties of defective graphene in nanometer regime has lagged behind. Objective: This report intends to characterize defective but practically useful graphene as nanometer devices. Method: A-few-layer-thick graphene was directly grown on SiO2 substrate by alcohol-chemical vapor deposition (alcohol-CVD) using ethanol as carbon source and without the use of any catalytic metal. The graphene film was delineated into nanometer structures by electron beam lithography to make the nanoscale devices. Results: The Raman spectra of the graphene sheet on SiO2 shows relatively large D peak, which means the graphene is defective and consists of nanograins with an estimated size of 17 nm. Modulation of the graphene resistance by the gate voltage Vg was studied at room temperature. The film shows only p-type conduction, with a sheet resistance of 3.7 kΩ/□ and field-effect mobility calculated to be 44 cm2/Vs. From the temperature dependence of the graphene sheet, it is found that the resistance increases only by 7% from room temperature to 10 K, indicating low potential barrier between the domains, even though the graphene film is as thin as 1.6 nm and defective. From the conductance (Id/Vd) contour plot measured at 10 K of these nanodevices, aperiodic Coulomb-blockade feature and transport with a large gap were observed. Conclusion: Correlation among narrowest constriction widths, the variation of the addition energies and transport gaps in disordered graphene nanostructures is evident. These graphene nanodevices may have promising application in various nanodevices like single-electron (or single-hole) transistor, single-molecule transistor, van-der-Waals stacked nanodevices, etc.
关键词： graphene nanometer devices,Graphene nanostructures,sheet resistance,Raman spectra,Coulomb blockade,alcohol chemical vapor deposition,electron beam lithography
更新于2025-09-23 15:21:01
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Enhancement for Potential-Induced Degradation Resistance of Crystalline Silicon Solar Cells via Anti-Reflection Coating by Industrial PECVD Methods
摘要： The issue of potential-induced degradation (PID) has gained more concerns due to causing the catastrophic failures in photovoltaic (PV) modules. One of the approaches to diminish PID is to modify the anti-re?ection coating (ARC) layer upon the front surface of crystalline silicon solar cells. Here, we focus on the modi?cation of ARC ?lms to realize PID-free step-by-step through three delicate experiments. Firstly, the ARC ?lms deposited by direct plasma enhanced chemical vapor deposition (PECVD) and by indirect PECVD were investigated. The results showed that the ef?ciency degradation of solar cells by indirect PECVD method is up to ?33.82%, which is out of the IEC 62804 standard and is signi?cantly more severe than by the direct PECVD method (?0.82%). Next, the performance of PID-resist for the solar cell via indirect PECVD was improved signi?cantly (PID reduced from ?31.82% to ?2.79%) by a pre-oxidation step, which not only meets the standard but also has higher throughput than direct PECVD. Lastly, we applied a novel PECVD technology, called the pulsed-plasma (PP) PECVD method, to deal with the PID issue. The results of the HF-etching rate test and FTIR measurement indicated the ?lms deposited by PP PECVD have higher potential against PID in consideration of less oxygen content in this ?lm. That demonstrated the ?lm properties were changed by applied a new control of freedom, i.e., PP method. In addition, the 96 h PID result of the integrated PP method was only ?2.07%, which was comparable to that of the integrated traditional CP method. In summary, we proposed three effective or potential approaches to eliminate the PID issue, and all approaches satis?ed the IEC 62804 standard of less than 5% power loss in PV modules.
关键词： solar cell,potential-induced degradation,anti-re?ection coating,plasma enhanced chemical vapor deposition
更新于2025-09-23 15:21:01
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Epitaxial lateral overgrowth of GaN on nano-cavity patterned sapphire substrates
摘要： The epitaxial lateral overgrowth of GaN by metal-organic chemical vapor deposition using a nano-cavity patterned sapphire substrate (NCPSS) was investigated. The NCPSS, with a hexagonal non-close-packed nano-cavity pattern on the sapphire substrate, was fabricated by polystyrene sphere coating and size reduction by reactive ion etching, followed by deposition of alumina and thermal oxidation. The coalescence of GaN on the NCPSS was achieved by the formation of relatively large GaN islands and enhanced lateral overgrowth of the GaN islands over several nano-cavity pattern areas. The threading dislocation density (TDD) measured by cathodoluminescence measurement was significantly reduced from 2.4 108 cm-2 to 6.9 107 cm-2 by using the NCPSS. Dislocation behaviors that contribute to the reduction of TDD of the GaN layer were observed by transmission electron microscopy. Raman spectroscopy revealed that the compressive stress in the GaN layer was reduced by 21% due to the embedded nano-cavities. In addition, the diffuse reflectance of GaN on the NCPSS was enhanced by 54% ~ 62%, which is attributed to the increased probability of light extraction through effective light scattering by nano-cavities.
关键词： A1. Nanostructures,B1. Nitrides,A2. Single crystal growth,A3. Metalorganic chemical vapor deposition,A3. Nanoscale epitaxial lateral overgrowth
更新于2025-09-23 15:21:01
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One-step synthesis of nitrogen-doped graphene from a sole aromatic precursor
摘要： A cheap aromatic precursor (1,10-phenanthroline) with heteroatom and planar-structure was designed to synthesize large-scale, continuous and mostly single-layer nitrogen-doped graphene (NG) films by one-step chemical vapor deposition method. The NG sheets can be obtained even at 600 ℃. The results indicated that the content and type of doped N are intensely relied on the growth temperature. Our fabrication approach provides an economic synthetic route and potentially promotes the practical application of graphene-based materials.
关键词： chemical vapor deposition,thin films,graphene,nitrogen-doped
更新于2025-09-23 15:21:01
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Controlled Growth of Vertically Oriented Trilayer MoS <sub/>2</sub> Nanoflakes for Rooma??Temperature NO <sub/>2</sub> Gas Sensor Applications
摘要： In present work, we introduce the controlled synthesis of few layer vertically oriented MoS2 flakes for high performance NO2 gas sensor applications. The density and the thickness of MoS2 nanosheets are controlled by varying the heating rate of the chemical vapor deposition process. Our study confirms that the nanoflakes of about three layers were obtained under the heating rate of 5 oC by using powders of MoO3 and S as precursors without using any catalyst. This is very advantageous because no catalyst was used, there was no need of buffer layer at the bottom of the MoS2 thin film flacks, thus omitting the leakage current when measuring the electrical signal and enhancing the gas sensing performance. Gas sensing measurements demonstrated that the interconnected vertically oriented MoS2 nanoflakes have a good response value of 20.1% to 0.5 ppm NO2 at RT, and 1.73% at 150 oC. The sensor showed full recovery characteristic at a measured temperature of 150 oC with response and recovery time of about 15 s, and 100 s, respectively. The sensor also exhibited good selectivity with the ignorable response to SO2, H2, NH3, H2S and a low detection limit of 42 ppb.
关键词： Few-layer MoS2,Gas sensors,Chemical vapor deposition,Vertically oriented
更新于2025-09-23 15:19:57
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Air-stable hybrid perovskite solar cell by sequential vapor deposition in a single reactor
摘要： Here we demonstrate a facile two-step low-pressure vapor deposition of methyl-ammonium lead iodide (MAPbI3) perovskite films in a single reactor. Continuous, poly-crystalline lead iodide (PbI2) films were deposited in the first step and successfully converted to high quality perovskite films in the second step during exposure of PbI2 films to methyl-ammonium iodide (MAI) vapor. A complete conversion was realized after 90 minutes of exposure with an average grain size of 3.70 ± 1.80 μm. The perovskite conversion starts at the PbI2 surface through the intercalation reaction of PbI2 and MAI vapor molecules and progresses towards the PbI2/substrate interface. The coverage and quality of the perovskite thin film is controlled by that of the pre-deposited PbI2 film. The absorbance measurements confirmed air stability of the fully converted perovskite for 21 days, ascribed to its superior morphology and grain size. Finally, a planar single-junction perovskite solar cell with no additives or additional interfacial engineering was fabricated and tested under open-air conditions, yielding a best power conversion efficiency of 11.7%. The solar cell maintains 85% of its performance up to 13 days in open-air with relative humidity up to 80%.
关键词： planar device,Two-step vapor deposition,large grains,intercalation,air-stable
更新于2025-09-23 15:19:57
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Chemical vapor deposition all-inorganic CsPbI <sub/>2</sub> Br perovskite nanofibers for photodetector
摘要： Chemical vapor deposition method can prepare perovskite films with controllable morphology and adjustable photoelectric properties. In this work, we have prepared CsPbI2Br films at 400 °C–700 °C using chemical vapor deposition method. The grain size of perovskite film increases with the deposition temperature increment because higher temperature provides greater driving force for nucleation expansion. CsPbI2Br film deposited at 600 °C shows nanofiber structure with polycrystalline property accompanied by local single crystal structure. Steady-state and time-resolved fluorescence measurement explored the charge carrier recombination process of perovskite films. The photodetector based on CsPbI2Br film deposited at 600 °C shows excellent photoelectric response and switching ratio characteristics. This is ascribed to low defect density and fast charge transport along 1D fiber channels.
关键词： photodetector,perovskite,chemical vapor deposition,nanofibers
更新于2025-09-23 15:19:57
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High performance Zn-diffused planar mid-wavelength infrared type-II InAs/InAs <sub/>1a??x</sub> Sb <sub/>x</sub> superlattice photodetector by MOCVD
摘要： We report a Zn-diffused planar mid-wavelength infrared photodetector based on type-II InAs/InAs1?xSbx superlattices. Both the superlattice growth and Zn diffusion were performed in a metal-organic chemical vapor deposition system. At 77 K, the photodetector exhibits a peak responsivity of 0.70 A/W at 3.65 μm, corresponding to a quantum efficiency of 24% at zero bias without anti-reflection coating, with a 50% cutoff wavelength of 4.28 μm. With an R0A value of 3.2 × 105 Ω cm2 and a dark current density of 9.6 × 10?8 A/cm2 under an applied bias of ?20 mV at 77 K, the photodetector exhibits a specific detectivity of 2.9 × 1012 cm Hz1/2/W. At 150 K, the photodetector exhibits a dark current density of 9.1 × 10?6 A/cm2 and a quantum efficiency of 25%, resulting in a detectivity of 3.4 × 1011 cm Hz1/2/W.
关键词： specific detectivity,metal-organic chemical vapor deposition,type-II InAs/InAs1?xSbx superlattices,quantum efficiency,Zn-diffused planar mid-wavelength infrared photodetector
更新于2025-09-23 15:19:57
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The Influence of Laser Modification on a Composite Substrate and the Resistance of Thin Layers Created Using the PVD Process
摘要： For physical vapor deposition (PVD) technology, cleaning a substrate is one of the key preliminary processes before depositing the metal layer. In this article, we present the results of research on the modification of a textile composite substrate using laser technology and its influence on the surface resistance of silver structures intended for use in wearable electronics. As a result of the substrate modification, the resistance of the layers increased as compared with the structures produced on an unmodified substrate. An experimental planning technique was used to optimize the laser modification process.
关键词： wearable electronics,textronics,design of experiments,physical vapor deposition,laser modification,PVD
更新于2025-09-23 15:19:57
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Vapora??Deposited Cs <sub/>2</sub> AgBiCl <sub/>6</sub> Double Perovskite Films toward Highly Selective and Stable Ultraviolet Photodetector
摘要： Double perovskites have shown great potentials in addressing the toxicity and instability issues of lead halide perovskites toward practical applications. However, fabrication of high-quality double perovskite thin films has remained challenging. Here, sequential vapor deposition is used to fabricate high-quality Cs2AgBiCl6 perovskite films with balanced stoichiometry, superior morphology, and highly oriented crystallinity, with an indirect bandgap of 2.41 eV. Using a diode structure, self-powered Cs2AgBiCl6 ultraviolet (UV) photodetectors are demonstrated with high selectivity centered at 370 nm, with low dark current density (≈10?7 mA cm?2), high photoresponsivity (≈10 mA W?1), and detectivity (≈1012 Jones). Its detectivity is among the highest in all double-perovskite-based photodetectors reported to date and surpassing the performance of other perovskite photodetectors as well as metal oxide in the UV range. The devices also show excellent environmental and irradiation stability comparable to state-of-the-art UV detectors. The findings help pave the way toward application of double perovskites in optoelectronic devices.
关键词： double perovskite films,sequential vapor deposition,selective detection,ultraviolet photodetectors
更新于2025-09-23 15:19:57