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Graphene for Si-based solar cells
摘要： In this paper, we report on the single layer graphene synthesis to establish the growth conditions and improve the opto-electronic properties that can be employed in silicon based heterojunction solar cells. To do this, the effect of hydrogen and methane flow on the graphene growth on copper foil in a CVD system was investigated. The analyses were conducted by changing either the hydrogen or the methane flow by keeping all the other growth parameters constant. Single layer graphene growth recipe was established in order to have the optimum optical transmission and sheet resistance values via amending the graphene growth conditions. It was found that the sheet resistance values of the single layer graphene should be lowered further to be used as transparent conductive electrode. However, the combination of graphene with indium tin oxide film functioned well as transparent conductive electrode in the silicon based the solar cells. Additionally, the cell efficiency increased by about 10% as a result of incorporating it with the single layer graphene.
关键词： Raman,Growth,CVD,Graphene,Copper,Solar Cell
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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Direct, transfer-free growth of large-area hexagonal boron nitride films by plasma-enhanced chemical film conversion (PECFC) of printable, solution-processed ammonia borane
摘要： Synthesis of large-area hexagonal boron nitride (h-BN) films for two-dimensional (2D) electronic applications typically requires high temperatures (~1000 oC) and catalytic metal substrates which necessitate transfer. Here, analogous to plasma-enhanced chemical vapor deposition, a non-thermal plasma is employed to create energetic and chemically-reactive states such as atomic hydrogen and convert a molecular precursor film to h-BN at temperatures as low as 500 oC directly on metal-free substrates – a process we term plasma-enhanced chemical film conversion (PECFC). Films containing ammonia borane as a precursor are prepared by a variety of solution processing methods including spray deposition, spin coating, and ink-jet printing, and reacted in a cold-wall reactor with a planar dielectric barrier discharge operated at atmospheric pressure in a background of argon or mixture of argon and hydrogen. Systematic characterization of the converted h-BN films by micro Raman spectroscopy shows that the minimum temperature for nucleation on silicon-based substrates can be lowered from 800 to 500 oC by the addition of a plasma. Furthermore, the crystalline domain size, as reflected by a decrease in the full-width-half-maximum, increased by more than 3 times (>40 cm-1 to ~13 cm-1). To demonstrate the potential of the h-BN films as a gate dielectric in 2D electronic devices, molybdenum disulfide field-effect transistors were fabricated and the field effect mobility was found to be improved by up to four times over silicon dioxide. Overall, PECFC allows h-BN films to be grown at lower temperatures and with improved crystallinity than CVD, directly on substrates suitable for electronic device fabrication.
关键词： two-dimensional (2D) material,plasma,chemical vapor deposition (CVD),boron nitride (BN)
更新于2025-09-11 14:15:04
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The Effect of Deposition Parameters on the Growth Rate of Microcrystalline Diamond Powders Synthesized by HFCVD Method
摘要： Conventional diamond powders (<10 μm) are generally produced from crushing large-sized diamonds synthesized by high-pressure and high-temperature (HPHT) technique, whereas they have many morphological imperfections. In the present work, these powders are served as diamond seeds and regrown by hot ?lament chemical vapor deposition (HFCVD). Deposition parameters—such as the carbon concentration, substrate temperature, and bias current—which play a determined role in the homoepitaxial growth rate of micron diamonds, are investigated in their respective usual ranges. As shown in the experimental results, under the preconditions of maintaining the good morphology of crystals and inhibiting polycrystal growth, the growth rate of isolated diamond crystals can be controlled at 0.9 μm/h. Besides, the ?nal improved powders have a wide range of particle sizes, which could fail to meet the requirements for commercial powders without the post-process of sieving.
关键词： CVD diamond powders,grain size distribution,homoepitaxial growth rate,deposition parameters
更新于2025-09-11 14:12:44
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The preparation and the photoelectric characteristics of graphene/MoSe <sub/>2</sub> heterojunction
摘要： The paper presents the preparation and optoelectronics characteristics of grapheme/molybdenum selenide (MoSe2) heterojunction.MoSe2 films was deposited on Si substratesusing used MoSe2 powder as a raw material by a chemical vapour deposition (CVD) method, and then the graphene/MoSe2 heterojunction was formed by grown a graphene layer on the MoSe2 film using methane (CH4) as a raw material. The prepared MoSe2 films were consisted of many nanowires about 2 nm in diameter and 7 nm in length perpendicular to the surface observed by an Atomic force microscopy (AFM), while many small graphene pieces were formed and dispersed on MoSe2film surface. Additionally, we found that the growth of MoSe2 film has a strong orientation growth in the (400) crystal plane, which consistent with the MoSe2 film composed of many parallel nanowires in the AFM picture. Moreover, we found that the graphene/MoSe2 heterojunction has good absorption properties for visible light and has a significant photocurrent generation under illumination, indicating that the graphene/MoSe2 heterojunction has excellent optical and electrical properties and has great potential for application in the field of optoelectronic devices.
关键词： MoSe2,graphene,CVD,photoelectric characteristics,heterojunction
更新于2025-09-10 09:29:36
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Magnetic Field Imaging of Superparamagnetic Particles Using High-Density, Perfectly Oriented NV Centers in Diamond CVD Film
摘要： The spatial and temporal resolutions of bio-imaging with magnetic nanoparticles (MNP) as a label and a diamond substrate as a magnetic field imager are investigated. To realize fast and accurate magnetic field imaging even for a substrate with unresolved hyperfine peaks, relative fluorescence is measured at four operation points corresponding to the steepest slopes of two dips in the ODMR spectrum. The (111) diamond substrate with a 3.5-μm thick chemical vapor deposition film with an NV density of 1.6 (cid:3) 1016 cm(cid:1)3 allows us to detect 1-μm MNPs scattered on its surface with an accumulated exposure time of 19 s under external DC magnetic field of 1.3 mT. Theoretical limit of temporal sensitivity is estimated to be more than four orders of magnitude smaller than measured. Although for measurement in culture medium, an objective lens with longer working distance is required and the condition will become somewhat worse, a spatiotemporal resolution of <1 s and <1 μm for the density and quality of the NV centers used in this study is expected if the already reported sensitivity enhancement technologies are further incorporated.
关键词： diamond,CVD,NV center,bio-imaging
更新于2025-09-10 09:29:36
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Assembly of β-SiC Nanowires film and humidity sensing performance
摘要： β‐SiC materials have been seen as the third‐generation semiconductor widely used in kinds of photoelectric device, high temperature electronics, and other fields. Compared with ordinary semiconductors, β‐SiC materials have huge potential application in replacing monocrystalline silicon in extreme environments because of their numerals extraordinary chemical and physical properties. Based on this, β‐SiC nanowires obviously are more desirable in any way. Here, we present a modified chemical vapor deposition (CVD) method to synthesis β‐SiC nanowires, which needs no protect gas, and transfer it to Si/SiO2 substrates equipped with Au electrodes. The microstructure of the as‐prepared samples is tested by field emission scanning electron microscopy (FESEM). The humidity sensing performance of electronic device is measured by electrochemical workstation test equipment. It shows that the resistance of β‐SiC nanowires increases with increasing environment humidity within very short response/recovery time‐0.5 seconds/0.5 seconds and also performs excellent cycling stability. Such advantage superiorities make it highly possible to apply β‐SiC nanowires into various environments.
关键词： β-SiC nanowires,CVD,electrodes,humidity sensing
更新于2025-09-10 09:29:36
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Graphene-oxide-semiconductor planar-type electron emission device and its applications
摘要： The planar type electron emission devices based on a graphene-oxide-semiconductor structure were developed. The GOS type electron emission devices fabricated by the combination of low temperature graphene deposition process of 800 ℃ and the post device annealing at 300 ℃ in vacuum achieved both of very high electron emission efficiency more than 10 % and high electron emission densities of around 100 mA/cm2.
关键词： Graphene,CVD,MOS,electron emission
更新于2025-09-09 09:28:46
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Top-gated graphene field-effect transistors by low-temperature synthesized SiN <i> <sub/>x</sub></i> insulator on SiC substrates
摘要： Top-gated devices made from an epitaxial graphene film on a 4H-SiC substrate were fabricated. Atomic force microscopy and Raman spectroscopy results showed that a large-scale highly uniform monolayer graphene film was synthesized on the SiC substrate. A SiNx passivation film was deposited on a SiC graphene device as a top gate insulator by catalytic chemical-vapor deposition (Cat-CVD) below 65 °C. After the top gate electrode was formed on the SiNx film, no leakage current flowed between the gate and source electrodes. The transport characteristics showed clear ambipolar characteristics from 8 to 280 K, and the temperature dependences of the conductance and field-effect mobility of the devices implied that monolayer graphene devices can be successfully fabricated. Moreover, the position of the charge neutrality point after SiNx deposition was around 0 V, indicating p-doping characteristics. These results indicate that SiNx films synthesized by Cat-CVD can be used as gate insulators and that the carrier type may be controlled by adjusting the deposition conditions.
关键词： SiNx,Cat-CVD,field-effect transistors,graphene,SiC substrates
更新于2025-09-09 09:28:46
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Direct synthesis of high-quality perovskite nanocrystals on a flexible substrate and deterministic transfer
摘要： Solid-state perovskite nanocrystals are promising coherent light sources, as there is optical feedback within the crystal structure. In order to utilize the high performance of perovskites for on-chip applications, or observe new physical phenomena, these crystals must be integrated with pre-fabricated electronic or photonic structures. However, the material’s fragility has made the deterministic transfer a great challenge thus far. Here, we report the first deterministic transfer of perovskite nanocrystals with sub-micron accuracy. Cesium lead halide (CsPbI3) nanocrystals were directly synthesized on flexible polydimethylsiloxane (PDMS) stamps via chemical vapor deposition (CVD) and subsequently transferred onto arbitrary substrates/structures. We demonstrated the transfer of a CsPbI3 crystalline nanoplate (NP) onto an 8 μm fiber core and achieved single-mode whispering gallery mode lasing. Our method can be extended to a variety of other arbitrary substrates (e.g., electrodes, photonic structures, micromechanical systems), laying the foundations for previously unattainable opportunities in perovskites-based devices.
关键词： CsPbI3 nanocrystals,PDMS substrate,CVD,Deterministic transfer
更新于2025-09-09 09:28:46