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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Ultrathin Self-feeding Metasurface with Broadband Polarization Conversion and Electromagnetic Emission
摘要： A model for controlling the two-dimensional distribution of negatively charged nitrogen-vacancy (NV?) fluorescent centers near the surface of a diamond crystal is presented, using only a microwave plasma-assisted chemical vapor deposition (CVD) method. In this approach, a CVD diamond layer is homoepitaxialy grown via microwave plasma-assisted CVD using an isotopically enriched methane (12CH4 ), hydrogen (H2 ), and nitrogen (N2 ) gas mixture on patterned diamond (0 0 1). When the surface is imaged by means of confocal microscope photoluminescence mapping, fine grooves are observed to have been generated artificially on the diamond surface. NV? centers are found to be distributed selectively into these grooves. These results demonstrate an effective means for the formation of NV? centers of selectable size and density via microwave plasma-assisted CVD, with potential application in the production of diamond quantum sensors.
关键词： doping,nitrogen-vacancy centers,homoepitaxial,groove structure,Diamond,microwave plasma-assisted chemical vapor deposition
更新于2025-09-19 17:13:59
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Suppression of Parasitic Epitaxy Growth and Realization of High-Quality Wafer Surface Passivation of Silicon Heterojunction Solar Cells
摘要： Intrinsic hydrogenated amorphous silicon (i-a-Si:H) ?lms lead to excellent surface passivation of crystalline silicon wafers. However, a-Si:H deposition on a crystalline silicon wafer often results in undesired epitaxy growth, which deteriorates the passivation property, In this paper, we studied the in?uence of varying plasma enhanced chemical vapor deposition (PECVD) parameters, such as the product of the gas pressure (P ) and the electrode distance (Di) and the hydrogen dilution ratio (R = SiH4/(H2 + SiH4) × 100), on the passivation quality and the properties of silicon heterojunction (SHJ) solar cells. Measurements showed that proper combinations of high P ×Di and large R values can yield high minority carrier lifetimes (MCLTs) of passivated silicon wafers. Also, the tendency of MCLTs measured from passivated wafers is the same as that for open circuit voltages (Voc) of fabricated SHJ solar cells. A high Voc is obtained from SHJ solar cells when unwanted epitaxial growth is minimized at the wafer surface.
关键词： Plasma-enhanced chemical-vapor deposition,Amorphous semiconductors,Silicon solar cells,Heterojunctions
更新于2025-09-19 17:13:59
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Structural and mechanical characterization of carbon fibers grown by laser induced chemical vapor deposition at hyperbaric pressures
摘要： Laser induced chemical vapor deposition (LCVD) of freestanding carbon fibers from ethylene at hyperbaric pressures was investigated. Relationships between processing conditions, growth behavior, microstructure, and mechanical properties of the carbon fibers were established. It is found that the fiber growth rates are limited by surface reaction kinetics at low temperatures and limited by gas phase nucleation at high temperatures. At higher pressures and intermediate temperatures, growth becomes mass transport limited whereupon the fibers exhibit drastic changes in morphology and microstructure from a core-shell, smooth appearance to nodular formations. The tensile strengths of the carbon fibers grown by LCVD are generally poor due to the nature of graphitic carbon deposits. However, the Weibull modulus among the LCVD grown carbon fibers was found to be very high. Effects of processing conditions and microstructure on the fiber strengths are observed and discussed.
关键词： Microstructure,Hyperbaric pressures,Laser induced chemical vapor deposition,Carbon fibers,Mechanical properties
更新于2025-09-19 17:13:59
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Effect of bending test on the performance of CdTe solar cells on flexible ultra-thin glass produced by MOCVD
摘要： The development of lightweight and flexible solar modules is highly desirable for high specific power applications, building integrated photovoltaics, unmanned aerial vehicles and space. Flexible metallic and polyimide foils are frequently used, but in this work an alternative substrate with attractive properties, ultra-thin glass (UTG) has been employed. CdTe solar cells with average efficiency reaching 14.7% AM1.5G efficiency have been produced on UTG of 100 μm thickness. Little has been reported on the effects on PV performance when flexed, so we investigated the effects on J-V parameters when the measurements were performed in 40 mm and 32 mm bend radius, and in a planar state before and after the bend curvature was applied. The flat J-V measurements after 32 mm bending test showed some improvement in efficiency, Voc and FF, with values higher than the first measurement in a planar state. In addition, two CdTe solar cells with identical initial performance were subjected to 32 mm static bending test for 168 hours, the results showed excellent uniformity and stability and no significant variation on J-V parameters was observed. External quantum efficiency and capacitance voltage measurements were performed and showed no significant change in spectral response or carrier concentration. Residual stress analysis showed that no additional strain was induced within the film after the bending test and that the overall strain was low. This has demonstrated the feasibility of using CdTe solar cells on UTG in new applications, when a curved module is required without compromising performance.
关键词： Ultra-thin glass,Thin films,Metalorganic chemical vapor deposition,CdTe solar cells,Bending test
更新于2025-09-19 17:13:59
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MOCVD Growth and Characterization of InN Quantum Dots
摘要： Metal-polar InN quantum dots (QDs) are grown by metalorganic chemical vapor deposition at temperatures between 500 and 600 °C. Dot densities between 4 × 10^8 and 4 × 10^10 cm^-2 are observed. InN QDs exhibit room-temperature photoluminescence (PL) with peak wavelengths from 1100 to >1550 nm. GaN cap layers grown on InN QDs have little effect on either peak PL wavelength or intensity, a step toward creating multilayer structures for InN QD devices.
关键词： quantum dots,thin films,metalorganic chemical vapor deposition,nitrides
更新于2025-09-19 17:13:59
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Controlled Synthesis of Large Scale Continuous monolayer WS2 Film by Atmospheric Pressure Chemical Vapor Deposition
摘要： Synthesis of monolayer transition metal dichalcogenides (TMDs) in large-size is crucial to their practical applications in electronics and optoelectronics. Here, large scale continuous monolayer WS2 film has been successfully grown by atmospheric pressure chemical vapor deposition (APCVD) method. By modulating three growth parameters, Ar gas flow rate, the temperature of WO3 precursor and the distance between substrate and WO3 precursor, WS2 film with different grain size can be obtained. At optimal processing condition, large-scale monolayer WS2 with lateral dimension can reach 1 millimeter above. This would pave the way for scale production of continuous monolayer TMDs film.
关键词： large scale,monolayer WS2,atmospheric pressure chemical vapor deposition,continuous film
更新于2025-09-16 10:30:52
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Electrical and optical properties of the specimens with graphene quantum dots prepared by different number of wet transfer
摘要： Graphene quantum dots (GQDs) are grown on the copper foil substrate by the chemical vapor deposition (CVD) synthesis. 1–3 wet transfer numbers are then used in the preparations of the GQDs/glass substrate in order to improve the density and uniformity of GQDs via the stacking of multiple layers. The CH4 input time, ?ow rate, and the number of wet transfer are determined to obtain the optimum conditions in electrical (resistivity) and optical (transmittance) properties. The multilayered graphene is characteristically close to the graphite-like material. The G-band peak intensity in Raman analyses is varied proportional to the density of GQDs. Increasing the wet transfer number can lead to increases in the mean diameter of GQDs and the amount of oxygen vacancies, thus resulting in the rise of carrier concentration and the lowering of carrier mobility. The resistivity varying with the wet transfer number is inversely proportional to the density of GQDs. A bandgap reduction can bring in the lowerings of photoluminescence peak intensities. The specimen with 2 wet transfers has the lowest resistivity and the second highest transmittance of these specimens. GQDs can bring in a signi?cant reduction of resistivity compared to the same substrate without GQD.
关键词： Graphene quantum dots,Wet transfer method,Chemical vapor deposition,Graphite-like material
更新于2025-09-16 10:30:52
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Development of a fully automated desktop chemical vapor deposition system for programmable and controlled carbon nanotube growth
摘要： We have rationally designed and developed a fully automated desktop furnace system that enables programmable chemical vapour deposition growth of carbon nanotubes with controlled height, density, and pattern architecture. Comprising several essential components involving a heating furnace, mass flowmeters, and computer controller, the developed system realizes controlled and practical carbon nanotube growth without resort to expensive and ponderous instruments. By programming, modifying, and loading the reusable recipes in the developed system, systematic and reproducible growths of carbon nanotubes with desired morphology and dimension can be performed. Growth results with controlled height, density, and pattern are demonstrated through the actual operations, confirming the validity and usefulness of the developed system towards various practical applications.
关键词： Furnace,Programmable growth recipe,Desktop system,Chemical vapor deposition,Micropattern,Automated control,Nanopattern,Carbon nanotube
更新于2025-09-16 10:30:52
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Chirality control for predominant metallic or semiconducting single-walled carbon nanotubes prepared using a mild etchant
摘要： Highly oriented metallic and semiconducting SWCNTs were synthesized with different carrier gas compositions and etchants by the floating catalyst chemical vapor deposition method. The addition of acetone as an etchant resulted in metallic nanotubes. The acetone acted as both an additional carbon source and etching agent for carbon nanotube nucleation.
关键词： Chirality control,Metallic,Floating catalyst chemical vapor deposition,Single-walled carbon nanotubes,Acetone,Semiconducting,Etchant
更新于2025-09-16 10:30:52
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Monolayer MoSe <sub/>2</sub> /NiO van der Waals heterostructures for infrared light-emitting diodes
摘要： Nowadays monolayer transition metal chalcogenides (TMCs) have been widely researched due to their excellent optoelectronic properties. However, the preparation of large-sized monolayer TMCs and high-power TMC-based light-emitting diodes are still full of challenges, which limit their application in two-dimensional devices. Here, the large-sized monolayer single-crystalline MoSe2 was synthesized by chemical vapor deposition. The influence of the relative gas pressure ratio of MoO3 to Se on MoSe2 morphology is discussed. The TEM analysis confirmed the presence of 2H-phase monolayer MoSe2. A photoluminescence peak from the MoSe2 monolayer is detected at about 804 nm, illustrating an intrinsic energy bandgap of 1.54 eV. Importantly, a novel 2D/3D heterostructure, monolayer MoSe2/NiO van der Waals heterostructure, is constructed for a light-emitting diode (LED). The electroluminescence peaks of n-MoSe2/p-NiO LED locate at 812 nm, 848 nm and 918 nm, all of which are in the infrared light range. Interestingly, the electroluminescence peaks of our n-MoSe2/p-NiO LED are close to those of conventional air conditioner telecontrollers. So the n-MoSe2/p-NiO infrared LED is forward to be used in infrared remote sensing systems in the future.
关键词： van der Waals heterostructures,infrared light-emitting diodes,Monolayer MoSe2,chemical vapor deposition,NiO
更新于2025-09-16 10:30:52