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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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Effect of N <sub/>2</sub> /H <sub/>2</sub> plasma on GaN substrate cleaning for homoepitaxial GaN growth by radical-enhanced metalorganic chemical vapor deposition (REMOCVD)
摘要： We developed a new method of GaN growth using Radical-Enhanced Metalorganic Chemical Vapor Deposition (REMOCVD) technology by which Gallium Nitride (GaN) grows at low temperatures without ammonia gas. In this method, we investigated the effect of N2/H2 plasma on the GaN substrate surface cleaning prior to the growth of homoepitaxial GaN. In-situ reflection high-energy electron diffraction (RHEED) and atomic force microscope (AFM) were used to investigate the surface morphology of the cleaned GaN substrates. The interface between GaN substrate and homoepitaxially grown GaN by REMOCVD was evaluated by transmission electron microscope and the crystal quality was evaluated by X-ray diffraction. The in-situ N2/H2 plasma cleaning at 600 ?C shows a smooth surface morphology with streak diffraction lines observed by RHEED. Since the homoepitaxial growth of GaN was performed at 800 ?C, the cleaned GaN substrate temperature was ramped up from 600 ?C to 800 ?C with and without plasma exposure to compare the effect of plasma. Homoepitaxially grown GaN on GaN substrates whose temperature was ramped up with plasma exposure showed good crystal quality with no threading dislocations at the interface. It was found that N2/H2 plasma plays a significant role in the GaN surface cleaning for good quality crystal growth.
关键词： surface cleaning,homoepitaxial growth,N2/H2 plasma,GaN,REMOCVD
更新于2025-09-04 15:30:14
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Low-temperature homoepitaxial growth of two-dimensional antimony superlattices in silicon
摘要： The authors present a low-temperature process for the homoepitaxial growth of antimony superlattices in silicon. The all low-temperature superlattice doping process is compatible as a postfabrication step for device passivation. The authors have used low-temperature molecular beam epitaxy to embed atomically thin (2D), highly concentrated layers of dopant atoms within nanometers of the surface. This process allows for dopant densities on the order of 1013–1014 cm?2 (1020–1021 cm?3); higher than can be achieved with three-dimensional doping techniques. This effort builds on prior work with n-type delta doping; the authors have optimized the growth processes to achieve delta layers with sharp dopant profiles. By transitioning from a standard effusion cell to a valved cracker cell for antimony evaporation, the authors have achieved carrier densities approaching 1021 cm?3 with peak distribution at ～10 ? FWHM for single delta layers. Even at the highest dopant concentrations studied, no deterioration in carrier mobility is observed, suggesting the upper limit for dopant incorporation and activation has not yet been met. The authors will discuss the details related to growth optimization and show results from in situ monitoring by electron diffraction. They will also report on elemental and electrical characterization of the films.
关键词： silicon,molecular beam epitaxy,surface passivation,homoepitaxial growth,delta doping,low-temperature,antimony superlattices
更新于2025-09-04 15:30:14