Papers by Keyword: Chemical Vapor Deposition (CVD)

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Authors: Sylvain Jacques, Houssam Fakih
Abstract: Thin (SiC/Ti3SiC2)n multi-layered coatings were deposited at 1100°C on ceramic substrates by chemical vapour deposition (CVD) methods. Each SiC sub-layer was classically processed from H2/CH3SiCl3. Each Ti3SiC2 sub-layer was obtained by reactive CVD (RCVD) from a H2/TiCl4 gaseous mixture reacting on each SiC solid sub-layer that was previously deposited. The growth of Ti3SiC2 by RCVD involves partial or total SiC consumption. The H2/TiCl4 ratio was chosen on the basis of a thermodynamic study. Using a sufficiently high H2/TiCl4 ratio and limiting the sub-layer thickness allowed the formation of TiC or binary titanium silicides to be avoided. By using a constant low gas pressure in the CVD reactor, it was possible to obtain nearly pure Ti3SiC2 sub-layers as thin as 0.8 μm. In that case, the ternary compound exhibits basal planes oriented perpendicular to the substrate surface. A way to obtain thinner sub-layers was the use of a pressurepulsed CVD method. In addition, the pressure-pulsed method allowed the preferential orientation to be prevented in the Ti3SiC2 coating.
Authors: Siti Nor Qurratu Aini Abd Aziz, Swee Yong Pung, Zainovia Lockman, Nur Atiqah Hamzah, Yim Leng Chan
Abstract: An ultraviolet (UV) shielding agent based on Fe-doped zinc oxide nanorods (ZnONRs) was synthesized by ex-situdoping using spray pyrolysis technique. These Fe-doped ZnO NRs could reduce the inherent photocatalytic activity of zinc oxide while still maintaining their ultraviolet filtering capability. In this work, the effect of doping duration by spray pyrolysis technique on the optical property and photocatalytic efficiency of ZnO NRs was studied. The room temperature photoluminescence (PL) analysis on the Fe-doped ZnO NRs indicates the red-shift of violet emission peak, i.e. from 378.97 nm (undoped) to 381.86 nm (60 mins.doping). Besides, the reduction of IUV/Vis ratio of PL reveals that the ex-situ Fe doping deteriorated the crystal quality of ZnO NRs. The photocatalytic study shows that the rate constant of Fe-doped ZnO NRs was smaller than the undoped ZnO NRs. It means that the Fe-doped ZnO NRs were less effective in degrading the RhB solution.
Authors: Xiao Ying Lu, Hao Wang, Sheng Yi Xia, Jian Xin Wang, Jie Weng
Abstract: Carbon nanotubes (CNTs)/hydroxyapatite (HA) nanocomposites have been successfully fabricated by a novel method for the biomedical applications, which is in situ growing CNTs in HA matrix in a chemical vapor deposition (CVD) system. The results show that it is feasible to in situ grow CNTs in HA matrix by CVD for the fabrication of CNTs/HA nanocomposites. Multi-walled CNTs with 50-80 nm in diameter have been grown in situ from HA matrix with the pretreatment of sintering at 1473K in air. The nanocomposites are composed with carbon crystals in CNTs form, HA crystallites and calcium phosphate crystallites, one of most important CaP bioceramics. And the CNTs content is about 1% proportion by weight among the composites in our experiments, which can enhance the HA mechanical properties and the CNTs content does not affect the HA performances. These CNTs/HA nanocomposites have the potential application in the biomedical fields.
Authors: Katja Tonisch, Wael Jatal, Ralf Granzner, Mario Kittler, Uwe Baumann, Frank Schwierz, Jörg Pezoldt
Abstract: We present the realization of high electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures grown on silicon substrates using a SiC transition layer. The growth of AlGaN/GaN heterostructures on Si (111) was performed using metalorganic chemical vapour deposition (MOCVD). The (111) SiC transition layer was realized by low pressure CVD and prevented Ga-induced meltback etching and Si-outdiffusion in the subsequent MOCVD growth. The two-dimensional electron gas (2DEG) formed at the AlGaN/GaN interface showed an electron sheet density of 1.5x1013 cm-3 and a mobility of 870 cm²/Vs proving the high structural quality of the heterostructure. Device processing was done using electron beam lithography. DC and RF characteristics were analysed and showed a peak cut-off frequency as high as 6 GHz for a 1.2 µm gate HEMT.
Authors: Wei Ji, Peter M. Lofgren, Christer Hallin, Chun-Yuan Gu
Authors: Tsunenobu Kimoto, Toshihiro Yamamoto, Zhi Yong Chen, Hiroshi Yano, Hiroyuki Matsunami
Authors: Toshiya Yokogawa, Kunimasa Takahashi, Osamu Kusumoto, Masao Uchida, Kenya Yamashita, Makoto Kitabatake
Authors: Hiroaki Saitoh, Tsunenobu Kimoto
Abstract: Chemical vapor deposition of 4H-SiC on (0001) substrates with various off-angles from 1o to 45o has been investigated. On large-off-angled (15o-45o) substrates, very smooth surface morphology is obtained in the wide range of C/Si ratio. The micropipe dissociation during epitaxial growth is observed on 4o-45o off-angled substrates with a low C/Si ratio. The incorporation of nitrogen was dramatically suppressed by increasing C/Si ratio irrespective of substrate’s off-angle.
Authors: Jawad ul Hassan, Peder Bergman, Anne Henry, Henrik Pedersen, Patrick J. McNally, Erik Janzén
Abstract: We report on the growth of 4H-SiC epitaxial layer on Si-face polished nominally on-axis 2” full wafer, using Hot-Wall CVD epitaxy. The polytype stability has been maintained over the larger part of the wafer, but 3C inclusions have not been possible to avoid. Special attention has given to the mechanism of generation and propagation of 3C polytype in 4H-SiC epilayer. Different optical and structural techniques were used to characterize the material and to understand the growth mechanisms. It was found that all 3C inclusions were generated at the interface between the substrate and the epitaxial layer, and no 3C inclusions were initiated at later stages of the growth.
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