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Flow Field and Temperature Field in GaN-MOCVD Reactor Based on Computational Fluid Dynamics Modeling 下载免费PDF全文
Metal organic chemical vapor deposition(MOCVD) growth systems are one of the main types of equipment used for growing single crystal materials, such as GaN. To obtain film epitaxial materials with uniform performance,the flow field and temperature field in a GaN-MOCVD reactor are investigated by modeling and simulating. To make the simulation results more consistent with the actual situation, the gases in the reactor are considered to be compressible, making it possible to investigate the distributions of gas density and pressure in the reactor.The computational fluid dynamics method is used to study the effects of inlet gas flow velocity, pressure in the reactor, rotational speed of graphite susceptor, and gases used in the growth, which has great guiding significance for the growth of GaN film materials. 相似文献
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总结了近年来用于不对称催化羟醛缩合反应的各种有机小分子催化剂, 简要阐述了每种类型的催化剂的催化机理以及它们的优缺点, 同时对有机小分子催化反应的发展进行了展望. 相似文献
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利用复变函数法和Stroh算法研究了反平面载荷作用下一维六方准晶压电材料中唇口次生裂纹的断裂问题,首次构造了唇口次生两不对称裂纹的缺陷力学模型,推出了含唇口次生两不对称裂纹的无限大区域到单位圆外部区域的保角变换公式,得到了裂尖处的场强度因子和能量释放率的解析表达式.数值算例揭示了缺陷尺寸,特别是唇口高度和裂纹长度对场强度因子和能量释放率的影响.结果表明:增加裂纹两边的长度会促进裂纹的扩展,增加唇口的高度,会抑制裂纹的扩展.最后,在给定条件下,这些解析结果可以简化为其它的缺陷模型的解,比如唇口次生单裂纹和唇口次生两对称裂纹的解,同时还可以退化为经典的Griffith裂纹和唇口无次生裂纹的解,以上结果与理论分析的结论是一致的. 相似文献
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The structural and magnetic properties of Sm ion-implanted GaN with different Sm concentrations are investigated. XRD results do not show any peaks associated with second phase formation. Magnetic investigations performed by superconducting quantum interference device reveal ferromagnetic behavior with an ordering tem- perature above room temperature in all the implanted samples, while the effective magnetic moment per Sin obtained from saturation magnetization gives a much higher value than the atomic moment of Sm. These results could be explained by the phenomenological model proposed by Dhar et al. [Phys. Rev. Lett. 94(2005)037205, Phys. Rev. B 72(2005)245203] in terms of a long-range spin polarization of the GaN matrix by the Sm atoms. 相似文献
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Jian-Kai Xu 《中国物理 B》2021,30(11):118101-118101
The effect of nitrogen flow and growth temperature on extension of GaN on Si substrate has been studied. By increasing the nitrogen flow whose outlet is located in the center of the MOCVD (metal-organic chemical vapor deposition) gas/particle screening flange and by increasing the growth temperature of HT-AlN and AlGaN buffer layers near the primary flat of the wafer, the GaN layer has extended more adequately on Si substrate. In the meantime, the surface morphology has been greatly improved. Both the AlN and GaN crystal quality uniformity has been improved. X-ray diffraction results showed that the GaN (0002) XRD FWHMs (full width at half maximum) decreased from 579 arcsec~ 1655 arcsec to around 420 arcsec. 相似文献
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猪、兔、羊、鸡肝脏中必需微量元素和脂肪酸含量的比较研究 总被引:4,自引:0,他引:4
以猪、兔、羊、鸡的肝脏为材料,利用高频电感耦合等离子体原子发射光谱仪(ICP-AES)测定了其微量元素Zn、Fe、Cu、Mn的含量,新极谱仪测定了Se的含量,气相色谱仪测定了必需脂肪酸亚油酸(C反18:2)和γ-亚麻酸(Cγ-18:3)的含量。结果表明,Fe在所测五种微量元素中含量最高,Zn其次,Se最低。四种动物肝脏中,兔肝的Zn、Fe、Se含量(鲜重)最高.分别为34.00μg/g,151.70μg/g和0.14μg/g;羊肝的Cu含量(鲜重)最高,为65.72μg/g;鸡肝的Mn含量(鲜重)最高,为1.94μg/g。此外,在所测定的两种必需脂肪酸中,兔肝的亚油酸含量(鲜重)最高,为24.08%;鸡肝中γ-亚麻酸含量最高,为1.08%。结果提示,在选用动物肝脏作为营养素源和制备保健品时,应考虑微量元素和必需脂肪酸的含量特点,有效利用其营养价值。 相似文献
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Pt Schottky diode gas sensors for CO are fabricated using A1GaN/GaN high electron mobility transistor(HEMTs)structure. The diodes show a remarkable sensor signal (3 mA, in N2, 2mA in air ambient) biased 2 V after 1% CO is introduced at 50℃. The Schottky barrier heights decrease for 36meV and 27meV in the two cases respectively. The devices exhibit a slow recovery characteristic in air ambient but almost none in the background of pure N2, which reveals that oxygen molecules could accelerate the desorption of CO and offer restrictions to CO detection. 相似文献