共查询到20条相似文献,搜索用时 62 毫秒
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本文在背景Ar气压力为8×104Pa、温度为1800~2000℃的条件下,对升华法生长SiC单晶的籽晶进行了原位退火处理,利用原子力显微镜和光学显微镜对退火后的6H-SiC晶片表面进行了观察,研究了退火温度和时间对晶片表面的影响.发现经过退火处理后的籽晶表面存在规则的生长台阶,有助于侧面生长模式的发展,进一步有助于台阶流生长模式的发展.通过对籽晶的退火处理,降低了螺旋生长中心的密度,从而减少多型夹杂、小角度晶界和微管等缺陷的出现,提高了晶体质量. 相似文献
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PVT法生长SiC单晶生长腔的温场分布是影响晶体质量的重要因素.采用数值模拟研究了保温层和坩埚结构以及线圈位置对6英寸SiC晶体生长温场的影响,优化出了适合高品质6英寸SiC晶体生长温场分布,在此条件下生长无裂纹的6英寸N型4H-SiC晶体.用高分辨率X射线衍射、拉曼光谱和缺陷检测系统对所加工的SiC衬底片的质量进行了表征.测试结果表明,晶型为单一的4H-SiC,微管密度小于1 cm-2,电阻率范围为0.02~0.022Ω·cm,X射线摇摆曲线半高宽为21.6″. 相似文献
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4H-SiC同质外延生长及Ti/4H-SiC肖特基二极管 总被引:2,自引:0,他引:2
利用台阶控制外延生长技术在偏晶向Si-面衬底上进行了4H-SiC的同质外延生长研究,衬底温度为1500℃,在厚度为32μm、载流子浓度为2~5×1015cm-3的外延材料上制备出了反向阻塞电压大于1kV的Ti/4H-SiC肖特基二极管,二极管的正向与反向电流的整流比(定义偏压为±1V时的电流比值)在室温下超过107,在265℃的温度下超过102,在20~265℃的温度范围内,利用电流电压测量研究了二极管的电学特性,室温下二极管的理想因子和势垒高度分别为1.33和0.905eV,开态电流密度在2.0V的偏压下达到150A/cm2,比开态电阻(Ron)为7.9mΩ·cm2,与温度的关系遵守Ron~T2.0规律. 相似文献
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A critical review is proposed of the different techniques of bulk growth of ZnO crystals for their use as a substrate in the homoepitaxial growth of this attractive compound. The crystals are assessed from their structural and electrical properties and from the structural properties and purity of homoepitaxial films grown on them by various techniques such as plasma-assisted molecular beam epitaxy, pulsed laser deposition, magnetron sputtering, chemical vapor deposition, metalorganic chemical vapor epitaxy, liquid phase epitaxy. 相似文献
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Detached (or dewetted) Bridgman crystal growth defines that process in which a gap exists between a growing crystal and the crucible wall. In microgravity, the parameters that influence the existence of a stable gap are the growth angle of the solidifying crystal, the contact angle between the melt and the crucible wall, and the pressure difference across the meniscus. During actual crystal growth, the initial crystal radius will not have the precise value required for stable detached growth. Beginning with a crystal diameter that differs from stable conditions, numerical calculations are used to analyze the transient crystal growth process. Depending on the initial conditions and growth parameters, the crystal shape will either evolve towards attachment at the crucible wall, towards a stable gap width, or inwards towards eventual collapse of the meniscus. Dynamic growth stability is observed only when the sum of the growth and contact angles exceeds 180°. 相似文献
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Several designs of air coolers (modular bilateral “crystallization shelves”), installed in laboratory furnaces are presented. The setup allows easy regulation and simultaneous crystallization of several substances at different temperature gradients, shapes of crystallization fronts and rate intervals, with the purpose of obtaining crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The top seeded infiltration and growth technique (TSIG) is an effective way for the preparation of bulk REBa2Cu3O7‐x (RE‐123, where RE denotes rare earth) with finely dispersed RE2BaCuO5 (RE‐211) particles compared to the conventional melt growth (MG) method. The nucleation temperature and the ending growth temperature are the most important parameters need to be optimized during the preparation of RE‐123 bulks by the TSIG process. In this paper, the effects of these parameters on the growth of single‐grain GdBa2Cu3O7‐x (GdBCO) superconductors have been investigated experimentally. It is found that the temperature for the growth of single‐grain GdBCO is in the region between 1040 °C and 1015 °C. In addition, the relation between growth rate and supercooling has been investigated in detail. The combined techniques of SEM and EDS were used to study the microstructure of the samples grown at different temperatures. Based on this, a two‐step slow cooling method during the crystallization process is proposed for the fabrication of RE‐123 bulks. Finally, the single‐grain GdBCO samples of the diameters 20 mm and 30 mm were fabricated successfully by the TSIG technique, with the slow‐cooling process in the temperature window 1030 °C–1020 °C for 60 h and 100 h respectively. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Cuprous iodide crystals have been grown with decomplexation method in silica gel. Various crystal morphologies, such as polycrystalline aggregate, skeletal, dendrite, hopper crystals and regular tetrahedron crystals, were observed in different growth regions with an optical microscope. Their surfaces were photographed using a binocular metallographic microscope and the results were explained with the crystal growth mechanism which was determined by supersaturation. These observations support the general hypothesis that the concentration of reactant affects the relative growth rate by controlling the nucleation and diffusion. The mutual influence of the crystals grown in different regions was also discussed. Additionally, the suitable condition for getting regular tetrahedron crystals or large hopper crystals was obtained by changing the concentration of CuI·HI complex in the later period of crystal growth. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The influence of significant dissolution and refaceting of KDP and Rochelle salt crystals on their further growth is studied. It is shown that the crystal growth rate ‐ initial crystal size dependence is better defined for growth after refaceting. Initial conditions for growth of individual crystals after refaceting are better defined, than in the case of classical seed nucleation. By dissolution and refaceting, it is easy to provide the same initial conditions for crystal growth in each of several experiments, preformed under the same macroscopic external conditions. 相似文献
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You-Jun Fu Zhang-Shou Gao Xun Sun Shen-Lai Wang Yi-ping Li Hong Zeng Jian-Ping Luo Ai-Dong Duan Ji-Yang Wang 《Progress in Crystal Growth and Characterization of Materials》2000,40(1-4):211-220
The synthesis of KDP from its raw material has been found exist in the growth solution. In the crystal growth experiment, significant extension of specific faces was observed at low dopant concentration. At high doping concentration, the growth rate of the whole crystal decreased with no significant habit modification. The inhibiting effects of phosphite and other H-bonding anionic ions on the growth of pyramidal faces are discussed. Rapid growth rate experiments have been carried out with purified material and an averaged growth rate of 18.6mm/day was obtained. 相似文献