SiC单晶的性质、生长及应用

本文综述了 Ｓｉ Ｃ 单晶的物理性质、晶体结构、制备过程以及应用等详细地介绍了大尺寸 Ｓｉ Ｃ 单晶的 Ｐ Ｖ Ｔ 法制备和该过程中的关键要素, 分析了 Ｐ Ｖ Ｔ 法制备的 Ｓｉ Ｃ单晶中所存在的缺陷及其成因     

新型硅氮烷先驱体的合成和表征

采用ＭｅＳｉＨＣｌ２和ＭｅＳｉＶｉＣｌ２共氨解方法制备出了流动性好的含Ｓｉ－Ｈ和Ｓｉ－Ｖｉ的低分子硅氮烷。结果表明，Ｈ２ＨｔＣｌ６（脱水）和ＤＣＰ是合适的硅氢化交联催化剂和双键交联的引发剂，交联产物在程序控温的管式炉中裂解，得到了高的陶瓷产率。     

聚碳硅烷／二乙烯基苯的高温裂解

采用ＴＧ－ＤＴＡ、ＩＲ、ＸＲＤ、ＸＰＳ、ＳＥＭ等手段研究了聚碳硅烷（ＰＣＳ）／二乙烯基苯（ＤＶＢ）的高温裂解行为及其裂解产物的结构与性能。结果表明，ＰＣＳ／ＤＶＢ的裂解过程可分成５个阶段，其裂解产物主要由ＳｉＣ、ＳｉＯ２和Ｓｉ－Ｏ－Ｃ非晶网络及游离Ｃ组成，其中游离Ｃ的含量随ＤＶＢ的增加而增加，且对β－ＳｉＣ的结晶有一定的抑制作用，裂解产物的形貌为不发泡的致密结构。     

溶胶—凝胶法有机—无机精细复合材料P（VDF／TeFE）—SiO2的制备与显微 …

用溶胶－凝胶法制备了有机－无机精细复合材料Ｐ（ＶＤＦ／ＴｅＦＥ）－ＳｉＯ２。利用水解－聚合反应由正硅酸乙酯（ＴＥＯＳ）合成ＳｉＯ２溶胶，乙醇作溶剂，盐酸作催化剂。将Ｐ（ＶＤＦ／ＴｅＦＥ）溶于丙酮，并与ＳｉＯ２溶胶均匀混合。凝胶后经干燥和热处理得到有机－无机精细复合材料Ｐ（ＶＤＦ／ＴｅＦＥ）－ＳｉＯ２。用红外光谱分析、扫描电镜分析、差示扫描热分析和热失重分析对有机－无机精细复事材料Ｐ（ＶＤＦ／ＴｅＦ     

溶胶-凝胶法有机-无机精细复合材料P(VDF/TeFE)-SiO_2的制备与显微结构

用溶胶－凝胶法制备了有机－无机精细复合材料Ｐ（ＶＤＦ／ＴｅＦＥ）－ＳｉＯ２。利用水解－聚合反应由正硅酸乙脂（ＴＥＯＳ）合成ＳｉＯ２溶胶，乙醇作溶剂，盐酸作催化剂。将Ｐ（ＶＤＦ／ＴｅＦＥ）溶于丙酮，并与ＳｉＯ２溶胶均匀混合。凝胶后经干燥和热处理得到有机－无机精细复合材料Ｐ（ＶＤＦ／ＴｅＦＥ）－ＳｉＯ２。用红外光谱分析、扫描电镜分析、差示扫描热分析和热失重分析对有机－无机精细复合材料Ｐ（ＶＤＦ／ＴｅＦＥ）－ＳｉＯ２进行了显微结构表征。     

BP－SiC晶须的特性及显微结构研究

本文对稻壳合成的ＳｉＣ晶须（简称ＳｉＣｗ）中试产品进行了分析，结果表明：三种ＢＰ－ＳｉＣｗ的形貌及结构各具特点，ＢＰ－１ＳｉＣｗ表面粗糙，呈多节状；ＢＰ－３ＳｉＣｗ表面光滑平整，为完整β－Ｓｉｃ单晶；ＢＰ－ＳｉＣｗ介于两者之间，并含有一定量的弯晶。ＢＰ－ＳｉＣｗ的质量达到了美国、日本同类产品的水平。     

PECVD方法制备SnO2气敏薄膜的电子显微镜研究

通过ＳＥＭ、ＴＥＭ研究了ＰＥＣＶＤ方法制备的ＳｎＯ＿２薄膜的显微结构，讨论了沉积速率与颗粒大小的关系；在Ｓｉ、陶瓷和ＫＢｒ３种不同衬底上沉积的ＳｎＯ＿２薄膜的差异以及退火对ＳｎＯ＿２膜结晶状态的影响。结果表明，ＰＥＣＶＤ方法制备的ＳｎＯ＿２薄膜是非晶态，具有柱状结构。退火使非晶ＳｎＯ＿２膜向着多晶方向转化，演化过程为：非晶大颗粒→超微粒多晶→晶粒长大。     

含活性基团硅氮烷先驱体的裂解

用ＴＧ－ＧＣ，ＩＲ，元素分析，ＸＲＤ研究ＭｅＳｉＨＣｌ２与ＭｅＳｉＶｉ（Ｖｉ：－ＣＨ＝ＣＨ２）Ｃｌ２共氨解产物的裂解过程。     

PECVD法淀积氟碳掺杂的氧化硅薄膜表征

以正硅酸乙酯（ＴＥＯＳ）和八氟环丁烷（Ｃ４Ｆ８）为原料,采用等离子体增强化学气相淀积（ＰＥＣＶＤ）方法制备了氟碳掺杂的氧化硅薄膜（ＳｉＣＯＦ）．样品的Ｘ射线光电子能谱（ＸＰＳ）和傅立叶变换红外光谱（ＦＴＩＲ）分析表明薄膜中含有Ｓｉ－Ｆ、Ｓｉ－Ｏ、Ｃ－Ｆ、Ｃ－ＣＦ_ｘ、ＣＦ₂等构型．刚淀积的薄膜的折射率约为１．４０．对暴露在空气中以及在不同温度下退火后薄膜的折射率做了测量,并对其变化机理进行了讨论,同时表明了理想的淀积温度应是３００℃．     

掺Si对MOCVD生长的GaN单晶膜的黄带发射及生长速率的影响

对ＭＯＣＶＤ生长ＧａＮ：Ｓｉ薄膜进行了研究,研究表明随ＳｉＨ４／ＴＭＧａ流量比增大,ＧａＮ：Ｓｉ单晶膜的电子浓度增大,迁移率下降,Ｘ射线双晶衍射峰半高宽增加,同时这发射强度得到了大大的提高,并报导了随ＳｉＨ４／ＴＭＧａ流量比增大,ＧａＮ：Ｓｉ的生长速率降低的现象,研究结果还表明,预反应对ＧａＮ：Ｓｉ单晶膜黄带发射影响很大,预反应的减小可以使黄带受到抑制。     

Orientation dependent growth of SiC nanocrystals at the SiO2/Si interface

Cubic SiC nanocrystals are formed epitaxially and void-free on single crystal Si substrate by reactive annealing in CO. In this study characterization of the nucleation, growth and morphology is presented on differently oriented single crystal Si substrates. It is found that SiC nanocrystals of various shape can be grown in different densities on the (100), (110) and (111) Si surfaces with an average size of 30-60 nm. Effect of annealing time, CO concentration, substrate orientation and crystal size on crystallite growth is discussed. Parameters to obtain increased SiC nucleation density are determined.     

SiC单晶生长研究进展

SiC单晶生长是一个引人注目的研究热点，受到各国政府、科研人员的广泛关注。本文综述了SiC单晶生长的研究进展，对目前广泛采用的PVT法进行了详细介绍，讨论了原料、籽晶、温度、温度梯度、载体气压对单晶生长和质量的影响。对今后的研究方向提出了看法。     

Thin-film PZT/SiC structure on silicon substrate: Formation,structural features,and dielectric properties

A new thin-film structure representing the Pt/PZT/SiC/Si system is obtained. The structure comprises a lead zirconate titanate Pb(Zr,Ti)O₃ (PZT) film deposited onto thin (90–100 nm) single crystal silicon carbide layers of 3C-SiC and 4H-SiC polytypes grown by a new solid-phase epitaxy on single crystal silicon substrates. Methods used for the formation of this multilayer structure are described, and its structural and dielectric characteristics are presented.     

Microstructure and microchemistry of the Al/SiC interface

The characteristics of the Al/SiC interface play a critical role in controlling the properties of SiC-reinforced aluminium composites and aluminium-brazed SiC ceramic joints. Recently, a detailed investigation on the wettability of SiC single crystals by aluminium and several of its alloys was conducted. In order to understand further the nature of the Al/SiC interface, high resolution and conventional transmission electron microscope techniques have now been used to investigate its microchemistry and microstructure. The results revealed the coexistence of two polytype structures, rhombohedral and hexagonal, in the SiC single crystal structure. Aluminium carbide (Al₄C₃) and silicon were the reaction products found at the Al/SiC interface. From diffraction patterns, epitaxial orientation relationships between the SiC substrate and Al₄C₃, Si were determined.     

Reflectance spectra of a 6H-SiC single crystal placed in a strong homogeneous magnetic field

We have made a theoretical study of the external reflection coefficients of a uniaxial anisotropic SiC (6H polytype) single crystal exposed to a strong homogeneous magnetic field (in the cases of Faraday and Voigt configurations). For the first time, in the external reflection spectra of a 6H-SiC single crystal, regions of the appearance of new oscillations due to the action of a strong homogeneous magnetic field have been revealed. The interrelationship between the phonons and plasmons in a 6H-SiC single crystal exposed to a strong homogeneous magnetic field has been studied.     

掺氮碳化硅晶体的近红外光谱研究

分别用红外光谱测量系统和双光束分光光度计研究了室温下碳化硅单晶的光学性质,测得碳化硅晶体的透射率和反射率随波变化的关系.通过掺氮与非掺杂碳化硅各种光谱的比较,发现掺氮不仅使近红外透射率降低,也导致反射率下降,掺氮碳化硅晶体在可见光部分出现了比较明显的吸收带.此外,利用透射谱还获得非掺杂6H-SiC晶体的折射率.     

Synthesis of silicon carbide nanorods without defects by direct heating method

High quality silicon carbide single crystal nanorods were successfully synthesized through gas–solid reaction between silicon and multiwall carbon nanotubes (CNTS) by direct heating methods. The X-ray diffraction (XRD) analysis showed that the reaction product of Si vapor with CNTS is β-SiC. SEM and HRTEM images suggested that the SiC nanorods are 3C-SiC single crystals almost free of defects. Based on these results, it is presumed that the reaction first took place at an end of CNTS giving β-SiC nuclei, one of which with its [111] parallel to the tube direction could grow consecutively along this direction so that a straight and solid SiC single crystal rod was formed without defects.     

Synthesis of High Purity SiC Powder for High-resistivity SiC Single Crystals Growth

High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.     

Synthesis of SiC nanowires with in-situ deposition of carbon coating

SiC nanowires are effective reinforcement materials in ceramic matrix composites. A compliant coating such as carbon on nanowires is necessary in order to moderate the nanowire/matrix interfacial bounding for taking the most advantages of SiC nanowires. SiC nanowires with an in-situ deposition of carbon shell coating were fabricated by a novel chemical vapor growth process. Highresolution transmission electron microscopy examinations showed that the nanowires consisted of a single crystal beta-SiC core with an amorphous carbon shell 2-5 nm in thickness. The nanowires were straight with a length generally over 10 microm and a diameter 15-150 nm. The growth direction of the core SiC nanowires is (111). A simple three-step growth model for SiC nanowires was proposed based on a vapor-solid growth mechanism. Because the carbon-coated nanowires were grown directly on continuous Tyranno-SA SiC fibers, in-situ application of the present technique on the fabrication of SiC nanowire-reinforced SiC/SiC composites is expected.