Simulations of the Dependence of Gas Physical Parameters on Deposition Variables during HFCVD Diamond Films

During the growth of the hot filament chemical vapor deposition （HFCVD） diamond films, numerical simulations in a 2-D mathematical model were employed to investigate the influence of various deposition parameters on the gas physical parameters, including the temperature, velocity and volume density of gas. It was found that, even in the case of optimized deposition parameters, the space distributions of gas parameters were heterogeneous due primarily to the thermal blockage come from the hot filaments and cryogenic pump effect arisen from the cold reactor wall. The distribution of volume density agreed well with the thermal round-flow phenomenon, one of the key obstacles to obtaining high growth rate in HFCVD process. In virtue of isothermal boundary with high temperature or adiabatic boundary condition of reactor wall, however, the thermal roundflow was profoundly reduced and as a consequence, the uniformity of gas physical parameters was considerably improved, as identified by the experimental films growth.     

Two-step growth of HFCVD diamond films over large areas

This paper reports the results of a two-step hot filament chemical vapor deposition method to improve the quality of diamond films. Diamond films were deposited on a Si(100) substrate having an area of 45 cm² and a thickness of 60 μm, employing a HFCVD system. The first step is the growth of CVD diamond in the HFCVD reactor. In the second step, the samples were treated in a saturated solution of H₂SO₄:CrO₃ and rinsed in a (1:1) solution of H₂O₂:NH₄OH. After this procedure, a second diamond layer was deposited. The diamond films were analyzed by Raman scattering spectroscopy (RSS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The films showed a high degree of purity with a thickness of 60 μm, presenting uniform characteristics over a large area.     

温度场对热丝化学气相沉积大面积生长金刚石膜的影响

用１００×１００ｍｍ大面积加热器进行了气相生长金刚石膜试验，对得到的金刚石膜样品作了拉曼光谱分析，并用扫描电镜观察了不同空间区域中金刚石形核的特点．拉曼光谱和扫描电镜观察的结果，均给出了与温度分布特点较好的对应．本研究的结果，指出厂热丝法大面积气相生长金刚石膜工业应用的可能性．     

热丝化学气相沉积纳米金刚石修复损伤PCD刀具的研究

利用热丝化学气相沉积装置, 以聚晶金刚石片为衬底, 在氢气/丙酮/氩气反应体系中研究了衬底温度对纳米金刚石生长的影响。采用扫描电子显微镜对生长结果进行了表征, 结果表明在衬底温度950℃的情况下, 金刚石薄膜表面结构呈\     

优化HFCVD系统内衬底温度场的数值研究

热丝对衬底的辐射是决定热丝化学气相沉积金刚石薄膜系统内衬底表面温度分布的主要因素。本文基于辐射传热基本原理 ,并考虑变热物性衬底的横向热传导 ,改进了衬底温度场的计算模型。数值模拟了衬底表面所受辐射热流密度分布和温度分布 ,结果表明辐射热流密度分布与辐射热平衡得到的温度分布形状一致 ,而衬底横向热传导提高了温度分布的均匀性。进一步计算并讨论了环境温度和热丝高度、数目、间距等几何参数对衬底表面所受辐射热流密度分布和温度分布的影响 ,给出获得 8cm× 8cm大面积均温区对应的热丝几何参数     

Bias enhanced nucleation of diamond thin films in a modified HFCVD reactor

In this study we investigated the nucleation of synthetic diamond thin films on Si substrates by double bias enhanced Hot Filament Chemical Vapour Deposition (HFCVD) method. First, we investigated the influence of the bias voltage and secondly the influence of the nucleation time under different bias voltages. The bias voltage was varied from −120 V up to −220 V as well as the nucleation time was changed from 30 up to 120 min in order to obtain the optimized nucleation conditions for following growth of continuous diamond layer. Samples were analyzed by Scanning Electron Microscopy (SEM) and Raman Spectroscopy. SEM was used for determination of cluster sizes and their distribution on the Si surface, while Raman Spectroscopy for determination and analysis of carbon phases.     

热丝CVD系统内衬底温度分布的数值研究

热丝法化学气相沉积金刚石薄膜系统内 ,衬底温度和碳源气体浓度是金刚石薄膜生长最为重要的参数。本文根据传热学基本原理 ,数值模拟了衬底表面辐照度、温度分布 ,讨论了衬底热传导等因素对衬底温度分布的影响 ,探讨了如何改善衬底温度均匀性。结果表明 ,考虑衬底横向热传导后 ,衬底表面温度分布均匀性明显优于基于辐射热平衡得到的温度分布 ,在一定程度上有利于生长大面积薄膜。     

复合材料结构固化温度场精化模拟

以往的复合材料固化过程模拟,大多只是在简单外部条件下,或者针对厚尺寸复合材料构件进行的厚度方向的温度场模拟,而与实际复合材料的固化过程有一定的偏差。本文在考虑辅助材料、模具以及罐内强迫对流换热现象的情况下,建立了复合材料热压罐工艺固化温度场的精化模拟方法。在此基础上,针对常用航空复合材料结构以及材料体系,进行了相应的固化温度场模拟,并对结果进行了分析。     

等离子体化学气相法沉积金刚石薄膜

本文介绍和评述了化学气相沉积法制备人造金刚石薄膜及其进展。重点评述了反应机理、发展历史、沉积方法、补底材料、检测手段。论述了有利于形成立方晶系金刚石材料的沉积条件。     

CVD金刚石膜紫外光探测器

宽禁带半导体金刚石具有许多独特特性，基于此种材料的紫外光探测器能在高温、强腐蚀和强辐射等恶劣环境下工作，成为近年来紫外探测技术研究的重点课题之一。本文综述了CVD金刚石膜紫外光探测器的研究及应用进展。     

燃焰法沉积金刚石薄膜的实验研究

研究分析了燃焰法沉积金刚石薄膜时基片表面处理状态，燃烧气体流量比基片温度对薄膜成核密度、质量和晶体形态的影响。结果表明，在不同粒度的研磨粉研磨的基片表面上金刚石薄膜成核密度不同；燃烧气体流量配比对金刚石薄膜的质量影响很大；基片温度是影响金刚石薄膜晶体形态的一个重要因素。     

镍衬底上定向金刚石膜的成核与生长

提出了一种包括晶粒接种、高温退火、成核、生长四过程的薄膜沉积新方法 ,用射频等离子体增强热丝化学气相沉积系统 ,在Ni衬底上制备了定向金刚石膜。通过对成核和生长两过程工艺条件的研究 ,掌握了提高成核密度和金刚石定向生长规律。实验还表明 ,膜与Ni衬底之间未见Ni C H界面层的形成     

掺B金刚石膜的电火花抛光实验研究

通过化学气沉积过程中掺B,制备的金刚石膜电阻率下降10-19,导致金刚石膜整体导电,可采用电火花抛光。用扫描电镜和Raman分析了金刚石膜电加工表面的形貌和成分。金刚石膜的电火花抛光是多种效应综合作用的结果,即金刚石膜熔化、汽化、碳的氧化和蒸发、爆炸抛出、界面的化学反应以及金刚石的石墨化。通过实验研究了电加工参数对表面粗糙度和加工速度的影响,通过回归分析得到电火花抛光表面粗糙度和加工速度的经验公式,其相关系数的平方分别为0.91和0.99,表明拟合精度高。试验结果表明,放电电流和脉冲宽度对加工面的表面粗糙度和加工速度影响很大。放电电流为5 A、脉冲宽度为380μs时,抛光后表面粗糙度Ra<1μm。     

用发射天线式微波等离子体CVD装置沉积大面积金刚石薄膜

在国内首次研制成功了高气压发射天线式微波等离子体辅助化学气相沉积金刚石薄膜装置，用该装置成功地在３英寸的单晶硅衬底上沉积了Φ７０ｍｍ的金刚石薄膜。这一成果填补了国内空白，对我国金刚石薄膜研究领域的设备更新换代和开发应用具有重要意义。     

微波等离子体低温制备金刚石薄膜

用微波等离子体法在低于６００℃的条件下合成了金刚石薄膜，分别用Ｒａｍａｎ光谱、ＸＲＤ、ＸＰＳ，红外光谱对薄膜进行了表征；讨论了工艺条件同薄膜结构，特别是表面形貌的关系，指出低温有利于（１００）面的形成。     

Effect of Seed Sizes on Growth of Large Synthetic Diamond Crystals

For the growth of large synthetic diamond crystals by temperature gradient method （TGM）, the grit sizes of seed crystals have great effects on the growth rate and quality of large grown crystals. Because of the limited area of seed surfaces, the maximum diffusion flux of carbon source, which could be absorbed by the seed, is related to the seed size. And with increasing the seed sizes, the growth rates also increase markedly. However, the seed sizes should be lower than a certain value, which determines the crystal quality directly. For example, with NiMnCo alloy as the metal solvent, when the seed size increases from 0.5 to 1.8 mm, the growth rate increases greatly from about 1.1 to 3.2 mg/h; when the size is beyond 2.0 mm, more and more metal inclusions would be incorporated into the grown crystals, and the crystal quality is destroyed heavily. Finite element analysis （FEA） shows that, due to the special assembly of growth cell, the diffusion of carbon source in the metal solvent is very inhomogeneous, which could be substantiated directly by the appearances and shapes of large grown crystals and the remains of carbon source. And this inhomogeneous diffusion of carbon source would be very harmful to the growth of large diamond crystals, especially when large-size seed crystals are used.     

热丝法化学气相沉积金刚石系统温度分布与薄膜生长关系研究

对热丝化学气相沉积金刚石薄膜系统内的三种传热方式（传导、对流和辐射）进行了比较分析,数值计算了气相空间温度分布和衬底表面二维温度分布。采用热丝化学气相沉积工艺制备了金刚石薄膜,扫描电镜结果显示金刚石薄膜在不同生长区域呈现出与温度分布相关的微观结构与形貌。     

金刚石和类金刚石膜研究及其在电声领域中的应用

金刚石和类金刚石膜是当今材料界的研究热点之一，有着极其诱人的应用前景。本文简要综述了该膜系的发展过程和现在水平。并结合作者自己的研究工作，对膜系应用于扬声器振膜上以提高其高频响应范围的研究和应用工作进行较全面的调研，综述了国内外在该领域的最新进展。     

大型铸钢件热场测定与计算机数值模拟的研究

本文报导了对大型铸钢件热场测定以及计算机数值模拟的结果。对大型铸钢件的温度场进行测定,并对检测得到的数据进行处理,获得有关浇注金属及铸型材料的热物理参数用于计算,从而获得铸件的温度场分布,以此核对铸件生产工艺的合理性,对不同工艺进行浇注的数值模拟计算,得到较为合理的铸件生产工艺,可供生产参考。     

基片位置对MWPCVD制备金刚石薄膜的影响

在石英钟罩式微波等离子体化学气相沉积实验装置中研究了基片位置对金刚石薄膜沉积质量的影响。扫描电子显微镜显微形貌观察和激光喇曼谱分析表明 ,对微波等离子体化学气相沉积制备金刚石薄膜而言 ,基片位置处于近等离子体球下游区域将有利于改善金刚石薄膜沉积质量。