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。     

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。     

多功能热丝化学气相沉积金刚石涂层制备设备的研制

根据国内热丝化学气相沉积金刚石制备设备现状现状,结合HFCVD法制备金刚石薄膜原理,研制多功能热丝化学气相沉积金刚石涂层制备设备。     

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     

热丝CVD大面积金刚石薄膜的生长动力学研究

在传统工业型热丝化学气相沉积（HFCVD）反应腔内，相关工艺参数取模拟计算优化值的条件下，采用XRD，SEM及Raman光谱等分析手段研究了单晶Si（100）上较大面积金刚石薄膜的动力学生长行为，讨论了晶格取向的变化规律。结果表明：优化工艺参数条件下，在模拟计算的衬底温度和气体温度分布均匀的区域内，沉积的金刚石薄膜虽存在一定的内应力，但整体薄膜连续、均匀，几何晶形良好，质量较高，生长速率达1．8μm／h。薄膜生长过程中晶形显露面受衬底温度和活性生长基团浓度的影响较大。     

等离子热丝化学气相沉积金刚石膜工艺参数研究

采用等离子热丝化学气相沉积(PHFCVD)装置进行了金刚石薄膜的制备实验。实验条件为：氢气流量为200sccm,甲烷流量为2～12sccm,基体温度为700～900℃,偏压为0～400V,真空室压力为4kPa。通过实验得出了甲烷含量、基体温度和偏压对沉积金刚石膜的影响,并运用扫描电子显微镜(SEM)、原子力显微镜(AFM)和X射线衍射(XRD)等测试方法对金刚石薄膜进行了观察分析。     

热丝CVD金刚石薄膜制备及碳纳米管形核作用的研究

利用热丝化学气相沉积法 (HF CVD)进行了金刚石薄膜制备和碳纳米管形核作用的研究。获得了制备金刚石薄膜的优化工艺参数。利用碳纳米管作为形核前驱获得了高质量的金刚石薄膜 ,其沉积速率可达 2 5 μm/h ,晶粒生长完美 ,而且没有出现聚晶现象。研究了碳纳米管涂料质量对薄膜沉积特性的影响 ,并对其机理进行了初步探讨     

CVD金刚石薄膜的成核机理研究

利用热丝化学气相沉积 ,在预沉积无定形碳的硅镜面基底及表面研磨预处理的铜基底上 ,实现了金刚石薄膜的沉积 ,并由此讨论了金刚石的成核机理。研究表明 ,无定形碳是金刚石成核的前驱态 ;成核密度不仅与基底材料有关 ,更主要由基底的表面状态决定 ,基底表面状态的设计是改善成核密度的最有效的方法。     

热丝CVD金刚石薄膜制备及碳纳米管形核作用的研究

利用热丝化学气相沉积法（HF－CVD）进行了金刚石薄膜制备和碳纳米管形核作用的研究。获得了制备金刚石薄膜的优化工艺参数。利用碳纳米管作为形核前驱获得了高质量的金刚石薄膜，其沉积速率可达2．5μm/h，晶粒生长完善，而且没有出现聚晶现象。研究了碳纳米管涂料质量对薄膜沉积特性的影响，并对其机理进行了初步探讨。     

化学气相沉积金刚石薄膜的摩擦学性能研究进展

介绍了化学气相沉积金刚石薄膜的主要方法 ,着重讨论了金刚石薄膜的摩擦学性能研究 ,简要分析了化学气相沉积金刚石薄膜中存在的问题。     

Filament-assisted growth of diamond films

Filament-assisted pyrolytic growth of diamond films on (100) Si wafers was investigated in an attempt to grow quality layers for semiconductor applications. The work was carried out in hydrogen ambient under a reduced pressure condition of about 100 torr (133, 322×10² Pa). Using isopropanol and methanol as carbon source chemicals, the growth process and film properties were characterized as functions of reactant concentration, filament and substrate temperature, reaction pressure and the total gas flow rate. Diamond films of good quality were grown under condition of low source concentration and small flow rate. However, the growth rates were generally slow. The films were polycrystalline. The filament and substrate temperatures were fairly critical to the nucleation and growth processes. The substrate surface finishing from diamond paste polishing predominated the nucleation site and grain size of the deposits.     

Diamond deposition on cemented carbide by chemical vapour deposition using a tantalum filament

Diamond deposition on WC-Co cemented carbide was examined by chemical vapour deposition using a tantalum filament. The filament was much superior to conventional tungsten filament for high-temperature use. Diamond film was deposited at a filament temperature up to about 2600 °C for tantalum filament, which was much higher than the maximum filament temperature available for tungsten (2000 °C). The critical methane concentration in H₂-CH₄ gas for diamond deposition became higher with increasing filament temperature. A deposition rate about 20 times higher was obtained when using a tantalum filament compared with a tungsten filament. The origin of the improved deposition rate of diamond on WC-Co substrate using a tantalum filament is discussed.     

Diamond deposition on copper: studies on nucleation, growth, and adhesion behaviours

This paper presents a systematic study on diamond growth on copper by microwave plasma chemical vapour deposition (MPCVD). It includes the following four main parts. 1. Effect of substrate pre-treatment on diamond nucleation. 2. Effect of deposition conditions on diamond nucleation and growth. 3.Preparation of free-standing diamond films using copper substrate. 4. Adherent diamond coating on copper using an interlayer. In the first part we show that diamond nucleation on copper is strongly affected by the substrate pre-treatment. The residues of abrasives left in the surface of the copper substrate play an important role in the diamond nucleation. In the second part we show that the diamond growth rate increases with microwave power and gas pressure. The effect of the microwave power is mainly an effect of substrate temperature. Increasing methane concentration results in a higher nucleation density and higher growth rate, but at the cost of a lower film quality. Gas flow rate has little influence on the diamond nucleation density and growth rate. In the third part we demonstrate the possibility of preparing large area free-standing diamond films using copper substrate, which has nearly no carbon affinity and usually leads to weak adhesion of the diamond films. The normally observed film cracking phenomenon is discussed and a two-step growth method is proposed for stress release. In the fourth part we show that adherent diamond coating on copper can be obtained using a titanium interlayer. Residual stress in the films is evaluated by Raman spectroscopy. It is found that with increase in the film thickness, the diamond Raman line shifts from higher wave numbers to lower, approaching 1332 cm–1. The stress variation along the depth of the film is also analysed using Airy stress theory.     

Effect of reaction pressure on the nucleation behaviour of diamond synthesized by hot-filament chemical vapour deposition

Synthetic diamond particles were deposited on a Si (1 0 0) substrate using a hot-filament chemical-vapour-deposition method in order to study the effect of the reaction pressure on the nucleation behaviour. The reaction pressure was controlled, as an experimental variable, from 2 to 50 torr under the following conditions: a filament temperature of 2200 °C, a substrate temperature of 850 °C, a total flow rate of 200 s.c.c.m. and a methane concentration of 0.8 vol%. Diamond deposits on the Si wafer were characterized by micro-Raman spectroscopy, scanning electron microscopy (SEM) and optical microscopy.The maximum nucleation density of diamond particles on the unscratched Si substrate is shown at the reaction pressure of 5 torr. These phenomena can be explained by the competition effect between -SiC formation, which increases the diamond nucleation density, and atomic-hydrogen etching which decreases the nucleation sites.A new fabrication method for a high-quality diamond film without any surface pretreatments is introduced using a combination process between diamond nucleation at low pressure (5 torr) and growth at high pressure (30 torr).     

Formation and Transport of Atomic Hydrogen in Hot-Filament Chemical Vapor Deposition Reactors

In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant is hydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless numbers for heat and mass transfer reveals that thermal conduction and diffusion are the dominant mechanisms for gas-phase heat and mass transfer, respectively. A simplified model has been established to simulate gas-phase temperature and H concentration distributions between the filament and the substrate. Examination of the relative importance of homogeneous and heterogeneous production of H atoms indicates that filament-surface decomposition of molecular hydrogen is the dominant source of H and gas-phase reaction plays a negligible role. The filament-surface dissociation rates of H2 for various filament temperatures were calculated to match H-atom concentrations observed in the literature or derived from power consumption by filaments. Arrhenius plots of the filament-surface hydrogen dissociation rates suggest that dissociation of H2 at refractory filament surface is a catalytic process, which has a rather lower effective activation energy than homogeneous thermal dissociation. Atomic hydrogen, acting as an important heat transfer medium to heat the substrate, can freely diffuse from the filament to the substrate without recombination.     

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     

Polishing of polycrystalline diamond by hot nickel surface

A microwave plasma technique has been employed to deposit polycrystalline diamond film over a molybdenum substrate button using a gas mixture of hydrogen and methane at a substrate temperature of 851°C. A CVD diamond coated molybdenum substrate button was mounted with a load against hot nickel plate and rotated for 3.45 h in a hydrogen ambient. Hot tungsten filament was used as a heat source to maintain the temperature of the nickel block and CVD diamond coated molybdenum button at 848°C. This experiment has reproducibly shown the successful polishing of polycrystalline CVD diamond by hot nickel. A Tencor profilometer and scanning electron microscope have been used to evaluate the surface smoothness and morphology before and after polishing the polycrystalline diamond thin films.     

大气下火焰法合成金刚石薄膜

本文介绍了用氧-乙炔火焰法在大气下合成金刚石薄膜的实验结果,初步研究了基板温度对金刚石晶体生长速度、结晶习性的影响,指出了在金刚石(111)及(100)晶面上外延单晶金刚石膜的温度范围,还探讨了氧对薄膜的质量均匀性的影响。     

Synthesis of Diamond Thin Films on TC4 by Using a Scanning Linear Flame

A scanning linear flame is used to deposit diamond films over a large area, and with high quality and good continuity by employing appropriate cooling means for the substrate. It is found that the structure and morphology of the deposited films mainly depend on the substrate temperature, the ratio of 0₂ to C₂H₂ flow rate and the relative position of the substrate with respect to the flame. These factors affecting the structure and morphology of diamond films are interrelated. Moreover, the influences of surface pretreatments on nucleation and growth of diamond films are also studied. The experimental results show that the nucleation density of diamond films is enhanced by scratching the surface of the substrate with diamond grit and initially coating a mechanical pump oil layer. For the substrate surface etched with metallographic etching acid, the nucleation and growth of diamond films are very uniform. In addition, the adhesion between the film and substrate is enhanced. Nucleation is favored on the prominent features of the substrate, i.e. scratch and crystal boundary.