反应气压对MWPCVD金刚石膜中非金刚石相碳含量的影响

在水冷反应室式MWPCVD装置中以CH4和H2为反应气体进行了金刚石膜的沉实验，研究了反应气体的压强对金刚石膜中非刚石碳相含量的影响，实验发现，当微波输入功率较小时，随着反应气压的上升，沉积膜中非金刚石相碳的含量单调下降，当微波输入功率较大时，沉积膜中非金铡石相碳的含量先随着反应气压的上升而降低，后又随着反应气压的上升而稍稍增加。     

氧气对MWPCVD制备金刚石膜的影响

在水冷反应室式微波等离子体化学气相沉积装置中以混合的CH4/H2/O2为反应气体,研究了O2浓度对制备金刚石膜的影响.实验发现,很低浓度的O2会显著促进金刚石的沉积,并稍稍抑制非晶C的沉积,因而沉积膜中非晶C的含量急剧下降;较高浓度的O2会同时抑制金刚石和非晶C的沉积,但由于抑制金刚石的作用更强烈,沉积膜中非晶C的含量反而有所升高.另外,O2的存在,有利于沉积颗粒较小的金刚石膜.     

氧气对MWPCVD制备金刚石膜的影响

在水冷反应室式微波等离子体气相沉积装置中以混合的CH4／H2／O2为反应气体,研究了O2浓度对制备金刚石膜的影响,实验发现,很低浓度的O2会显著促进金刚石的沉积,并稍稍抑制非晶C的沉积,因而沉积膜中非晶C的含量急剧下降;较高浓度的O2会同时抑制金刚石和非晶C的沉积,但由于抑制金刚石的作用更强烈,沉积膜中非晶C的含量反应有所升高,另外,O2的存在,有利于沉积颗粒较小的金刚石膜。     

气压和偏流对高掺硼金刚石晶体性质的影响(英文)

采用热丝化学气相沉积法,改变工作气压和偏流,在硅基片上沉积了高掺硼金刚石膜。利用扫描电镜(SEM)、拉曼光谱和X射线衍射仪对沉积的金刚石膜表面形貌和结构进行表征。结果显示:当气体压强从3kPa降低到1.5kPa时,金刚石膜有较平的表面形貌和和较好的晶形,薄膜的晶体性质得到良好的改善。但是继续降气体压强,从1.5kPa到0.5kPa时,却呈现出相反的趋势。固定气体压强(1.5kPa),改变偏流,结果表明:适当的偏流(3A)可以改善掺硼金刚石的质量,偏流较高会导致薄膜中非金刚石相增多。     

不同反应气源对制备纳米金刚石膜的影响

为确定两种典型的反应气源对制备纳米金刚石膜的影响,分别以CH4/Ar/H2及CH4/N2混合气体作为反应源,用微波等离子体化学气相沉积(MWPCVD)法制备纳米金刚石薄膜.XRD和Raman分析表明两种气源条件下得到的膜材均为金刚石多晶膜,但用CH4/N2气为反应源沉积的膜材中非金刚石相成分明显更多;AFM和SEM对照分析证实所有膜层的平均晶粒尺寸及表面粗糙度均在几十纳米量级,但CH4/N2气源沉积的膜中容易形成异常长大的晶粒,不利于表面质量的提高.研究结果表明,以CH4/Ar/H2混合气体作为反应气源可制备物相组成纯度更高、表面形态更为优越的纳米金刚石膜.     

用于二次电子发射阴极的纳米金刚石膜

为获得导电性和二次电子发射性能均好的金刚石阴极材料,分别以CH4/Ar/H2、CH4/N2及CH4/N2/H2混合气体作为反应气源,用微波等离子化学气相沉积(MWPCVD)法制备出不同组成结构特点的纳米金刚石薄膜.XRD和Raman检测表明3种气源条件下得到的膜材均为金刚石多晶膜,但用CH4/N2反应源沉积的膜材中非金刚石相成分明显更多;AFM分析证实所有膜层的平均晶粒尺寸均在100nm以下,属纳米晶金刚石膜.用自行设计的二次电子发射系数测量装置对比检测所得膜层的二次电子发射特性,结果表明各金刚石膜均在初级入射电子能量达约1keV时,有最高的二次发射系数(δmax);并且以CH4/Ar/H2反应源制备的金刚石相纯度最高的膜材的δmax最大,达到17左右,是适用于二次电子发射阴极的潜在材料.     

含氧碳源提高金刚石膜沉积速率的研究

采用微波等离子体化学气相法合成的金刚石膜质量好，但采用常规CH4-H2反应气体体系，金刚石膜的沉积速率较慢。为此，实验研究了C2H5OH-H2、CH3COCH3-H2等含氧体系下碳源浓度、微波功率、气体压力对金刚石膜沉积速率、表面形貌、电阻率的影响。结果表明，使用C2H5OH—H2、CH3COCH3-H2等含氧体系，金...     

温度场对金刚石薄膜质量的影响

在引进的韩国微波等离子化学气相沉积（MPCVD）设备中,利用氢气和甲烷作为气源,在单面抛光的（100）单晶硅片上研究了不同的形核温度和生长温度条件下制备出金刚石薄膜。通过Raman光谱、XRD光谱和扫描电子显微镜（SEM）对制备的金刚石膜的质量进行表征。研究结果表明,形核温度和生长温度对金刚石膜的生长均有影响。形核温度过低会增大薄膜中的非金刚石相的含量,促使二次形核增加,降低了金刚石薄膜质量。随着生长温度的升高,金刚石中非金刚石相含量越少,金刚石的质量提高,但金刚石的晶面同时也被大量刻蚀。     

金刚石薄膜材料的研制进展

早期,在低压高温下,沉积金刚石膜主要依赖于通过化学气相沉积工艺使碳氢化物气体发生热分解。苏联科学家在这方面进行了开拓性的工作。在低压下形成的这种膜具有一系列的结构、形态、物理性质特征。它含有较大百分比的石墨碳及其它碳或碳-氢结构。在低压下,甚至形成金刚石薄膜的过渡物——类金刚石碳膜和类金刚石碳氢膜。早期的金刚石生长速率极小,约0.1μm/h,以致于它无多少实用价值。1982年,S.Ma-tsumoto采用热灯丝化学气相沉积法,1983年M.Kamo用微波等离子体化学气相沉积法制     

水冷反应室式MWPCVD制备金刚石膜装置研制

微波等离子体化学气相沉积(MWPCVD)是制备金刚石膜的一种重要方法.为了获得金刚石膜的高速率大面积沉积,研制成功了水冷反应室式MWPCVD制备金刚石膜的装置.装置在微波输入功率为3.0 kW时能长时间稳定运行,并在硅衬底上沉积出金刚石膜.     

新型MPCVD装置在高功率密度下高速沉积金刚石膜

使用自行研制的新型MPCVD装置,以H2-CH4为气源,在输入功率为5kW,沉积压力分别为13.33、26.66kPa和不同的甲烷浓度下制备了金刚石膜。利用等离子体发射光谱法对等离子体中的H原子和含碳的活性基团浓度进行了分析。用扫描电镜、激光拉曼谱对金刚石膜的表面和断口形貌、金刚石膜的品质等进行了表征。实验结果表明,使用新型MPCVD装置能够在较高的功率密度下进行金刚石膜的沉积;提高功率密度能使等离子体中H原子和含碳活性基团的浓度明显增加,这将提高金刚石膜的沉积速度,并保证金刚石膜具有较高的质量。     

基片位置对微波等离子体合成金刚石的影响

用自制的微波功率为5kW的微波等离子体(MPCVD)装置、用H2/CH4/H2O作为反应气体在较高的沉积气压(12.0kPa)条件下,研究了基片放置在等离子体球边缘附近不同位置对CVD金刚石沉积和生长的影响。结果表明,CVD金刚石的形核和生长对环境的要求是不同的;在等离子体球边缘处不利于金刚石的形核,但有利于高质量金刚石的沉积。     

圆柱谐振腔式MPCVD装置中氢、氩微波等离子体分布规律的数值模拟

在使用简化的等离子体放电模型的基础上,模拟了圆柱谐振腔式微波等离子体沉积室中,不同金刚石膜生长条件下微波等离子体的分布状态。在模拟中,针对纳米金刚石的生长环境,就纯氩气反应气体中,不同的输入功率、不同气体压力条件下,沉积室中形成的等离子体分布的变化规律进行了模拟,将其与一般氢气气氛下的相应模拟结果相对比。模拟所获得的结果,对微波等离子体方法沉积金刚石膜的操作环境的优化,有着一定的指导意义。     

Uniform coating of CVD diamond on metallic wire substrates

Diamond was coated onto wire substrates of various transition metals (Mo, W or Ti) of 0.5 mm diameter by the microwave plasma CVD method from a gas mixture of the CO–H₂ system. The CVD conditions for a uniform diamond coating were microwave power, 750–1100 W; total pressure, 2000 Pa; total flow rate, 200 ml min-1; CO concentration, 5 vol%; treatment time, 5 h. The wire substrates were mounted vertically or horizontally on a pyrophyllite susceptor, which was placed parallel to the irradiation direction of microwave power. Homogeneous and fine-grained diamond film was prepared on the whole surface of horizontal W wire substrate with a wire height of 2 mm from the susceptor. To obtain a dense diamond coating, the height has to be as low as possible in the plasma region, where the plasma density is higher at lower substrate temperature. Low pressure and high microwave power were suited for fine-grained coating. Diamond deposition rate was found to be more dependent on pressure than substrate temperature. As the pressure increased, a glassy carbon film was formed instead of diamond. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of Plasma Power on the Deposition of Diamond Coatings on Pure Titanium

Diamond coatings appear to be a promising solution for the improvement of tribological behavior of titanium alloys. By means of microwave plasma assisted chemical vapor deposition (MW-PACVD), diamond coating was deposited on pure titanium using CH₄/H₂ gas mixtures under different plasma powers. Surface and interface characterization of the deposited coating under different plasma powers was carried out using SEM, grazing incidence x-ray diffraction (GIXD) and Raman spectroscopy. Adhesion of diamond coating with substrate was evaluated using an indentation tester. Results showed that adhesion of diamond coatings was not good under high plasma power, whereas the crystallinity of diamond coating was not good under low plasma power. The higher the plasma power, the larger the diamond crystal size, the less content of non-diamond carbon and the poorer the adhesion strength. During the diamond deposition, growth of TiC competed with diamond formation for the available carbon content. Relatively low plasma power inhibited TiC formation more than diamond formation. Under a high plasma power, the formation of a thick and porous TiC layer appeared to promote interfacial debonding and spallation of the diamond coating.     

金刚石薄膜在氧化铝陶瓷上低压成核

在微波等离子体化学气相沉积（MPCVD）系统中,用低压成核方法,在氧化铝陶瓷基片上获得了高成核密度的金刚石薄膜.实验表明,金刚石成核密度随系统压强减小而提高.在此基础上,提出一种MPCVD系统中金刚石成核的动力学模型,并指出对应于最高成核密度有一临界压强存在.     

Growth behavior of CVD diamond films with enhanced electron field emission properties over a wide range of experimental parameters

In this study, diamond films were synthesized on silicon substrates by microwave plasma enhanced chemical vapor deposition (CVD) over a wide range of experimental parameters. The effects of the microwave power, CH₄/H₂ ratio and gas pressure on the morphology, growth rate, composition, and quality of diamond films were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). A rise of microwave power can lead to an increasing pyrolysis of hydrogen and methane, so that the microcrystalline diamond film could be synthesized at low CH₄/H₂ levels. Gas pressure has similar effect in changing the morphology of diamond films, and high gas pressure also results in dramatically increased grain size. However, diamond film is deteriorated at high CH₄/H₂ ratio due to the abundant graphite content including in the films. Under an extreme condition of high microwave power of 10 kW and high CH₄ concentration, a hybrid film composed of diamond/graphite was successfully formed in the absence of N₂ or Ar, which is different from other reports. This composite structure has an excellent measured sheet resistance of 10–100 Ω/Sqr. which allows it to be utilized as field electron emitter. The diamond/graphite hybrid nanostructure displays excellent electron field emission (EFE) properties with a low turn-on field of 2.17 V/μm and β = 3160, therefore it could be a promising alternative in field emission applications.     

Diamond synthesis from methane-hydrogen-water mixed gas using a microwave plasma

Fine particles of diamond or diamond-like carbon were synthesized from methane-hydrogen-water mixed gas using a microwave plasma. The growth rate was several times as fast as that of methane-hydrogen mixed gas, which is the conventional method to prepare diamond from the gas phase. Promotion of the methane decomposition reaction and the removal reaction of byproduct graphite by OH radicals produced in the plasma were credited with enhancing the rate.     

Deposition of diamond coating on pure titanium using micro-wave plasma assisted chemical vapor deposition

The nucleation and growth of diamond coatings on pure Ti substrate were investigated using microwave plasma assisted chemical vapor deposition (MW-PACVD) method. The effects of hydrogen plasma, plasma power, gas pressure and gas ratio of CH₄ and H₂ on the microstructure and mechanical properties of the deposited diamond coatings were evaluated. Results indicated that the nucleation and growth of diamond crystals on Ti substrate could be separated into different stages: (1) surface etching by hydrogen plasma and the formation of hydride; (2) competition between the formation of carbide, diffusion of carbon atoms and diamond nucleation; (3) growth of diamond crystals and coatings on TiC layer. During the deposition of diamond coatings, hydrogen diffused into Ti substrate forming titanium hydride and led to a profound microstructure change and a severe loss in impact strength. Results also showed that pre-etching of titanium substrate with hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Plasma power had a significant effect on the surface morphology and the mechanical properties of the deposited diamond coatings. The effects of gas pressure and gas ratio of CH₄ and H₂ on the nucleation, growth and properties of diamond coatings were also studied. A higher ratio of CH₄ during deposition increased the nuclei density of diamond crystals but resulted in a poor and cauliflower coating morphology. A lower ratio of CH₄ in the gas mixture produced a high quality diamond crystals, however, the nuclei density and the growth rate decreased dramatically.