我国CVD金刚石制备技术再上新台阶

<正>近日,河北省激光研究所研发的直径5英寸CVD金刚石窗口制备技术再上台阶,其产品厚度达到1mm,比之前的0.7mm高出0.3mm。这标志着我国915MHz、75kW的微波CVD金刚石设备基本成熟,实现了赶超国外先进水平的目标。CVD金刚石膜研究已有30余年的历史,不断有新的亮点和新的研究方向出现。纳米(NCD)和超纳米(UNCD)金刚石膜及相关应用研究在相当长一段时间内将继续是国内CVD金刚石膜研究的热点之一。"基于金刚石膜的SOD、SAW,行波管和其它高功率器件,光学窗口(球罩)等高技术应用将有可能得到更     

不同晶粒尺寸对CVD金刚石膜机械性能的影响

采用热丝辅助化学气相沉积（CVD）工艺制备出纳米、微米及细晶粒金刚石膜材料。观察了这三种金刚石膜的表面形貌并对上述金刚石膜的物理机械性能包括抗弯强度和耐磨性进行了实验性研究。结果表明,细晶粒结构的金刚石膜具有最高的抗弯强度．纳米结构的金刚石膜耐磨性最好。综合两个技术指标认为：细晶粒金刚石膜是三种晶粒结构中最佳的刀具制造材料。     

B掺杂CVD金刚石厚膜的应力研究

在HFCVD系统中采用B2O3作为掺杂源制备了B掺杂CVD金刚石厚膜,利用X-射线衍射仪研究了B掺杂对CVD金刚石厚膜应力的影响.结果显示,B元素的掺杂改变了金刚石膜的成分和结构,膜中非晶态碳含量随着掺杂浓度的增加而增加.在低掺杂时CVD金刚石厚膜成核面上的应力状态为压应力,在高掺杂时应力状态为张应力,张应力值随着掺杂浓度的增加而增加.掺杂CVD金刚石厚膜生长面的应力为张应力,在高掺杂时的张应力值较高.     

CVD金刚石衬底上抗氧化、增透膜的制备与性能

采用射频磁控反应溅射法在化学气相沉积(chemical vapor deposition,CVD)的金刚石衬底上制备了AlN薄膜以及AlN/Si和AlN/Ge膜。通过X射线衍射分析了衬底加热温度对薄膜微结构的影响和薄膜高温下的氧化行为。结果表明:在衬底加热温度低于380℃时制备的AlN薄膜为非晶态,480℃时AlN薄膜为六方多晶。AlN薄膜在800℃热暴露后开始氧化,900℃时基本被氧化为Al2O3。在CVD金刚石上制备的AlN/Si和AlN/Ge膜都能提高金刚石在长波红外波段(8～10μm)的透过性能,单面最大增透分别为8%和3%。镀有AlN/Ge膜的CVD金刚石在800℃高温热暴露实验中,有AlN/Ge膜保护的金刚石表面未发生刻蚀。高温下AlN/Ge膜对金刚石有很好的保护作用,同时增透效果没有明显下降。     

CVD金刚石制备方法及其工业化前景分析

文章对多种CVD金刚石膜制备方法进行了介绍,同时对近年来国内外CVD金刚石技术及其产业发展状况、应用领域开发、潜在的市场前景等方面进行了分析讨论.指出:作为21世纪的高新材料,CVD金刚石及其工具产品的产业化发展,必将在科技、军工及民用工业等技术领域起非常重要的作用.     

单晶金刚石膜与多晶金刚石膜的制备工艺及性能

本文主要介绍了用微波等离子体化学气相沉积法(以下简称MP CVD法)以甲醇-氢气混合气和丙酮-氢气混合气为源气体,分别以单晶硅的(111)面和人造金刚石的(100)面为衬底材料,制备出了面积为20mm×20mm厚为10μm的多晶金刚石膜和面积为1.0mm×1.0mm厚为5μm的单晶金刚石膜。通过试验发现,源气体配比和衬底温度对薄膜质量起决定性作用。另外,衬底在反应腔中的位置对薄膜的生成也有很大影响。单晶金刚石膜制备过程中衬底金刚石的晶体取向与金刚石薄膜的生长及质量有密切的关系。在金刚石的(100),(110)和(111)面上分别获得了单晶金刚石膜和金刚石多晶粒子。选用扫描电镜、显微激光拉曼、反射电子衍射对多晶金刚石膜及单晶金刚石膜的性能进行了测试。     

CVD金刚石膜超精密度刀具技术研究

文章对CVD金刚石的物理特性进行了描述,研究了CVD金刚石膜制作超精密刀具的工艺技术方法,设计了生产工艺流程,对生产的CVD金刚石膜直刃和圆弧超精密刀具的精度及加工件的精度进行了测试,表明CVD金刚石膜是一种非常优异的超精密刀具的制作材料,应用前景非常广阔.     

河北省科学院高品级CVD金刚石引关注

正近日,河北省激光研究所又一批高质量CVD(化学气相沉积)金刚石刀具产品如期发货美国,标志着该所2017年美国市场的产品订单全部完成。近年来,河北省激光研究所大力推进CVD金刚石材料研究与开发,产业化制备技术优势不断凸显,目前已成为世界范围内少数能生产高品级CVD金刚石的厂商之一,步入了产业化的快车道。     

论化学气相沉积(CVD)金刚石技术最新发展

描述了国内外化学气相沉积(CVD)金刚石技术研究及产业最新进展,介绍了CVD金刚石的基本生产方法、加工手段、产品类型及应用领域。通过对国内外CVD金刚石技术及产品研究最新进展情况的介绍,指出了我国与世界先进的(CVD)金刚石技术存在的差距,阐述了CVD金刚石市场发展存在的问题并提出改进的建议。     

CVD金刚石膜投资财务分析

文章从经济的角度,通过专业的财务分析,对CVD金刚石膜这一新型材料的投资价值进行研究。研究认为,CVD金刚石膜将成为金刚石材料未来发展的主流,其材料和制品具有广阔的市场前景。因此,投资CVD金刚石膜将获得丰厚的经济回报。     

Improvement of Cutting Performance of Silicon Nitride Tool by Adherent Coating of Thick Diamond Film

A thick diamond film was coated using two-stage microwave plasma CVD in the COH, system on a pretreated silicon nitride substrate for a cutting tool. The effects of acid treatment and microflawing treatment of the substrate on adherence of the film and cutting performance were investigated as well as the effects of two-stage CVD conditions. The combination of substrate pretreatment in a hot, strong acid solution of HF and HNO₃ and subsequent ultrasonic microflawing pretreatment with diamond grains resulted in the anchored deposition of CVD diamond into the micropores in the silicon nitride substrate. An excellent adherence of the diamond film to the substrate was attained by the two-stage CVD, which consists of a first CVD of fine diamond grains into the micropores and a second higher rate CVD of thick diamond film (thickness >30 pm). A dense layer composed of diamond-like carbon and silicon nitride was formed deep in the boundary region of the substrate during long CVD treatment. Long tool life of the silicon nitride chip coated with a thick diamond film was verified by a milling test using Al-20 wt% Si alloy as the work material.     

Partially stabilized zirconia substrate for chemical vapor deposition of free-standing diamond films

In this work we investigated the use of partially stabilized zirconia (PSZ) as the substrate for deposition of CVD diamond films. The polycrystalline PSZ substrates were sintered at high temperatures and the results showed that this material has unique properties which are very appropriated for the growth of free-standing diamond films. The diamond nucleation density on PSZ is high, even without seeding, and the CVD diamond film was totally released from the substrate after the deposition process, without cracking. Micro-Raman analysis revealed that the free-standing diamond film had a good crystallinity on both surfaces with practically no stress in the structure. The same PSZ substrate can be reutilized for the deposition of a large number of diamond films. The average growth rate is about 5–6 μm/h in a microwave plasma reactor at 2.5 kW. The deposition process causes the reduction of ZrO₂, producing ZrC. The high mobility of oxygen in the zirconia matrix at high temperature would probably help to etch the interface region between the substrate surface and the diamond film, decreasing the adhesion strength and eliminating some defects in the film structure related to non-diamond carbon phases.     

Thermal oxidation of CVD diamond

A thermal oxidation process of diamond films grown by chemical vapor deposition (CVD) has been studied. The oxidation was realized via heating of the CVD films in air. Pristine and oxidized CVD diamond films were analyzed with Raman spectroscopy and scanning electron microscopy (SEM) techniques. Raman spectroscopy revealed substantial changes in the polycrystalline diamond film composition induced by oxidation. A selective oxidation of disordered carbon and small size diamond crystallites was obtained at appropriate temperatures. A model explaining the formation and oxidation of the CVD diamond films containing the micrometer single diamond cores surrounded by the nanocrystalline diamond and disordered carbon has been proposed on the basis of the obtained results.     

Diamond nucleation suppression in chemical vapor deposition process

A systematic study of the effect of different pre-treatments of the Si substrate surface in suppressing diamond nucleation was performed to investigate the nature of the nucleation centers in chemical vapor deposition (CVD) of diamond. The Si substrates were initially scratched with diamond powder and then submitted to one of the following pre-treatments: thermal annealing in high vacuum and in air, deposition of an amorphous silicon film, and ⁸⁴Kr⁺ ion implantation. The pre-treated substrates were used in a hot filament CVD diamond process, and the diamond films obtained were analyzed by different techniques. The results suggest that the observed nucleation reduction under certain pre-treatment conditions is related to modifications induced on the original topographical features of the scratched substrate surface, which would be responsible for the CVD diamond nucleation. The dimensions of these surface features are estimated to be of the order of 5 nm.     

Diamond coating on hard metals by traveling methods in a plasma-assisted chemical vapor deposition method above the liquid

In this work, two approaches were developed to extend the coating area of diamond by continuous deposition in a plasma-assisted chemical vapor deposition (CVD) method above the liquid. The techniques were based on the methods previously developed by our research group and the characteristic was to use dc (direct current) plasma generated between the liquid surface and the metal electrode. In the first approach, a tungsten rod was rotated in a chamber at reduced pressure so that a diamond film was formed as a ‘belt’ in 6 mm width around the side of the rod. The deposited diamond was polycrystalline with a grain size of 1–3 μm. The film thickness increased almost linearly with deposition time, whereas the grain size was almost constant against the deposition time. The second approach was for a plate substrate. A tungsten plate was hung with an iron wire and the plasma was horizontally generated between the liquid and plate surfaces. When the W plate was vertically slid down slowly, a diamond film was continuously deposited on the surface. The deposited film was covered with a soot-like carbon layer on the top and the post-treatment with H₂O/N₂ gas at 600 °C was effective in removing it. The continuous deposition successfully demonstrated the expansion of the deposition area with the novel plasma CVD method above the liquid.     

Friction force microscopy study of diamond films modified by a glow discharge treatment

A glow discharge treatment technique has been developed which enables control of the surface roughness and morphology of diamond films for applications in optical and electrical components. A conventional hot filament chemical vapour deposition (CVD) system was used to deposit the diamond films onto silicon substrates via a three-step sequential process: (i) deposition under normal conditions; (ii) exposure to either a pure hydrogen plasma or 3% methane in an excess of hydrogen using DC-bias; and (iii) diamond deposition for a further 2 h under standard conditions. The frictional characteristics and roughness of the film surfaces were investigated by atomic force microscopy (AFM) and the morphology and the growth rates determined from scanning electron microscope images. Lateral force microscopy (LFM) has revealed significant differences in frictional behaviour between the high quality diamond films and those modified by a glow discharge treatment. Friction forces on the diamond films were very low, with coefficients ∼0.01 against silicon nitride probe tips in air. However, friction forces and coefficients were significantly greater on the DC-biased films indicating the presence of a mechanically weaker material such as an amorphous carbon layer. A combination of growth rate and frictional data indicated that the exposure to the H₂ plasma etched the diamond surface whereas exposure to CH₄/H₂ plasma resulted in film growth. Re-Nucleation of diamond was possible (stage iii) after exposure to either plasma treatment. The resultant friction forces on these films were as low as on the standard diamond film.     

Diamond films grown by a 60-kW microwave plasma chemical vapor deposition system

In order to use chemical vapor deposition (CVD) diamond films for electronic devices, it is necessary to establish technologies for producing diamond wafers with controlled quality. Most of existing diamond CVD systems are, however, designed primarily for laboratory use. To cross the technological gap between the commercial production and the laboratory experiments, the current CVD technologies of diamond must be scaled up and upgraded. Development of large-scale diamond deposition processes was undertaken by using a microwave plasma CVD system, equipped with a 915-MHz, 60-kW generator for generating a large-size plasma. Polycrystalline diamond films were deposited from a hydrogen/methane gas mixture with typical gas pressures and substrate temperatures of 80–120 torr and 800–1050°C, respectively. It was found that depending on the growth conditions, the deposited films have various surface morphologies. Some of the samples have well-defined {111} and {100} facets of up to tens of micrometers in size. The Raman spectra had an intense main peak due to diamond at 1333 cm⁻¹ without a trace of non-diamond carbon. The film quality in terms of Raman spectra was relatively uniform across the samples of 100 mm in diameter. Both 〈111〉 and 〈001〉 textured diamond films were obtained by selected growth conditions.     

Simulation of morphological instabilities during diamond chemical vapor deposition

The diamond chemical vapor deposition (CVD) process has been investigated theoretically and the morphological instabilities associated with the growth of diamond films have been examined with a model based on the continuum species conservation equation coupled to surface reaction kinetics. A linear stability analysis and numerical calculations have been carried out to determine critical parameters affecting the diamond deposition layer morphology. A two-dimensional model describes the evolution of the gas-solid interface. The dynamic behavior of the interface depends on the reactants' diffusivity and surface kinetics. These factors depend upon the reactant material properties and film growth conditions such as the reactor temperature and pressure. From the analyses, it has been found that the ratio ( /k) of gas phase diffusivity ( ) to the surface reaction rate constant (k) plays the critical role in promoting diamond morphological instabilities because the film morphology stabilizing processes of surface diffusion and re-evaporation are absent or negligible during diamond CVD. It is found that the film nonuniformity increases as the ratio ( /k) decreases. Increasing growth rates also result in increasing morphological instability, leading to rough surfaces. It is shown that increasing reactor pressure and decreasing gas-phase temperature and/or substrate temperature promote deposition layer nonuniformity. An approach to avoiding these instabilities is proposed.     

Fracture toughness of the interface between CVD diamond film and silicon substrate in the relation with methane concentration in the source gas mixture

Diamond films produced by chemical vapor deposition (CVD) have been reported to show various excellent properties. However, low toughness of diamond films, especially the interface between the films and substrates, has been a severe problem. In order to find the dominant factors to control the adhesive strength of CVD diamond films, we obtained diamond films with various crystalline structures deposited on silicon (100) substrates under various methane concentrations in the source gas mixture. The toughness of the interface between the diamond film and silicon substrate was evaluated for the first time by a recently developed method. The toughness showed an interesting behavior with respect to the variation of methane concentration. The obtained results were quantitatively compared to the data already obtained for the case of CVD diamond particles deposited on silicon substrates.     

Single-crystal diamond microneedles shaped at growth stage

Single-crystal diamond microneedles were extracted from (001) textured polycrystalline films. The films were produced using a plasma enhanced chemical vapor deposition (CVD) from a CH₄/H₂ gas mixture activated by a direct current discharge. The as-grown textured polycrystalline CVD films consist of pyramid-shaped micrometer size diamond crystallites embedded into a nanodiamond ballas-like material. The less ordered fraction of the CVD film material was removed selectively using thermal oxidation. A dependence of the diamond needle shape on the CVD and the oxidation process parameters was revealed via a computer simulation and experimental studies. Ability for mass production of the diamond microneedles of different shapes was demonstrated. The needles are suitable for various applications from microcutting tools to quantum information processing.