OES study of the gas phase during diamond films deposition in high power DC arc plasma jet CVD system

This paper used optical emission spectroscopy （OES） to study the gas phase in high power DC arc plasma jet chemical vapour deposition （CVD） during diamond films growth processes. The results show that all the deposition parameters （methane concentration, substrate temperature, gas flow rate and ratio of H2/Ar） could strongly influence the gas phase. C2 is found to be the most sensitive radical to deposition parameters among the radicals in gas phase. Spatially resolved OES implies that a relative high concentration of atomic H exists near the substrate surface, which is beneficial for diamond film growth. The relatively high concentrations of C2 and CH are correlated with high deposition rate of diamond. In our high deposition rate system, C2 is presumed to be the main growth radical, and CH is also believed to contribute the diamond deposition.

Ohmic and Schottky contacts of hydrogenated and oxygenated boron-doped single-crystal diamond with hill-like polycrystalline grains

Hill-like polycrystalline diamond grains(HPDGs)randomly emerged on a heavy boron-doped p+single-crystal diamond(SCD)film by prolonging the growth duration of the chemical vapor deposition process.The Raman spectral results confirm that a relatively higher boron concentration(~1.1×10^(21) cm^(-3))is detected on the HPDG with respect to the SCD region(~5.4×10^(20) cm^(-3)).It demonstrates that the Au/SCD interface can be modulated from ohmic to Schottky contact by varying the surface from hydrogen to oxygen termination.The current-voltage curve between two HPDGs is nearly linear with either oxygen or hydrogen termination,which means that the HPDGs provide a leakage path to form an ohmic contact.There are obvious rectification characteristics between oxygen-terminated HPDGs and SCD based on the difference in boron doping levels in those regions.The results reveal that the highly boron-doped HPDGs grown in SCD can be adopted as ohmic electrodes for Hall measurement and electronic devices.

Synthesis of Boron-doped Diamond/Porous Ti Composite Materials——Effect of Carbon Concentration

Highly boron-doped diamond films were deposited on porous titanium substrates by hot filament chemical vapor deposition technique. The morphology variation of highly boron-doped diamond films grown on porous titanium substrates was investigated, and the effects of carbon concentration on nucleation density and diamond growth were also studied. The continuous change of surface morphology and structure of diamond film were characterized by scanning electron microscopy. The structures of diamond film and interlayer were analyzed by X-ray diffraction. The quality of boron-doped diamond film was confirmed by visible Raman spectroscopy. The experimental results reveal that surface morphology and quality of boron-doped diamond films are various due to the change of carbon concentration. The thickness of intermediate layer decreases with the carbon concentration increasing.

Diagnosis of gas phase near the substrate surface in diamond film deposition by high-power DC arc plasma jet CVD

Optical emission spectroscopy （OES） was used to study the gas phase composition near the substrate surface during diamond deposition by high-power DC arc plasma jet chemical vapor deposition （CVD）. C2 radical was determined as the main carbon radical in this plasma atmosphere. The deposition parameters, such as substrate temperature, anode-substrate distance, methane concentration, and gas flow rate, were inspected to find out the influence on the gas phase. A strong dependence of the concentrations and distribution of radicals on substrate temperature was confirmed by the design of experiments （DOE）. An explanation for this dependence could be that radicals near the substrate surface may have additional ionization or dissociation and also have recombination, or are consumed on the substrate surface where chemical reactions occur.

AFM Study on Interface of HTHP As-grown Diamond Single Crystal and Metallic Film

The study for the interface of as-grown diamond and metallic film surrounding diamond is an attractive way for understanding diamond growth mechanism at high temperature and high pressure (HTHP), because it is that through the interface carbon atom groups from the molten film are transported to growing diamond surface. It is of great interest to perform atomic force microscopy (AFM) experiment; which provides a unique technique different from that of normal optical and electron microscopy studies, to observe the interface morphology. In the present paper, we report first that the morphologies obtained by AFM on the film are similar to those of corresponding diamond surface, and they are the remaining traces after the carbon groups moving from the film to growing diamond. The fine particles and a terrace structure with homogeneous average step height are respectively found on the diamond (100) and (111) surface. Diamond growth conditions show that its growth rates and the temperature gradients in the boundary layer of the molten film at HTHP result in the differences of surface morphologies on diamond planes, being rough on (100) plane and even on the (111) plane. The diamond growth on the (100) surface at HPHT could be considered as a process of unification of these diamond fine particles or of carbon atom groups recombination on the growing diamond crystal surface. Successive growth layer steps directly suggest the layer growth mechanism of the diamond (111) plane. The sources of the layer steps might be two-dimensional nuclei and dislocations.

MECHANISM OF THE GROWTH, NUCLEATION, AND HETEROEPITAXY OF METASTABLE DIAMOND FILMS ON ATOMIC SCALE

The mechanism of chemical-vapor-deposited (CVD) diamond film growth has attracted increasing attention recent years, mainly due to the fact that further technological advancement (such as obtaining high-quality films, controlling film growth, and heteroepitaxial growth, etc.) requires a more detailed understanding of the fundamental phenomena responsible for diamond growth.

掺硅类金刚石薄膜的HiPIMS-MFMS共沉积制备及其高温摩擦学行为研究

元素掺杂是提高类金刚石(DLC)薄膜高温耐摩擦性能的重要途径.本文中采用高功率脉冲磁控溅射(HiPIMS)和中频磁控溅射(MFMS)复合技术在304不锈钢表面沉积具有不同Si含量的掺硅类金刚石(Si-DLC)薄膜,利用原子力显微镜、扫描电子显微镜(SEM)、X射线衍射(XRD)、拉曼光谱(Raman)、纳米压痕和UMT-TriboLab摩擦试验机等系统分析了Si含量对Si-DLC薄膜的结构、力学性能及不同温度下的摩擦学性能的影响,重点探讨了Si-DLC薄膜在高温下摩擦磨损机制.结果表明:Si-DLC薄膜中Si以四面体碳化硅的形式随机分布于无定型DLC基体中,增强薄膜的韧性.同时,Si掺杂使DLC薄膜向金刚石结构发生转变并显著提高了薄膜的硬度.摩擦结果表明,当Si原子分数为15.38%时,Si-DLC薄膜在常温下的摩擦系数和磨损率最低,同时该薄膜在300℃下能维持在较低的摩擦系数(约0.1),主要是由于Si-DLC薄膜中的四面体碳化硅结构能够提升sp^(3)键的稳定性.此外,Si-DLC薄膜中的Si在高温摩擦时会在对偶球表面形成1层SiO_(2)保护层,减缓Si-DLC薄膜和过渡层的氧化,使得薄膜能够在高温下持续润滑.当Si含量进一步增加时,Si-DLC薄膜的力学性能显著提升,然而其摩擦学性能发生明显降低,主要是当DLC薄膜中的硅含量过高时,大气环境下的高温摩擦使得薄膜内的氧化加剧,过量氧化硅的生成破坏了薄膜结构从而导致摩擦性能下降.

高速钢表面类金刚石薄膜的掺氮改性研究

高速钢表面类金刚石(diamond-like carbon,DLC)薄膜的沉积效率和膜-基结合力影响其在切削刀具领域的应用。基于空心阴极原理,利用等离子体增强化学气相沉积(plasma-enhanced chemical vapor deposition,PECVD)的方法,在体积比为1∶3的CH_(4)和C_(2)H_(2)的混合气体中加入N_(2)在高速钢表面制备类金刚石薄膜,研究了N_(2)体积分数对DLC薄膜结合力和耐磨性的影响。结果表明:掺氮可提高DLC薄膜的沉积效率,改善膜结构。随着N_(2)体积分数的增加,DLC薄膜中sp^(3)键含量和摩擦因数均先增大后减小。掺10%体积分数N_(2)的DLC薄膜厚度达1543 nm,膜-基结合力等级从HF4提高到HF2,摩擦因数降至0.139,耐磨性提高。

离子氮化对高速钢表面类金刚石膜性能的影响

根据空心阴极原理,研究了离子氮化对高速钢表面渗氮层的厚度、硬度等影响.在此基础上,研究了气体体积配比对渗氮后高速钢表面沉积的类金刚石膜的结合力、sp3键含量和耐磨性能的影响.研究结果表明:离子氮化后,高速钢表面镀膜结合力明显提高,由10.35 N提高至18.56 N;降低气体体积配比中CH_(4)的含量有利于提高膜层中sp3键的含量,高速钢耐磨性能明显提升,摩擦系数由0.175降至0.1.离子氮化可有效提高高速钢表面沉积的类金刚石膜性能.

White electroluminescence of n-ZnO:Al/p-diamond heterostructure devices

An n-ZnO：A1/p-boron-doped diamond heterostructure electroluminescent device is produced, and a rectifying be- havior can be observed. The electroluminescence spectrum at room temperature exhibits two visible bands centred at 450 nm-485 nm （blue emission） and 570 nm-640 nm （yellow emission）. Light emission with a luminance of 15 cd/m2 is observed from the electroluminescent device at a forward applied voltage of 85 V, which is distinguished from white light by the naked eye.

Direct and Simultaneous Determination of Phenol, Hydroquinone and Nitrophenol at Boron-Doped Diamond Film Electrode

The electrochemical characteristics of multi-component phenolic pollutants, such as phenol （Ph）, hydroquinone （HQ） and 4-nitrophenol （4-NP）, were investigated on boron-doped diamond （BDD） film electrode by differential pulse voltammetry （DPV） technique. A simple and feasible platform was accordingly established for the direct and simultaneous determination of these three phenolic pollutants. Results showed that, Ph, HQ and 4-NP gave obvious oxidation peaks on BDD electrode at the potential of 1.24, 0.76 and 1.52 V, respectively. Each of them displayed good linear relationship between their oxidation peak currents and their corresponding concentrations in a rather wide range coexisting with one or two of the other phenolic pollutants. The detection limits of Ph, HQ and 4-NP were estimated to be as low as 1.82×10^-6, 1.67×10^-6 and 1.44×10^-6 mol·L^-1, respectively. Therefore, a promising direct and simultaneous electrochemical determination method of multi-component phenolic pollutants in wastewater samples was constructed successfully on BDD electrode with advantages being rapid, simple, convenient, sensitive, in situ and inexpensive.

温度对n-ZnO/p-diamond薄膜异质结器件制备和电学性质的影响

采用反应磁控溅射法在p型硼掺杂金刚石(BDD)薄膜衬底上制备了非有意掺杂n型氧化锌(ZnO)薄膜。利用XRD、SEM、I-V特性曲线对n-ZnO/p-BDD薄膜复合结构进行表征分析。n-ZnO多晶膜沉积在p-BDD膜上形成了具有良好整流特性的异质结。在空气中对异质结进行退火处理,研究了退火(400℃,700℃)对异质结性质的影响。实验表明,较高退火温度处理,可获得多取向的ZnO膜,晶粒尺寸增大,n-ZnO/p-BDD异质结开启电压减小。不同温度下的电学性质测量结果证明该异质结适合在高温环境下工作。

TiZrNbTaMo高熵合金表面化学气相沉积制备多晶金刚石膜

本文以亲碳元素组成的TiZrNbTaMo高熵合金作为基材,通过化学气相沉积的方法在其表面沉积金刚石膜。结果表明:金刚石能够在TiZrNbTaMo高熵合金表面快速形核,形核密度高达7.53×109cm^(-2),且在30 min内形成连续的金刚石膜;金刚石在TiZrNbTaMo高熵合金表面的形核密度及生长速率远高于在组成高熵合金的单质金属表面的形核密度及生长速率。这是由于在金刚石形核及生长初期,高熵合金表面能够快速形成混合碳化物层,阻碍碳原子向合金基材扩散,使其富集在碳化物层表面,促进金刚石的形核和生长。沉积金刚石后的Ti ZrNbTaMo高熵合金在3.5%(质量分数)NaCl溶液中的抗腐蚀能力显著提升。本文结果为金属材料表面高效率沉积高形核密度的金刚石以及改善高熵合金表面硬度和耐腐蚀性能提供了新的思路和方法。

Influence of tribofilm on superlubricity of highly-hydrogenated amorphous carbon films in inert gaseous environments

In this study,we mainly focus on the structural morphology and inter-atomic bonding state of tribofilms resulting from a highly-hydrogenated amorphous carbon(a-C:H) film in order to ascertain the underlying mechanisms for its superlubric behavior(i.e.,less than 0.01 friction coefficient).Specifically,we achieved superlubricity(i.e.,friction coefficients of down to 0.003) with this film in dry nitrogen and argon atmospheres especially when the tribo-pair is made of an a-C:H coated Si disk sliding against an a-C:H coated steel ball,while the a-C:H coated disk against uncoated ball does not provide superlubricity.We also found that the state of superlubricity is more stable in argon than in nitrogen and the formation of a smooth and uniformly-thick carbonaceous tribofilm appears to be one of the key factors for the realization of such superlubricity.Besides,the interfacial morphology of sliding test pairs and the atomic-scale bond structure of the carbon-based tribofilms also play an important role in the observed superlubric behavior of a-C:H films.Using Raman spectroscopy and high resolution transmission electron microscopy,we have compared the structural differences of the tribofilms produced on bare and a-C:H coated steel balls.For the a-C:H coated ball as mating material which provided superlow friction in argon,structural morphology of the tribofilm was similar or comparable to that of the original a-C:H coating;while for the bare steel ball,the sp^2-bonded C fraction in the tribofilm increased and a fingerprint-like nanocrystalline structure was detected by high resolution transmission electron microscopy(HRTEM).We also calculated the shear stresses for different tribofilms,and established a relationship between the magnitude of the shear stresses and the extent of sp^3-sp^2 phase transformation.

铁基触媒合成金刚石形成的金属包膜的组织结构

利用SEM ,TEM和Raman光谱检测手段 ,研究了铁基触媒合成金刚石形成的金属包膜的组织结构。结果表明 :包膜与合成后触媒的组织形貌不完全相同 ,包膜内无金刚石 ,在靠近金刚石的包膜内层没有石墨和无定型碳。据此并结合包膜所起的溶碳和催化作用分析 ,在高温高压下 ,金刚石成核和生长的碳来源于靠近金刚石的包膜层 (Fe,Ni) 3C的分解产物 ,分解后的 (Fe,Ni) 3C转变为γ -(Fe,Ni) ,这时的γ -(Fe ,Ni)与未分解的 (Fe,Ni)

新型高功率MPCVD金刚石膜装置的数值模拟与实验研究

根据高功率MPCVD装置所需要具备的条件,提出一种新型的高功率MPCVD装置结构。先使用HFSS软件对模型的各部分尺寸进行了初步优化;然后使用COMSOL软件通过对高功率、高气压条件下气体电离形成等离子体时的电场和等离子体分布的模拟,并对气体进出方式进行了验证;最后根据模拟结果建立了新型MPCVD装置,并使用所制造的装置在高功率、高气压条件下进行了大面积金刚石膜的制备。结果表明:所提出的高功率MPCVD装置模型经过结构优化后,在基片上方对电场具有较好的聚焦能力,强度高于同类装置;高功率、高气压条件下所产生的等离子体也仅在基片上方均匀分布,与石英环之间被中间腔体隔离,有效避免其对石英环的刻蚀;所设计的进出气方式能够保证反应气体在基片表面均匀分布;使用所制造的装置能够在高功率、高气压条件下实现大面积高品质金刚石膜的快速沉积。

高品质金刚石膜微波等离子体CVD技术的发展现状

金刚石膜拥有许多优异的性能。在制备金刚石膜的各种方法之中,高功率微波等离子体化学气相沉积(MPCVD)法因其产生的等离子体密度高,同时金刚石膜沉积过程的可控性和洁净性好,因而一直是制备高品质金刚石膜的首选方法。在世界范围内,美、英、德、日、法等先进国家均已掌握了以高功率MPCVD法沉积高品质金刚石膜的技术。但在我国国内,高功率MPCVD装备落后一直是困扰我国高品质金刚石膜制备技术发展的主要障碍。首先综述国际上高功率MPCVD装备和高品质金刚石膜制备技术的发展现状,包括各种高功率MPCVD装置的特点。其后,回顾了我国金刚石膜MPCVD技术的发展历史,并介绍北京科技大学近年来在发展高功率MPCVD装备和高品质金刚石膜制备技术方面取得的新进展。

高速钢表面渗硅沉积金刚石

研究了利用表面扩散渗硅 ,在高速钢基底上沉积金刚石的工艺方法 利用SEM ,X射线衍射技术检验了金刚石膜和试样表面组织的变化 结果表明 ,利用表面扩散渗硅 ,在高速钢表面形成富硅层 ,使过渡层有较高的含硅量 。

大面积高光学质量金刚石自支撑膜的制备

介绍了一种新型的磁控／流体动力学控制的大口径长通道直流电弧等离子体炬，并据此设计建 造了 １００千瓦级高功率 ＤＣ Ａｒｃ Ｐｌａｓｍａ Ｊｅｔ ＣＶＤ金刚石膜沉积系统 讨论了该系统采用的半封闭式 气体循环系统的工作原理。

低浓度氩气对金刚石薄膜的影响及机理研究

提高生长速率是降低金刚石薄膜应用成本的关键因素之一,目前研究的提高速率的方法中以偏压电子增强为主,而该方法不适宜表面复杂的刀具涂层。本文通过在无偏压热丝化学气相沉积沉积金刚石薄膜条件下添加少量的Ar,成功将生长速率提高3倍,并采用等离子发射光谱研究了其反应机制,尤其对反应系统电子温度的变化做出了详细推理分析。实验结果采用扫描电镜、Raman光谱进行表征。结果表明:氩气的添加不仅可促进二次成核,使得晶粒尺寸达到纳米级,而且一定量的氩气(8%~32%)可提高金刚石薄膜的生长速率,当氩气含量在8%~32%范围内时,金刚石薄膜的生长速率随氩气浓度增大而增大,本实验获得最高生长速率达3.75μm/h,是无Ar情况下的3倍。光谱诊断显示的主要基团为CO(283~370nm),CH(387.0 nm),H_β(486 nm),H_α(656.3 nm),氩气添加后这些基团的光谱强度均显著增强。当氩气含量为7%~30%时,电子温度与氩气浓度成正比,为金刚石薄膜的生长提供了更优越的条件,生长速率得到提高。