Study of diamond film nucleation by ultrasonic seeding in different solutions

In this study we have investigated diamond nucleation on Si substrates by ultrasonic seeding with different liquid solutions of Ultradispersed Detonation Diamond (UDD) powder in a mixture of metal nano- or microparticles (Ni, Co, Y). The influence of different solutions on nucleation efficiency was investigated. For highlighting nucleation centers and better evaluation of the nucleation process the nucleated samples were moved into a Microwave Plasma Enhanced Chemical Vapor Deposition (MW CVD) reactor and a ”short-time” (10 min), then followed by a ”long-time” (+1 hour), diamond deposition was performed. The morphology of samples was characterized by Scanning Electron Microscopy (SEM) and the chemical composition of grown diamond layer was investigated by Raman Spectroscopy. From the measurements we found out that microsized metal particles positively influenced nucleation and the uniformity of the deposited diamond thin film. The lowest surface roughness was achieved in the case of nanodiamond powder mixed with Co and Y metal powder. The influence of Ni, Co and Y to the nucleation and early growth stage are discussed.     

负偏压热灯丝CVD金刚石膜核化和早期生长的研究

利用扫描电子显微镜、Raman谱和X射线光电子能谱，研究了Si衬底上热灯丝CVD金刚石膜的核化和早期生长.在-300V和100mA条件下预处理15min，镜面抛光的Si(100)表面上金刚石核密度超过了10⁹cm^-2，但是核的分布极不均匀且可分为三个区域：A区，边缘处以锥体为主；B区，位于边和中心之间过渡区是纳米金刚石；C区，中心处有SiC层.无偏压下生长4h后，A区形成许多大而弧立的金刚石颗粒，B区成为织构金刚石膜，而C区变为含有大量缺陷的连续金刚石膜.衬底负 关键词：     

Optical and structural properties of polycrystalline CVD diamond films grown on fused silica optical fibres pre-treated by high-power sonication seeding

In this paper, the growth of polycrystalline chemical vapour deposition (CVD) diamond thin films on fused silica optical fibres has been investigated. The research results show that the effective substrate seeding process can lower defect nucleation, and it simultaneously increases surface encapsulation. However, the growth process on glass requires high seeding density. The effects of suspension type and ultrasonic power were the specific objects of investigation. In order to increase the diamond density, glass substrates were seeded using a high-power sonication process. The highest applied power of sonotrode reached 72 W during the performed experiments. The two, most common diamond seeding suspensions were used, i.e. detonation nanodiamond dispersed in (a) dimethyl sulfoxide and (b) deionised water. The CVD diamond nucleation and growth processes were performed using microwave plasma assisted chemical vapour deposition system. Next, the seeding efficiency was determined and compared using the numerical analysis of scanning electron microscopy images. The molecular composition of nucleated diamond was examined with micro-Raman spectroscopy. The sp³/sp² band ratio was calculated using Raman spectra deconvolution method. Thickness, roughness, and optical properties of the nanodiamond films in UV–vis wavelength range were investigated by means of spectroscopic ellipsometry. It has been demonstrated that the high-power sonication process can improve the seeding efficiency on glass substrates. However, it can also cause significant erosion defects at the fibre surface. We believe that the proposed growth method can be effectively applied to manufacture the novel optical fibre sensors. Due to high chemical and mechanical resistance of CVD diamond films, deposition of such films on the sensors is highly desirable. This method enables omitting the deposition of an additional adhesion interlayer at the glass–nanocrystalline interface, and thus potentially increases transmittance of the optical system.     

富勒烯作为过渡层生长金刚石薄膜研究

采用微波等离子体化学气相淀积法，以Ｃ６０膜过渡层，在光滑的单晶Ｓｉ衬底（１００）表面的研磨的石英衬底表面等光学衬底上，首次在无衬底负偏压条件下生长出多晶金刚石薄膜，通过扫描电镜观察到生长膜晶粒呈莱花状，生长表面为金刚石（１００）界面。     

Nucleation and initial growth of diamond by biased hot filament chemical vapour deposition

6 cm^-2 for non-scratched silicon. The maximum value of the nucleation density was over 10¹¹ cm^-2 on mirror-polished Si(100) at -300 V. The transportation process of the ion flux from the filament to the substrate is discussed in detail for biased substrates. The nucleation enhancement by the positive bias is believed to be a result of the increased impingement of the electrons emitted from the filament to the substrate surface. The studies have shown that electron emission from diamond plays a key role in negative-bias-enhanced nucleation by accelerating the dissociation of molecular hydrogen and hydrocarbon species into various free radicals and causing a plasma to be ignited near the substrate surface. The negative bias pretreatment is also a critical step in growing heteroepitaxial diamond films: the enlargement of the area of diamond clusters in contact with the substrate enhances the orientated growth of the films. Received: 18 October 1996/Accepted: 4 February 1997     

Mechanisms of CVD diamond nucleation and growth on mechanically scratched Si(100) surfaces

The diamond nucleation has been studied on scratched Si(100) both by surface analyses (XPS, AES, ELS) and microstructural probes (AFM, SEM). Two pathways for diamond formation and growth are detected: A seeding pathway occurs by direct growth from part of diamond seeds left by the mechanical pretreatment. Not all of these seeds however are prone to diamond growth as they can be either dissolved or carburized. A nucleation pathway occurs through a stepwise process including the formation of extrinsic (pretreatment) or intrinsic (in situ) nucleation sites, followed by formation of carbon-based precursors. It is believed that nucleation sites could be either grooves of scratching lines or protrusions produced by etching-redeposition. The size of these protrusions is not larger than 100 nm. On top of these protrusions as well as on the bare substrate, a thin layer of silicon carbide rapidly forms and DLC carbon likely. This complex process on top of protrusions may constitute carbon-based embryos for further diamond nucleation. Received 21 December 1998     

织构金刚石薄膜的成核与生长

在加衬底偏压和不加衬底偏压两种情况下，用微波等离子体化学汽相沉积（MWCVD）技术在Ｓｉ（１００）衬底上合成了织构的金刚石薄膜使用扫描电子显微镜（ＳＥＭ）和取向Ｘ射线衍射技术证实了我们得到的样品是织构的金刚石薄膜观察了织构的金刚石薄膜的成核和生长过程，从理论上对金刚石薄膜异质外延的成核和生长机理进行了探讨 关键词：     

GROWTH MODEL OF TEXTURED DIAMOND (111) FILM IN CH4/O2/H2 ATMOSPHERE

Partially oriented and highly textured diamond films on Si( 111 ) substrates were achieved by hot-filament chemical vapor deposition(HFCVD). High nucleation density greater than 5×10⁸cm^-2 was realiged in 3 min by near-surface glow discharge. The os-grown films were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD) and Raman spectroscopy. It was found that by adding a small amount of oxygen to the mixture of CH₄/H₂, the appearance of facet(111) was well controlled, and the secondary nucleation on the facet(111) was suppressed greatly. Growth feature of homoepitaxy on diamond (111) surface was demonstrated to be in Stranski-Krastanov model by SEM.     

Use of ultrafine-dispersed nanodiamond for selective deposition of boron-doped diamond films

A suspension of ultrafine-dispersed nanodiamond was used for introducing (in particular, selectively) high-density centers of diamond nucleation on various substrates. High-quality doped diamond films to be used as electrochemistry electrodes were deposited from the gas phase in a microwave discharge on certain substrates treated using ultrafine-dispersed nanodiamond. A uniform distribution of nucleation centers with concentrations greater than 10¹⁰ cm^-2 on silicon substrates was obtained. Electrochemical current-potential curves were measured for continuous films. Diamond meshes of different transparency were grown using selective nucleation. Successful production of high-quality doped diamond meshes gives grounds to consider them the most promising electrodes for use in electrochemistry.     

GROWTH MODEL OF TEXTURED DIAMOND (111) FILM IN CH4/O2/H2 ATMOSPHERE

Partially oriented and highly textured diamond films on Si( 111 ) substrates were achieved by hot-filament chemical vapor deposition(HFCVD). High nucleation density greater than 5×10⁸cm^-2 was realiged in 3 min by near-surface glow discharge. The os-grown films were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD) and Raman spectroscopy. It was found that by adding a small amount of oxygen to the mixture of CH₄/H₂, the appearance of facet(111) was well controlled, and the secondary nucleation on the facet(111) was suppressed greatly. Growth feature of homoepitaxy on diamond (111) surface was demonstrated to be in Stranski-Krastanov model by SEM.     

同质与异质外延掺杂CVD金刚石薄膜的结构与性能

采用化学气相沉积(CVD)技术,以高温高压(HTHP)合成的(100)金刚石和p型(100)Si为衬底制备了硫掺杂和硼-硫共掺杂金刚石薄膜,利用原子力显微镜(AFM)、扫描隧道显微镜(STM)及隧道电流谱(CITS)等手段分析同质和异质外延CVD掺杂金刚石薄膜的结构和性能.结果表明:异Si衬底上CVD金刚石的形核密度低,薄膜表面比较粗糙,粗糙度达到18.5nm;同质HTHP金刚石衬底上CVD金刚石薄膜晶粒尺寸约为10—50nm,表面平整,表面粗糙度为1.8nm.拉曼测试和电阻测量的结果显示,在HTHP金刚 关键词： 金刚石 掺杂 外延     

Rapid nucleation of diamond films by pulsed laser chemical vapor deposition

The nucleation of diamond films could be greatly enhanced on mirror-polished Si substrate by a pulsed Nd:YAG laser beam without any thermal- and plasma-assisted processes during a very short time. The nucleation density increased with decreasing laser power density from 1.38×10¹⁰ to 1.17×10⁹ W/cm² and deposition pressure from 1013 to 4 mbar. The pulsed laser beam made no contribution to enhance nucleation at substrate temperature as low as 650°C. X-ray diffraction measurements showed the (1 1 1) diffraction peak of diamond for the samples obtained using only pulsed laser during 40 min. The enhanced nucleation and growth of diamond crystallites were attributed to effective excitation of reactive gases and etching of non-diamond carbon phases by the pulsed laser beam.     

Dependence of plastic relaxation in GaAs films on nucleation of the first as monolayer on Si(001) substrates

The structure of GaAs films grown on Si(001) vicinal substrates (6° rotation about 〈011〉 axis) formed in two ways of nucleation, As deposition on Si and substitution of Si monolayer by As monolayer, is studied. X-ray diffractometry is used to find that the rotation direction of a crystal lattice depends on the manner of nucleation. An optional model of the formation of film dislocation structures is proposed.     

大面积均匀纳米金刚石薄膜制备研究

报道了一种利用偏压恒流等离子辅助热丝化学气相沉积城硅基板上制备大面积均匀纳米金刚石薄膜的新工艺，在不同沉积条件下研究了纳米金刚石薄膜的成核和生长过程，并通过扫描电镜、拉曼光谱和表面粗糙度测试仪观察了纳米金刚石薄膜的结构特征。最后成功制备了直径100mm、平均晶粒尺寸10nm的光滑纳米金刚石薄膜。     

掺杂CVD金刚石薄膜的应力分析

在不同实验条件下，用微波等离子体化学气相沉积(MPCVD)技术在Si基体上制备了S掺杂和B-S共掺杂CVD金刚石薄膜，利用X射线衍射仪和拉曼光谱仪研究掺杂对CVD金刚石薄膜的应力影响.研究结果发现，随着S掺杂浓度的增加，薄膜中sp²杂化碳含量和缺陷增多，CVD金刚石薄膜压应力增加；小尺寸的B原子与大尺寸的S原子共掺杂时，微量B的加入改变了CVD金刚石薄膜的应力状态，共掺杂形成B-S复合体进入金刚石晶体后降低金刚石晶体的晶格畸变程度，减少S原子在晶界上偏聚数量和晶体中非金刚石结构相含量，降低由于杂质、缺陷及sp²杂化碳含量产生的晶格畸变和薄膜压应力，提高晶格完整性. 关键词： 金刚石薄膜 掺杂 应力     

CVD金刚石中的氮对等离子体刻蚀的影响

采用非对称磁镜场电子回旋共振等离子体分别对沉积过程中掺氮和未掺氮的化学气相沉积金刚石膜进行了刻蚀研究, 结果表明: 掺氮制备的金刚石膜的刻蚀主要集中在晶棱处, 经过4h刻蚀后其表面粗糙度由刻蚀前的4.761 μm下降至3.701 μm, 刻蚀对金刚石膜的表面粗糙度的影响较小; 而未掺氮制备的金刚石膜的刻蚀表现为晶面的均匀刻蚀, 晶粒坍塌,刻蚀4h后其表面粗糙度由刻蚀前的3.061 μm下降至1.083 μm. 刻蚀导致表面粗糙度显著降低. 上述差别的主要原因在于金刚石膜沉积过程中掺氮导致氮缺陷在金刚石晶棱处富集, 晶棱处电子发射加强, 引导离子向晶棱运动并产生刻蚀, 从而加剧晶棱的刻蚀. 而未掺氮金刚石膜,其缺陷相对较少且分布较均匀 ,刻蚀时整体呈现为 (111) 晶面被均匀刻蚀继而晶粒坍塌的现象. 关键词： 掺氮 金刚石膜 刻蚀 非对称磁镜场     

Synthesis of micro- or nano-crystalline diamond films on WC-Co substrates with various pretreatments by hot filament chemical vapor deposition

Diamond films deposited on tungsten carbide can lead to major improvements in the life and performance of cutting tools. However, deposition of diamond onto cemented tungsten carbide (WC-Co) is problematic due to the cobalt binder in the WC. This binder provides additional toughness to the tool but results in poor adhesion and low nucleation density of any diamond film. A two-step chemical etching pretreatment (Murakami reagent and Caro acid, (MC)-pretreatment) and a boronization pretreatment have both been used extensively to improve adhesion of CVD diamond film on WC-Co substrates. Here we discuss the applicability of MC-pretreatment for a range of Co-containing WC-Co substrates, and demonstrate a controlled synthesis process based on liquid boronizing pretreatment for obtaining smooth and dense micro- or nano-crystalline diamond films on high Co-containing WC-Co substrates. Substrate treatments and deposition parameters were found to have major influences on the smoothness, structure and quality of the diamond films. The best quality diamond films were achieved under conditions of relatively high substrate temperature (T_s) and the best adhesion was achieved at T_s = 800 °C.     

高温高压下Fe-Ni-C系合成金刚石的研究

 以工业纯单质铁粉和单质镍粉为主要原料,采用粉末冶金方法制备了Fe-Ni-C系反应体系,在六面顶压机上进行了金刚石合成实验。Raman光谱和X射线衍射结果表明,采用这种方法获得的粒径为200~500 μm,呈六-八面体聚形的晶体为立方金刚石单晶。通过对常规力学性能的检测发现,金刚石的品位较高,超过SMD25级锯片级金刚石的要求。分析认为,高温高压下金刚石自Fe-Ni-C系形核是一个触媒不断溶解催化碳原子的过程。大量的实验结果可以证实,金刚石在Fe-Ni-C系长大所需的碳原子来自于在γ-(Fe,Ni)吸引作用下、从(Fe,Ni)₃C中不断脱溶的碳。金属包覆膜在这一过程中不但起到了输送碳原子的作用,还以独特的方式促成了碳原子由sp²π杂化态向sp³杂化态的转变。     

不同晶化工艺对非晶PZT纳米薄膜形核取向生长机理的影响

射频磁控溅射法室温下在Pt/Ti/SiO2/Si上制备非晶Pb(Zr048Ti052)O3薄膜，非晶PZT薄膜分别经常规炉退火(CFA)处理和快速热退火(RTA)处理晶化为（100），（111）不同择优取向的多晶薄膜. 采用x射线衍射测定了薄膜相组分、择优取向度；用原子力显微镜和压电响应力显微镜观察了薄膜表面形貌，以及对应区域由自发极化形成的铁电畴像，观察了不同取向薄膜的电畴分布特征. 结果表明，RTA晶化过程钙钛矿结构PZT结晶主要以PZT/Pt界面处的PtPb化合物为成核点异质形核并类似外延的结晶生长，沿界面结晶速率远大于垂直膜面结晶速率，而CFA晶化样品成核发生在膜内杂质缺陷处，以同质成核为主. 不同的成核机理导致了不同晶面择优取向生长. 关键词： PZT薄膜 结晶 形核 力显微技术     

Comparison of diamond film adhesion on molybdenum substrates with different surface morphologies

To evaluate the effect of substrate morphology on the adhesion of diamond film, two types of substrate morphology of molybdenum (Mo) were compared. The two morphology types were formed by polishing a Mo substrate with SiC abrasive paper along one direction (anisotropic morphology) and by polishing the Mo substrate with diamond powder in a random direction (isotropic morphology).Ultrasonic cavitation tests were conducted to evaluate the adhesion of the diamond films on these Mo substrates. In the case of low surface roughness, there was very little difference between the effects of SiC abrasive paper polishing and diamond powder polishing. In the case of high surface roughness, the adhesion of the diamond film on the SiC paper polished Mo substrate was larger than that of the diamond film on the diamond powder polished Mo substrate. Detachment of the diamond film from the SiC paper polished Mo substrate progressed along the polishing direction; while detachment of the diamond film from the diamond powder polished Mo substrate progressed in a random direction. It was thought that the detachment of the diamond film from a Mo substrate having an anisotropic polishing trace was suppressed because the anisotropic grooves restricted the formation of connections between the points of detachment at right angles to the groove direction. Therefore, the anisotropic surface morphology of the Mo substrate is effective for improving the adhesion of diamond film.