Diamond and diamond-like carbon films

Polycrystalline diamond films are grown from low pressure gas mixtures, the deposition techniques are Microwave Plasma Chemical Vapour Deposition and Hot filament Chemical Vapour Deposition, in both techniques the deposition temperature is close to 900°C. The film growth process is strongly dominated by the initial nucleation stage, after this stage, the film grows at a rate of one micron per hour. The carbon atoms in the diamond film are fully fourfold (sp³) co-ordinated and the film properties are close to those of single crystalline diamond: extremely hard, resistant and transparent from UV to IR.Diamond-like carbon (DLC) films are amorphous and contain a variable amount of hydrogen in their structure, the carbon atoms are partially threefold (sp²) co-ordinated. Films are obtained at temperatures below 250°C and deposited on almost any substrate. Film composition, structure and functional properties are strongly dependent on the level of ionic bombardment of the film during growth. DLC films are very hard, have a low friction coefficient and good wear resistance, are chemically inert and are transparent in the IR.     

Structure of diamond and diamond like carbon thin films grown by hot-filament chemical vapour deposition technique

Micro-crystalline diamond (MCD) and diamond like carbon (DLC) thin films were deposited on silicon (100) substrates by hot-filament CVD process using a mixture of CH₄ and H₂ gases at substrate temperature between 400–800°C. The microstructure of the films were studied by X-ray diffraction and scanning electron microscopy. The low temperature deposited films were found to have a mixture of amorphous and crystalline phases. At high temperatures (> 750°C) only crystalline diamond phase was obtained. Scanning electron micrographs showed faceted microcrystals of sizes up to 2μm with fairly uniform size distribution. The structure of DLC films was studied by spectroscopic ellipsometry technique. An estimate of the amount of carbon bonds existing insp ² andsp ³ form was obtained by a specially developed modelling technique. The typical values ofsp ³/sp ² ratio in our films are between 1·88–8·02. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Improved electrochemical performance of nitrocarburised stainless steel by hydrogenated amorphous carbon thin films for bone tissue engineering

In this study, hydrogenated amorphous carbon thin films, structurally similar to diamond‐like carbon (DLC), were deposited on the surface of untreated and plasma nitrocarburised (Nitrocarburizing‐treated) stainless steel medical implants using a plasma‐enhanced chemical vapour deposition method. The deposited DLC thin films on the nitrocarburising‐treated implants (CN+DLC) exhibited an appropriate adhesion to the substrates. The results clearly indicated that the applied DLC thin films showed excellent pitting and corrosion resistance with no considerable damage on the surface in comparison with the other samples. The CN+DLC thin films could be considered as an efficient approach for improving the biocompatibility and chemical inertness of metallic implants.Inspec keywords: tissue engineering, bone, biomedical materials, electrochemistry, amorphous state, carbon, hydrogen, thin films, plasma CVD, adhesion, corrosion resistance, surface hardeningOther keywords: electrochemical performance, plasma nitrocarburised stainless steel medical implants, hydrogenated amorphous carbon thin films, bone tissue engineering, plasma‐enhanced chemical vapour deposition method, adhesion, corrosion resistance, biocompatibility, chemical inertness, metallic implants, C:H     

Correlation between diamond grain size and hydrogen incorporation in nanocrystalline diamond thin films

Hydrogen-incorporated nanocrystalline diamond thin films have been deposited in microwave plasma enhanced chemical vapour deposition (CVD) system with various hydrogen concentrations in the Ar/CH₄ gas mixture. The bonding environment of carbon atoms was detected by Raman spectroscopy and the hydrogen concentration was determined by elastic recoil detection analysis. Incorporation of H₂ species into Ar-rich plasma was observed to markedly alter the microstructure of diamond films. Raman spectroscopy results showed that part of the hydrogen is bonded to carbon atoms. Raman spectra also indicated the increase of non-diamond phase with the decrease in crystallite size. The study addresses the effects of hydrogen trapping in the samples when hydrogen concentration in the plasma increased during diamond growth and its relation with defective grain boundary region.     

沉积参数对化学气相沉积纳米金刚石薄膜的影响

用强电流直流伸展电弧化学气相沉积金刚石薄膜装置,在CH4-Ar和CH4-H2-Ar气氛中沉积了纳米金刚石薄膜,研究了沉积气氛中H2加入量和沉积压力对金刚石薄膜显微组织和生长机制的影响.沉积气氛中H2含量对金刚石薄膜的表面形貌、晶粒尺寸和生长速度有显著影响,随着H2含量增加,金刚石晶粒尺寸增大,薄膜生长速度提高.在1%CH4-Ar气氛中沉积的纳米金刚石薄膜,晶粒尺寸细小,薄膜表面形貌光滑平整.在1%CH4-少量H2-Ar气氛中沉积的金刚石薄膜,晶粒尺寸小于100nm,薄膜表面形貌较平整.随着沉积压力提高,金刚石薄膜的生长速度增大.用激光Ram an对金刚石薄膜进行了表征.     

fabrication of diamond membranes for MEMS using reactive ion etching of silicon

Polycrystalline diamond thin film has been grown on a silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950°C. A simple process flow has been developed to fabricate optically transparent polycrystalline synthetic diamond membranes/windows employing reactive ion etching (RIE) of a single crystal silicon substrate using an electron beam evaporated aluminum thin film mask pattern formed by photolithography. Scanning electron microscopy has been used to study the morphology of as-grown diamond thin films.     

Abscheidung superharter Kohlenstoffschichten mittels Laser‐Arco® auf dem Weg vom Labor in die industrielle Serienfertigung

Superhard carbon film deposition by means of Laser‐Arco® on the way from the Laboratory into the industrial series coating Diamond‐like carbon films (DLC) are more and more applied as wear protection coatings for components and tools due to their unique combination of high hardness, low friction and sticking tendency to metallic counter bodies. Up to now applied DLC films are hydrogen containing (a‐C:H) or metal carbon films (Me‐C:H) deposited by a plasma assisted CVD process from carbon‐hydrogen gas mixtures. Their wide industrial effort results from that the can be deposited with slowly modified coating machines for classical hard coating (e.g. TiN or CrN). A new generation DLC films are the hydrogen‐free ta‐C films (ta‐C = tetrahedral bounded amorphous carbon) with a between two and three‐times higher hardness and with a resulting higher wear resistance under extreme condition than classical DLC films. They have excellent emergency running properties at lubrication break down. Their industrial application is more difficult due to that they cannot deposited with modified coating machines for classical hard and DLC coating and a new technology with corresponding equipment was not available up to now. The laser controlled, pulsed arc deposition technology (Laser‐Arco®) of the Fraunhofer IWS Dresden has this potential. In kind of a Laser‐Arc‐Module‐source the ta‐C film deposition can be integrated in every industrial used deposition machine.     

Low resistive diamond like carbon film development technique

Low-temperature plasma-enhanced diamond like carbon (DLC) film chemical deposition technique is developed. Emission spectra of plasma is digitized and processed for deposition process control. Electric field - transversely applied to plasma stream - permits to obtain coatings with predefined properties. The influence of this field on plasma characteristics and hence - on the properties of deposited coatings is studied. The specific resistance of nitrogen doped, hydrogenised DLC films could be varied from typically isolators down to ~ 10^− 4 Ohm cm. The coatings were of n-type. Mobility of major carriers approaches up to 40 cm²V^− 1s^− 1 depending on the technological parameters. Obtained films were durable, transparent and have high refractive index reaching up to 3.1.     

Characterization of hypervelocity impact craters on chemical vapour-deposited diamond and diamond-like carbon films

Microwave plasma chemical vapour-deposited (CVD) process has been used to grow polycrystalline diamond films over silicon substrates. Diamond-like carbon (DLC) thin films were grown over silicon substrates using a microwave plasma disc reactor. Reactant gases of CH4 and H2 were used in both CVD processes. Some preliminary feasibility tests were performed on the possible applicability of diamond and diamond-like carbon thin films for space-protective applications against artificially simulated electrically actuated plasma drag hypervelocity impact of olivine particles. As-deposited films were analysed by Raman for their chemical nature. The morphology and dimensions of hypervelocity impact craters in diamond and DLC films was also studied by scanning electron microscopy (SEM) and optical microscopy. The velocity of debris particles was determined by high-speed photography using a streak camera. The size of the impact particles was determined by measuring the size of the holes formed in the mylar sheet mounted just above the target diamond and DLC film/silicon and coordinates of the impact sites were determined using the same apparatus. This revised version was published online in November 2006 with corrections to the Cover Date.     

Coating of diamond-like carbon nanofilm on alumina by microwave plasma enhanced chemical vapor deposition process

Diamond-like carbon (DLC) nanofilms with thickness varied from under one hundred to a few hundred nanometers have been successfully deposited on alumina substrates by microwave plasma enhanced chemical vapor deposition (MW-PECVD) process. To obtain dense continuous DLC nanofilm coating over the entire sample surface, alumina substrates were pre-treated to enhance the nucleation density. Raman spectra of DLC films on samples showed distinct diamond peak at around 1332 cm(-1), and the broad band of amorphous carbon phase at around 1550 cm(-1). Full width at half maximum height (FWHM) values indicated good formation of diamond phase in all films. The result of nano-indentation test show that the hardness of alumina samples increase from 7.3 +/- 2.0 GPa in uncoated samples to 15.8 +/- 4.5-52.2 +/- 2.1 GPa in samples coated with DLC depending on the process conditions. It is observed that the hardness values are still in good range although the thickness of the films is less than a hundred nanometer.     

Flächeneinfluss bei der PACVD‐Beschichtung

Impact of the active surface on properties of DLC films in the PACVD coating chamber. In the automotive industry, economic and stable industrial processes to apply hard coatings for tribological applications are required. Hence detailed knowledge about the influence of coating parameters on the film characteristics is essential. the following paper deals with the process of plasma activated chemical vapor deposition with focus on the effect of the parameter “active area in the coating chamber“ on the properties of diamond‐like‐carbons (DLC). the coatings are deposited in an industrial coating chamber using reactive magnetron sputtering with a pulsed bias voltage (40 kHz) and at constant pressure. During the investigation of the influence of active area and current density on the mechanical and tribological properties of the DLC films, the expected correlation between active area and current density could be confirmed. By regulating the current density, consistent film properties could be achieved, independently of the active area in the chamber. Furthermore improved wear characteristics of the film – crucial for the endurance of heavily loaded automotive components – were achieved by adapting the load pattern of the chamber.     

Nanoindentation and AFM studies of PECVD DLC and reactively sputtered Ti containing carbon films

Amorphous carbon film, bdalso known as DLC film, bdis a promising material for tribological application. It is noted that properties relevant to tribological application change significantly depending on the method of preparation of these films. These properties are also altered by the composition of the films. In view of this, bdthe objective of the present work is to compare the nanoindentation and atomic force microscopy (AFM) study of diamond like carbon (DLC) film obtained by plasma enhanced chemical vapour deposition (bdPECVD with the Ti containing amorphous carbon (Ti/a- C : H) film obtained by unbalanced magnetron sputter deposition (UMSD). Towards that purpose, DLC and Ti/a- C : H films are deposited on silicon substrate by PECVD and UMSD processes, respectively. The microstructural features and the mechanical properties of these films are evaluated by scanning electron microscopy (SEM), bdtransmission electron microscopy (TEM), nanoindentation and by AFM. The results show that the PECVD DLC film has a higher elastic modulus, hardness and roughness than the UMSD Ti/a- C : H film. It also has a lower pull off force than Ti containing amorphous carbon film.     

Optical emission spectroscopy study of positive direct current bias enhanced diamond nucleation

High nucleation density and crystalline diamond films were deposited on a mirror-polished Si(100) substrate by horizontal microwave plasma chemical vapor deposition using a two step process consisting of positive direct current (dc) bias enhanced nucleation and growth. Optical emission spectroscopy was employed to investigate in situ the plasma emission characterization during positive biasing process. Emission lines from the Balmer series of atomic hydrogen, molecular hydrogen, CH, C₂, and Ar were observed in the visible and ultraviolet ranges when CH₄, H₂, and Ar were used as the reactant gases. The dependence of plasma emission spectra on the deposition parameters, such as biasing voltage, methane concentration and working pressure was investigated. The relative concentrations of neutral atomic hydrogen were estimated by using the Ar emission at 750.4 nm as an actinometer. A significant variation in the emission intensity of the radicals was measured with a change in the biasing voltage. The correlation between the spectra of some species and the quality of diamond films was studied. The results show that CH and C₂ both were important precursor in the diamond deposition, while C₂ was associated with the presence of amorphous phase in the films during positive dc biasing process.     

液相电沉积金刚石薄膜的研究进展

评述了液相沉积(类)金刚石薄膜的研究现状,介绍了液相合成(类)金刚石薄膜的装置、液态源及薄膜的性能,分析了如何更好地提高(类)金刚石薄膜质量,并在此基础上提出了一种可能制备出高质量金刚石薄膜的脉冲电弧放电沉积装置.     

Growth and characterization of diamond particles,diamond films,and CNT-diamond composite films deposited simultaneously by hot filament CVD

It is important to understand the growth of CNT-diamond composite films in order to improve the inter-link between two carbon allotropes, and, in turn, their physical properties for field emission and other applications. Isolated diamond particles, continuous diamond thin films, and thin films of carbon nanotubes (CNTs) having non-uniformly distributed diamond particles (CNT-diamond composite films) were simultaneously grown on unseeded, seeded, and catalyst pre-treated substrates, respectively, using a large-area multi-wafer-scale hot filament chemical vapor deposition. Films were deposited for four different growth durations at a given deposition condition. The changes in surface morphology and growth behavior of diamond particles with growth duration were investigated ex situ using field emission scanning electron microscopy and 2D confocal Raman depth spectral imaging, respectively. A surface morphological transition from faceted microcrystalline nature to nanocrystalline nature was observed as a function of growth duration in the case of isolated diamond particles grown on both unseeded and catalyst pre-treated substrates. However, such a morphological transition was not observed on the simultaneously grown continuous diamond thin films on seeded substrates. 2D confocal Raman depth spectral imaging of diamond particles showed that the local growth of CNTs did not affect the growth behavior of neighboring diamond particles on catalyst pre-treated substrates. These observations emphasize the importance of surface chemical reactions at the growth site in deciding sp² or sp³ carbon growth and the final grain size of the diamond films.     

霍尔离子源制备类金刚石薄膜研究

采用霍尔离子源沉积类金刚石薄膜是近年来新出现的一种方法 ,本文研究了自行研制的霍尔离子源的性能以及采用此离子源制备类金刚石薄膜及工艺参数的影响。结果表明 ,霍尔离子源在较低的电压即可起辉 ,可提供稳定的能量较低的离子束流。采用霍尔离子源沉积类金刚石薄膜的沉积速率约为 0 5nm/s。随着霍尔离子源灯丝电流的升高 ,离子源放电电压下降 ,制备的类金刚石薄膜的硬度下降。放电电流的变化对类金刚石薄膜的硬度影响不大。     

Study on hybrid nano-diamond films formed by plasma chemical vapor deposition (CVD)

Diamond-like carbon (DLC) films made by plasma chemical vapor deposition (CVD) have many useful properties for tribological characteristics. Especially, friction coefficient is very low. However, the films have weak points i.e., very low heatproof temperature of less than 300 °C and low hardness insufficient for industrial applications like machine tools. On the other hand, it is well known that diamond films made by plasma CVD have excellent hardness. But, they also have inferior properties for industrial applications, such as higher surface roughness and lower critical load than DLC films. In this study, we developed hybrid nano-diamond (HND) films that are formed by alternately depositing DLC films and diamond films in a same chamber. The HND films have sufficiently high hardness as well as excellent tribological characteristics due to the multi-layer structure of DLC and diamond. The process of forming HND films are discussed.     

类金刚石膜的性能及应用研究

研究了利用低能离子束技术，在单晶硅片等多种基体表面形成类金刚石薄膜（ＤＬＣ膜）的工艺，测试了其物理化学力学性能，在硅片，硅太阳电池和半导体等表面进行了形成类金刚石膜的应用研究。     

X-ray reflectivity study of bias graded diamond like carbon film synthesized by ECR plasma

Diamond like carbon (DLC) coatings were deposited on silicon substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using plasma of Ar and CH ₄ gases under the influence of negative d.c. self bias generated on the substrates by application of RF (13·56 MHz) power. The negative bias voltage was varied from ?60 V to ?150 V during deposition of DLC films on Si substrate. Detailed X-ray reflectivity (XRR) study was carried out to find out film properties like surface roughness, thickness and density of the films as a function of variation of negative bias voltage. The study shows that the DLC films constituted of composite layer i.e. the upper sub surface layer followed by denser bottom layer representing the bulk of the film. The upper layer is relatively thinner as compared to the bottom layer. The XRR study was an attempt to substantiate the sub-plantation model for DLC film growth.     

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.