The kinetics of a diamond-like film growth in a microwave gas discharge plasma

Spontaneous variations of the microstructure and properties of carbon films during deposition in a microwave gas discharge plasma were studied. The ion current component of the gas discharge plasma favors the selective growth of a diamond-like phase with a thickness exceeding that achieved in the case of a pyrolytic deposition process.     

Preparation and antibacterial properties of Ag-containing diamond-like carbon films prepared by a combination of magnetron sputtering and plasma source ion implantation

Ag-containing diamond-like carbon (DLC) films were prepared on austenitic type stainless steel SUS316L and silicon wafer substrates by a process combining reactive magnetron sputtering with plasma source ion implantation (PSII). An Ag disc was used as a target for the sputter source with an RF power of 100 W. A mixture of the gases Ar and C₂H₂ was introduced into the discharge chamber while a negative high voltage pulse was applied to the substrate holder. By changing the gas flow ratios the resulting Ag content of the films could be varied. The prepared films were composed of amorphous carbon with crystalline Ag, as observed by X-ray diffractometry and TEM. Additional sample characterizations were performed by X-ray photoelectron spectroscopy, secondary ion mass spectrometry and Raman spectroscopy. The surface morphology was observed by scanning electron microscopy. The antibacterial activity was determined using Staphylococcus aureus bacteria. All Ag-containing diamond-like carbon films exhibited an antibacterial activity with only small variations depending on the Ag content.     

微波ECR等离子体特性及其对DLC膜性能的影响

为了解并优化在微波ECR等离子体增强化学气相沉积制备类金刚石膜工艺研究中的等离子体特性，利用朗缪尔探针法系统地测量了等离子体密度(Ne)、电子温度(Te)随工作气压(p)变化的关系。DLC膜的结构和性能依赖于沉积条件，提高等离子体密度有利于DLC膜的生长。本文示出了不同的CH4流量时，DLC膜的拉曼光谱和表面均方根粗糙度Rmax变化曲线，阐述了等离子体密度Ne、电子温度Te对DLC膜结构和性能的影响。     

Growth and properties of the ion beam deposited SiOx containing DLC films

In the present study SiO_x containing diamond-like carbon (DLC) films were synthesized by the closed drift ion source from hexamethyldisiloxane vapor. Kinetics of the growth of DLC films was investigated using optical emission spectroscopy (OES). Structure, chemical composition, electrical and optical properties of the synthesized films were studied. The effects of ion beam energy were investigated. The main atomic hydrogen Balmer series lines and the intense broad CH group related peak were detected in the OES spectra registered in-situ during SiO_x containing diamond-like carbon film synthesis. The intensity ratio of H-β/CH peaks increased with the increase of applied ion beam energy. It was explained by activation of the dissociation of the hexamethyldisiloxane molecules. Changes of the structure of the diamond-like carbon films were observed for the films deposited under intense dissociation conditions.     

Microstructural and frictional control of diamond-like carbon films deposited on acrylic rubber by plasma assisted chemical vapor deposition

In this paper we concentrate on the microstructure of diamond-like carbon films prepared by plasma assisted chemical vapor deposition on acrylic rubber. The temperature variation produced by the ion impingement during plasma cleaning and subsequent film deposition was monitored and controlled as a function of bias voltage and treatment time. Its influence during film growth on the appearance of patterns of cracks and wrinkles, caused by the thermal stresses is evaluated. Different growth modes are proposed in order to explain the smaller patch sizes observed at negative variations of temperature. The coefficient of friction (CoF) of the samples is measured using a pin-on-disk tribometer in non-lubricated conditions. Much lower CoF values than unprotected rubber are seen, which can be correlated with the observed patch size.     

Effect of dilution gases in methane on the deposition of diamond-like carbon in a microwave discharge II: Effect of hydrogen

The effect of hydrogen as a dilution gas on the deposition of diamond-like carbon by the decomposition of methane in a microwave discharge was studied from surface analysis of the substrate and from plasma diagnostics. When carbon deposited from a CH₄-Ar plasma and consisting of large amounts of graphite and small amounts of diamond, was placed in the hydrogen plasma chemical sputtering of carbon to form hydrocarbons and adsorption of hydrogen on the carbon substrate were observed. The reaction occured only on graphite and not on diamond. The effects of hydrogen as a dilution gas on the deposition of diamond-like carbon from CH₄-H₂ plasma are to cause the formation of CH₃ radicals in the plasma, the removal of graphite from the deposit and the adsorption of atomic hydrogen on the deposit as an active participant in the diamond crystallization process.     

Tribological performance of DLC coatings deposited by ion beam deposition under dry friction and oil lubricated conditions

Understanding the reaction between lubricant additives and diamond-like carbon coatings is imperative for the improvement of the friction and wear properties of mechanical parts with diamond-like carbon coatings. Diamond-like carbon coatings were deposited with ion beam deposition and the influence of lubricant additives on the friction coefficients and wear rates of diamond-like carbon coatings under the lubricated conditions was studied. It was revealed that the wear rates of diamond-like carbon coatings under unlubricated conditions are 1.5 × 10⁻¹⁴ m³/(Nm) while they are decreased to 3 × 10⁻¹⁷ m³/(Nm) to 1.7 × 10⁻¹⁶ m³/(Nm) when lubricated by PAO-4 base oil with three additives. The addition of molybdenum dithiocarbamate in PAO-4 base oil decreases the friction coefficients of diamond-like carbon coatings to 0.07, but increases the wear rate of diamond-like carbon coatings. The addition of zinc dialkyl dithiophosphate to PAO-4 can slightly decrease the friction coefficient of diamond-like carbon coatings and improve the wear resistance of diamond-like carbon coatings. The addition of amine sulfuric-phosphate diester in PAO-4 can greatly decrease the wear rate of diamond-like carbon coatings to 3 × 10⁻¹⁷ m³/(Nm) but has a negligible effect on the friction coefficients of diamond-like carbon coatings.     

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.     

Electrochemical Corrosion Behavior of the DLC Coated and Uncoated NiTi Alloys

A dense and well-adhered diamond-like carbon （DLC） coating was prepared on the nickel-titanium （NiTi） alloys by plasma immersion ion implantation and deposition （PIIID）. Potentiodynamic polarization tests indicated the corrosion resistance of the NiTi alloys was markedly improved by the DLC coating. The Ni ions release of the NiTi alloys was effectively blocked by the DLC coating.     

Diamond-like carbon films produced in a butane plasma

Diamond-like carbon films produced in an r.f. butane plasma were characterized by X-ray photoemission analysis of the deposits. It was confirmed that films produced at low deposition rates were more diamond-like than films produced at high deposition rates. An investigation of the electrical properties of the films showed that the low deposition rate films were highly insulating whereas the high deposition rate films were conducting.     

Multiple microscale plasma CVD apparatuses on a substrate

Plasma chemical vapor depositions (CVD) of carbon films using a CH₄---H₂ gas system have been performed with a prototype 2×2 plasma chip which consists of 2×2 coplanar film electrodes (CFE). Using this chip, we could perform four plasma processing experiments simultaneously. A plasma chip on which plasma-processing apparatuses are integrated has advantages in plasma processing compared to conventional ones, such as high processing speed due to the high density of the microscale plasma, and high efficiency due to parallel processing. We have obtained various carbon films easily, such as glassy carbon and diamond-like carbon, with this simple prototype plasma chip. This is the first report on plasma processing with this innovative processing device, the plasma chip.     

9Cr18轴承钢表面不同等离子体浸没离子注入强化处理技术研究

采用不同的等离子体浸没离子注入(PⅢ)工艺在9Cr18轴承钢表面进行了气体、金属、金属加气体的离子注入和碳化钛(TiC)、类金刚石(DLC)薄膜的等离子体浸没离子注入与沉积(PⅢD).对处理后的试样进行了X射线光电子能谱(XPS)、X射线衍射(XRD)、俄歇电子能谱(AES)和拉曼光谱(Raman)分析;测试了处理前后试样的显微硬度、磨痕宽度和摩擦系数.结果表明:处理后试样表面均形成了不同的改性层,且改性层中化学组成和各元素的浓度-深度分布随处理工艺的不同而变化;处理后试样的显微硬度都有较大提高,最大增幅达77.7%;表面摩擦系数由0.8下降到0.16;磨痕宽度减少了23倍;与PⅢ工艺相比,相同参数下,PⅢD处理后的试样表面综合性能更加优异.     

Field emission from diamond and diamond-like carbon films

Field emission from diamond and diamond-like carbon thin films deposited on silicon substrates has been studied. The diamond films were synthesized using hot filament chemical vapor deposition technique. The diamond-like carbon films were deposited using the radio frequency chemical vapor deposition method. Field emission studies were carried out using a sphere-to-plane electrode configuration. The results of field emission were analyzed using the Fowler-Nordheim model. It was found that the diamond nucleation density affected the field emission properties. The films were characterized using standard scanning electron microscopy, Raman spectroscopy, and electron spin resonance techniques. Raman spectra of both diamond and diamond-like films exhibit spectral features characteristic of these structures. Raman spectrum for diamond films exhibit a well-defined peak at 1333cm^?1. Asymmetric broad peak formed in diamond-like carbon films consists of D-band and G-band around 1550 cm^?1 showing the existence of both diamond (sp³ phase) and graphite (sp² phase) in diamond-like carbon films.     

Precursor gas effect on the mechanical and optical properties of ion beam deposited diamond-like carbon films

The effect of precursor gases on the diamond-like carbon (DLC) film deposition was investigated by the direct ion beam deposition method. DLC films were deposited using methane and benzene as the precursor gases. Ion energies for the deposition range from 100 to 700 eV were achieved by adjusting the beam voltage. The residual stresses, refractive indices and optical band gaps were compared at the same ion energy. We observed significant differences in residual stress and optical properties between these films. As in r.f. plasma-assisted CVD, the residual stresses of the films deposited from benzene show a characteristic behaviour of lower ion energy deposition than those deposited from methane. The present observations are discussed in terms of the difference in ion energy per carbon atom at the growth surface. We also observed that the Ar addition effect on the residual stress is strongly dependent on the precursor gases.     

A planar diamond-like carbon nanostructure for a low-voltage field emission cathode with a developed surface

Issues pertaining to the effective solution of problems related to the creation of durable low-voltage field emission cathodes with developed working surface and high density of emission current are considered. Results of practical implementation of the concept of multielectrode field emission planar nanostructures based on diamond-like carbon are presented. High average current density (0.1–0.3 A cm^–2) is ensured by the formation of a controlled zone of electrostatic field localization at the planar-edge structure. The working life of cathode samples reaches 700–3000 h due to several positive factors, such as the stabilizing properties of a diamond-like carbon film, protection of the emitter from ion bombardment, use of a system of ballast resistors, and low-voltage operation of submicron interelectrode gaps.     

Effects of SiNx interlayer on characterisation of amorphous diamond-like carbon films

The magnetron sputtering amorphous diamond-like carbon film is successfully deposited by SiN_x interlayer approach. The scanning electron microscopy study reveals the creation of high uniform surface micrograph diamond-like carbon films with SiN_x interlayer. For comparison, diamond-like carbon films with different interlayers are also grown. The Raman spectra are analyzed in order to characterize the stressed induce peak shifts of the films. The interactions of C atom with Si(100) and SiN_x surface are studied by density functional theory simulation. The effects of interlayers on the films deposition and the considering deposition mechanism are discussed. It is suggested that the diamond-like carbon and SiN_x bilayer structure can help to render applications in protective coatings and high quality silicon on diamond related radiation tolerance devices.     

Contact damage evolution in a diamond-like carbon (DLC) coating on a stainless steel substrate

A diamond-like carbon thin film was coated onto a stainless steel substrate using plasma assisted chemical vapour deposition (PACVD). Instrumented indentation and scratching were used, supported by focused ion beam (FIB) microscopy, to explore deformation and fracture behaviours of this coating system. The formation and growth of ring and radial cracks in the coating, as well as plastic flow in the ductile substrate, were observed to be the predominant deformation processes for this coating system. Lateral cracking occurred at the interface of the coating/substrate following indentation, but in the middle of the coating following scratching. No evidence of plastic flow within the coating was observed. Coating deformation is, therefore, controlled by its fracture energy. An indentation-energy-based model was applied to evaluate the fracture toughness of the coating.     

Transport of vacuum arc plasma through an off-plane double bend filtering duct

A new magnetic macroparticle filter design consisting of an off-plane double-bend (OPDB) filter is described. The transport of the vacuum arc plasma through this OPDB filter is investigated using Langmuir and deposition probes. Films of amorphous hard carbon have been deposited using a 90° single bend and the OPDB filter and the macroparticle contents of the films are compared. The experimental results were found to be in good agreement with the simulations results based on an improved drift approximation model. The results demonstrate that OPDB filter has a relatively better transmission efficiency than the 90° single bend filter, lower macroparticle counts and is suitable for preparation of diamond-like carbon coatings with high quality.     

Nucleation and growth mechanism of diamond during hot-filament chemical vapour deposition

High-resolution transmission electron microscopy (HRTEM) was employed to study the nucleation and subsequent growth mechanism of crystalline diamond grown on copper TEM grids by the hot-filament chemical vapour deposition process. The HRTEM revealed direct evidence for the formation of a diamond-like amorphous carbon layer 8–14 nm thick, in which small diamond microcrystallites about 2–5 nm across were embedded. These diamond microcrystallites were formed as a result of direct transformation of the diamond-like carbon into diamond. Large diamond crystallites were observed to grow from these microcrystallites. The diamond surface was found to be non-uniform. It is envisaged that the diamond microcrystallites present in the amorphous, diamond-like carbon layer provide nucleation sites on which the large diamond crystallites grew. A mechanism of diamond growth has been proposed, based on the experimental findings, and is consistent with available theoretical models and numerous experimental observations reported in the literature.     

Coating NiTi archwires with diamond-like carbon films: reducing fluoride-induced corrosion and improving frictional properties

This study aims to coat diamond-like carbon (DLC) films onto nickel–titanium (NiTi) orthodontic archwires. The film protects against fluoride-induced corrosion and will improve orthodontic friction. ‘Mirror-confinement-type electron cyclotron resonance plasma sputtering’ was utilized to deposit DLC films onto NiTi archwires. The influence of a fluoride-containing environment on the surface topography and the friction force between the brackets and archwires were investigated. The results confirmed the superior nature of the DLC coating, with less surface roughness variation for DLC-coated archwires after immersion in a high fluoride ion environment. Friction tests also showed that applying a DLC coating significantly decreased the fretting wear and the coefficient of friction, both in ambient air and artificial saliva. Thus, DLC coatings are recommended to reduce fluoride-induced corrosion and improve orthodontic friction.