Effects of CPII implantation on the characteristics of diamond-like carbon films

A diamond-like carbon film (DLC) was successfully synthesized using a hybrid PVD process, involving a filter arc deposition source (FAD) and a carbon plasma ion implanter (CPII). A quarter-torus plasma duct filter markedly reduced the density of the macro-particles. Graphite targets were used in FAD. Large electron and ion energies generated from the plasma duct facilitate the activation of carbon plasma and the deposition of high-quality DLC films. M2 tool steel was pre-implanted with 45 kV carbon ions before the DLC was deposited to enhance the adhesive and surface properties of the film. The ion mixing effect, the induction of residual stress and the phase transformation at the interface were significantly improved. The hardness of the DLC increased to 47.7 GPa and 56.5 GPa, and the wear life was prolonged to over 70 km with implantation fluences of 1 × 10¹⁷ ions/cm² and 2 × 10¹⁷ ions/cm², respectively.     

Nanoindentation measurements on modified diamond-like carbon thin films

In the present study, we explored the effect of metallic interlayers (Cu and Ti) and indentation loads (5-20 mN) on the mechanical properties of plasma produced diamond-like carbon (DLC) thin films. Also a comparison has been made for mechanical properties of these films with pure DLC and nitrogen incorporated DLC films. Introduction of N in DLC led to a drastic decrease in residual stress (S) from 1.8 to 0.7 GPa, but with expenses of hardness (H) and other mechanical properties. In contrast, addition of Cu and Ti interlayers between substrate Si and DLC, results in significant decrease in S with little enhancement of hardness and other mechanical properties. Among various DLC films, maximum hardness 30.8 GPa is observed in Ti-DLC film. Besides hardness and elastic modulus, various other mechanical parameters have also been estimated using load versus displacement curves.     

Formation of diamond-like carbon (DLC) film on the NiTi alloys via plasma immersion ion implantation and deposition (PIIID) for improving corrosion resistance

NiTi alloys are potentially useful in biomedical application due to their unique superelasticity and shape memory effect. However, the materials are vulnerable to surface corrosion and the most serious issue is out-diffusion of toxic Ni ions from the substrate into body tissues and fluids. In this paper, Diamond-like carbon (DLC) film is fabricated on the NiTi alloys using plasma immersion ion implantation and deposition (PIIID) at room temperature to improve their corrosion resistance and block the out-diffusion of the Ni ions. The results show that the DLC films cannot only improve the corrosion resistance of the NiTi substrate, but also effectively suppress the Ni ions release from the substrate. The reason that the corrosion resistance of the coated samples is markedly improved due to the DLC films formation is systematically investigated.     

Studies of diamond-like carbon （DLC） films deposited on stainless steel substrate with Si/SiC intermediate layers

In this work, diamond-like carbon （DLC） films were deposited on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced sputtering physical vapour deposition （PEUMS-PVD） and microwave electron cyclotron resonance plasma enhanced chemical vapour deposition （MW-ECRPECVD） techniques. The influence of substrate negative self-bias voltage and Si target power on the structure and nano-mechanical behaviour of the DLC films were investigated by Raman spectroscopy, nano-indentation, and the film structural morphology by atomic force microscopy （AFM）. With the increase of deposition bias voltage, the G band shifted to higher wave-number and the integrated intensity ratio ID/IG increased. We considered these as evidences for the development of graphitization in the films. As the substrate negative self-bias voltage increased, particle bombardment function was enhanced and the sp^3-bond carbon density reducing, resulted in the peak values of hardness （H） and elastic modulus （E）. Silicon addition promoted the formation of sp^3 bonding and reduced the hardness. The incorporated Si atoms substituted sp^2- bond carbon atoms in ring structures, which promoted the formation of sp^3-bond. The structural transition from C-C to C-Si bonds resulted in relaxation of the residual stress which led to the decrease of internal stress and hardness. The results of AFM indicated that the films was dense and homogeneous, the roughness of the films was decreased due to the increase of substrate negative self-bias voltage and the Si target power.     

Effect of substrate morphology on the roughness evolution of ultra thin DLC films

The effect of substrate roughness on growth of ultra thin diamond-like carbon (DLC) films has been studied. The ultra thin DLC films have been deposited on silicon substrates with initial surface roughness of 0.15, 0.46 and 1.08 nm using a filted cathodic vacuum arc (FCVA) system. The films were characterized by Raman spectroscope, transmission electron microscope (TEM) and atomic force microscopy (AFM) to investigate the evolution of the surface roughness as a function of the film thickness. The experimental results show that the evolution of the surface morphology in an atomic scale depends on the initial surface morphology of the silicon substrate. For smooth silicon substrate (initial surface roughness of 0.15 nm), the surface roughness decreased with DLC thickness. However, for silicon substrate with initial surface roughness of 0.46 and 1.08 nm, the film surface roughness decreased first and then increased to a maximum and subsequently decreased again. The preferred growth of the valley and the island growth of DLC were employed to interpret the influence of substrate morphology on the evolution of DLC film roughness.     

Atmospheric effects on the adhesion and friction between non-hydrogenated diamond-like carbon (DLC) coating and aluminum - A first principles investigation

Experimentally, non-hydrogenated DLC coatings were tested against 319 Al alloy in the nitrogen, hydrogen, dry air (0% RH), and ambient air (40% RH) environments using a vacuum pin-on-disc tribometer. The average coefficient of friction (COF) and the material transfer changed dramatically depending on the test environment. Density functional theory (DFT) calculations were performed to investigate the interaction of diamond surface, to represent non-hydrogenated DLC, with N₂, H₂, and H₂O molecules. These calculations suggested that hydrogen and water would dissociate and be chemically adsorbed at a diamond surface whereas the dissociation of nitrogen is very unlikely to happen. Therefore, the diamond/DLC surface is passivated by -H termination in hydrogen and by -OH termination in water vapor, but not passivated in nitrogen. The calculated work of separation for Al with non-passivated and reacted diamond surfaces indicated the same tendency of adhesive transfer as observed in the pin-on-disc tests. The calculated work of separation at the interfaces formed after material transfer has the same trend with the measured COF. Therefore, DFT calculations successfully explained the atmospheric dependency of the tribological behavior of non-hydrogenated DLC coatings.     

Diamond-like carbon films deposited by a hybrid ECRCVD system

A novel hybrid technique for diamond-like carbon (DLC) film deposition has been developed. This technique combines the electron cyclotron resonance chemical vapor deposition (ECRCVD) of C₂H₂ and metallic magnetron sputtering. Here we described how DLC film is used for a variety of applications such as stamper, PCB micro-tools, and threading form-tools by taking advantage of hybrid ECRCVD system. The structure of the DLC films is delineated by a function of bias voltages by Raman spectroscopy. This function includes parameters such as dependence of G peak positions and the intensity ratio (I_D/I_G). Atomic force microscope (AFM) examines the root-mean-square (R.M.S.) roughness and the surface morphology. Excellent adhesion and lower friction coefficients of a DLC film were also assessed.     

Improving the conductivity of diamond-like carbon films with zinc doping and its material properties

Zinc doped diamond-like carbon (DLC) nanocomposite thin films are fabricated by KrF pulsed laser deposition. Carbon targets containing 3.0, 5.0 and 10.0 atomic percentages of zinc are used as the source for the laser system. Investigation of electrical properties by the four-point probe shows that doping zinc into DLC can lower the electrical sheet resistivity. Microstructural analysis by Raman spectroscopy and XPS show a lower sp³ content but a higher SiC content with an increasing amount of zinc incorporation. The increase of SiC leads to an increase in adhesion strength. Surface roughness of the films also increases while the coefficients of friction for the films do not change.     

Evaluation of bacterial adhesion on Si-doped diamond-like carbon films

Diamond-like carbon (DLC) films as biomaterial for medical devices have been attracting great interest due to their excellent properties such as hardness, low friction and chemical inertness. It has been demonstrated that the properties of DLC films can be further improved by the addition of silicon into DLC films, such as thermal stability, compressive stress, etc. However no research work on anti-bacterial properties of silicon-doped diamond-like carbon films has been reported. In this paper the surface physical and chemical properties of Si-doped diamond-like carbon films with various Si contents on 316 stainless steel substrate prepared by a magnetron sputtering technique were investigated, including surface topography, surface chemistry, the sp³/sp² ratio, contact angle, surface free energy, etc. Bacterial adhesion to Si-doped DLC films was evaluated with Pseudomonas aeruginosa, Staphylococcus epidermidis and Staphylococcus aureus which frequently cause medical device-associated infections. The experimental results showed that bacterial adhesion decreased with increasing the silicon content in the films. All the Si-doped DLC films performed much better than stainless steel 316L on reducing bacterial attachment.     

Influence of crystalline diamond nanoparticles on diamond-like carbon friction behavior

Crystalline diamond (CD) particles have been incorporated in diamond-like carbon (DLC) film structure in order to improve DLC electrochemical corrosion resistance. This paper shows the investigation of CD-DLC friction behavior according to the CD average sizes and concentration. The films were growth over 304 stainless steel using plasma enhanced chemical vapor deposition. The response surface methodology was used to develop a mathematical modeling of friction for these films, using the experimental results, in order to identify parameters that control friction and construct tribological maps according to the CD average sizes. The presence of bigger CD particles (250 and 500 nm) increased the film roughness. Films with CD particles of 4 nm presented the most homogeneous friction map, with minor variation in friction coefficient with the increase/decrease of load and sliding speed even when the CD concentration increase. This result suggests that in CD-DLC films containing CD particles of 4 nm average size, the nanoparticles are better incorporated in DLC structure due to its average size (4 nm) that is near than DLC grain size and could occupy the nanospaces between DLC grains.     

Electrodeposition of diamond-like carbon (DLC) films on Ti

Diamond-like carbon films (DLC) were deposited on titanium substrates in acetonitrile and N,N-dimethyl formamide (DMF) liquids by the liquid-phase electrodeposition technique at ambient pressure and temperature. The applied voltage between the electrodes was high (1200 V) due to the use of resistive organic liquids. The surface morphology was examined by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Corrosion performance of the coatings was investigated by potentiodynamic polararization tests in phosphate buffer saline solution. Raman spectroscopy analysis of the films revealed two broad bands at approximately 1360 cm⁻¹ and 1580 cm⁻¹, related to D and G-band of DLC, respectively. The coated Ti was tested in a ball-on-plate type wear test machine with Al₂O₃ balls. The films presented a low friction coefficient (about 0.1), and the films deposited from DMF presented the best wear resistance.     

含氮类金刚石薄膜的紫外辐照研究

 用射频等离子体方法在玻璃基底上制备的类金刚石（DLC）薄膜，采用离子注入法掺氮，并对掺氮DLC薄膜紫外（UV）辐照前后的性能变化进行了研究。研究结果表明：随氮离子注入剂量及UV辐照时间的增加，位于2 930cm^-1附近的SP ³C-H吸收峰明显变小，而位于1 580cm^-1附近的SP2C-H吸收峰则明显增强，薄膜的电阻率明显呈下降趋势；随UV辐照时间的增加，位于1 078cm^-1附近的Si-O-Si键数量及位于786cm^-1附近的Si-C键数量明显增加。即氮离子注入和UV辐照明显改变了DLC薄膜的结构与特性。     

Wettability and antibacterial activity of modified diamond-like carbon films

Diamond-like carbon (DLC) films can be used in a numerous industrial applications, including biomedical coatings with bactericidal properties. It has been demonstrated that DLC surface can be modified with oxygen plasma treatment. The purpose of this paper is to study the wettability and bactericidal activity of oxygen plasma-treated DLC films produced by plasma enhanced chemical vapor deposition technique. The sp³/sp² ratio increased after the treatment due to the increase in the generation of the unstable carbon bonds caused by the energetic ions, especially O-H group. The treated DLC surface becomes superhydrophilic and rougher, although the roughness values are still lower. DLC antibacterial activity did not increased with plasma treatment. Therefore, oxygen plasma treatment can be used to make superhydrophilic DLC but not to increase its bactericidal properties.     

Effect of deposition voltage on the field emission properties of electrodeposited diamond-like carbon films

Diamond-like carbon (DLC) films were deposited on Al substrates by electrodeposition technique under various voltages. The surface morphology and compositions of synthesized films were characterized by scanning electron microscopy and Raman spectroscopy. With the increase of deposition voltage, the sp² phase concentration decreased and the surface morphology changed dramatically. The influence of deposition voltage on the field electron emission (FEE) properties of DLC films was not monotonic due to two adverse effects of deposition voltage on the surface morphology and compositions. The DLC film deposited under 1200 V exhibited optimum FEE property, including a lowest threshold field of 13 V/μm and a largest emission current density of 904.8 μA/cm² at 23.5 V/μm.     

椭偏光散射分析类金刚石薄膜的散射特性

 基于光学薄膜反射椭偏法的测量原理,对光学薄膜散射椭偏特性进行了研究。给出了光学薄膜散射逆问题的解决方法,并对不同脉冲频率下采用脉冲真空电弧离子镀技术沉积的类金刚石薄膜的散射特性进行了研究。分析了光学薄膜界面的相关特性以及膜层中局部缺陷对散射光椭偏特性的影响。结果表明:随着脉冲频率的增加,所沉积的类金刚石薄膜的相关性变差,且薄膜中的局部缺陷引起的体散射越明显。     

Tip-induced oxidative nano-machining of conducting diamond-like carbon (DLC)

Electrically conducting diamond-like carbon films have been nano-machined by local deposition of thermal energy at the tip-to-film point of contact; the process is implemented on an atomic force microscope platform. Features with linewidth resolution down to 20 nm have been demonstrated; lateral irregularities along edges were less than 5 nm, while the radius of curvature at the edges was less than 10 nm; and the slope of features was limited by the aspect ratio of the tip. The mechanism arises from prompt thermal oxidation by intermittent transfer of heat from an ohmically heated tip, where Fowler–Nordheim tunnelling is likely to play a role in completing an electrical circuit when the physical continuity of the thermal circuit is interrupted. When heat transfer is insufficient to ensure prompt oxidation, then formation of a metastable low-density carbon phase is found to take place. That phase will then, at room temperature and in the presence of oxygen, relax back to a normal higher density phase over a period of one hour. The many desirable physico-chemical properties of diamond-like carbon, in combination with the good spatial resolution of local probe methodology, suggest that the outcomes could have significant implications for next-generation nano-machine and nano-templating technologies. PACS 07.79.Lh; 81.16.Nd; 81.16.Pr; 81.16.Rf     

Gas barrier properties of diamond-like carbon films coated on PTFE

Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapour deposition (PE-CVD). Before the DLC coating, the PTFE substrate was modified with a N₂ plasma pre-treatment to enhance the adhesive strength of the DLC to the substrate. The influences of the N₂ plasma pre-treatment and process pressure on the gas permeation properties of these DLC-coated PTFE samples were investigated. In the Raman spectra, the G peak position shifted to a lower wave number with increasing process pressure. With scanning electron microscopy (SEM), a network of microcracks was observed on the surface of the DLC film without N₂ plasma pre-treatment. The density of these cracks decreased with increasing process pressure. In the film subjected to a N₂ plasma pre-treatment, no cracks were observed at any process pressure. In the gas barrier test, the gas permeation decreased drastically with increasing film thickness and saturated at a thickness of 0.2 μm. The DLC-coated PTFE with the N₂ plasma pre-treatment exhibited a greater reduction in gas permeation than did the samples without pre-treatment. For both sample types, gas permeation decreased with increasing process pressure.     

Influences of ultraviolet irradiation on structure and tribological properties of diamond-like carbon films

Two types of diamond-like carbon (DLC) films with different bonding configurations were produced by pulse-assisted and DC-assisted plasma chemical vapor deposition. The chemical composition, surface morphology, microstructure, internal stress and tribological properties of the two films before and after the ultraviolet (UV) irradiation were investigated and compared. It was found that the UV irradiation had little effects on the chemical composition and surface morphology of both the films, but greatly influenced their tribological properties in the opposite trends. This result was attributed to the different changing outcomes of the bonding configuration induced by the UV actions of primary photo-dissociation and secondary recombination, wherein the inherent bonding configuration and internal stress played important roles.     

Target-plane deposition of diamond-like carbon in pulsed laser ablation of graphite

In pulsed Nd:YAG laser ablation of highly oriented pyrolytic graphite (HOPG) at 10⁻⁶ Torr, diamond-like carbon (DLC) are deposited at laser wavelengths of 1064, 532, and 355 nm on substrates placed in the target-plane. These target-plane samples are found to contain varying sp³ content and composed of nanostructures of 40-200 nm in size depending on the laser wavelength and laser fluence. The material and origin of sp³ in the target-plane samples is closely correlated to that in the laser-modified HOPG surface layer, and hardly from the backward deposition of ablated carbon plume. The surface morphology of the target-plane samples shows the columnar growth and with a tendency for agglomeration between nanograins, in particular for long laser wavelength at 1064 nm. It is also proposed that DLC formation mechanism at the laser-ablated HOPG is possibly via the laser-induced subsurface melting and resolidification.     

Surface modification of diamond-like carbon films with protein via polydopamine inspired coatings

In this paper, we report a facile two-step approach to immobilize proteins onto DLC surfaces. The first step was a simple immersion of DLC in a solution of dopamine. Polydopamine was deposited on DLC as a stable anchor to present protein molecules. Then the protein ad-layer was deposited on it. The chemical components of the modified DLC surfaces were characterized by Fourier transform infrared spectra and X-ray photoelectron spectroscopy. The biocompatibility of it was evaluated in vitro by the tetrazolium salt method. And it was indicated that the BSA modified surface had good haemocompatibility properties, and was cytocompatible to PC-12 cells.