Microstructure Of Diamond-like Carbon Films Research Articles

Micro-structural and optical properties of diamond-like carbon films grown by magnetic field-assisted laser deposition

Inhomogeneous magnetic field is introduced into pulsed laser deposition process, in order to find new properties of diamond-like carbon film grown under magnetic field, thereby offering the theoretical and experimental basis for further enhancing sp<sup>3</sup>-bond content in this film. Distribution of the magnetic strength and flux lines induced by a rectangular permanent magnet is calculated. And then, flying trace of the carbon ions in the magnetic field is also simulated by the iterative method, which indicates that the carbon ions cannot expand freely and they are confined and accumulate around the center region of the magnet source. Beside the surface interference, the measurement and the fitted results of ellipsometry parameters show that magnetic field exerts an important influence on layer-thickness distribution and optical constant of the pulsed laser deposition-grown diamond-like carbon film. Meanwhile, it is indicated that the inhomogeneity of the layer-thickness distribution and optical constant increase when the magnetic strength is higher. Micro-structure of diamond-like carbon film is affected seriously by magnetic field, which is indicated by Raman spectra. Magnetic field can enhance the local stress in the carbon matrix net, increasing the sp<sup>3</sup>-bond content. Theoretical research and experimental research both show that a suitable magnetic strength can excite micro-structure of diamond-like carbon film significantly, and the high-quality diamond-like carbon coating with practical application value will be obtained by technological adjustment.

Regulating the fretting behavior of diamond-like carbon films by changing the composition and structure

Reducing or eliminating the slip regime and mix regime is an effective way to reduce the fretting wear, while the diamond-like carbon (DLC) film, as a self-lubricating solid lubricant, can reduce friction coefficient while improving the surface strength. The most valuable thing is that DLC film can change the film's composition, structure, and physical and chemical properties by controlling its deposition process. This regularability can realize the reduction or elimination of slip regime and mix regime under different fretting conditions, so it is important to explore the changing regulation law of the fretting regime by changing the sp2/sp3 hybrid bond content ratio and microstructure of DLC film. Here, DLC films with different sp2/sp3 hybrid carbon content ratios were obtained by annealing; the fretting performance was studied under different normal loads and amplitudes. The following rules are obtained by drawing the running conditions fretting map and analyzing the tangential stiffness, friction coefficient and dissipation energy: with increasing the sp2/sp3 hybrid carbon content of DLC film, the fretting regime moves towards the slip regime, while the friction coefficient and dissipated energy will increase. In addition, the short-range ordered microstructure, such as onion-like carbon structure, will facilitate the fretting regime towards the partial slip regime. This work demonstrates the controllability and potential of DLC films in fretting.

Effects of external magnetic field on the micro-structure of diamond-like carbon film prepared by pulsed laser deposition

The DLC film was deposited by pulsed laser deposition in an external magnetic field, and its optical property, surface morphology and atomic bonds were researched. The simulated flight tracks of the carbon ions in the magnetic field showed that a number of the carbon ions were constrained by the Lorentz force, fling onto the substrate and forming the DLC film. The contrast between the micro-structures of the DLC films deposited in or out the magnetic field showed that the external magnetic field changed the expansion of the laser-produced plume and confined the surface diffusion of the charged particles on the substrate, improving the content of the sp3 bonds in the DLC film.

Influences of Pulse Frequency on Structure and Mechanical Properties of DLC Films Synthesized by Pulsed Cathodic Arc Evaporation

Diamond-like carbon (DLC) films were prepared on the Si (100) substrates by pulsed cathodic arc plasma. The influences of given pulse frequency on the microstructure, morphology, mechanical and optical properties of DLC films were investigated by Raman spectroscopy, atomic force microscopy, Knoop sclerometer, X-ray double-crystal surface profilometer. The results showed that the variation of pulse frequency could significantly change the microstructure of DLC films, including the size and ordering of sp2carbon clusters and movement or diffusion of carbon atoms. The increasing of pulse frequency led to the variation of the relative fraction of Csp3/Csp2. The hardness and internal stress of the DLC films were affected accordingly. The results might contribute to the synthesis of DLC films with excellent structure and properties by cathodic arc evaporation.

衬底对脉冲激光沉积类金刚石薄膜微观结构的影响

衬底对脉冲激光沉积类金刚石薄膜微观结构的影响

衬底对脉冲激光沉积类金刚石薄膜微观结构的影响

衬底对脉冲激光沉积类金刚石薄膜微观结构的影响

Superlubricity behaviors of Si3N4/DLC Films under PAO oil with nano boron nitride additive lubrication

The tribological properties of Si3N4 ball sliding against diamond‐like carbon (DLC) films were investigated using a ball‐on‐disc tribometer under dry friction and oil lubrications, respectively. The influence of nano boron nitride particle as lubricant additive in poly‐α‐olefin (PAO) oil on the tribological properties of Si3N4/DLC films was evaluated. The microstructure of DLC films was measured by Raman spectroscopy and X‐ray photoelectron spectroscopy. The experimental results show coefficient of friction (COF) of Si3N4/DLC films was as low as 0.035 due to the formation of graphite‐like transfer films under dry friction condition. It also indicates that the tribological properties of Si3N4/DLC films were influenced significantly by the viscosity of oil and the content of nano boron nitride particle in PAO oil. COF increases with the viscosity of PAO oil increasing. Si3N4/DLC films exhibit the superlubricity behaviors (μ=0.001 and nonmeasurable wear) under PAO 6 oil with 1.0 wt% nano boron nitride particle lubrication, indicating that the improved boundary lubrication behaviors have indeed been responsible for the significantly reduced friction. Nano boron nitride additive is used as solid lubricant‐like nano scale ball bearing to the pointlike contact and a soft phase bond with the weak van der Waals interaction force on the contact surface to improve the lubrication behaviors of Si3N4/DLC films. The potential usefulness of nano boron nitride as lubricant additive in PAO oil for Si3N4/DLC films has been demonstrated under oil lubrication conditions. The present work will extend the wide application of nano particle additive and introduce a new approach to superlubricity under boundary lubrication in future technological areas. Copyright © 2013 John Wiley & Sons, Ltd.

Effects of electrical conductivity of substrate materials on microstructure of diamond-like carbon films prepared by bipolar-type plasma based ion implantation

Diamond-like carbon (DLC) films are prepared by a bipolar-type plasma based ion implantation, and the structural differences between DLC films deposited on different electrical conductive substrates, i.e., conductive Si wafers and insulating glass plates are examined by Raman spectroscopy and x-ray photo emission spectroscopy (XPS). In the Raman measurements, graphite (G) and disorder (D) peaks are observed for both samples. However, the additional photo luminescence is overlapped on the spectra in the case of on-glass sample. To elucidate the structural difference, the intensity ratio of D to G peak (I(D)/I(G)), G peak position and full width at half maximum (FWHM) are obtained by curve fitting using Gaussian function and linear baseline. It is found that the I(D)/I(G) is lower, G peak position is higher and FWHM of G peak is narrower for on-glass sample than for on-Si sample. According to Robertson [1], lower I(D)/I(G) seems more sp3 C-C bonding in amount for on-glass sample. In contrast, higher G peak position and narrower FWHM of G peak suggest less sp3 C-C bonding in amount for on-glass sample. The results of XPS analysis with C1s spectra reveal that sp3 ratio, i.e., the intensity ratio of sp3/(sp3+sp2) is smaller for on-glass sample than for on-Si sample. The inconsistency of the trend between I(D)/I(G) and other parameters (G peak position and FWHM of G peak) might be caused by the overlap of photo luminescence signal on Raman spectrum as to on-glass sample. From these results, it is considered that sp3 C-C bonding is reduced in amount when using insulating substrate in comparison with conductive substrate.

Properties of DLC Film Deposited on Mould with Micro-Cavity Used in Microforming

Micro-forming as a kind of metal forming process is very suitable for massive production of micro-parts with high mechanical properties. To eliminate the scaling effects of friction in micro-forming, diamond-like carbon (DLC) film of nano-thickness was deposited on the micro mould with plasma based ion implantation and deposition (PBII&D) method for its excellent tribological behaviors. The effects of mould cavity dimensions were investigated, for example distribution of thickness, surface topography and microstructure of DLC film. The result shows that the thickness of DLC film decreases from 554 nm to 47 nm with the increasing of depth into mould cavity. And ripple topography appears when the cavity dimension is small. The ratio between ID and IG increases with the increasing of cavity dimension, which means that the amount of SP3 bonds becomes smaller. With the DLC film deposited female die, micro-cups of 1.1 mm in diameter were manufactured successfully using copper thin sheet of 0.04 mm in thickness with a blanking-deep drawing process. And the surface quality and dimension accuracy of micro-cup were analyzed in details. The results show that DLC film is feasible alternative to micro-forming.

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 nitrogen pressure on optical properties and microstructure of diamond-like carbon films grown by pulsed laser deposition

The effect of nitrogen pressure on optical properties of hydrogen-free diamond-like carbon (DLC) films deposited by pulsed laser ablation graphite in different background pressures of nitrogen is reported. By varying nitrogen pressures from 0.05 to 15.00 Pa, the photoluminescence is gradually increased and optical transmittance is gradually decreased. Atomic force microscopy (AFM) is used to observe the surface morphology of the DLC films. The results indicate that the surface becomes unsmoothed and there are some globose particles on the films surface with the rise of nitrogen pressures. The microstructure of the films is characterized using Raman spectroscopy.

Nano- and microstructure of diamond-like carbon films modified by Ca–O incorporation

In the present study, the nano- and microstructure of diamond-like carbon (DLC) coatings on Ti6Al4V substrates were changed by Ca–O incorporation. For the deposition of Ca–O-DLCs, a gaseous hydrocarbon precursor (e.g. methane) and CaO–H 2O vapour were decomposed together in plasma using a direct current discharge. The hardness, Young's modulus and relative elastic recovery of Ca–O-modified DLCs are reduced in comparison to unmodified DLC. However, the adherence of the Ca–O-DLCs is improved. With increasing relative partial pressure of the CaO–H 2O vapour during DLC coating deposition, the size of the sp 2-hybridised carbon islands, which were observed via high-resolution transmission electron microscopy, increased and the shape changed from oval islands to strips of several 10 nm. This finding is in good accordance with the results from Raman spectroscopy, which also pointed to an increase in the size and/or number of sp 2-hybridised crystalline carbon clusters in the amorphous carbon matrix. The DLCs have increased oxygen content due to the decomposition of CaO–H 2O vapour, in addition to hydrocarbon. As detected by IR and X-ray photoelectron spectroscopy, Ca is incorporated as carbonate into the DLC.

Microstructure of diamond-like carbon films prepared by cathodic arc deposition

Diamond-like carbon films were synthesized under vacuum, argon, methane and hydrogen circumstance by cathodic arc deposition from graphite cathodes. Electron diffraction patterns and high resolution micrographs indicated that graphite crystal cathodes were decomposed under plasma circumstance and amorphous carbon films were formed in all the cases of film deposition. The sp 3/sp 2 ratio was measured by energy loss electron spectroscopy and X-ray photoelectron spectroscopy. The films, synthesized under hydrogen plasma, had the largest sp 3/sp 2 ratio, compared with those under vacuum, argon and methane circumstances.

Influence of Xe +-ion irradiation on the microstructure of diamond-like carbon films

The optical and electrical properties of diamond-like carbon films irradiated with Xe + ions (energy: 80 keV, fluence range: 6×10 12–1.2×10 16 cm −2) have been investigated. It was shown that high-density cascades developing under irradiation with heavy Xe ions lead to changes of the subsystem of graphite-like nanoclusters in diamond-like carbon films, which essentially differ from changes due to irradiation with light ions. The changes can be divided into five subsequent steps: (1) destruction of some nanoclusters, initially existing in diamond-like carbon films; (2) ballistic shrinkage of clusters; (3) the sharp increase of nanocluster sizes because of hydrogen desorption; (4) strong reduction of the cluster growth; (5) accumulation of defects in clusters. The steps are clearly distinguished in the optical and electrical characteristics of the investigated films.

Characterization of pulsed laser-deposited diamond-like carbon films

Diamond-like carbon (DLC) films are excellent prospective materials for a wide range of high-technology applications, but their precise structure and properties are not well understood. The purpose of this present work was to use different analytical techniques to characterize the nature, structure and microstructure of DLC films. The pulsed laser-deposition (PLD) technique was used to deposit DLC films on Si(100) and 7059 Corning glass substrates. The deposition was carried out in a high vacuum (≤10 −6 Torr) at different temperatures ranging from room temperature to 600 °C. The films were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and Raman spectroscopic techniques. The films deposited at lower temperatures showed the characteristic features of DLC films and had better hardness and modulus properties compared with the films fabricated at higher temperatures. The results from the various techniques are combined and discussed in the context of developing additional insight into the synthesis–structure–property relationship of these films.

Effect of substrate temperature and heat treatment on the microstructure of diamondlike carbon films

Nonhydrogenated diamondlike carbon films prepared at a substrate temperature (ST) of 100, 300, and 500 °C by the laser ablation of graphite on a single-crystal silicon substrate have been characterized by scanning tunneling microscopy for the surface structure and Raman spectroscopy for the microstructure. Distorted pentagonal and hexagonal rings are observed on the surface of the film grown at 100 °C while only hexagonal rings are observable for the one grown at 500 °C. The rise in ST is found to increase the surface roughness. To assign the various coexisting carbonaceous species formed at different growth temperatures and to check their thermal stability, heat treatment was performed at up to 1300 °C in vacuum and 600 °C in air. The changes occurring on heat treatment in vacuum in these films around 600 °C have been correlated with the release of defects from the threefold network. Likewise, 950 °C temperature has been associated with the conversion of disordered tetrahedral bonding to a distorted trigonal one. The heat treatment in air shows that the microstructure induced due to lower ST is thermally more stable.

Characterization of ion-beam-deposited diamond-like carbon films

Diamond-like carbon (DLC) films are excellent prospects for a wide range of high-technology applications but their precise structure and properties are not well understood. The purpose of the present work was to use several complementary techniques to characterize the nature, structure and microstructure of DLC films. Thin DLC films were deposited on various substrates in the presence of a Si interlayer (500 Å thick) using CH 4 ion-beam deposition at an acceleration energy of 750 eV and a current density of about 2.5 mA cm −2. The Si interlayer was deposited by either e-beam evaporation or Si evaporation enhanced by Ar + beam bombardment (1 keV). The produced DLC films were featureless, very smooth and of high hardness (2900–3300 kg mm −2). Auger electron spectroscopy and electron diffraction showed that the films were mainly amorphous. Their microstracture was characterized by a three-dimensional network structure with a medium-range order of about 25 nm. Fourier transform infrared and Raman spectroscopies showed that the films were mainly composed of sp 3 and sp 2 carbon-bonded hydrogen. The sp 3 sp 2 ratio varied from 3.2 to 4.1 and was found to depend on the nature of the Si bond layer. The results showed that the nucleation of the diamondlike structure was promoted on the Si interlayer that was deposited under Ar + beam bombardment. This effect can be explained by the higher surface roughness produced in this interlayer as suggested by the reflectivity measurements. Spectroscopic ellipsometry revealed that the films had an optical band gap between 1.56–1.64 eV. The present results are consistent with previous proposals suggesting that the DLC structure is composed of small graphitelike clusters (involving fused six-fold rings) that are interconnected by sp 3-bonded carbon.