Deposition Of Diamond-like Carbon Films Research Articles

Influence of substrate surface topography in the deposition of nanostructured diamond-like carbon films by high density plasma chemical vapor deposition

In this work, we have studied the influence of the substrate surface condition on the roughness and the structure of the nanostructured DLC films deposited by High Density Plasma Chemical Vapor Deposition. Four methods were used to modify the silicon wafers surface before starting the deposition processes of the nanostructured DLC films: micro-diamond powder dispersion, micro-graphite powder dispersion, and roughness generation by wet chemical etching and roughness generation by plasma etching. The reference wafer was only submitted to a chemical cleaning. It was possible to see that the final roughness and the sp 3 hybridization degree strongly depend on the substrate surface conditions. The surface roughness was observed by AFM and SEM and the hybridization degree of the DLC films was analyzed by Raman Spectroscopy. In these samples, the final roughness and the sp 3 hybridization quantity depend strongly on the substrate surface condition. Thus, the effects of the substrate surface on the DLC film structure were confirmed. These phenomena can be explained by the fact that the locally higher surface energy and the sharp edges may induce local defects promoting the nanostructured characteristics in the DLC films.

Correlations between process parameters and film properties of diamond-like carbon films formed by hydrocarbon plasma immersion ion implantation

Plasma immersion ion implantation with hydrocarbon gases (HC-PIII) leads to both carbon implantation and carbon thin film deposition. The films are diamond-like carbon (DLC), mostly amorphous carbon with hydrogen (a-C:H). In the present review, examples from the literature on the deposition of HC-PIII DLC films are discussed. The process parameters of HC-PIII, including bias voltage, plasma-forming gas, and experimental setup, are correlated with the properties of the DLC film, such as bonding characteristics, hardness, stress state, and the resulting tribological performance, as shown in friction and wear tests.

Bonding strength of DLC film on zirconia coating prepared by gas tunnel type plasma spraying

Bonding strength of diamond-like carbon (DLC) films on zirconia coatings prepared using a novel gas tunnel plasma spraying method has been studied and discussed. The emphasis is on the getting better characteristics of such doubly structured coatings (DSC) as comparing compared with properties of both components involved in the coatings. For the study of various failure mechanisms zirconia coatings of different thicknesses on aluminum substrates were prepared. The as-sprayed coatings were firstly polished and then subjected to deposition of DLC films. Adhesion of the DSC has been evaluated using a scratch test method. It has been found that the thicker coatings have higher hardness and lower porosity. The adhesion failures of DLC films on zirconia coatings (DSC) are caused by two different main mechanisms: (i) DLC films separation from the zirconia coatings, and (ii) DLC films breaking under stress load due to the brittleness of the material. In addition the adhesion failures are due to flaking of DLC films on the thinner zirconia coatings caused by a distortion of the aluminum alloy substrate coatings; and, chipping of DLC films themselves on the thicker zirconia coatings.

Effect of bias voltage on Diamond-like carbon film deposited on PMMA substrate

Bilayered films composed of Diamond-like carbon (DLC) and silicon (Si) were prepared on the surface of polymethylmethacrylate (PMMA) substrates using plasma enhanced chemical vapor deposition (PECVD) and magnetron sputtering deposition. The deposited films were investigated by means of Atomic force microscopy, X-ray photoelectron spectroscopy and UV-Raman spectroscopy. Subsequently, the following mechanical and friction properties of the films were measured: The hardness by Nano-indenter, the friction coefficient and the wear rate by a ball-on-disk tribometer. After DLC film deposition, the higher hardness, lower friction coefficient and lower wear rate can be obtained for PMMA substrate. Results indicate that Chemical state, hardness and friction properties of DLC films on PMMA greatly depend on the negative bias voltage, applied on the substrate during the deposition. The friction coefficient values and the wear rate of DLC films are correlated to the hardness and sp3 content.

Deposition of Diamond-Like Carbon Films on Polyoxymethylene Substrates by Magnetic Filtered Cathodic Vacuum Arc Deposition

In order to improve the abrasion property of polyoxymethylene (POM)，diamond like carbon (DLC) film was deposited on POM substrate by the method of magnetic filtered cathodic vacuum arc deposition (MFCVAD). X-ray photoelectron spectroscopy (XPS) showed that the sp3 fraction decreased with the negative bias voltages increased. According to the result of the nano-indenter, the hardness of POM plates coated with DLC films was significantly harder than POM substrate. The results of ball-on-disc tribological testing demonstrated that the hardest DLC film had the lowest friction coefficient (0.11). The evaluation of in vitro platelet adhesion test indicates that the numbers of adhered and activated platelet on the DLC film deposited under the condition of 0V and 9min were remarkably decreased compared with that of the untreated POM.

Femtosecond Laser Ablation of Frozen Alcohols for Deposition of Diamond-Like Carbon Thin Films

A 790 nm, 130 fs Ti:sapphire laser pulse ablated various frozen alcohols (CnH2n + 1OH, n = 1–6) to deposit diamond-like carbon (DLC) thin films. The larger the carbon number (n) of the alcohols, the higher the hydrogen content of the DLC films; the sp3 carbon content ranged from 35 to 45%. The hydrogen content caused a change in the optical band gap of the films. Moreover, the deposition rate of the films increased linearly as the carbon number increased. The deposition rate did not simply relate to the amount of carbon species ejected from the frozen alcohols. Even though carbon species were largely generated, the ejected oxygen radicals etched the carbon to lower the deposition rate. When we used frozen benzene as a laser target, DLC thin films were not deposited. By dissolving boric acid in an alcohol, we could deposit boron-doped DLC thin films.

Femtosecond pulsed laser deposition and optical properties of diamond-like amorphous carbon films embedded with sp-bonded carbon chains

Diamond-like amorphous carbon films have been deposited on silicon and quartz substrates by ablation of graphite using 120 fs pulses from an amplified Ti:sapphire laser operating at 800 nm. The results clearly show that fs-DLC films are composed of sp, in addition to sp 2 and sp 3 bonded species. We find that the sp concentration can be somewhat increased by deposition in vacuum at liquid nitrogen temperature. Vibrational modes involving sp, sp 2 and sp 3 bonds in putative molecular species in these materials have also been studied using surface enhanced Raman spectroscopy (SERS) and these results are compared to DFT simulations of Raman spectra of several linear carbon chains. It is found that the chain length of sp-bonded carbon species increases when deposition occurs in a He buffer gas indicating that sp-bonded chains present in the gas phase also become incorporated in the film during condensation. SERS spectra together with spectral simulations using DFT show that fs-DLC contains a limited number of well-defined structural components formed as the result of mixed sp, sp 2 and sp 3 bonding.

Investigating the Mechanical Property and Rolling Contact Fatigue Life of Diamond-Like Carbon Films on Bearing Steel

Microstructure and properties of plasma immersion ion implantation and deposition diamond-like carbon (DLC) films on bearing steel substrate were studied. Raman spectroscopy analysis indicates that PIII&D DLC consists of a mixture of amorphous and crystalline phases, with a variable ratio of sp2/sp3 carbon bonds, and the sp3 bonds content more than 10%. The nanohardness (H) and the elastic modulus (E) of DLC films measurement indicate that the maximum H (E) value is 40GPa (430GPa). The corrosion polarization curves prove that the corrosion resistance of DLC samples is much better than that of substrate. The friction and wear behaviors and rolling contact fatigue (RCF) life of these samples show that the friction coefficient decrease from 0.87 to 0.2; the L10 , L50 , La and L life of treated sample increases by 9.1, 3.2, 2.5 and 2.4 times, respectively. The RCF life scatter extent of treated samples is improved significantly.

Application of Nitrified Steel Deposit Diamond-Like Carbon Film in Explosive Environment

In this study, the deposition of diamond-like carbon (DLC) films for fabricating a wear-resistant and anti-corrosive barrel bore using a microwave plasma chemical vapor deposition system was investigated. Coatings were deposited on a nitrified steel substrate at a pressure of 5 kPa and temperatures of 450–650 °C. Before depositing the DLC films, a Si+Ag interlayer was employed to enhance adhesion. The mechanical properties of the DLC films were evaluated by nano-hardness and explosion tests, while the physical properties were evaluated by Raman spectral analysis. The result of the nano-hardness test showed that the adhesion of the DLC films was superior to that of the HF1 grade, and the explosion test showed that the DLC films were able to withstand this pressure without peeling off. Also, according to the characteristics of the films determined by Raman spectral analysis, the intensity ratio of the D-band to the G-band I(D)/I(G), increased after the explosion test while the positions of the D-band and G-band shifted upward, which indicates that the sp3 structure gradually changed into an sp2 structure. This research shows that, in a explosion test, DLC films can withstand intense but very brief temperatures.

Molecular Dynamics Studies on the Growth and Structural Properties of Hydrogenated DLC Films

The novel frictional properties of hydrogenated DLC (Diamond-like Carbon) films have been reported for nearly ten years. But up to now, researchers still haven’t known the exact mechanism resulting in the super-low frictional performance of hydrogenated DLC films. Especially they have little knowledge on the molecular configuration and structural properties of these kinds of films. In this paper, CH3 radicals with different impact energies are selected as source species to deposit DLC films on diamond (100) by molecular dynamics simulation. Results show hydrogenated DLC films can be successfully obtained when impact energy is in an appropriate scope that is no less than 20eV. The depositing processes involve impinging diamond surface and bonding procedure. Some atoms, instead of bonding with substrate atoms, fly away from the diamond surface. Only suitable impact energy can improve the growth of the film. Within 30eV to 60eV, the maximum deposition ratio is attained. In addition, when carbon atoms act as the deposition sources, the deposition ratio is relatively higher. Furthermore, the authors find that species with higher concentration of carbon atoms in deposition sources lead to a better deposition rate. Carbon atoms are more reactive than hydrogen atoms. Then the relative densities of DLC films are calculated. The density curves indicate that the structures of the films vary obviously as the impact energy augments. The average relative density is generally monotone increase with the increment of impact energy. The hybridization of carbon atoms greatly affects the properties of hydrogenated DLC films. The transition between sp2 and sp3 will result in the graphitization and reduce the frictional coefficient when DLC films are used as tribo-pair in friction.

Humidity effect on friction behaviors of nano-undulated diamond-like carbon films

Humidity dependency of friction behavior of nano-undulated diamond-like carbon (DLC) films was investigated by a home-made ball-on-disk type tribometer under controlled relative humidity of 0, 50, and 90%. Nano-undulated DLC films with surface roughness ranging from 0.2 to 13.4 nm were prepared by deposition of DLC film on the Si substrate with Ni nanodots. Friction coefficient of the flat DLC surface increased with the relative humidity, while that of the nano-undulated surfaces revealed smaller dependence on the relative humidity. When the surface roughness increased to 13.4 nm, friction behavior was observed to be independent of the relative humidity. The analysis of chemical composition and atomic bond structure of the debris and the transfer layer revealed that the humidity dependence on the nano-undulated surface was minimized by suppressing the graphitization of the transfer layer even with high concentration of Fe in the debris.

Electrical and piezoresistive properties of ion beam deposited DLC films

In present study diamond like carbon (DLC) films were deposited by closed drift ion source from the acetylene gas. The electrical and piezoresistive properties of ion beam synthesized DLC films were investigated. Diode-like current–voltage characteristics were observed both for DLC/nSi and DLC/pSi heterostructures. This fact was explained by high density of the irradiation-induced defects at the DLC/Si interface. Ohmic conductivity was observed for DLC/nSi heterostructure and metal/DLC/metal structure at low electric fields. At higher electric fields forward current transport was explained by Schottky emission and Poole–Frenkel emission for the DLC/nSi heterostructures and by Schottky emission and/or space charge limited currents for the DLC/pSi heterostructures. Strong dependence of the diamond like carbon film resistivity on temperature has been observed. Variable range hopping current transport mechanism at low electric field was revealed. Diamond like carbon piezoresistive elements with a gauge factor in 12–19 range were fabricated.

Duplex diamond-like carbon film fabricated on 2Cr13 martensite stainless steel using inner surface ion implantation and deposition

A duplex plasma immersion ion implantation and deposition (PIIID) process, involving carbon ion implantation and diamond-like carbon (DLC) film deposition, is proposed to treat the inner surface of a tube. Samples of 2Cr13 martensite stainless steel were placed inside the tube to investigate the performance of the films. Carbon ion implantation was finished by biasing the tube with a high voltage, and the DLC film deposition was obtained by biasing the tube with a medium voltage. Raman spectrum, ball-on-disc, indentation and scratch tests were used to investigate the structure, tribological property and adhesion strength of the as-deposited films. The Raman spectrum shows that the sp 3 bonding is formed in the as-synthesized film. Tribological and scratch test results reveal that the duplex DLC coating with the implantation time of 1 h has the largest adhesion strength and the best wear resistance.

One-step deposition of diamond-like carbon films containing self-assembled metallic nanoparticles, by femtosecond pulsed laser ablation

Femtosecond pulsed laser ablation has been used for the deposition of various thin films by co-ablating pure graphite and pure metallic targets (nickel or tantalum) under vacuum conditions with an amplified Ti:sapphire laser working at 800 nm, with about 1.5 mJ per pulse at a repetition rate of 1 kHz. The plasma plume created during the femtosecond pulsed laser deposition process has been investigated, by fast imaging and spectroscopic characterizations, depending on the ablated target and deposition conditions. Particular attention has been paid to the correlation between the film nanostructure and the plasma plume properties, in terms of ejected species and energies of impinging species on the substrate. The tantalum clusters in the tantalum-doped carbon films appear under two crystalline phases: a stable phase (α-Ta) corresponding to that of the target, and a metastable phase (β-Ta), already observed at high temperatures. The presence of this metastable phase (β-Ta) is correlated to the temperature of the clusters measured from the plasma plume investigation.

Plasma deposition and characterization of silicon oxide-containing diamond-like carbon films obtained from CH 4:SiH 4:O 2 gas mixtures

In this work silicon oxide-containing diamond-like carbon films were deposited from gaseous mixtures of CH 4 + SiH 4 + O 2 and characterized. The effects of the self-bias voltage and O 2 content on deposition and properties of the films were investigated. At low self-bias voltages (| V B| < 200 V) films present reduced residual stress due to the smaller internal stress of a silicon oxide-rich (SiO x ) network. At high values of self-bias (| V B| > 200 V), on the other hand, the film residual stress is comparable to oxygen-free films although a considerable concentration of oxygen is present. Hardness of the films are somewhat reduced by oxygen incorporation in the whole range of bias voltages investigated. An increasing value of hardness was observed as | V B| is increased. The refractive index of films increased with increasing | V B| due to both the relative reduction of the SiO x content and to the increased sp 2 character of the diamond-like carbon network. Oxygen incorporation results in important structural changes: i. a strong reduction of the density of C–H bonds with a reduction of C–H n sp 3/sp 2 ratio and ii. a dramatic increase of Si–O bonds that substitute Si–H n ones, suggesting the formation of a non-hydrogenated a–SiO x -rich network. Refractive index measurements indicated a strong decrease of the material density as a result of the formation of Si–O–Si bonds. Scratch hardness measurements revealed that the obtained films can be used as highly transparent scratch resistant coatings for polycarbonate substrates. These results show that films with properties equivalent to those obtained with liquid siloxane precursors can be produced when using CH 4 + SiH 4 + O 2 mixtures as gas feeds.

Carbon cone arrays by double-bias assisted hot filament plasma chemical vapor deposition

Double-bias-assisted hot-filament chemical vapor deposition has been applied for the formation of micro- and nano-sized cones on Si substrates during deposition of diamond-like carbon (DLC) films. It is found that the grid current strongly affects the substrate current–voltage characteristics due to the adding of ion fluxes from the grid region to the substrate region. High-density carbon needles are initially aligned, and then large-scale cones form as the growth time is increased. An intrinsic model that carbon of sp 3 phase serves as the etching mask is proposed for the cone formation. With a further increase of the growth time, these cones sharpen, and there presents higher density of cone because of the secondary nucleation effect. The sizes of cones change with the grid and substrate currents. These results indicate that a tuning of the relative fluxes of ions and reactive species on growing surface can be achieved in this double biasing system, which provides a possibility of structuring surface geometry for DLC films.

Duplex DLC coatings fabricated on the inner surface of a tube using plasma immersion ion implantation and deposition

A duplex plasma immersion ion implantation and deposition (PIIID) process, involving carbon ion implantation and diamond-like carbon (DLC) deposition, is proposed to modify the inner surface of a tube. In the research, samples of GCr15 bearing steel were placed inside a tube in the vacuum chamber. After the vacuum chamber was evacuated to a base pressure of 6 × 10 − 3 Pa, C 2H 2 gas was introduced into the chamber, and the tube was biased by a negative pulsed bias. Since a pulsed glow discharge (PGD) plasma can be formed by the bias, carbon ion implantation and DLC film deposition process can be obtained by biasing the tube with a high and low bias, respectively. To synthesize different DLC films, single PIIID processes employing a low voltage (several kV) PGD method and duplex PIIID processes combining the high (several tens kV) and low voltage PGD techniques were carried out. The as-synthesized films were characterized by Raman spectrum, nano-indentation, scratch, tribological and electrochemical tests. Raman results show that duplex DLC films were synthesized by this duplex PIIID process. In addition, compared with the single DLC film synthesized by the low voltage PGD process, the duplex DLC films can obtain a high wear and corrosion resistances. Furthermore, using this duplex PIIID method, batch treatment of outer-rings of the bearing was realized.

Femtosecond-pulsed laser deposition of diamond-like carbon films onto silicone rubber

Low frictional, textured diamond-like carbon (DLC) films were deposited onto silicone [SiO(CH3)2]n] rubber by femtosecond laser ablation of frozen pentanel (C5H11OH). Deposition rate of the films for silicone rubber was higher than that for Si wafer. A broad Raman peak centred at 1530 cm−1 was measured from the films deposited on silicone, showing a DLC film. The Raman spectra of the DLC films on silicone and Si wafer, a textured DLC films were also formed on silicone rubber. A coarse texture of the films was obtained by increasing the deposition time. The textured DLC films could improve frictional property of a sticky silicone rubber.

The effects of Si incorporation on the thermal and tribological properties of DLC films deposited by PBII&D with bipolar pulses

In the present study, the thermal stability and tribological properties of silicon-incorporated diamond-like carbon (DLC) films were investigated. The DLC films were deposited using a bipolar-type plasma based ion implantation and deposition (PBII&D) technique, and the Si contents in the films were varied from 0 to 29 at.%. The deposited DLC films were annealed at 500 °C for 30 min in ambient air. The structure and mechanical properties of the Si-DLC films with a high Si content (≥ 21 at.%) were not affected by the thermal annealing. The 21 at.% Si-DLC film annealed at 500 °C shows low wear as well as low friction, whereas the 29 at.% Si-DLC film exhibited a high friction due to the creation of cracks on the worn surface related to the SiC-like nature. The 11 at.% Si-DLC film annealed at 500 °C shows the lowest friction coefficient at the cost of significant wear in the graphitized film. The formation of a thick silicon oxide layer on the Si-DLC film could be favorable for low friction and wear.

Deposition of diamond-like carbon film using dense plasma focus

This paper reports the deposition of amorphous diamond-like carbon (DLC) films on Si 〈1 0 0〉, using a low energy (1.45 kJ) dense plasma focus. The high purity graphite is inserted at the tip of the tapered anode, which serves as a carbon source. Silicon substrates are placed in front of the anode tip at different axial and angular positions. The films are deposited using multiple focus shots. Raman spectroscopy and X-ray diffractometer (XRD) are used to carry out the structural information of these deposited films. The elemental composition is studied by energy dispersive X-ray spectroscopy (EDX) whereas scanning electron microscope (SEM) is employed for the study of the surface morphology. Raman spectroscopy shows the deposition of both diamond type tetragonal sp 3 and graphite type trigonal sp 2 films. The results point towards the formation of good quality amorphous carbon (DLC) films with higher sp 3 content as compared to sp 2 content. XRD pattern confirms the amorphous nature of the films showing no additional peak except a peak at 2 θ = 69° which corresponds to substrate original peak Si(4 0 0). SEM results demonstrate that the smoothness of the surface decreases with increasing value of angles with respect to anode axis. The substrates placed closer to anode axis have higher carbon content as compared to those placed away from anode axis whereas carbon content decreases with increasing axial distances from anode tip.