Diamond-like Carbon Deposition Research Articles

A new approach to create isolated carbon particles by sputtering: A detailed parametric study and a concept of carbon particles embedded carbon coatings

This article describes the in-situ creation of isolated carbon particles by quenching argon plasma with helium pulses. The carbon entities are created on the top of diamond-like carbon (DLC) coating by quenching the plasma with He gas during the coating deposition. A general four-phase model is presented to understand the mechanism of in-situ particle formation. The helium based plasma quenching does not produce carbon entities always. Thus, a parametric study is performed which involves the effects He pulse orientation to the plasma plume, He gas flow rate, He injection duration, and the target to substrate distance. The plasma quenching outputs depends on the above-described parameters and the different combinations creates isolated and identical particles or agglomerated entities or homogenous granular coating. He based plasma quenching creates isolated particles in the range of ~75nm to ~800nm with particles isolation distance from less than 1μm to more than 20μm at different quenching conditions. After repeatability and confirmation of particles formation with proposed plasma quenching method, the particles are created simultaneously to the DLC deposition. Thus a new coating architecture of isolated carbon particles embedded carbon coating has been developed.

A preliminary wear studies of isolated carbon particles embedded diamond-like carbon coatings

This article reports the preliminary wear studies of isolated carbon particles embedded amorphous diamond-like carbon (DLC) coatings. The isolated carbon particles are first created on top of DLC surface by plasma quenching. After repeatability, the particles are created simultaneous to DLC deposition and embedded in DLC at a controlled depth. The effects of embedded particles on DLC properties are analyzed by change in atomic structure, hardness, Young's modulus, friction coefficient, wear volume, and wear rate. It is observed that, a small amount of embedded particles increases the hardness by ~18% and reduces the wear volume by a factor of 3. Whereas, the friction coefficient increases by ~20% and hardness reduces around ~12% by embedding a large amount of carbon particles.

Kinetically driven graphite-like to diamond-like carbon transformation in low temperature laminar diffusion flames

Historically, the synthesis of diamond and graphite via combustion flames stands out as a simplified, scalable and inexpensive approach. Unfortunately, this method is not beneficial for industrial applications in coatings due to limitations related with the high flame and substrate temperatures. Here, we report novel findings about the formation mechanism of graphite-like and diamond-like supported nanostructures in low temperature laminar diffusion flames. Both materials are formed upon controllable combustion at atmospheric pressure of a cylindrical paper wick immersed in rapeseed oil. An accurate adjustment of the incident air flow and the amount of available fuel allow deposition of carbon soot or diamond-like carbon (DLC). The DLC formation is favorable in a narrow stoichiometric range at flame temperatures within ~210–260°C and beyond this range the particles precipitate as soot. The comparative structural analysis using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy, along with the full thermal and stoichiometric profiles for the chosen combustion conditions, suggest a kinetically driven graphite-to-diamond transformation rather than a thermodynamically induced phase transition. Our results reveal a new direction in the principles of graphite and diamond formation in flames that could be applied to surmount the existing shortcomings in flame synthesis.

Frictional characteristics of diamond like carbon and tungsten carbide/carbon coated high carbon high chromium steel against carbon in dry sliding conformal contact for mechanical seals

The present work investigates the friction characteristics of high carbon high chromium steel (HCHCr) stationary seal in contact with resin impregnated carbon rotating seal without any interfacial lubricant. An experimental setup was designed and fabricated to study the frictional characteristics of the seal for varying normal load and at a constant speed. The reliability and frictional performance had been improved further by providing DLC (diamond like carbon) and WC/C (tungsten carbide/carbon) coating over the substrate HCHCr D2 steel surface. Compared with the conventional stainless steel (316 SS) mechanical seals, uncoated HCHCr D2 steel had shown better frictional characteristics. Also further deposition of DLC and WC/C film on HCHCr D2 steel had shown significant improvement in the frictional torque, frictional coefficient and face temperature rise. The high hardness and low surface roughness of DLC and WC/C coated seal resulted in low and stable friction coefficient in the range of 0.04–0.05 without any measurable wear.

Ferromagnetism in a diamond-like carbon film after nickel implantation

Mass selective ion beam deposited diamond-like carbon (DLC) films were implanted with Ni+ ions at 30 keV with a fluence of 3.6 × 1016 atoms cm−2. The peak concentration of nickel in the implanted film was calculated to be 12.5% at an implantation depth of ∼30 nm into the DLC film. Raman measurements showed that the integrated intensity of the D peak at ∼1370 cm−1 divided by the G peak at ∼1560 cm−1 increases after ion implantation, which indicates that the implanted films are more graphitic. The implanted film shows ferromagnetic order at room temperature. However the saturation moment of the implanted film increased significantly when the measurement temperature was lowered. This may suggest that implantation leads to a dilute ferromagnetic semiconductor although more research is required.

New Method for Diamond-Like Carbon Deposition on Ceramic Cutting Tools in Vacuum-Arc Plasma

A study of diamond-like carbon coatings deposition has been carried out. The coatings were deposited on ceramic cutting tools. Vacuum-arc plasma has been used for deposition. Dependencies of the coatings microhardness and density on the tools bias voltage U are presented. The microhardness reaches 50 GPa at U=100 V. With increasing U and temperature it decreases to 15 GPa at U=500 V. Effect of the coatings on oxide ceramics properties was revealed. They were used for lathe turning of hardened steel. The tests proved a high efficiency of the coatings.

Self-enhanced plasma discharge effect in the deposition of diamond-like carbon films on the inner surface of slender tube

Enhanced glow discharge plasma immersion ion implantation and deposition (EGD-PIII&D) have been proved to be highly effective for depositing diamond-like carbon (DLC) films on the inner surface of the slender quartz tube with a deposition rate of 1.3μm/min. Such a high-efficiency DLC films deposition was explained previously as the short electrons mean free path to cause large collision frequency between electrons and neutral particles. However, in this paper, we found that the inner surface material of the tube itself play a vital role on the films deposition. To disclose the mechanism of this phenomenon, the effect of different inner surface materials on plasma discharge was experimentally and theoretically investigated. Then a self-enhancing plasma discharge is discovered. It is found that secondary electrons emitted from the inner surface material, whatever it is the tube inner surface or deposited DLC films, can dramatically enhance the plasma discharge to improve the DLC films deposition rate.

Improvement of the properties and the adherence of DLC coatings deposited using a modified pulsed-DC PECVD technique and an additional cathode

Deposition of hard and adherent diamond-like carbon (DLC) coatings employing an asymmetrical bipolar pulsed-DC PECVD system and an active screen that functioned as an additional cathode is presented. This novel system represents a step forward for thin coating growth by using much lower pressure (about 0.1Pa) in an almost collision-less regime, with higher plasma density than the conventional PECVD system. In order to overcome the low adherence of DLC coatings to 316 stainless steel substrates, a thin amorphous silicon interlayer was deposited as an interface. The interlayer was synthesized using silane as precursor gas and varying the applied DC bias voltage during deposition. The DLC coatings were produced using acetylene gas as the precursor. Both the amorphous silicon interlayers and the DLC films were analyzed according to their microstructural, mechanical, and tribological properties as a function of the applied substrate bias voltage. The film's atomic arrangements were estimated by means of Raman spectroscopy, while the hydrogen content was determined via elastic recoil detection analysis (ERDA). The nanoindentation experiments helped determine the films' hardness and other nanomechanical parameters. The friction coefficient was determined using a tribometer in unlubricated sliding friction experiments, while the adhesion of the films was determined through a classic Rockwell C indentation test. The results showed an improvement of the properties and the adherence of the DLC coatings deposited using a modified experimental setup and an amorphous silicon interlayer. The composition, microstructure, and mechanical and tribological properties of the films were dependent on the applied DC bias voltage and, consequently, on the intensity of ion bombardment during coating growth. These results suggest that a combination of a modified pulsed-DC PECVD system, the use of an active screen as an additional cathode, and acetylene as a precursor gas for growing DLC films may represent a new and useful alternative for mechanical and tribological applications.

Magnetic-field enhanced plasma immersion ion implantation and deposition (PIII&D) of diamond-like carbon films inside tubes

The present work deals with Diamond-like Carbon (DLC) films deposition inside metallic tubes using magnetic field generated in a PIII&D system. Firstly, the features of plasma discharges with the magnetic field application were studied using different feeding gases as nitrogen, methane and acetylene. The experimental results demonstrate that a stable hollow cathode discharge can be established inside the tubes as the magnetic field is applied. The discharge breakdown is strongly affected by the presence of the magnetic field during the treatment. Secondly, PIII&D experiments regarding DLC films deposition inside the inner surface of the tubes are also described and those ones enhanced by the applied magnetic field are emphasized. The sample tubes used in both experimental stages are of austenitic stainless steel with 150mm in length and different diameters: 110mm, 40mm and 20mm. For the case of DLC deposition, polished steel samples were fixed in the bottom of the inner tube wall for subsequent analysis of the coatings. The as-coated DLC samples surface were analyzed by Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), optical profilometry and also pin-on-disk tests. The properties of the obtained DLC films are correlated to the magnetic field used during the PIII&D process. In this work, the optimal range of magnetic field intensity is shown for depositing DLC films with acceptable adhesion strength on the inner surface of steel tubes.

Evaluation of Stoney equation for determining the internal stress of DLC thin films using an optical profiler

Excessive internal stresses in Diamond-like Carbon (DLC) films induced by the energetic ion bombardment during the deposition cause poor adhesion even delamination of the thin films from the substrate surfaces. As a result, determination of internal stresses in DLC films is essential for their applications. In this study, DLC thin films were prepared on thin silicon wafers with different shapes and sizes by end hall ion beam deposition. Optical profiler was used to measure the curvature of the samples before and after DLC deposition and then the Stoney equation was used to calculate the residual stress of DLC thin films in order to evaluate the feasibility of this method for measurement of DLC stress. For this purpose, the curvature radius in different directions of all the samples was measured before and after DLC deposition by the optical profiler. The calculated stress values using Stoney equation for all the samples are the same within reasonable errors. These results show that this simple method is appropriate and reliable for stress measurement of DLC films.

Study of layered diamond like carbon and PECVD fluorocarbon films for ultra low dielectric constant interlayer dielectric applications

Abstract

Surface enhanced Raman spectroscopy platform based on graphene with one-year stability

We report the synthesis, characterization and use of a robust surface enhanced Raman spectroscopy platform with a stable detection for up to one year of Rhodamine R6G at a concentration of 10−6M. The detection of aminothiophenol and methyl parathion, as active molecules of commercial insecticides, is further demonstrated at concentrations down to 10−5–10−6M. This platform is based on large scale textured few-layer (fl) graphene obtained without any need of graphene transfer. The synthesis route is based on diamond-like carbon films grown by pulsed laser deposition, deposited onto silicon substrates covered by a Ni layer prior to diamond-like carbon deposition. The formation of fl-graphene film, confirmed by Raman spectroscopy and mapping, is obtained by thermal annealing inducing the diffusion of Ni atoms and the concomitant formation of nickel silicide compounds, as identified by Raman and Auger electron spectroscopies. The textured fl-graphene films were decorated with gold nanoparticles to optimize the efficiency of the SERS device to detect organic molecules at low concentrations.

Effect of additional sample bias in Meshed Plasma Immersion Ion Deposition (MPIID) on microstructural, surface and mechanical properties of Si-DLC films

Meshed Plasma Immersion Ion Deposition (MPIID) using cage-like hollow cathode discharge is a modified process of conventional PIID, but it allows the deposition of thick diamond-like carbon (DLC) films (up to 50μm) at a high deposition rate (up to 6.5μm/h). To further improve the DLC film properties, a new approach to the MPIID process is proposed, in which the energy of ions incident to the sample surface can be independently controlled by an additional voltage applied between the samples and the metal meshed cage. In this study, the meshed cage was biased with a pulsed DC power supply at −1350V peak voltage for the plasma generation, while the samples inside the cage were biased with a DC voltage from 0V to −500V with respect to the cage to study its effect. Si-DLC films were synthesized with a mixture of Ar, C2H2 and tetramethylsilane (TMS). After the depositions, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy and nanoindentation were used to study the morphology, surface roughness, chemical bonding and structure, and the surface hardness as well as the modulus of elasticity of the Si-DLC films. It was observed that the intense ion bombardment significantly densified the films, reduced the surface roughness, reduced the H and Si contents, and increased the nanohardness (H) and modulus of elasticity (E), whereas the deposition rate decreased slightly. Using the H and E data, high values of H3/E2 and H/E were obtained on the biased films, indicating the potential excellent mechanical and tribological properties of the films. In this paper, the effects of the sample bias voltage on the film properties are discussed in detail and the optimal bias voltage is presented.

Formation of diamond-like carbon thin films using barrier-type surface discharge plasma under atmospheric pressure

We studied the deposition of diamond-like carbon (DLC) thin films using barrier-type surface discharge plasma under atmospheric pressure. The main radicals generated by the barrier-type surface discharge using H2, CH4, and He as the plasma gases were Hα, Hβ, and CH. The emission intensities increased as the ratio of CH4 in the mixed gas decreased, and the mixed gas ratios of 2% CH4, 18% H2, 80% He were appropriate for the generation of the barrier-type surface discharge. The gas flow rate and applied voltage required to achieve a suitable plasma state for deposition of the DLC films varied depending on the polarity of the applied pulse. When a negative pulse is used, homogenous films can be obtained on the silicon wafer under the entire hole of the electrode; however, the deposition rate becomes very low in the range of 1.8–5.8 nm/min because the surface streamer plasma is very weak. On the other hand, using a bipolar and a positive pulse, a relatively high deposition rate in the range of 10–30 nm/min can be achieved on the silicon wafer under the central part of the electrode, although the thickness of the DLC films becomes nonuniform at the edge part of the electrode. The appropriate conditions of the DLC film deposition in this study were the pulse voltages of 6–8 kV and a gas flow rate of 1500 mL/min when using bipolar- and positive-pulse voltages. The relatively hard DLC films (6–8 GPa) were obtained under these conditions.

Conditions for forming composite carbon nanotube-diamond like carbon material that retain the good properties of both materials

Carbon nanotubes are of wide interest due to their excellent properties such as tensile strength and electrical and thermal conductivity, but are not, when placed alone on a substrate, well resistant to mechanical wear. Diamond-like carbon (DLC), on the other hand, is widely used in applications due to its very good wear resistance. Combining the two materials could provide a very durable pure carbon nanomaterial enabling to benefit from the best properties of both carbon allotropes. However, the synthesis of high-quality diamond-like carbon uses energetic plasmas, which can damage the nanotubes. From previous works it is neither clear whether the quality of the tubes remains good after DLC deposition, nor whether the DLC above the tubes retains the high sp3 bonding fraction. In this work, we use experiments and classical molecular dynamics simulations to study the mechanisms of DLC formation on various carbon nanotube compositions. The results show that high-sp3-content DLC can be formed provided the deposition conditions allow for sidewards pressure to form from a substrate close beneath the tubes. Under optimal DLC formation energies of around 40–70 eV, the top two nanotube atom layers are fully destroyed by the plasma deposition, but layers below this can retain their structural integrity.

Wear and Friction Characteristics of AlN/Diamond-Like Carbon Hybrid Coatings on Aluminum Alloy

The use of diamond-like carbon (DLC) coatings has the potential to greatly improve the wear resistance and friction of aluminum alloys, but practical application has so far been limited by poor adhesion due to large difference in hardness and elasticity between the two materials. This study investigates the deposition of DLC onto an Al-alloy using an intermediate AlN layer with a graded hardness to create a hybrid coating. By controlling the hardness of the AlN film, it was found that the wear life of the DLC film could be improved 80-fold compared to a DLC film deposited directly onto Al-alloy. Furthermore, it was demonstrated through finite element simulation that creating a hardness gradient in the AlN intermediate layer reduces the distribution of stress in the DLC film, while also increasing the force of adhesion between the DLC and AlN layers. Given that both the DLC and AlN films were deposited using the same unbalanced magnetron sputtering method, this process is considered to represent a simple and effective means of improving the wear resistance of Al-alloy components commonly used within the aerospace and automotive industries.

Researches on uniformity of diamond-like carbon films deposited on inner surface of long and slender quartz glass tube by enhanced glow discharge plasma immersion ion implantation and deposition

Enhanced glow discharge plasma immersion ion implantation and deposition (EGD-PIII&D) has been successfully used for depositing diamond-like carbon (DLC) on the inner surface of the quartz glass tube with an inner diameter as small as 0.9mm and aspect ratios of over 100. And the uniformity is a key problem for the DLC films deposited on the inner surface. By changing the C2H2 flow rate and negative voltage, the effects of the gas flow rate and voltage on the uniformity of the DLC films deposited on the inner surface of the quartz glass tube are experimentally examined. The electron-neutral collision frequency, νe, is used to qualitatively analyze the mechanism of uniformizing DLC films. The results reveal that uniform DLC films may be obtained by balancing both the gas flow rate and the negative voltage.

Study on Anti-Adhesion Layers Using AFM for Nanoimprint Process

This study investigates how to improve the anti-adhesion issues between Silicon mold and nanostructures of hard polydimethylsiloxane (H-PDMS). A Silicon mold with different depths and widths was made using a focused ion beam (FIB). During the soft-lithography molding process, anti-adhesion layers were needed between the Silicon mold and H-PDMS samples to prevent the de-molding failure caused by the adhesion issues between the interfaces. This study adopts three methods to deposit anti-adhesion layers, such as liquid immersion, vapor deposition, and fluorine-doped diamond-like carbon (F-DLC) film. Perfluorooctyl-trichlorosilane (PFOTCS) was used as a mold-releasing agent for the liquid immersion and vapor deposition methods. The contact angles between each film were measured to determine the effect of anti-adhesion on the molding process. In addition, atomic force microscopy (AFM) was used to measure the adhesion force between the H-PDMS and anti-adhesion layers. The results show that the coatings of anti-adhesion layers are an effective approach to improve the formability of molding.

Flame retardant properties of plasma pre-treated/diamond-like carbon (DLC) coated cotton fabrics

Textiles with superior anti-flammability properties combined with minimal environmental impact are extremely necessary to reduce fire-related issues. In this regard, diamond-like carbon (DLC) coatings on cotton fabrics may represent promising candidates as potential flame-retardant (FR) materials. Herein, superhydrophobic and fire-resistant cotton fabrics were fabricated through a two-step plasma strategy by alternately exposing substrates to H2 and O2 plasma pre-treatments and subsequent DLC deposition. Fourier transform-infrared spectroscopy analysis has revealed that different plasma pre-treatments can impose surface modifications on the chemical structure of cotton, especially in carboxylic and hydroxyl groups, leading to a radical alteration of surface roughness and of the crystalline cellulosic external structure. These changes deeply influenced the growth of DLC thin films and the surface properties of cotton fabric because of the combination of a hierarchical structure and surface chemistry as verified using field emission gun-scanning electron microscopy and water contact angle measurements. The effects of both specific gases used in the pre-treatment step and duration of pre-treatment were analysed and compared using thermogravimetric analyses. The H2-pre-treated DLC cottons exhibited good potential as an FR material, showing improved thermal stability in respect to untreated cotton, as evidenced by increased ignition times. Moreover, vertical burning tests have demonstrated that DLC-cotton systems exhibit enhanced flammability resistance.

Study of facing target sputtered diamond-like carbon overcoats for hard disk drive media

The demand for higher areal density in the hard disk drive industry has fuelled extensive research efforts and focuses on magnetic spacing reduction. In the head–disk interface arena, one of the key focuses is to reduce the carbon overcoat thickness without compromising the overcoat protection performance. Thus, in the search for alternative methods to reduce the carbon overcoat thickness, the facing target sputtering (FTS) process for diamond-like carbon deposition has been investigated. The resulting properties have been presented in this paper, with comparison to conventional diamond-like carbon (DLC) layers by other processes such as chemical vapor deposition and reactive sputtering with nitrogen. X-ray reflectometry results showed that facing target sputtered DLC samples displayed significantly higher density, at 2.87g/cm3, as compared to hydrogenated and nitrogenated DLC samples. This was attributed to the higher sp3 content, as obtained by X-ray photoelectron spectroscopy measurements. As a result of the high sp3 content, hardness of the FTS deposited samples was higher than that of the hydrogenated and nitrogenated DLC samples. In addition, the surface energy of FTS samples was observed to be comparable, but lower, than that of nitrogenated DLC samples through contact angle measurements. Clearances comparable to that of conventional DLC samples were achieved and the sample disks were flyable. Wear performance tests also revealed more wear resistance for the FTS deposited DLC samples, but also higher head wear.