Diamond-like Carbon Films Research Articles

Alleviating internal stress in diamond-like carbon films for enhanced tribological performance under high contact pressure via interface texturing

Diamond-like carbon (DLC) films have found widespread applications across numerous fields due to their exceptional properties. Nevertheless, their significant internal stress has restricted their further utility, particularly in scenarios involving high-contact pressure conditions. In response to this challenge, we fabricated diamond-like carbon films with nano-depth interface texture. This nano-depth interface texturing technique helps alleviate the internal stress within the carbon film, thereby enhancing the tribological performance of diamond-like carbon films with textured interfaces, especially under high contact pressure. We successfully fabricated textured carbon films with a thickness of 1 μm, which exhibited excellent tribological performance even under pressures exceeding 1 GPa. Through atomistic molecular dynamics simulations, internal stress testing, and cross-sectional transmission electron microscopy imaging, we observed that the incorporation of nano-depth interface texturing resulted in an approximate 47.62 % increase in the thickness of the transition layer between the silicon substrate and the carbon film. Furthermore, there was a notable reduction of about 30 % in the internal stress exhibited by the carbon films. These findings are expected to expand the application of carbon films under higher contact pressure and facilitate the production of thicker films.

Characterization of structural and mechanical properties of DLC films deposited on the surface of minute-scale 3D objects: Changes in the incident behavior of carbon ions

Diamond-like carbon (DLC) films have attracted great interest from the industry because they have beneficial mechanical properties such as low friction, high hardness, and wear resistance. DLC films have been used for the surface modification of various mechanical components, although many components that require surface treatments have complex three-dimensional (3D) surface structures. To date, 3D deposition of DLC films remains difficult using conventional methods. Particularly, uniform deposition technology on 3D components has not been developed for tetrahedral amorphous carbon (ta-C) films, which possess high CC sp3 bonds with high hardness. In this study, the filtered cathodic vacuum arc (FCVA) method was used to synthesize ta-C films on Si substrates placed on the sidewalls of trench-shaped and one-side tilted samples at various tilt angles and investigated their microstructure and hardness by Raman spectroscopy and nanoindentation. The results showed that the G peak position, full width at half maximum of G peak (FWHM (G)), and hardness of the ta-C film on the trench sidewall decreased as the depth from the top surface increased, similar to previous research. In contrast, ta-C films deposited on one-side tilted sample showed little depth dependence, and the film properties were determined by the tilt angle. We revealed that the film property dependence on the trench depth direction is due to the sputtered particles from the opposing trench sidewalls, resulting in graphitization of the film.

A novel diamond-like carbon based photocathode for PICOSEC Micromegas detectors

The PICOSEC Micromegas (MM) detector is a precise timing gaseous detector based on a MM detector operating in a two-stage amplification mode and a Cherenkov radiator. Prototypes equipped with cesium iodide (CsI) photocathodes have shown promising time resolutions as precise as 24 picoseconds (ps) for Minimum Ionizing Particles. However, due to the high hygroscopicity and susceptibility to ion bombardment of the CsI photocathodes, alternative photocathode materials are needed to improve the robustness of PICOSEC MM. Diamond-like Carbon (DLC) film have been introduced as a novel robust photocathode material, which have shown promising results. A batch of DLC photocathodes with different thicknesses were produced and evaluated using ultraviolet light. The quantum efficiency measurements indicate that the optimized thickness of the DLC photocathode is approximately 3 nm. Furthermore, DLC photocathodes show good resistance to ion bombardment in aging test compared to the CsI photocathode. Finally, a PICOSEC MM prototype equipped with DLC photocathodes was tested in muon beams. A time resolution of around 42 ps with a detection efficiency of 97% for 150 GeV/c muons were obtained. These results indicate the great potential of DLC as a photocathode for the PICOSEC MM detector.

Comparison of contact time dependence of adhesion force between silica/DLC and silica/graphene interfaces by AFM at different humidities

Abstract Understanding adhesion mechanisms is one way to address failures in micro-nano devices. In this paper, the adhesion forces of diamond-like carbon film (DLC) and graphene were measured, and the differences between them were compared. The results show that the adhesion forces on the DLC are dependent on the contact time, but this dependence is disrupted by repeated contacts. The impact of repeated contacts is inevitable. With the increase of repeated contacts, the size of the liquid bridge was changed, and the time to reach saturation became shorter. Finally, at low relative humidity (RH), the adhesion behaviors become independent. In contrast, the adhesion forces of graphene had no contact time dependence under each RH. The adhesion forces remained stable at low and medium RH, and the influence of repeated contacts was weak. At high RH, a sudden increase in adhesion forces caused by repeated contacts can be observed. The adhesion behaviors under different RHs are attributed to the size change of the liquid bridge. The results help people understand the adhesion mechanisms and provide some help in solving the failure problem of micro-nano devices.

Fabrication and Tribological Properties of Diamond-like Carbon Film with Cr Doping by High-Power Impulse Magnetron Sputtering

The present study aims to investigate the advantages of diamond-like carbon (DLC) films in reducing friction and lubrication to address issues such as the low surface hardness, high friction coefficients, and poor wear resistance of titanium alloys. Cr-doped DLC films were deposited by high-power impulse magnetron sputtering (HiPIMS) in an atmosphere of a gas mixture of Ar and C2H2. The energy of the deposited particles was controlled by adjusting the target powers, and four sets of film samples with different powers (4 kW, 8 kW, 12 kW, and 16 kW) were fabricated. The results showed that with an increase in target power, the Cr content increased from 3.73 at. % to 22.65 at. %; meanwhile, the microstructure of the film evolved from an amorphous feature to a nanocomposite structure, with carbide embedded in an amorphous carbon matrix. The sp2-C bond content was also increased in films, suggesting an intensification of the film’s graphitization. The hardness of films exhibited a trend of initially increasing and then decreasing, reaching the maximum value at 12 kW. The friction coefficient and wear rate of films showed a reverse trend compared to hardness variation, namely initially decreasing and then increasing. The friction coefficient reached a minimum value of 0.14, and the wear rate was 2.50 × 10−7 (mm3)/(N·m), at 8 kW. The abrasive wear was the primary wear mechanism for films deposited at a higher target power. Therefore, by adjusting the target power parameter, it is possible to control the content of the metal and sp2/sp3 bonds in metal-doped DLC films, thereby regulating the mechanical and tribological properties of the films and providing an effective approach for addressing surface issues in titanium alloys.

Contact fatigue of thin hard diamond-like carbon films on M50 steels under cyclic spherical micro-indentation

Contact fatigue behaviors of thin hard diamond-like carbon (DLC) films on M50 steels during cyclic spherical micro-indentations were investigated. The stress-strain evolution of the entire system was analyzed by finite element methods. The film fracture mechanisms and interfacial bearing responses under monotonic and repeated contacts were comprehensively explored. Concentrated tensile and shear stresses were found to, respectively, govern the initiation and propagation of the surface ring cracks. Elevated tensile stresses at the initiation and epilogue of each indentation cycle enhanced bottom radial cracking. At the interfaces, the maximum tensile (σnmax) and shear (σtmax) stresses occurred at the end of unloading and loading processes, respectively. With increasing maximum indentation forces, σnmax initially increased and then gradually decreased, while σtmax increased monotonically.

Microstructure and optical properties of Au:N doped diamond-like carbon films: Effect of working pressure

In recent years, the incorporation of impurities (metallic or non-metallic) into diamond-like carbon films for industrial and biological applications has garnered considerable attention from researchers. In this study, gold nanoparticles and nitrogen impurities were introduced into diamond-like carbon using a co-deposition method involving Radio Frequency Plasma-Enhanced Chemical Vapor Deposition (RF-PECVD) and Radio Frequency Sputtering (RF-sputtering),modifying the working pressure from 14.5 to 19.5 mTorr. X-ray Diffraction (XRD) patterns confirmed the presence of gold nanocrystals in the samples. The surface morphology of the films was analyzed using images obtained from Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) subjected to statistical and fractal analyses. These investigations revealed non-symmetric Gaussian distributions of the grains, demonstrating a multifractal nature in all samples, as well as a complex relationship between film roughness and working pressure. Films prepared at working pressures of 16.5 and 18.5 mTorr exhibited the roughest and smoothest surfaces, respectively. Fast Fourier Infrared (FTIR) spectroscopy was used to identify functional groups and to estimate the sp2/sp3 ratio. Raman spectra show D and G bands associated with the disordered graphitic carbon of the DLC, with the intensity of the G band being higher than that of the D band, indicating a higher sp2 bonding content compared to sp3 bonding. Subsequently, the absorption UV–visible spectrum of the samples was examined, confirming the presence of gold nanoparticles in the films, as evidenced by the occurrence of a Localized Surface Plasmon Resonance peak, whose location dependent on the working pressure used during deposition. These observations are consistent with other microscopic and structural analyses.

Effect of pulse interval on deposition of diamond-like carbon through high-power impulse magnetron sputtering

A diamond-like carbon (DLC) film was deposited using unipolar-double-pulse high-power pulsed magnetron sputtering, aimed at enhancing both film density and deposition rate. The pulse interval between the 1st and 2nd pulses, with negative polarity applied to the target, was varied from 15 to 200 μs. Temporal variations in the flux and energy of C+ and Ar+ incident to the DLC film were analyzed through energy-resolved and time-resolved mass spectrometry to clarify the ion generation process during the 1st and 2nd pulses. The contribution of ionic species in forming the DLC film through HiPIMS was clarified through mass spectrometry, Raman scattering spectroscopy, and X-ray reflectivity analyses. Reducing the pulse interval increased the deposition rate, and the film density of the DLC film was improved at a pulse interval of approximately 40 μs. Overall, the implementation of a double pulse with the appropriate pulse interval can help enhance both the film density and deposition rate.

Multilayer Diamond‐Like Carbon Films on Monocrystalline Diamond

Multilayer films of diamond‐like carbon (DLC) on monocrystalline diamond substrates have been for the first time obtained by plasma‐chemical deposition. Their chemical composition and structural and morphological properties are studied. The DLC individual layers differ in their sp3 carbon content. The multilayer nature of the resulting coatings is confirmed by periodic density modulation on the small‐angle X‐ray reflectometry curve and modulations in the CsC8, CsC6, CsC4 lines on the crater depth profile of secondary ions of elements (secondary ion mass spectrometry). The dependence of the deposition rate of multilayer DLC films on diamond, their composition and properties on the argon additive to the reaction gas mixture, as well as on methane flow, pressure and growth time, are studied.

DLC FILMS ON Ti6Al4V SUBSTRATES OF NANOINDENTATION, SURFACE ROUGHNESS FOR LASER POWDER BED FUSION WAS PERFORMED UTILIZING ORTHOPEDIC IMPLANT MATERIALS

Diamond-like carbon (DLC) films on titanium alloy Ti6Al4V substrates were tested with nanoindentation and surface roughness to look at the hardness and roughness of the coating and substrate systems as well as their mechanical properties. The powdered titanium alloy Ti6Al4V used in the substrate specimen was produced using laser powder bed fusion, an additive manufacturing process. In this study, we investigated the influence of substrates on the nanoindentation and surface roughness of the DLC film layer with an estimated [Formula: see text]m thickness on Ti6Al4V substrates. The findings of the nanoindentation show that the reaction to the impact was more flexible than expected. Maximum load, residual nanoindentation depth, hardness, and modulus may influence mechanical properties. The DLC-film Ti6Al4V substrate materials’ top surface roughness is measured. As a result of the increased load-carrying ability of DLC/Ti6Al4V, Ti6Al4V is a superior choice for substrate materials for DLC films, A DLC coating, measuring [Formula: see text] m in thickness, was applied to a Ti6Al4V substrate utilizing a 5-min chromium deposition process. The biocompatibility of the substrates plays a crucial role in determining the DLC films capacity to prolong the lifespan of bone implants.

Extremely enhanced friction and wear performance of hydrogen-free DLC film at elevated temperatures via Si doping

Hydrogen-free diamond-like carbon (DLC) films have garnered significant attention as a highly efficient solid lubrication material, but poor high-temperature lubrication and wear resistance limit their further application. Here, silicon-doped DLC (Si-DLC) films with different Si contents were deposited using a superimposed HiPIMS-DCMS deposition system to improve their high-temperature lubrication and wear resistance performance. The influence of Si content on the microstructure, mechanical and high-temperature friction and wear behavior of Si-DLC films was investigated. The results showed that Si-DLC films had a dense structure and nanoscale smooth surface. The Si doping enhanced the adhesion strength and relieved the residual stress of Si-DLC films, but decreased the hardness and Young's modulus. Meanwhile, Raman and XPS spectroscopy revealed significant local structural changes in Si-doped DLC films. Furthermore, the results showed that DLC films doped with low Si content displayed excellent tribological performance at elevated temperatures due to the graphite lubricating layer on the surface of wear marks. Specifically, Si-DLC film with 3.31 at% Si had an ultra-low average friction coefficient of 0.04 at 450 °C and still provided effective lubrication at temperatures up to 500 °C. In contrast, pure DLC film failed to lubricate at 450 °C due to the severe graphitization transition and Si-DLC film with 17.47 at% Si quickly failed to lubricate at 200 °C due to the SiC and SiO2. This work sheds light for the high-temperature application of DLC films doped with low Si content by superimposed HiPIMS-DCMS deposition system.

Anti-Corrosion SiOx-Doped DLC Coating for Raster Steel Linear Scales

In this study, we investigated the efficacy of SiOx-doped diamond-like carbon (DLC) films for enhancing the corrosion resistance of raster steel linear scales. The research work highlights the significant role of DLC film materials in enhancing corrosion resistance, making them a promising solution for various industrial applications. The Raman spectroscopy analysis of SiOx-doped DLC films, synthesized via a direct ion beam technique with HMDSO vapor, revealed prominent D and G bands characteristic of amorphous carbon materials, with a high degree of disorder indicated by an ID/IG ratio of 1.85. X-ray diffraction patterns confirmed the amorphous nature of the SiOx-doped DLC films and the minimal impact of the DLC deposition process on the underlying crystalline structure of steel. UV–Vis-NIR reflectance spectra of SiOx-doped DLC on stainless steel demonstrated improvements in the blue wavelength region compared to stainless steel with ripples alone, which is beneficial for applications utilizing blue light. Corrosion tests, including immersion in a 5% salt solution and salt spray testing, showed that SiOx-doped DLC-coated stainless steel exhibited superior corrosion resistance compared to uncoated steel, with no significant signs of corrosion observed after extended exposure. These findings underscore the potential of SiOx-doped DLC coatings to provide long-term corrosion protection and maintain the structural integrity and surface quality of steel components in harsh environments.

Effect of temperature on the friction behavior and mechanism of DLC film in CO2 foam fracturing environment

Diamond-like carbon (DLC) film is considered to be an attractive candidate material for reducing friction and wear in oil and gas equipment due to its low friction and high wear resistance. This study investigated the evolution of friction interfaces and tribochemical reaction at three different temperatures through reactive molecular dynamics simulations. The results reveal that the synergistic effect of atomic transfer layer and chemical passivation of DLC film leads to the decrease of friction force with increasing ambient temperature. The cumulative atomic transfer layer with increasing ambient temperature also contributes to the increase of wear amount, while the atomic lattice transition dominates friction temperatures. More importantly, the phenomenon of increased sp3 carbon atoms in DLC film is also temperature dependent.

Interfacial tribochemical kinetics: A new perspective on superlubricity of diamond-like carbon films

Interfacial tribochemical kinetics: A new perspective on superlubricity of diamond-like carbon films

The mechanical and tribological properties of polyether ether ketone coated by diamond-like carbon film with plasma-induced transition layer

Polyether ether ketone (PEEK) has been broadly utilized in aerospace due to its excellent properties. Nevertheless, when applied as sealing components in harsh environments, virgin PEEK still faces defects in mechanical behavior and wear resistance. To address these issues, the deposition of diamond-like carbon (DLC) films has been employed as a viable solution. In this study, the DLC film with plasma-induced transition layer was fabricated on PEEK via direct current magnetron sputtering technology. Compared with previous studies, the evolutions of interfacial structures and plasma-induced layer were investigated, and their roles on the tribological performance of PEEK/DLC were analyzed in detail. Results show that an increase in etching duration promotes the formation of cauliflower pits and enhances the hardness of plasma-induced layer on PEEK, which are facilitated by high-energy plasma bombardment. When the etching time comes to 20 min, these features endow PEEK/DLC with good interfacial adhesion and mechanical properties. Besides, the cauliflower pits could fill debris and help to form graphitized transfer films. The friction coefficient and wear rate of PEEK/DLC both exhibit a declining trend as the etching duration prolongs. Notably, compared to virgin PEEK, the tribological performance of PEEK/DLC with 20-min etching displays lower friction coefficient of 0.2 and lower wear rate of 1.22 × 10−8 mm3/N·m. Finally, a wear failure mechanism for PEEK/DLC with 20-min etching was proposed. This provides a simple and effective approach to improve the tribological behavior of carbon-based films applied on PEEK, it also assists in the development of efficiently wear-resistant materials for aerospace.

Chemometric Raman Spectral Analysis of Diamond-like Carbon Films Deposited by Plasma Discharge

Chemometric Raman Spectral Analysis of Diamond-like Carbon Films Deposited by Plasma Discharge

Quantification of the sp3 content in Diamond-Like carbon Films: Effects of Ne plasma addition in Deep Oscillation Magnetron sputtering

Diamond-like carbon (DLC) films are a class of amorphous carbon materials with unique properties, including high hardness and wear resistance, making them attractive for aerospace and automotive applications. Recently, High Power Impulse Magnetron Sputtering (HiPIMS) has emerged as a new route for magnetron-sputtered hard DLC films. The authors have previously demonstrated that adding Ne to the plasma significantly improves the properties of DLC films deposited by Deep Oscillation Magnetron Sputtering (DOMS), a HiPIMS variant. In this study, the sp3 content evolution with DLC film thickness was measured by Electron Energy Loss Spectroscopy (EELS) and Near Edge X-ray Absorption Spectroscopy (NEXAFS). The sp3 content in the top section of the film deposited in Ar + Ne plasma is close to 40 % and remains constant across the film thickness. Conversely, in films deposited in pure Ar plasma, the sp3 content decreases from approximately 30 % to 18 % towards the surface. Ne addition increases the sp3 content by enhancing the carbon ion flux and counteracting the atomic shadowing effect. These findings provide novel insights into the role of Ne in reducing the atomic shadowing effect and improving the overall quality of DLC films, paving the way for their optimized industrial use.

Processing and analysis of friction vibration signal of diamond-like carbon film microtextured dry gas seal rings

PurposeThis paper aims to analyze the characteristics of friction vibration signals and identify the vibration excitation source at the start and stop stage of microtextured end face of dry gas seals.Design/methodology/approachThe friction pair consists of a diamond-like carbon (DLC) film microtextured seal ring and a spiral groove seal ring. Friction vibration signal feature extraction method based on harmonic wavelet packet and spectrum analysis was proposed. Signals were collected using acceleration sensor, acquisition card and LabVIEW software. Vibration acceleration signal was decomposed into 32 frequency bands using MATLAB wavelet packet transformation. The 32nd band coefficient was extracted for reconstruction, time-domain and spectral waveforms were obtained and spectra before/after denoising were compared.FindingsThe end face of the DLC film microtextured seal ring generates a good dynamic pressure effect, and the friction and vibration reduction effects are obvious. The harmonic wavelet packet can decompose the vibration signal conveniently and precisely. In the case of this experiment, the frequency of vibration of the seal ring is 7500 HZ.Originality/valueThe results show that the method is effective for the processing of friction vibration signal and the identification of vibration excitation source. The findings will provide ideas for the frictional vibration signal processing and basis for further research in the field of tribology of dry gas seal ring.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0084/

Enhancing sp3 content in diamond-like carbon thin film electrodes by pulsed laser annealing for durable charge storage performance

In this work, diamond-like carbon (DLC) thin film electrodes were grown on Si substrate by pulsed laser deposition (PLD) technique, and the implication of pulsed laser annealing (PLA) treatment on their electrochemical supercapacitor performance was examined by three electrode systems in 1 M Na2SO4 electrolyte solutions. The SEM micrographs exhibit a sheet-like wrinkled surface of DLC film on Si which later transformed into tiny hierarchical heap-like structures with enhanced surface roughness. The Raman spectra confirm signature of the D and G peaks of pristine DLC film at ∼1352 cm−1 (1356 cm−1 after PLA) and 1591 cm−1 (1589 cm−1 after PLA), and appearance of minor T2g (diamond) (1332 cm−1) peaks with an increment of the sp3 content after PLA treatment. The X-ray photoelectron spectroscopy (XPS) spectra were deconvoluted into three different contributions CC (sp2), CC (sp3), and CO, and their sp3 percentages were estimated ∼48.9 %, and 64.7 % before and after annealing. The area under cyclic voltammetry (CV) curve and galvanostatic charging discharging (GCD) performance of PLA-treated DLC film were improved and the highest areal-specific capacitance was obtained to be ∼48.25 mF/cm2 for scan rate of 5 mV/s and 36.01 mF/cm2 for current density of 2 mA/cm2, respectively. Excellent charging discharging cyclic stability of PLA treated electrode was observed over 5000 cycles, and Coulombic efficiency and capacitance retention were determined to be ∼93.5 % and ∼ 97.3 %, respectively. The electrochemical impedance spectroscopy (EIS) was performed to obtain the Nyquist plot (Z′vs.Z′′) of both electrodes before and after the stability test, and a small degradation in impedance was observed. The Nyquist plots were fitted with the well-known Randles equivalent circuit model Rs(Cdl(RctZw)) and substantial curtailment of Warburg resistance (Zw) in PLA-induced DLC electrode signifies the dominance of the diffusion-controlled region in the charging-discharging process. Minor changes in the Nyquist plot before and after the stability test manifest the enduring charge kinetics of both electrodes and PLA-treated DLC exhibits better cyclic stability. PLA techniques have a great impact on upgrading the areal-specific capacitance, capacitance retention with high Coulombic efficiency, and stability with negligible impedance loss of the DLC film electrodes.

A NOVEL MODEL FOR THE RELATIONSHIP BETWEEN THE HEALING TIME OF THE INERT FILM AND THE INCUBATION PERIOD OF LOCALIZED CORROSION

A model for the relationship between the healing time of the scratched diamond-like carbon (DLC) film and the localized corrosion incubation period of metal was established. Based on model calculations combined with experimental results, the scratched DLC film on 13Cr stainless steel was able to heal within 10–16[Formula: see text]h in NaCl solution with an adsorbent-type corrosion inhibitor. However, the localized corrosion incubation time was 30–40[Formula: see text]h. Healing of the scratched DLC film can be completed before localized corrosion occurs. This model provides a theoretical reference for the scratch-repassivation of inert films in corrosion inhibitors solutions.