Properties Of Diamond-like Carbon Films Research Articles

Contact fatigue property of diamond-like carbon films with different structure in cyclic impact conditions

Repeated contact with high loads can cause damage to the surface of the DLC films and thus affect their fatigue strength. This study systematically investigates the contact fatigue damage of the DLC films with different carbon structures (a-C, a-C:H, and ta-C) by macro-scale cyclic impact tests with alternating loads. The results reveal that the a-C film possesses significantly superior contact fatigue property compared to the a-C:H and ta-C films under high load. The graphitization transformation of the a-C and a-C:H films lead to a decrease in hardness and elastic modulus. The work-hardening of the ta-C films results in an increase in hardness and elastic modulus. The findings indicate that under cyclic load impact conditions, films need a combination of load support and fatigue resistance to achieve optimum lifetime, and solely increasing film hardness could be accompanied by brittle fracture and higher wear.

Tribological properties of diamond-like carbon films lubricated with water-emulsified engine oil

In this work, the tribological properties of two diamond-like carbon (DLC) films were investigated at different temperatures using water-engine oil emulsions as lubricants, considering emerging fuel systems such as hydrogen and ammonia. The results revealed that the friction coefficient of a-C film raised with the increasing water content at 80 °C. The friction coefficient of a-C:H film initially raised and then decreased with varying water fractions at different temperatures. Elevated temperature exacerbated the wear of both DLC films at high water contents. The most significant wear was observed for a-C film at 80 °C and a-C:H film at 50 °C. The a-C:H film exhibited more sensitive wear characteristics to water content than the a-C film. Surface analysis indicated that water-engine oil emulsions prevented the formation of phosphate tribo-film on steel friction pair for two DLC films but promoted the tribo-oxidation of steel pair sliding contact with a-C film, especially at higher temperatures. Distinct reactivities of two DLC films towards water molecules could affect the adsorption of lubricants on DLC surfaces, leading to their different friction and wear behavior. It suggests that the water-caused emulsification of lubricating oil will be a pivotal consideration in tribological applications of DLC films in future internal combustion engines.

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.

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.

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.

Nitrogen-Doped Diamond-like Carbon Buffer Layer Enhances the Mechanical and Tribological Properties of Diamond-like Carbon Films Deposited on Nitrile Rubber Substrate

The poor adhesion between the DLC film and rubber restricts its application of seals. Introducing a suitable interlayer can bolster the adhesion of the coating or film. In this study, nitrogen-doped diamond-like carbon (N-DLC) emerged as the optimal intermediate layer between rubber and DLC. A series of N-DLC/DLC multilayer films were fabricated via DC magnetron sputtering on nitrile rubber (NBR) substrates, varying the substrate bias voltage (0 V, 100 V, 200 V). A scanning electron microscopy analysis revealed that the composite film surface was smoother than the DLC film alone. The results of Raman spectroscopy and X-ray photoelectron spectroscopy indicated a robust bond between nitrogen and carbon atoms in the composite film, with nitrogen facilitating the conversion of sp3C-C bonds into sp2C=C. Mechanical tests demonstrated that the N-DLC interlayer improved film adhesion and reduced the CoF of the composite film to 0.2–0.3. Specifically, the CoF of the N-DLC/DLC film prepared at 100 V was as low as 0.20, with a wear amount of 1.13 mg. Consequently, the inclusion of the N-DLC interlayer substantially enhanced the mechanical and tribological properties of DLC-coated NBR, rendering this coating highly advantageous for various applications.

Effect of bias gradient delta on mechanical and tribological properties of DLC films sputtered on ACM

Diamond-like carbon (DLC) films were prepared on acrylate rubber (ACM) by varying the substrate bias voltage with bias gradient deltas of 25 V, 50 V, and 100 V during magnetron sputtering. The microstructure, mechanical and tribological properties of DLC films on ACM substrate were systematically investigated by SEM, AFM, Raman and XPS et.al in detail. The results show that the DLC film with a bias gradient delta of 25 V exhibited the most sp3 content and with the decrease of bias voltage gradient delta, the sp3 content in DLC films shows an increasing trend. The ratio of H/E increases as the bias gradient delta decreases. The results of friction tests indicated that the wear resistance of DLC films is influenced by their bias gradient deltas, surface roughness, residual stress, adhesive strength, and the ratio of H/E&H3/E2. Furthermore, decreasing the bias gradient delta resulted in a reduction in wear volume. Among the tested films, the DLC film with a bias gradient delta of 25 V exhibited the lowest CoF of 0.14 and the least wear volume of 0.98 mg, respectively. These findings suggest that the said film prepared on ACM displays excellent wear resistance.

Deposition processes of superhard diamond-like carbon films co-adjusted by ion energy and ion flux in arc discharges

As a kind of protective material, Diamond-Like Carbon (DLC) film can effectively improve the mechanical and tribological properties of the substrate surface. In DLC family, tetrahedral amorphous carbon (ta-C) with ultra-high hardness and excellent protective properties has been widely concerned in the field of hard protective materials. It is well known that the structure and properties of ta-C are strongly dependent on carbon plasma characteristics in the plasma environment. Therefore, it is extremely crucial to obtain the optimal process window of ta-C described by plasma micro-parameters with general significance. This paper proposed the Langmuir probe was used to diagnose the carbon plasma of the afterglow generated by arc evaporation, aiming to investigate the characteristics of carbon plasma and sheath. The effect of ion energy and ion flux adjusted by the pulse bias voltage and arc current on the sp3 hybrid bonds and hardness of DLC films was studied, aiming to find out which conditions satisfied the formation of ta-C. The results showed the microstructure and properties of DLC films were co-adjusted by ion energy and ion flux. When the carbon ions met the appropriate ion energy range (50–300 eV) and low ion flux (<8.99 × 1010 cm−2 s−1), the films tended to form ta-C structures with high sp3 bonds. However, under the condition of high ion energy and high ion flux, the structure of the films changed from sp3 bonds to sp2 bonds, resulting in the graphitization and formation of DLC films with high sp2 bonds. This work will provide new solutions to guide the design and acquisition of high-performance DLC films.

Friction and wear behavior of molybdenum-disulfide doped hydrogen-free diamond-like carbon films sliding against Al2O3 balls at elevated temperature

Diamond-like carbon (DLC) films quickly experience lubrication failure due to oxidation and mechanical degradation when used above 300 °C, which limits their application. Molybdenum disulfide (MoS2) doping is considered as a feasible method to improve high-temperature properties of DLC films. However, the effect of MoS2 doping on the high-temperature friction behavior of MoS2-DLC composite films and its mechanism remain unclear. Here, MoS2-DLC composite films with different contents of MoS2 were synthesized by a superimposed deposition system consisting of high-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS). The MoS2 content in the films was controlled by varying the number of MoS2 pellets in the graphite-MoS2 (C–MoS2) mosaic target. The effect of MoS2 doping content on the structure and mechanical properties of MoS2-DLC films was analyzed. In addition, the friction and wear behavior and mechanism of MoS2-DLC composite films sliding against Al2O3 balls at 25–450 °C were studied. The results indicated that MoS2 was successfully incorporated into DLC matrix, and the content of Mo in the films ranged from 0 to 6.15 at. %. The as-deposited MoS2-DLC composite films exhibited a dense and featureless structure. The doping of MoS2 improved the adhesion strength and released the internal stress of MoS2-DLC composite films, but reduced the hardness and elastic modulus of the films. In particular, MoS2-DLC composite films with 3.78–6.15 at. % Mo maintained excellent anti-friction and anti-wear performances in the temperature range of 25–450 °C. Abrasive wear and fatigue wear occurred in the friction test of the films at different temperatures. However, the friction mechanism of the films varied with the temperature of friction test. At 25 °C, MoS2-DLC composite films showed excellent lubrication and anti-wear abilities due to the carbon suspension bond was passivated by H2O molecules. At 250 °C, MoS2 phase precipitated on the surface of the films, resulting in low friction. At 350 °C, MoS2-xOx solid solution was generated on the surface of the wear track to maintain lower friction and wear. Interestingly, MoS2-DLC composite films with high Mo content still achieved relatively low coefficient of friction and wear rate up to 450 °C due to the continuous availability of MoS2-xOx generated on the surface of wear track.

Investigation of the Mechanical and Tribological Properties of Diamond-Like Carbon Films on YG8 and High-Speed Steel Substrates with W Buffer Layers

Investigation of the Mechanical and Tribological Properties of Diamond-Like Carbon Films on YG8 and High-Speed Steel Substrates with W Buffer Layers

Effects of sp3 bond ratio and modulation ratios on nanotribology behaviors of diamond-like carbon coatings investigated using atomistic nanoscratching simulations.

Diamond-like carbon (DLC) films are amorphous solids in which carbon atoms are linked by hybridized sp3, sp2, and sp bonds. The mechanical and tribological properties of DLC films can be adjusted by tuning the sp2/sp3 bond ratio. These films are typically used as protective coatings for components such as dies, automotive engines, mechanical seals, hard disk drives, biological engineering devices, and micro/nano-electromechanical systems. Further exploration of the mechanical and tribological behavior of DLC films is important for enhancing functional design for the above applications. The simulation results show that single-layer DLC with a higher sp3 ratio has better resistance to indentation. Single-layer DLC with a lower initial sp3 ratio has lower friction and a shorter repeated cycle in the friction force curve due to an increase in the graphitization of the friction interface. Single-layer DLC with a higher sp3 ratio has a higher coefficient of friction because compared with the normal force, the friction force is much more sensitive to an increase in the sp3 ratio. Molecular dynamics simulations based on the Tersoff potential were performed using the open-source code LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator).

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&lt;sup&gt;3&lt;/sup&gt;-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&lt;sup&gt;3&lt;/sup&gt;-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.

Effects of deposited particle energy on the structure and properties of diamond-like carbon films

Using plasma-enhanced chemical vapor deposition (PECVD), a series of diamond-like carbon (DLC) films were prepared on YG8 carbide substrate by changing the enhancement mode and the negative bias voltage of the substrate. The structure and properties of the deposited films were tested by a series of analytical and testing instruments.During the deposition of DLC films, the ability of electrons to collide and ionize the gas is enhanced by increasing the number of electrons and extending the movement path of electrons, which is called electron-assisted enhanced gas ionization. Four different experimental modes (A mode, B mode, C mode, D mode) were set up. Different experimental modes have different degrees of electron-assisted enhancement ability of gas ionization, so different experimental modes are called different enhancement modes. The ions ionized by the electrons participate in the deposition of the film under the traction of the negative bias voltage of the substrate. The results show that: when depositing diamond-like carbon films, the energy of the ion beam is indirectly affected by electron collisions in different enhancement modes and directly affected by the negative bias voltage of the substrate. The higher the enhancement mode, the higher the ion beam energy. The higher the substrate negative bias voltage, the higher the ion beam energy generated by gas source discharge. Under the dual action of enhancement mode and substrate negative bias voltage, the total energy of ions involved in deposition should not be too high or too low, and the synergy of the two makes the properties and quality of the deposited film reach a better value. For industrial large-scale production of tool protection film for cutting aluminum alloy, it is more suitable for high enhancement mode and low negative bias voltage production.Through a series of process optimization to improve and enhance the comprehensive performance of DLC film, it is further applied to the actual processing application field, which has great industrial and social value to realize the large-scale application of DLC film in the field of hard to cut metal processing.

Nanoscale friction of tetrahedral amorphous diamond-like carbon film after thermal annealing

Diamond-like carbon (DLC) coatings have demonstrated significant potential as solid lubricants for a wide range of applications. However, thermal-induced structural changes lead to alterations in its mechanical and frictional properties. In this study, we investigate the friction properties of DLC films after high-temperature annealing, by conducting reciprocating single asperity scanning experiments of self-mated hydrogen-free DLC tribopair under ultra-high vacuum (UHV) conditions. As the annealing temperature increases, the coefficients of friction (COFs) first increase owing to the desorption of water molecules; while, with the further increase of temperature, friction shows a decreasing trend because of the high-temperature-induced sp3-to-sp2 rehybridization which lowers the interfacial shear strength. The insights gained from this study provide a better understanding of the frictional properties of DLC films.

Influence of molybdenum concentration on the microstructure and nanotribological properties of diamond-like carbon films

Influence of molybdenum concentration on the microstructure and nanotribological properties of diamond-like carbon films

Effect of local pressure difference caused by argon flow on properties of DLC films on rubber

The application of a diamondlike carbon (DLC) coating on rubber surfaces is a promising method to enhance the tribological properties of rubber and alleviate its poor wear resistance. However, in the preparation of DLC films, accurate pressure detection in the sputtering region is challenging due to the single detection position in common sputtering systems. In this paper, the direct current magnetic sputtering method was used to prepare DLC films on nitrile butadiene rubber (NBR). A set of Faraday beam detection device (FBDD) was employed to monitor the current density in the sputtering region. It was found that even if the pressure at the detection position of the vacuum gauge is consistent, the actual pressure in the sputtering region may be different under different rates of argon flow based on the detection results from the FBDD. The surface energy of DLC films was also calculated and researched. According to the results of FBDD, a series of analytical characterization methods were selected to explore the influence mechanism of changing the Ar flow rate on the properties of DLC films on NBR when the initial sputtering pressure remained consistent. The results of FBDD show that the density of the beam in the sputtering region increases with the increase in the Ar flow rate introduced into the vacuum chamber. The surface energy of DLC films was also calculated and evaluated by a contact angle tester. Raman and x-ray photoelectron spectroscopy results indicate that the increase in the Ar flow rate leads to an increase in pressure, which is conducive to the formation of sp3 in DLC films, and the increase in sp3 improves the surface energy of DLC films. The highest sp3 content and surface energy among as-prepared DLC films are observed when the argon flow rate was 40 SCCM. Ball-on disk friction experiment was used to characterize the tribological performance of DLC films on NBR rubber and the adhesion between DLC films and NBR rubber was evaluated by a nanoscratching test. Combining the results of tribology and nanoscratching testing, it can be inferred that the Ar flow rate plays an important role in improving the mechanical properties of DLC films on NBR rubber. Furthermore, the results of scanning electron microscopy confirmed that the sputtering atoms can effectively fill in the grooves of the rubber substrate. This finding is of significance for controlling the sputtering process of preparing DLC on rubber and improving the frictional properties of rubber.

Study on properties of diamond-like carbon films deposited by RF ICP PECVD method for micro- and optoelectronic applications

In this paper, a comparison of Diamond-like Carbon (DLC) films with different sp3 fraction content prepared by Radio Frequency Inductively Coupled Plasma Enhanced Chemical Vapour Deposition (RF ICP PECVD) was presented. Structural, surface, optical, and mechanical properties of deposited DLC films were analyzed with the use of awide range of measurement techniques. The investigated films were deposited on silicon (Si), amorphous silica (SiO2), and metallic (Ti6Al4V) substrates at room temperature. The deposited DLC films have sp3 fraction content ranging from 35 % to 70 %, uniform, compact and dense microstructure. The investigation indicates that the properties of DLC films required for micro- and optoelectronic applications improve with the sp3 fraction content. The refractive index (n) increased from 1.976 to2.086, packaging density (PD) from 0.964 to 0.744, electrical resistivity (ρ) from 2.1 ∙ 1010 to 4.4 ∙ 1011 Ωcm, hardness (H) from 16.4 19.1 to GPa and elastic modulus (E) from 109 to 129 GPa. However, the 50 % sp3 DLC thin film exhibited the highest resistance to cracking (H3/E2 = 0.44). The decrease of Urbach energy (EU) from 0.75 to 0.46 eV was observed for the DLC film with the highest sp3 fraction content, while all investigated DLC samples had similar optical bandgap energy (Egopt ≈ 1.3 eV). The research has shown that it is possible to obtain DLC coatings using the RF ICP PECVD technique that has better properties than films deposited by the classic PECVD technique.

Design of an Ultra-Thick Film and Its Friction and Wear Performance under Different Working Conditions

Tantalum (Ta)/Ti/TiN/Ti/diamond-like carbon (DLC) (referred to as TTTD film) and Ta/Ti/TiN/TiCuN/Ti/DLC (referred to as ultra-thick film) films were designed in this study, and the factors affecting the friction and wear properties of DLC films in sodium bicarbonate and lactic acid solutions were analyzed. Moreover, a thin film with a thickness exceeding 50 microns was prepared. Morphology and tribological and mechanical properties were analyzed by scanning electron microscopy, friction and wear testing machine, and nanoindentation instrument, respectively. The results show that the presence of a TiCuN interlayer increases the defects in the DLC film and the roughness of surface, reaching a roughness of 0.19 µm. Compared with the TTTD film, the TiCuN interlayer reduces the hardness and increases the residual stress, which is 0.52 Gpa and −6.08 GPa, respectively. The TTTD film has a smooth and dense surface structure and high hardness, causing it to more easily form boundary lubrication. However, the ultra-thick film has lower hardness and rough surface, which cannot effectively form boundary lubrication. Therefore, the friction coefficient of the ultra-thick film is higher than that of the TTTD film under different working conditions. In sodium bicarbonate solution, a double-hydrolysis reaction is more likely to occur, resulting in a higher friction coefficient than in lactic acid solution. The friction coefficient of the TTTD film has a longer running-in period, which is attributed to the oxides generated by the double-hydrolysis reaction and the precipitated sodium bicarbonate crystals. Finally, it was concluded that the surface quality and the internal bond structure of DLC film have a significant impact on the friction and wear properties. This provides a theoretical basis for the design of multilayer structures.

Structure and mechanical properties of diamond‐like carbon films prepared by pulsed laser‐induced cathodic vacuum arc technique

Diamond‐like carbon (DLC) films are prepared by pulsed laser‐induced cathodic vacuum arc technique with various arc voltages. The purpose of the research is to investigate the influence of the arc voltage on the structure, mechanical, and tribological properties of DLC films. The results from Raman spectra and XPS show that with increasing arc voltage from 180 to 280 V, the sp3 content in the DLC film increases from 43.2 to 56.9 at%, then follows by a significant decrease with further increasing arc voltage to 330 V. The trend in the mechanical properties of DLC films correlates well with the sp3 content in the films. The maximum hardness, modulus, and adhesion critical load (Lc) of the DLC film is obtained in the film deposited at 280 V; the values of that are 46.4 GPa, 380.6 GPa, and 620 mN, respectively. The friction coefficient of the films is between 0.1 and 0.2, and the film deposited at 280 V has the minimum wear rate with a value of 3.2 × 10−17 m3/m.N. It is concluded that the DLC films with high sp3 content (ta‐C, tetrahedral amorphous carbon) not only have good mechanical properties but also have excellent tribological properties, which provides a promising application for wear resistance parts.

Effects of Element Doping on the Structure and Properties of Diamond-like Carbon Films: A Review

Diamond-like carbon (DLC) films with excellent anti-friction and wear resistance, can effectively reduce the energy loss of tribosystems and the wear failure of parts, but the high residual stress limits their application and service life. Researchers found that doping heterogeneous elements in the carbon matrix can alleviate the defects in the microstructure and properties of DLC films (reduce the residual stress; enhance adhesion strength; improve tribological, corrosion resistance, hydrophobic, biocompatibility, and optical properties), and doping elements with different properties will have different effects on the structure and properties of DLC films. In addition, the comprehensive properties of DLC films can be coordinated by controlling the doping elements and their contents. In this paper, the effects of single element and co-doping of carbide-forming elements (Nb, W, Mo, Cr, Ti, Si) and non-carbide-forming elements (Cu, Al, Ag, Ni) on the properties of microstructure, mechanical, tribological, optical, hydrophobic, corrosion resistance, etc. of DLC films are reviewed. The mechanisms of the effects of doping elements on the different properties of DLC films are summarized and analyzed.