Diamond-like Carbon Matrix Research Articles

Weak oxidant fraction in the microwave plasma influencing the evolution of nanocrystalline-diamond–imbedded diamond–like carbon network at low temperatures and its orbital hybridization dependent wide optical band gaps

The diamond-like carbon (DLC) thin films having intrinsic nanocrystalline diamond (NCD) components were synthesized on bare glass substrates at 300 °C, employing a (C2H2/CO2/H2/) gas mixture in MW-PECVD. Relevant influence of the weak oxidant fraction [F = CO2/(CO2 + C2H2)] in the plasma on the specific hybridized constituents (sp3 and sp2) in the C-network, optical transmission characteristics of the film, and its accomplished degree of nanocrystallinity were investigated. A substantial segment of the NCD was achieved in the DLC matrix. An optimized diamond-phase component corresponding to the minimized bond angle disorder in the matrix was accounted from the manifestation of the maxima of IDia/IG and IDia/ID simultaneous to the minimum of ID/IG ratio in Raman response, along with an allied diamond peak appearing near 1332 cm−1. The optimal DLC film at F = 0.23 revealed a wide optical band gap (Eg) of ∼3.60 eV, ∼59% sp3-hybridized C component of the diamond phase, and a significant sp3/sp2 ratio of ∼2.1. The film microstructure seemed homogeneous with uniformly distributed NCDs of average diameter ∼7.5 nm and dominant 〈111〉 crystallographic orientation. The sp3/sp2 fraction in the film matrix has been correlated directly to the IDia/IG and IDia/ID, and inversely to ID/IG ratios of the Raman data. Atomic-O, including atomic-H, remains instrumental in chemical reactions, facilitating the etching of graphitic and a-C phases while preserving the superior sp3-hybridized NCD component growing uninterruptedly in the DLC network that subsists shielded from the high-energy ion impact within secondary plasma under the shadow mask.

Nanocomposite materials based on amorphous SiC-containing DLC structures modified with rhodium nanoparticles

From the 1980s to the present, interest in carbon has remained very high. The variety of polytypic forms of carbon is expected to have a large number of possible applications. The creation of electronic and optical devices based on them is a promising direction. One of the most interesting carbon materials could be amorphous diamond-like carbon (DLC) films. This work considers nanocomposite materials based on DLC with nanostructures of SiC components. Thin composite DLC:Si films modified with Rhodium nanoparticles (Rh NPs) were synthesized by magnetron sputtering. The structure of the films has been studied by transmission electron microscopy, Raman and X-ray photoelectron spectroscopy (XPS). It is shown that a diamond-like carbon matrix with inclusions of SiC nanostructures and Rh nanocrystals is formed. Significant influence of Rh NPs on the structures of the carbon matrix and SiC during the formation of the DLC: Si matrix is revealed. In addition, X-ray photoelectron spectroscopy shows a considerable effect of Rh NPs on the edge of the valence zone and the density of localized states. The significant effect of rhodium nanoparticles on the electronic component of the valence band of DLC:Si films can be used in the development of new optoelectronic devices.

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.

Dielectric response and current-voltage characteristic of Mo-doped diamond-like carbon thin films at room temperature

Herein we have reported the effect of molybdenum (Mo) doping and acetylene (C2H2) gas flow rate, during deposition, on the electrical properties of diamond like carbon (DLC) films. The frequency dependent dielectric response of the undoped and doped DLC films has been discussed in details. Mo doping also increases the dielectric constant value owing to interfacial polarization and the corresponding change with C2H2 gas flow rate has been attributed to the formation of sp2 bonding over sp3 bonding, favoring the emergence of a graphite-like phase. The ac conductivity of DLC films has been observed to increase with frequency following a power law behavior. However, with 29 % Mo doping we have noticed two plateau regions having different slopes which has been explained on the basis of the jump relaxation model (JRM). The theoretical fitting of the experimental data indicates occurrence of ionic conduction along with polaron hoping. The dc contribution part (σdc) of the measured ac conductivity is found to vary with the acetylene (C2H2) gas flow dependent sp2 bonding formation. The σdc is extracted to be 2351 S/m for the 29 % Mo doped DLC films. From the Nyquist plot in impedance spectroscopy single relaxation phenomena have been observed for the no or low Mo doping but with 29 % Mo doping both the grain and grain boundary effect are prominent. This also suggests the presence of sp2 hybridization and formation of dangling bonds between the metal carbide and DLC film. From the current voltage characteristics, the development of high sp2 bonding and high electron injection into the DLC matrix with subsequent change in nature of the DLC from semiconducting to metallic with high Mo doping has been reported. From the capacitance voltage characteristics study it has been found that either increase in acetylene gas flow during deposition or Mo doping increases the space charge and trap carrier densities.

Diamond-like carbon graphene nanoplatelet nanocomposites for lubricated environments

The tribological behaviour of diamond-like carbon (DLC) and graphene nanoplatelets (GNP) nanocomposite has not been previously explored in a lubricated environment, with some previous studies reporting only on graphene materials on the surface of the DLC. In this study DLC-GNP nanocomposite films with various GNP coverages were synthesised by a 3 step process: spin coating a GNP suspension, heat treatment, and DLC deposition. In this study, the effect of the GNP coverage on the mechanical properties, and tribological response of the DLC-GNP nanocomposite film were studied at elevated temperatures against a cast iron pin in a base-oil lubricated environment. The study shows decrease in friction and wear of the DLC-GNP nanocomposites as the GNP coverage increased, with the lowest friction (COF ∼0.03) and wear (∼1.6 × 10−19 m3/Nm−1) achieved with a 4.5% coverage. This study reports the addition of GNP into the DLC matrix reduced both friction and wear by creating a highly graphitic transfer film on the counter-body, but for higher GNP coverages agglomeration during the spin coating of GNP islands were recorded, leading to removal of the GNP during sliding wear negating the friction reduction effect of the GNP.

Comparison of mechanical and tribological properties of diamond-like carbon coatings doped with Europium and Gadolinium produced by HiPIMS

Hydrogen-free diamond-like carbon (DLC) thin films can be employed for numerous applications, including engine components, once they exhibit good properties for that. They have been used as coatings due to their attractive properties, including high hardness, high wear resistance, and low CoF even under high load/pressure. One of the major limitations of hard hydrogen-free ta-C coatings applications is related to the low reactivity with oil additives used nowadays. The Ionic liquids (ILs) emerged as a novel class of lubricants that can be used in future lubricated systems due to possessing unique physical properties, like high thermal stability and conductivity. To improve the lubrication performance of DLC with ILs, the films were doped with rare earth metals such as Gd and Eu. These non-carbide-forming elements can be introduced in the DLC matrix, incorporated as single atoms, and improve the surface adsorption and reactivity of phosphorus-based IL, and consequently, the lubricating properties of DLC/ILs sliding contacts. However, many demanding applications require good performance across the different regimes (from boundary to hydrodynamic regime). Across all regimes, the boundary is the most challenging, where metal-to-metal contact occurs. Therefore, it is essential to study the influence of the doping elements on the doped-DLCs performance under the boundary regime. For comparison, a pure-DLC was used. In this study, Eu and Gd-DLC tribological systems are characterized by pin-on-disk test in dry conditions and by scratch test. Also, mechanical properties are studied through nano-indentation. Results show that samples doped with a low atomic concentration of Eu or Gd (1%–3%), despite having a CoF higher than un-doped DLC films, show typical values for pure-DLC coatings, like low specific wear rate (<10−16 m3/Nm) and high hardness (23 GPa), permitting, in the future, the combination of novel nanostructured alloyed-DLCs and ILs needed to achieve the optimal lubrication performance.

Boron doping of diamond-like carbon films by pulsed laser deposition technique for photovoltaic application

Diamond-like carbon (DLC) films were deposited by pulsed laser deposition technique using a glassy carbon disc as carbon source material. Boron doping in DLC films was carried out by ablating boron disc sequentially during the synthesis of DLC films. Field emission scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and Raman measurements were utilized to characterize the films. Hot-probe study indicated the films to be p-type. Core level XPS spectra of B1s appeared at ∼ 189.5 eV and indicated that boron atoms are in form of B-C network connect. Raman studies indicated a dilatation of host lattice with the incorporation of boron in DLC matrix favouring graphitization. Band gap of the thin films decreased from ∼2.0 eV (pure DLC) to ∼1.76 eV with increased incorporation of boron. A photovoltaic cell structure (glass/indium tin oxide)/B:DLC/ZnO/Ag) conceived here, indicated an open circuit voltage ∼110 mV, short circuit current density ∼7.5 mA/cm2 with a fill factor ∼0.3, and a low conversion efficiency (η) ∼ 0.23%.

Effective target arrangement for detecting the properties of Ni doped diamond-like carbon by pulsed laser deposition

In the current study, diamond-like carbon (DLC) was synthesized by pulsed laser deposition (PLD) in a vacuum at room temperature, focusing on Ni-dopant concentration and arrangement of Ni strips in both parallel and transverse positions. The morphology and structural properties of Ni-DLC films were analyzed by Raman spectroscopy, atomic force microscopy (AFM) analysis, cross-section analysis, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), contact angle (CA), and nanoindentation test. AFM images exhibit the new shapes of Ni-DLC thin films, named conic and nano-mushroom particles. The Raman spectra of Ni-DLC films show that the calculated intensities D-line to G-line ratio experiences a decrease with increasing Ni dopants in the transverse arrangement while the parallel arrangement represents a different trend. The stoichiometry of Ni-DLC thin films has been reported from the cross-section of thin films. It is also observed from the measured CA that the hydrophilic properties of Ni-DLCs increase in the transverse arrangement. Low nickel content in diamond-like carbon matrix exhibited the dominance of diamond phase and good mechanical properties have been found.

Formation of wear-resistant graphite/diamond-like carbon nanocomposite coatings on Ti using accelerated C60-ions

The nanostructural and tribological characteristics of carbon nanocomposite coatings (CNCs), deposited by accelerated C 60 ions at high temperatures, were studied. The CNCs were successfully fabricated on Ti-alloy using a flux that contained C 60 ions with 5 and 10 keV energies. Unlike the previous studies, ion mass-separator was not implemented to the deposition process. This enabled deposition of sp 2 -rich CNCs with a lower coefficient of friction (COF) at a higher deposition rate. Laser confocal microscopy , atomic force microscopy transmission electron microscopy , Raman spectroscopy , X-ray photoelectron spectroscopy, and X-ray Auger Electron Spectroscopy were used to investigate the structure of the coatings and friction test results. A carbon nanocomposite film consisting of graphite nanocrystals enclosed in an amorphous diamond-like matrix was formed at a deposition temperature of 300–400 °C. Upon deposition of the CNC, a COF of ~0.06 was achieved, which was almost one order of magnitude lower than that of bare Ti-alloy substrate. The surface wear was reduced by 360 times. The wear mechanism was changed from abrasive wear (on bare Ti-alloy) to a burnishing smoothening of the surface roughness (on CNCs). The transfer of graphite nanocrystals from the coating to the counter surface was identified and observed to act as a solid lubricant . • Carbon nanocomposite coatings were deposited on Ti using accelerated C 60 -ions. • Graphite nanocrystals embedded in amorphous diamond-like carbon matrix were formed. • The coatings were deposited without the implementation of ion mass-separator. • Deposition temperature significantly affected the size of graphite nanocrystals. • The coatings reduced the COF and wear rate of Ti by 8 and 360 folds, respectively.

Diamond-like/graphite-like carbon composite films deposited by high-power impulse magnetron sputtering

Diamond-like carbon (DLC)/graphite-like carbon (GLC) composite films were prepared with high-power impulse magnetron sputtering (HiPIMS) using a mixture of Ar and Ne as the sputtering gas. The effect of the Ne fraction in the sputtering gas on the surface morphology, carbon bonding structure, microstructure, mechanical properties, residual stress, and tribological performance of the deposited films were characterized using laser scanning confocal microscopy, Raman spectroscopy, nano-indentation, residual stress tester, and friction and wear testing using a ball-on- plate tribometer, respectively. The films have a composite surface structure consisting of sp2-rich GLC microparticles embedded in an sp3-rich DLC matrix. Both components can be controlled to some degree by varying the Ne fraction. Specifically, as the Ne fraction is increased, both the number and size of the GLC microparticles decreases, while the sp3 content increases. The GLC microparticles in the film can reduce the real contact area in friction testing, decreasing the friction coefficient, while the sp3-rich DLC phase enables the high hardness and wear resistance of the films. By adjusting the Ne fraction during the HiPIMS process, DLC/GLC composite films with low friction and high wear resistance can be generated.

Compositionally modulated multilayer diamond-like carbon coatings with AlTiSi multi-doping by reactive high power impulse magnetron sputtering

Diamond-like carbon (DLC) coatings with AlTiSi multi-doping were prepared by a reactive high power impulse magnetron sputtering with using a gas mixture of Ar and C2H2 as precursor. The composition, microstructure, compressive stress, and mechanical property of the as-deposited DLC coatings were studied systemically by using SEM, XPS, TEM, Raman spectrum, stress-tester, and nanoindentation as a function of the Ar fraction. The results show that the doping concentrations of the Al, Ti and Si atoms increased as the Ar fraction increased. The doped Ti and Si preferred to bond with C while the doped Al mainly existed in oxidation state without bonding with C. As the doping concentrations increased, TiC carbide nanocrystals were formed in the DLC matrix. The microstructure of coatings changed from an amorphous feature dominant AlTiSi-DLC to a carbide nanocomposite AlTiSi-DLC with TiC nanoparticles embedding. In addition, the coatings exhibited the compositionally modulated multilayer consisting of alternate Al-rich layer and Al-poor layer due to the rotation of the substrate holder and the diffusion behavior of the doped Al which tended to separate from C and diffuse towards the DLC matrix surface owing to its weak interactions with C. The periodic Al-rich layer can effectively release the compressive stress of the coatings. On the other hand, the hard TiC nanoparticles were conducive to the hardness of the coatings. Consequently, the DLC coatings with relatively low residual stress and high hardness could be acquired successfully through AlTiSi multi-doping. It is believed that the AlCrSi multi-doping may be a good way for improving the comprehensive properties of the DLC coatings. In addition, we believe that the DLC coatings with Al-rich multilayered structure have a high oxidation resistance, which allows the DLC coatings application in high temperature environment.

The role of substrate bias and nitrogen doping on the structural evolution and local elastic modulus of diamond-like carbon films

Diamond-like carbon (DLC) films are synthesized on Si using plasma enhanced chemical vapor deposition. The role of substrate bias and nitrogen doping on the structural evolution and local elastic modulus of DLC films are systematically investigated. Raman spectroscopic studies reveal that the amount of graphitic C = C sp2 bonding increases with substrate bias and nitrogen doping. The density and hydrogen concentration in the films are found to vary from 0.7 to 2.2 g cm−3 and 16 to 38 atomic %, respectively, depending upon the substrate bias and nitrogen concentration in the DLC films. Atomic force acoustic microscopy (AFAM) analysis shows a direct correlation between the local elastic modulus and the structural properties estimated by Raman spectroscopy, Rutherford back scattering and elastic recoil detection analysis. AFAM analysis further confirms the evolution of soft second phases at high substrate biases (⩾ −150 V) in undoped DLC films. Further, N doping leads to the formation of such soft second phases in DLC films even at a lower substrate bias of −100 V. The AFAM studies provide direct microscopic evidence for the ‘sub-implantation growth model’, which predicts the formation of graphitic second phases in the DLC matrix at high substrate biases.

Plasmon-enhanced optical absorption with graded bandgap in diamond-like carbon (DLC) films

Diamond-like carbon (DLC) films with tunable optical bandgap (Eg) were successfully deposited on glass and n-Si (100) substrates by radio frequency (RF)-sputtering technique in different argon (Ar) and acetylene (C2H2) plasmas. The bandgap of the films can be tuned from 1.41 to 1.28 eV, which correlates with the sp2 content, which increases from 56.3 to 63.7 %, respectively. The different ratios of sp2/sp3 lead to different bandgaps of the DLC films. Plasmonic nanoparticles of silver (Ag) were also embedded in the DLC matrix by reactive magnetron sputtering to study the enhancement of light absorption in DLC films. The absorption coefficient significantly increased when the DLC films were incorporated with 10 at.% of silver nanoparticles. Raman and X-ray photoelectron spectroscopy (XPS) studies were utilized to determine the bonding nature and sp2/sp3 ratios of DLC–Ag films.

Linear and Nonlinear Absorption Properties of Diamond-Like Carbon Doped With Cu Nanoparticles

Ultrafast relaxation processes in diamond-like carbon (DLC) thin films with embedded Cu nanoparticles (DLC:Cu nanocomposites) were investigated by means of transient absorption spectroscopy focusing on localized surface plasmon resonance (LSPR) of photoexcited Cu nanoparticles. Absorption spectra of the composite films correspond to the sum of absorption spectra of DLC matrix and Cu nanoparticles; however, Cu nanoparticles strongly dominate in the transient differential absorption. Excitations of DLC matrix and of Cu nanoparticles relax independently revealing no strong interaction. High sensitivity measurements enabled to obtain the hot electron relaxation dynamics in Cu nanoparticles in the low excitation intensity conditions. The relaxation time was found to be independent of the excitation intensity up to tens of microjoule per square centimeter per pulse and to increase at higher intensities. The relaxation time obtained at low excitation intensity was also found to increase by about 30 % in the samples with high Cu concentration, where larger nanoparticles were formed.

Influence of Cr content on the micro-structural and tribological properties of PLD grown nanocomposite DLC-Cr thin films

Improved adhesion and low friction coefficient of diamond-like carbon (DLC) films has been a major challenge which otherwise would have opened door to many engineering applications. Amorphous DLC films doped with different concentrations of Chromium (Cr) (5, 10, 15 & 20 at%) were deposited on to stainless steel (AISI SS304) substrate using Nd-YAG pulsed laser deposition technique (PLD). Raman spectroscopy was used to calculate the internal stress of the films. DLC with lower Cr concentration (5 at%) showed significant internal stress reduction (3 GPa) compared to DLC with higher Cr concentration. Formation of Cr3C2 nanoclusters in the DLC matrix was confirmed by XPS and TEM analysis which enhanced the adhesion strength of the film. DLC films with lower Cr concentration exhibited ultra-low friction coefficient (0.04–0.09) and the value increased significantly in higher Cr concentration. An optimum metal concentration in DLC film leads to improved adhesion and friction behaviour that houses many engineering applications.

Silver-doped nanocomposite carbon coatings (Ag-DLC) for biomedical applications – Physiochemical and biological evaluation

The formation of bacteria biofilm on the surface of medical products is a major clinical issue nowadays. Highly adaptive ability of bacteria to colonize the surface of biomaterials causes a lot of infections. This study evaluates samples of the AISI 316 LVM with special nanocomposite silver-doped (by means of ion implantation) diamond-like carbon (DLC) coating prepared by hybrid RF/MS PACVD (radio frequency/magnetron sputtering plasma assisted chemical vapour deposition) deposition technique in order to improve the physicochemical and biological properties of biomaterials and add new features such as antibacterial properties. The aim of the following work was to evaluate antimicrobial efficacy and biocompatibility of gradient a-C:H/Ti+Ag coatings in relation to the physiochemical properties of the surface and chemical composition of coating. For this purpose, samples were tested in live/dead test using two cell strains: human endothelial cells (Ea.hy926) and osteoblasts-like cells (Saos-2). For testing bactericidal activity of the coatings, an exponential growth phase of Escherichia coli strain DH5α was used as a model microorganism. Surface condition and its physicochemical properties were investigated using SEM, AFM and XPS. Examined coatings showed a uniformity of silver ions distribution in the amorphous DLC matrix, good biocompatibility in contact with mammalian cells and an increased level of bactericidal properties. What is more, considering very good mechanical parameters of these Ag including gradient a-C:H/Ti coatings, they constitute an excellent material for biomedical application in e.g. orthopedics or dentistry.

Electrical and magnetic properties of electrodeposited nickel incorporated diamond-like carbon thin films

Abstract Nanocomposite diamond-like carbon (DLC) thin films have been synthesized by incorporating nickel (Ni) nanoparticles in DLC matrix with varying concentration of nickel. DLC and Ni-DLC thin films have been deposited on ITO coated glass substrates employing low voltage electrodeposition method. Electrical properties of the samples were studied by measuring current–voltage characteristics and dielectric properties. The current approaches toward an ohmic behavior with metal addition. This tendency of increasing ohmicity is enhanced with increase in dilution of the electrolyte. The conductivity increases with Ni addition and interestingly it continues to increase with dilution of Ni concentration in the electrolyte in the range of our study. Magnetic properties for DLC and Ni-DLC thin film samples were examined by electron paramagnetic resonance (EPR) measurements and Super Conducting Quantum Interference Device (SQUID) measurements. g -Value for DLC is 2.074, whereas it decreases to 2.055 with Ni addition in the electrolyte. This decrement arises from the increased sp 2 content in DLC matrix. The magnetic moment vs. magnetic field ( m – H ) curves of Ni-DLC indicate superparamagnetic behavior which may be due to ferromagnetic contribution from the incorporated nickel nanoparticles in the DLC matrix. The ZFC curve of Ni-DLC after the blocking temperature shows a combined contribution of ferromagnetic, superparamagnetic and paramagnetic nature of the materials persisting up to 300 K.

Synthesis of Ag-doped hydrogenated carbon thin films by a hybrid PVD–PECVD deposition process

Silver-doped hydrogenated amorphous carbon (Ag-DLC) films were deposited on Si substrates using a hybrid plasma vapour deposition–plasma enhanced chemical vapour deposition (PVD–PECVD) process combining Ag target magnetron sputtering and PECVD in an Ar–CH4 plasma. Processing parameters (working pressure, CH4/Ar ratio and magnetron current) were varied to obtain good deposition rate and a wide variety of Ag films. Structure and bonding environment of the films were obtained from transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy studies. Variation of processing parameters was found to produce Ag-doped amorphous carbon or diamond-like carbon (DLC) films with a range of characteristics with CH4/Ar ratio exercising a dominant effect. It was pointed out that Ag concentration and deposition rate of the film increased with the increase in d.c. magnetron current. At higher Ar concentration in plasma, Ag content increased whereas deposition rate of the film decreased. FTIR study showed that the films contained a significant amount of hydrogen and, as a result of an increase in the Ag content in the hydrogenated DLC film, sp 2 bond content also increased. The TEM cross sectional studies revealed that crystalline Ag particles were formed with a size in the range of 2–4 nm throughout an amorphous DLC matrix.

Microstructure and properties of (Cr:N)-DLC films deposited by a hybrid beam technique

In this paper, diamond-like carbon (DLC) films doped with CrN nano-crystalline were prepared on 316L stainless steel using a hybrid beam deposition system (including a linear ion source (LIS) and a DC magnetron sputtering of Cr target). The microstructure and composition of the films were studied using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Mechanical and tribological properties were investigated using nano-indentation and tribological tester. The results showed that an N doping could significantly influence the microstructure and properties of the as-deposited films. On one hand, the N atoms doped in the film tended to form Cr–N, –CN–H and C–N bonding, which would enhance the binding strength. On the other hand, the formation of CrN/CrC nano-crystalline due to N doping dispersed in the amorphous DLC matrix could play an important role and increase its hardness. In addition, the (Cr:N)-DLC showed low friction coefficient and wear rate compared with the Cr-DLC film.

Nickel concentration dependent structural and optical properties of electrodeposited diamond like carbon thin films

Diamond like carbon (DLC) and composite nickel incorporated diamond-like carbon (Ni-DLC) films have been synthesized on ITO coated glass substrates using low voltage electrodeposition method. Modifications of structural and optical properties of thin films have been investigated with varying Ni concentration. Average grain size of Ni-DLC granules is found to decrease with increasing molarity of Ni in electrolytic solution. XRD pattern depicts multi-phase nature of Ni-DLC film. Incorporation of Ni nanoparticles in DLC matrix has been confirmed by TEM. Interestingly optical bandgap energy decreases from 2.31 to 1.58 eV with decrease in nickel content in the electrolytic bath. Simultaneously Urbach energy exhibits an increasing trend from 1.972 to 2.374 eV. Presence of sp2 and sp3 bonded carbons has been indicated by FTIR spectra. The number of sp2 bonding in carbon matrix is enhanced with dilution of electrolyte. The peaks in the range of ~600–750 cm−1 in Ni-DLC films have been attributed to metal incorporation into DLC matrix. Study reveals that the bandgap and the particle size of carbon nanocomposite films can be tailored by controlling the amount of nickel in the electrolyte.