Diamond-like Carbon Thin Films Research Articles

Structural properties of protective diamond-like-carbon thin films grown on multilayer graphene

In spite of the versatility of electronic properties of graphene, its fragility and low resistance to damage and external deformations reduce the practical value of this material for many applications. Coating of graphene with a thin layer of hard amorphous carbon is considered as a viable solution to protect the 2D material against accidental scratches and other external damaging impacts. In this study, we investigate the relationship between the deposition condition and quality of diamond-like-carbon (DLC) on top of multilayer graphene by means of molecular dynamics simulations. Deposition of carbon atoms with 70 eV incident energy at 100 K resulted in the highest content of -bonded C atoms. An increase of the number of dangling bonds at the interface between the top graphene layer and the DLC film indicates that decrease of the incident energy reduces the adhesion quality of DLC thin film on graphene. Analysis of radial distribution function indicates that hybridized carbon atoms tend to grow near already existing -atoms. This explains why the quality of the DLC structures grown on graphene have generally a lower content of C atoms compared to those grown directly on diamond. Ring analysis further shows that a DLC structure grown on the -rich structures like graphene contains a higher fraction of disordered ring structures.

Fabrication of arrayed microwells with wrinkle microstructure by ink-jet and diamond-like carbon thin film deposition process

Fabrication of microwells is an important technology to create and enhance the functions needed for the biological applications of microfluidic devices. In this paper, how to fabricate arrayed microwells on poly(dimethylsiloxane) (PDMS) substrates handily using an ink-jet processing was presented. More, the microwells having wrinkle microstructures with several μm size on the surfaces were fabricated by a combination procedure of the ink-jet and diamond-like carbon (DLC) thin film deposition. The shapes of the microwells were hexagon and circle, and the sizes were in the ranges of 100–170 μm in diagonal or diameter and 3–30 μm in depth. To investigate the effect of the microwells on cellular behaviors, mouse myoblast cells were cultured on the PDMS substrates. The results demonstrated that the microwells with wrinkle microstructures had the ability to form spherically shaped cell aggregates of around 100 μm size, which were considered to be multicellular spheroids.

Effects of process parameters on optical characteristics of diamond-like carbon thin films deposited using high-power impulse magnetron sputtering

High-power impulse magnetron sputtering (HiPIMS) is a physical vapor deposition technique, developed specifically for the low-temperature deposition of functional thin films. In this study, a graphite target was used for the deposition of diamond-like carbon (DLC) thin films of high optical transmittance on a quartz glass substrate at 25 °C – 30 °C using HiPIMS in unipolar and bipolar modes. Experiments were conducted to determine the influence of DC input power, deposition time, and bias voltage with a fixed duty cycle on the optical characteristics of the resulting amorphous DLC thin films. During deposition, the current-voltage characteristics of discharge with a graphite target were recorded. The optical characteristics were assessed using a UV/visible light-absorption detector and the structure of the DLC thin films was confirmed by Raman spectroscopy. DLC thin films produced in unipolar mode with deposition time of 1 min presented the highest best transmittance of 86%.

Comparison of Wound-Healing Characteristics with Minimally Invasive Systems in 3D Liver Model

The object of this research was to investigate the thermal injury in the liver after a minimally invasive devices with a titanium dioxide (TiO2), a chromium nitride (CrN) and a diamond-like carbon (DLC) surface modifications. In 3D computer-aided models, needle type monopolar device equipped with TiO2, CrN and DLC thin films were used to simulate cutting livers. Data indicated that the temperature decreased significantly when minimally device with nanostructured TiO2, CrN and DLC thin films were used. Thermography revealed that the surgical temperature was significantly lower in the minimally invasive device with DLC thin film compared to untreated device. On the other hand, DLC device created a relatively small thermal injury and lateral thermal area. This research reveals that the novel nanostructured thin film on electrode substrates is an effective means of improving the performance of reducing excessive thermal injury and uniformly distributing temperature in livers.

Optical and Electrical Properties of Diamond-Like Carbon Thin Film with Deposition by ECR-CVD System

In this paper, evolution of optical and electrical properties of diamond-like carbon (DLC) films deposited by ECR-CVD system are reported. By varying the deposition different substrates bias (0, -55, -100 V) and volume amount of C2H2 from 40 to 55 cc onto substrate Si/TiN and quarts. The structure of the DLC films were analyzed from Raman spectroscopy. DLC films deposited bias at-100 V and C2H2 at 40 cc show excellent optical transmittance and high resistivity. As a result, ID/IG ratio corresponds to the optical transmittance and resistivity with ID/IG ratio decreased making the film like to the diamond. Most importantly, the transparency and resistivity properties of the DLC films can be tailored to approaching diamond by adjusting substrates bias and volume C2H2, is important to many applications, which is improve film properties.

Metal concentration dependent mechanical properties of electrodeposited nickel incorporated diamond like carbon (Ni-DLC) thin films studied by nanoindentation

Abstract Effect of nickel incorporation in diamond-like carbon (DLC) matrices has been investigated on the mechanical properties of Ni-DLC thin films by nanoindentation. DLC and Ni-DLC thin films of different nickel content were electrodeposited on ITO coated glass substrates at room temperature and low voltage. Raman spectrum analysis confirms the formation of the sp2 and sp3 phases of carbon in DLC and in some of Ni-DLC thin films. Microstructural studies by SEM reveal a variation in microstructures from finely granular to cluster like features with change in molar concentration of nickel in the electrolyte. GIXRD profiles demonstrate the presence of graphite, diamond and crystalline nickel phases in the thin films. EPMA study indicates the increase in nickel content in carbon matrix of prepared thin films with increase in nickel ions in the electrolyte. Depth controlled mode of nanoindentations was performed on the films to investigate their mechanical properties like hardness, elastic modulus, stiffness and elasto-plastic properties of the thin films. Nickel concentration dependent bilayer nature of heterogeneous growth structure has been revealed through force-distance curves. A hard and strong adhesive layer of DLC is formed immediately above the ITO surface, over which a much softer less adhesive layer is produced. With the increase in nickel content, bottom layer grows in thickness by the expense of the top layer. Hence at very low nickel content, the effect of top soft layer dominates the mechanical properties of the films, while at high nickel content gradually the effect of the soft layer vanishes. With increasing nickel content hardness of the films also shows an increasing trend contrary to the usual behavior of metal incorporated DLC thin films which may be due to multiple counter-interacting processes occurring simultaneously within the carbon matrix inducing changes in phase and hence in sp2/sp3 hybridization ratio.

Tribological performance and corrosion behavior of aluminum alloy protected by Cr-doped diamond-like carbon thin film

AbstractA gradient layer of Al/Cr diamond-like carbon film has been prepared by magnetron sputtering on 2024 Al-alloy. Emphasis has been placed on the anti-corrosion and tribological properties of the Cr-doped diamond-like film. Experimental research: scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectrometry, nano-indentation testing, potentiodynamic polarization, electrochemical impedance spectroscopy and tribological tests were undertaken to investigate the surface morphology, surface structures, chemical composition, anti-corrosion and mechanical properties of the as-prepared gradient diamond-like carbon film. The results indicated that the Cr-doped diamond-like carbon film with intermediate transition chromium layer showed improvements with regards to hardness and corrosion prevention due to the dense surface structure and decreased electrical conductivity. Cr-doped diamond-like carbon film also displayed excellent tribological properties such as a low friction coefficient and wear rate during tribological testing.

Synchrotron-based NEXAFS analysis of thermal-treated diamond-like carbon films

Diamond-like carbon (DLC) film properties are known to vary with important factors such as the ratio of sp3 to sp2 hybridization, film thickness, and contaminations. In this work, the carbon bonding contents in DLC thin films, thermal-treated with various temperatures between room temperature to 250 °C, were studies by near-edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. From NEXAFS measurements, the sp3/sp2 ratios of DLC films were found to be unaffected by the thermal treatments. The results indicate that thermal treatment below 250 °C does not affect the carbon bonding contents in DLC thin film.

Genetically optimized diamond-like carbon thin film coatings

ABSTRACTDiamond-like carbon (DLC) thin films find extensive applications in manufacturing, aerospace, and medical sector and thus, a huge need exists to optimize its deposition process. However, the experimental complexity and high costs involved limits the conduction of exhaustive experiments to determine the best process combinations. Consequently, in this research, a predictive modeling approach is coupled with global optimization procedures to find the optimum combination of deposition parameters. The prediction model is based on response surface methodology modeling of 20 LPCVD deposition experiments carried out as per central composite design. Scanning electron microscopy is used for morphology characterization of the DLCs and nanohardness is measured by nanoindentation technique. Raman spectroscopy and X-ray diffraction is used for characterizing the structural properties. Using a genetic algorithm, single- and multiobjective Pareto optimal solutions are reported which are validated experimentally. It is seen that for single-objective optimization, the best-predicted solutions for maximized hardness and maximized Young’s modulus are only 2% and 12% away from their true experimental values. Similarly, the most-desirable solution selected by TOPSIS from a Pareto optimal solution of 96 nondominated solutions (simultaneously maximized Young’s modulus and hardness) is only 2% away from their respective true values.

A quantitative wear measurement method on production engine parts: Effect of DLC thin films on wear

The automotive industry is facing worldwide pressure to reduce carbon emission to meet the Paris Accord target of 2 °C increase in global average temperature by the end of the century. One way to reduce carbon emission is to improve fuel economy of cars and trucks. Recent emergence of ultralow viscosity lubricants has shown significant fuel economy benefits. However, the resulting low oil film may cause increased surface contacts and could lead to increased wear. The ability to measure the initiation phase of wear before it accelerates towards failure is an important issue today. Quantitative measurement of wear in engine parts has always been a challenge. In today’s fuel efficient engines, coatings increasingly being introduced into engine component manufacturing, wear metrology of small amount of wear spread over a large area of rough surfaces presents even a greater challenge.This paper describes the development of a quantitative measurement technique to measure mild wear over a relatively large area of rough production engine surfaces. One of the critical engine sliding components is the piston ring vs cross-hatched cylinder liner contact interface. The availability of a quantitative wear measurement technique would allow comparison of various materials, including coated rings, and liner surface treatments. In this study, production rings and liners were obtained from cooperative engine manufacturers under non-disclosure agreements. A reciprocating ring-liner test rig was used to conduct the wear tests, using a newly developed cyclic wear test procedure, sequence of speed and load cycles were used for simulating sliding motions. Mini-cycles (a constant speed with varying loads from 160 N to 240 N) at 120 °C, and at 6 Hz reciprocating frequency were used. An experimental 0 W-16 lubricant, which has gone through engine testing, was used in the wear tests. A dual white light interferometric microscope (Z resolution 1 Å) was used to measure the liner wear. An analytical balance with 1 µg resolution was used to measure the ring segment weight loss. After the wear measurement procedure was established, diamond-like carbon (DLC) coated rings were also used to assess the effect of the DLC on the wear, and the measurement technique. A digital 3D surface topography subtraction technique was successfully developed to measure quantitative wear of the liner. This technique can be used for other wearing engine parts.

Studying the effects of plasma produced species on the optical characteristics and bonding structure of diamond-like carbon films deposited by direct current unbalanced magnetron sputtering

Abstract In the present study, the influence of target power and plasma produced species on optical, structural and morphological properties of diamond-like carbon thin films deposited by direct current unbalanced magnetron sputtering is investigated. Raman spectroscopy and spectroscopic ellipsometry are used to study the structural properties and optical characteristics, respectively. Additionally, optical spectroscopy is used to measure the optical band gap of the films and investigate the produced active species in the plasma. Optical emission spectroscopy of the plasma shows that increasing the target power from 60 W to 120 W, increases the hydrogen containing species in the plasma which was due to the water vapor remained in the vacuum chamber. Surface topography of the films illustrates that the surface roughness of the films decreases slightly which leads to the smoother surfaces. Raman spectroscopy shows that ID/IG ratio decreases and the G peak position shifts toward lower wavenumber. Indirect optical band gap also increases from 1.77 eV to 2.18 eV. Results of spectroscopic ellipsometry measurements illustrate that the refractive index decreases from 2.01 to 1.67 at 550 nm and the spectrum of the extinction coefficient decreases as well. These results indicate that increasing the sputtering power, increases the sp3 C H bonding more than C C bonding in the matrix of the film.

Optical and structural study for DLC thin films prepared by plasma jet

Diamond-like carbon (DLC) homogeneous thin films were deposited from cyclohexane (Ccyclohexane (Ccyclohexane (Ccyclohexane (C cyclohexane (Ccyclohexane (Ccyclohexane (C cyclohexane (Ccyclohexane (C 6H12 ) liquid by using a plasma jet system which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5 which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5which operates with alternating high voltage 7.5 kv and kv and kv and kv and frequency 28 frequency 28frequency 28 frequency 28frequency 28frequency 28frequency 28frequency 28 kHz. kHz. The optical and structural properties and chemical bonding of these films were investigated. In this work, the effect of changing the distance between the substrate and the plasma torch (2, 2.5 and 3 cm) was studied. The flow rate of argon gas which used to generate the plasma was fixed (0.5 L/min). These films were characterized by UV–Visible spectrophotometer, X-ray diffractometer (XRD) and scanning electron microscopy (SEM) and Fourier transformation infrared spectroscopy (FTIR). The maximum absorption (λmax) appears around 312, 298.3 and 293.2 nm at the three distance between plasma torch and the substrate 2.5, 2 and 3 cm, respectively. The values of the optical energy gap are 3.47, 3.65 and 3.76 eV at a different distance (2, 2.5 and 3cm), respectively. In XRD diffraction pattern, The occurrence of diamond peaks and graphite peaks in the x-ray spectrum for these films Indicates that there is an occurrence of local ordered sp3 and sp2 for carbon domains and graphite respectively.

Multifractal analysis of DLC thin films deposited by pulsed laser deposition

In this study, multifractal analysis was performed on the atomic force microscopy (AFM) images of the surface morphologies of the diamond-like carbon (DLC) thin films deposited by pulsed laser deposition (PLD) method on the silicon (Si) substrate at different substrate temperatures. In order to do this, multifractal spectra f(α) of AFM micrographs was used to characterize the surface morphology of thin films. The results obtained from multifractal spectra f(α) illustrate that the effect of substrate temperatures on the width of spectrum and ∆f is apparent. Multifractal analysis indicated that the surface of DLC thin films deposited at different substrate temperatures have a multifractal nature. It was observed that the width of the singularity spectrum, non-uniformity of the height distributions and also surface roughness of the DLC thin films increase with increasing substrate temperature. Our results clearly demonstrate that multifractal approach could efficiently describe the AFM images of the surface morphologies of the DLC thin films.

Correlation study of structural, optical, and hydrophobicity properties of diamond-like carbon films prepared by an anode layer source

Diamond- like carbon (DLC) thin films were deposited using anode layer source system on glass substrate at substrate temperature ranging from room temperature (RT) to 375 °C. An anode layer source is a specific ion gun, which can be fed with carbon precursors like propane to deposit hard and highly defect-free hydrogenated DLC thin films. The morphological, structural, optical, and hydrophobicity properties of DLC thin films were characterized by atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, UV- Vis spectrophotometer, and water contact angle (CA) measurement. The surface roughness was found to increase with substrate temperature. Disorder (D) and graphite (G) peak positions have been observed to respectively move toward 1400 cm−1 and 1546 cm−1, with substrate temperature, indicating a graphitization of DLC thin films, which may probably be ascribed to the sp2 cluster sites growth. The full width at half maximum (FWHM) of G peak increased upon increasing the substrate temperature. From the FWHM values of G peak, the clusters became more ordered with increasing the substrate temperature of DLC thin films. The G peak position changed by increasing the substrate temperature that in turn led to increment in the ID/IG ratio from 0.71 to 0.85, and also the graphite cluster size increased from 1.07 to 1.24 nm. Optical transmittance in UV and near infrared regions of the prepared DLC thin films found to decrease with the increase of substrate temperature. The refractive index (n) and extinction coefficient (k) of the films have been found to increase with substrate temperature. The CA of DLC thin films slightly increased with increasing substrate temperature from 80° at RT to 94° at 300 °C.

Diamond-like carbon films prepared by high power impulse magnetron sputtering

Abstract Diamond-like carbon (DLC) thin films were prepared by high power impulse magnetron sputtering (HiPIMS) with different deposition conditions. The main variable parameters were the argon flow rate, and deposition time. The carbon films were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The results from the XPS measurements show that the DLC films are composed of two main different carbon species; i.e. carbon with sp3 and sp2 configurations. The XAS measurements reveal that the DLC films contain hydrogen. The present of hydrogen affects the sheet resistivity of the films. The resistance of the DLC films increases exponentially when the temperature decreases.

Fabrication and characterization of optical, mechanical and chemical properties of diamond-like carbon thin film deposited on polymer substrate

In this research, diamond-like carbon (DLC) thin films were deposited on polycarbonate (PC) substrates by a R.F. plasma-enhanced chemical vapor deposition method. Before film deposition, PC substrates were cleaned and activated by O2 plasma etching. The effect of O2 plasma etching on wetting angle, chemical structure of the surface and the morphology of the samples was investigated by a contact angle analyzer, Fourier transform infrared spectroscopy and atomic force microscopy, respectively. The adhesion, structure, surface morphology and topography of the films deposited on the PC substrates were investigated. The chemical stability of the thin films was evaluated by exposing them to acetone and sodium hydroxide. The effect of UV irradiation on the properties of the films was investigated. Chemical stability investigations showed that DLC thin film deposited on the PC substrate improved the chemical resistance of the PC against alkaline environment. After UV-radiation, the scratch resistance and light transmittance of the samples were increased and maintained constant, respectively. While, the uncoated PC showed a decrease in scratch resistance and light transmittance after UV-radiation. It was found that the gas barrier performance of the PC coated DLC is three times larger than that of the uncoated PC substrate.

Kinetics of graphitization of thin diamond-like carbon (DLC) films catalyzed by transition metal

In this paper, we have studied the kinetics of graphitization at 773 K of thin diamond-like carbon (DLC) films coated with minute amount of Ni metallic particles. DLC films are deposited at room temperature by pulsed laser deposition (PLD) on a transparent quartz substrate, and Ni is deposited on the surface of DLC using molecular beam epitaxy technique at room temperature. The ultra-high vacuum thermal (range 573–873 K with 60 min annealing treatments) and kinetic (range 30–3760 min at 773 K) behaviors of the deposited films are investigated. Surface and interface characterizations indicate that the growth of graphitic sp2 clusters starts at temperatures lower than 573 K. The kinetics of graphitization is recorded at 773 K. Thus, the continuous growth of graphitic clusters leads to a long-range kinetics. These clusters are responsible for the increase in the electrical conductivity and carrier mobility, reaching values of 6.103 Siemens/cm and 20 V/cm2 × s, respectively. This continuous change is not only explained by the nucleation and growth of graphitic clusters, but also by some reorientation of them alongside both the surface and the quartz substrate. The obtained results demonstrate that thermally post-treated catalytic metal/DLC films are promising materials for conductive electrodes and sensing applications.Prime novelty and projected interestKinetics of graphitization at 773 K of thin diamond-like carbon (DLC) films coated with minute amount of Ni metallic particles;High surface electrical conductivities, which are quite promising and competitive in comparison to literature data dealing with transparent electrodes.Correlation between conductivity models and Raman measurements in Catalytic Metal/DLC material.

Mechanical Properties of Hydrogen Free Diamond-Like Carbon Thin Films Deposited by High Power Impulse Magnetron Sputtering with Ne

Hydrogen-free diamond-like carbon (DLC) thin films are attractive for a wide range of industrial applications. One of the challenges related to the use of hard DLC lies in the high intrinsic compressive stresses that limit the film adhesion. Here, we report on the mechanical and tribological properties of DLC films deposited by High Power Impulse Magnetron Sputtering (HiPIMS) with Ne as the process gas. In contrast to standard magnetron sputtering as well as standard Ar-based HiPIMS process, the Ne-HiPIMS lead to dense DLC films with increased mass density (up to 2.65 g/cm3) and a hardness of 23 GPa when deposited on steel with a Cr + CrN adhesion interlayer. Tribological testing by the pin-on-disk method revealed a friction coefficient of 0.22 against steel and a wear rate of 2 × 10−17 m3/Nm. The wear rate is about an order of magnitude lower than that of the films deposited using Ar. The differences in the film properties are attributed to an enhanced C ionization in the Ne-HiPIMS discharge.

Effects of diamond-like carbon thin film and wrinkle microstructure on cell proliferation

This paper aims to clarify the effects of diamond-like carbon (DLC) thin film and the wrinkle microstructure formed by depositing the DLC thin film on a poly(dimethylsiloxane) (PDMS) substrate on cell proliferation with a view to applying to cell scaffolds, which are essential technologies to control cellular activity and behaviors for cell therapy and therapeutic applications. Mouse myoblast cell (C2C12) culture tests using substrates with/without the DLC thin film and the wrinkle microstructure revealed that the cell proliferation was largely enhanced by the existence of the DLC thin film on the substrate. Moreover, it was examined how the size of the wrinkle of the DLC thin film deposited PDMS substrates affected cellular growth, and it was found that the wrinkle microstructure had the optimum range of the height difference of the wrinkle, from 0.7 to 1.0 μm as the surface roughness (Rc), for promoting cell proliferation.

UV laser annealing of Diamond-Like Carbon layers obtained by Pulsed Laser Deposition for optical and photovoltaic applications

One of the biggest challenge in optoelectronic devices is the necessity to provide a viable and reliable alternative to Transparent Conducting Oxide (TCO) and especially to Indium Tin Oxide (ITO). Graphene is a widely studied material and one of the best alternative to be used as conductive and transparent electrodes. It is well known that the difficulty to transfer graphene on another substrate is a serious limitation for its use on large scale devices. In this work, we explore Diamond-like Carbon (DLC) thin films prepared by Pulsed Laser Deposition (PLD) to be used as substrate for graphene-like layers. DLC thin films are excellent candidates due to their visible-range transparency being also a very good electrical insulator. Transmission measurements show the UV opaque character of the DLC layers, independently to the experimental parameters used to produce them. Thus, top-hat UV laser surface annealing can strongly modify the DLC thin film structure in order to bring conductivity to the first atomic layers. Raman spectroscopy and X-ray photoemission spectroscopy permit to confirm the graphitic character of the DLC surface. Optimizing PLD as well as laser annealing parameters is explored in detail in order to obtain comparable performances (conductivity and transparency) to ITO typical properties. Moreover, using a full-based laser process offers a complete compatibility with all technical steps of the microelectronic domain.