Diamond-like Carbon Growth Research Articles

Investigating different carbon-based target materials: Can we improve ionization in HiPIMS for the deposition of diamondlike carbon films?

Investigating different carbon-based target materials: Can we improve ionization in HiPIMS for the deposition of diamondlike carbon films?

On the growth of functionally graded self-lubricating layer during a plasma-assisted thermochemical treatment of M50NiL steel

Diamond-like carbon (DLC) with excellent mechanical properties has aroused great interest. However, the weak adhesion between the DLC film and steel substrate restricts its application. Considering that the addition of interlayers needs cumbersome steps, fabricating a functionally graded self-lubricating layer through one-step remains a challenge. We reported a novel integrated self-lubricating layer, inspired by the gradient structure formed during the traditional thermochemical treatment. That integrated layer from DLC structure gradual transition to nitrided diffusion layer is in-situ fabricated on the M50NiL steel through a plasma-assisted thermochemical treatment. The gradient structure possesses excellent wear resistance due to the self-lubricating of the DLC structure and provides sufficient adhesion strength. A deep insight into the relation between Fe5C2 crystal facet and growth of DLC is conducted by first-principle calculation and find low Miller Index of Fe5C2 facets are favorable for the growth of DLC. The thermodynamic calculation reveals that gradient structure formation is the collaboration effect of non-equilibrium and equilibrium processes.

Characterization and Parametric Optimization of Performance Parameters of DLC-Coated Tungsten Carbide (WC) Tool Using TOPSIS

In this work, we have deposited the diamond-like carbon (DLC) coating on the tungsten carbide (WC) tool insert using the thermal chemical vapor deposition (CVD) method. For the growth of DLC coating, sugarcane bagasse was used as a carbon precursor. Raman spectroscopy, a field emission scanning electron microscope (FESEM), and X-ray diffraction (XRD) were used to confirm the presence of DLC coating on the tungsten carbide tool inserts. The hardness tests were also performed for inspecting the microhardness induced by the self-developed DLC coating on the tungsten carbide (WC) tool insert. To determine the optimum process parameters for the turning operation on an aluminum (6061) workpiece using a self-developed DLC-coated tungsten carbide (WC) tool insert, we have applied the technique for order preference by similarity to ideal solution (TOPSIS) methods. The process parameters considered for the optimization were feed rate, cutting speed, and depth of cut. Whereas chosen response variables were flank wear, temperature in the cutting zone, and surface roughness. TOPSIS is utilized to analyze the effects of selected input parameters on the selected output parameters. This study in this paper revealed that it was advantageous to develop the DLC coating on the tungsten carbide tool inserts for the machining applications. The results also revealed that a 0.635 mm depth of cut, feed rate of 0.2 mm/rev, and cutting speed of 480 m/min were the optimum combination of process parameters.

Ion induced stress relaxation in dense sputter-deposited DLC thin films

Deposition of high-density and low-stress hydrogen-free diamond like carbon (DLC) thin films is demonstrated using a pulsed ionized sputtering process. This process is based on high power impulse magnetron sputtering, and high C ionization is achieved using Ne as the sputtering gas. The intrinsic compressive stress and its evolution with respect to ion energy and ion flux are explained in terms of the compressive stress based subplantation model for DLC growth by Davis. The highest mass density was ∼2.7 g/cm3, and the compressive stresses did not exceed ∼2.5 GPa. The resulting film stresses are substantially lower than those achieved for the films exhibiting similar mass densities grown by filtered cathodic vacuum arc and pulsed laser deposition methods. This unique combination of high mass density and low compressive stress is attributed to the ion induced stress relaxation during the pulse-off time which corresponds to the post thermal spike relaxation timescales. We therefore propose that the temporal ion flux variations determine the magnitude of the compressive stress observed in our films.

Catalytic growth of diamond-like carbon on Fe3C-containing carburized layer through a single-step plasma-assisted carburizing process

This article reports a study on catalytic growth of diamond-like carbon (DLC) on the Fe3C-containing carburized surface layer of M50NiL steel through a single-step plasma-assisted carburizing process. The catalytic effect of Fe3C on DLC growth was investigated by means of X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical and tribological tests demonstrate that the DLC growth endows the treated specimens with higher hardness, lower coefficient of friction and increased wear resistance than traditional carburization layer. First-principles calculations were conducted to verify the experimental observations and elucidate the mechanism for the catalytic growth of DLC on Fe3C surface. This study demonstrates that DLC can simultaneously form during carburization of steel under suitable processing conditions, resulting in a combination of DLC and carburized layers through a single-step process with help of the catalytic effect of Fe3C. This finding shows a promising approach to maximize the benefits of carburization treatment, and provides new clues for facilitating DLC production and improving traditional surface treatments for steels.

Growth of Diamond-Like Carbon and Icosahedral Boron Carbide by Chemical Vapor Deposition System

Diamond-like carbon (DLC) possesses an array of valuable properties: outstanding abrasion and wear resistance; chemical inertness; exceptional hardness; low coefficient of friction; and high dielectric strength. Methods used to deposit DLC include ion beam deposition, cathodic arc spray, pulsed laser ablation, argon ion sputtering, and plasma-enhanced chemical vapor deposition. In the present work, carbon nano-structures were doped by boron atoms to synthesize icosahedral boron carbide using Hot Filament Chemical Vapor Deposition(HFCVD) system. Raman spectroscopy, X-ray diffraction technique, Debye-Scherrer calculation, Tuinstra-Koenig formula and scanning electron microscopy results were presented and discussed.

Multifunctional three-dimensional nanodiamond-nanoporous alumina nanoarchitectures

Hybrid composite nanomaterials provide an attractive and versatile material platform for numerous emerging nano- and biomedical applications by offering the possibility to combine diverse properties which are impossible to obtain within a single material. In this work, we present the fabrication of novel hybrid diamond and amorphous diamond-like carbon (DLC) coated nanoporous alumina materials that exhibit multiple functionalities, such as high surface area, quasi-ordered nanopore structure, tunable surface chemistry and electrical conductivity, excellent biological, chemical and corrosion resistance. These multifunctional nanohybrid materials are fabricated using the plasma-induced carbonization method that effectively modifies the surface and the inside of the nanopores of anodic alumina, producing a homogenous ultrathin DLC protecting layer over the whole external and internal surfaces of the membranes. We demonstrate that the interplay between internal and external carbon supply is a critical factor for the formation of the ultrathin sp3-bonded carbon layer in the nanopores. This study brings new insights in the DLC growth mechanisms in confined nanospaces and opens new avenues to fabricate hybrid, chemically resistant and biocompatible carbon-coated nanoarchitectures on other inorganic supports.

Interlayer formation of diamond-like carbon coatings on industrial polyethylene: Thickness dependent surface characterization by SEM, AFM and NEXAFS

The coating of materials with diamond-like carbon (DLC) is a very common way to change and improve their basic characteristics. Although DLC is used on several substrates, the chemical and physical properties throughout the coating process on plastics are yet sparsely investigated. Two types of protective coatings one sp3-enriched (robust, r-type) and one with more sp2-centers (flexible, f-type) have been realized on polyethylene by PECVD deposition. SEM and AFM analysis of coated samples of DLC types revealed diverse surface topographies on different scales and images appeared even differently smoothed by the carbonaceous deposits. Grains of both DLC types are platelet-shaped and nearly double in size for the robust type indicating fundamental differences in the epitaxial DLC growth. NEXAFS spectroscopy showed significant details of carbon centers in chemically different neighborhood displaying a characteristic fingerprint behavior. Comparison of deposition models revealed a mechanism of interlayer formation which is discussed in detail. Interlayer formation is clearly the appropriate explanation of the process for the current carbon deposition between these two unequal materials. An improved understanding of hard DLC and soft polyethylene assembly is given in the presented work.

Estimation of Growth Rate of Diamond-Like Carbon Films Prepared by Pulse Plasma Chemical Vapor Deposition

The relationships between pulse frequency and growth rate and between pulse frequency and hardness were investigated for DLC (diamond-like carbon) films prepared by dc pulse plasma CVD (chemical vapor deposition). This study was focused on considering the overlap of the attenuation curve for the chemical species generated by a certain pulse with that for the species generated by the next pulse during DLC film fabrication. As a first-order approximation, the attenuation curves of all ion and radical species were assumed to follow the formula y=y0 · exp(-λt), where yo and λ are coefficients. The relationship between pulse frequency and growth rate was derived and compared with the experimental results. The theoretical curve agrees well with the experimental growth rate, indicating that the above approximation for all ion and radical species is useful for estimating the growth rate of DLC films in dc pulse plasma CVD. Moreover, a pulse frequency that gives the maximum film hardness existed. The higher the pulse frequency becomes, that is, the smaller the nonoverlapping ratio becomes, the greater the contribution of ion species to film fabrication. The hardness of the DLC films is small at low frequencies because insufficient numbers of ion species exist in the plasma. In contrast, the hardness slightly decreases at high frequencies owing to the excessive ion contribution to the growth of DLCs.

Comparative surface and nano-tribological characteristics of nanocomposite diamond-like carbon thin films doped by silver

In this study we have deposited silver-containing hydrogenated and hydrogen-free diamond-like carbon (DLC) nanocomposite thin films by plasma immersion ion implantation-deposition methods. The surface and nano-tribological characteristics were studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and nano-scratching experiments. The silver doping was found to have no measurable effect on sp 2–sp 3 hybridization of the hydrogenated DLC matrix and only a slight effect on the hydrogen-free DLC matrix. The surface topography was analyzed by surface imaging. High- and low-order roughness determined by AFM characterization was correlated to the DLC growth mechanism and revealed the smoothing effect of silver. The nano-tribological characteristics were explained in terms of friction mechanisms and mechanical properties in correlation to the surface characteristics. It was discovered that the adhesion friction was the dominant friction mechanism; the adhesion force between the scratching tip and DLC surface was decreased by hydrogenation and increased by silver doping.

Effect of substrate morphology on the roughness evolution of ultra thin DLC films

The effect of substrate roughness on growth of ultra thin diamond-like carbon (DLC) films has been studied. The ultra thin DLC films have been deposited on silicon substrates with initial surface roughness of 0.15, 0.46 and 1.08 nm using a filted cathodic vacuum arc (FCVA) system. The films were characterized by Raman spectroscope, transmission electron microscope (TEM) and atomic force microscopy (AFM) to investigate the evolution of the surface roughness as a function of the film thickness. The experimental results show that the evolution of the surface morphology in an atomic scale depends on the initial surface morphology of the silicon substrate. For smooth silicon substrate (initial surface roughness of 0.15 nm), the surface roughness decreased with DLC thickness. However, for silicon substrate with initial surface roughness of 0.46 and 1.08 nm, the film surface roughness decreased first and then increased to a maximum and subsequently decreased again. The preferred growth of the valley and the island growth of DLC were employed to interpret the influence of substrate morphology on the evolution of DLC film roughness.

Diamond like carbon coatings deposited by microwave plasma CVD: XPS and ellipsometric studies

Diamond-like carbon (DLC) films were deposited by microwave assisted chemical vapour deposition system using d.c. bias voltage ranging from −100 V to −300 V. These films were characterized by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry techniques for estimating sp 3/sp 2 ratio. The sp 3/sp 2 ratio obtained by XPS is found to have an opposite trend to that obtained by spectroscopic ellipsometry. These results are explained using sub-plantation picture of DLC growth. Our results clearly indicate that the film is composed of two different layers, having entirely different properties in terms of void percentage and sp 3/sp 2 ratio. The upper layer is relatively thinner as compared to the bottom layer.

Substrate bias effects during diamond like carbon film deposition by microwave ECR plasma CVD

Abstract Diamond like carbon (DLC) coatings were deposited on silicon(1 1 1) substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using a plasma of Ar and CH4 gases under the influence of DC self bias generated on the substrates by application of RF (13.56 MHz) power. DLC coatings were deposited under the varying influence of DC bias (−60 V to −150 V) on the Si substrates. Deposited films were analyzed by different techniques like: X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), Hardness and elastic modulus determination technique, Raman spectroscopy, scanning electron microscopy (SEM) and contact angle measurement. The results indicate that the film grown at −100 V bias has optimised properties like high sp3/sp2 ratio of carbon bonding, high refractive index (2.26–2.17) over wide spectral range 400–1200 nm, low roughness of 0.8 nm, high contact angle (80°) compared to the films deposited at other bias voltages (−60 V and −150 V). The results are consistent with each other and find august explanation under the subplantation model for DLC growth.

Simulations of the structure characteristic of diamond-like carbon films formed by ion-beam-assisted deposition

Molecular dynamics (MD) simulation was used to study the growth process of dia mond_like carbon (DLC) films synthesized via ion_beam_assisted deposition (IBAD ). The C2 molecules and Ar ions were selected as deposition and assis tance pr ojectiles, respectively. The influence of the impact energy of Ar as well as the assistance/deposition atomic ratio (Ar/C), on the film structure was investiga ted. The transient mobility and the migration of C adatoms caused by Ar impact were studied. Our results indicate that the impact-induced high recoil energy a nd displacement of deposited C atoms play a leading role in the growth of DLC f ilms. This can be attributed to the incident energy and momentum of assistance Ar. Our results agree well with the experimental observation. Furthermore, it e xplains the growth mechanism partly.

Mechanism of sp 3 bond formation in the growth of diamond-like carbon

The existing model of the mechanism of sp 3 bond formation is modified to include interstitials as an explicit species of higher total energy. The interstitial species is equivalent to the free interstitial in a radiation enhanced diffusion process, and the model is a simple way to include this process in a mechanism. The interstitial becomes an sp 3 or sp 2 site by passing over a small potential barrier, during the cascade. Sp 3 formation occurs by densification as previously. The sp 3 sites can anneal or relax into sp 2 by passing over a large potential barrier.

Investigation of ion-beam-assisted deposition of DLC films by molecular dynamics simulation

In this paper, the growth of diamond-like carbon (DLC) films via ion-beam-assisted deposition (IBAD) is simulated using molecular dynamical simulation. The C2 molecules and Ar ions are selected as deposition and assistance projectiles, respectively. The impact energy of Ar ranges from 10, 30, 50 to 100 eV. We focus our examination on the effects of the assistance/deposition atomic ratio and the incident energy of Ar ions on the growth dynamics and film structure. Simulation results show that the mobility of surface atoms in the cascade region is enhanced by impacting energetic Ar ions, especially at elevated flux and moderate energy, which favor the growth of denser and smoother films with better adhesion to the substrate. Our results agree well with the experimental observation.

Observation and characteristics of mechanical vibration in three-dimensional nanostructures and pillars grown by focused ion beam chemical vapor deposition

The Young’s modulus of diamond-like carbon (DLC) pillars was measured by means of mechanical vibration using scanning electron microscopy. The DLC pillars were grown using Ga+ focused ion beam-induced chemical vapor deposition with a precursor of phenanthrene vapor. The Young’s modulus of the DLC pillars was around 100 GPa at vapor pressure of 5×10−5 Pa and it had a quality (Q) value of resonance exceeding 1200. There seemed to be a balance between the DLC growth rate and surface bombardment by the ions, and this played an important role in the stiffness of the pillars. Some of the DLC pillars showed a very large Young’s modulus over 600 GPa at low gas pressure conditions.

Changing the mechanical and structural properties of diamond-like carbon by Ca-O-incorporation

Diamond-like carbon (DLC) is an amorphous carbon coating with partly diamond-like properties which exhibit superior mechanical as well as tribological behavior. Due to their chemical and wear resistance, the low permeability and the promising biocompatibility DLC is a potential candidate for protective thin coatings in various applications [1]. The metastable DLC consists of carbon in different hybridization for example sp3, sp2 or sp1 bonded atoms. DLC is a so called hydrogenated amorphous carbon film. The hydrogen is incorporated into the carbon network or exists in a metastable solid solution, because DLC is far away from equilibrium conditions. Additional elements like nitrogen, silicon and titanium may effect a further adaptation of the DLC properties according very specific demands [1, 2]. In order to enlarge the applicability of DLC for biomedical purposes, the addition of calcium should be able to influence bone formation may be of considerable relevance. The intention of the following study is to gain first the information about the influence of Ca-O-incorporation on the mechanical and structural properties of DLC. The generation of the conventional DLC and the CaO-DLC was carried out by exploiting a direct current discharge for plasma formation. Before coating deposition the titanium-substrates were polished to a 1 μm finish and cleaned ultrasonically in ethanol. After an additional in situ cleaning by bombarding with argon ions the generation of the metastable amorphous coatings took place. The substrate is sufficiently negative biased in relation to the plasma in order to achieve ion bombardment before and during the DLC growth. The CaO was dissolved in water, and the CaO-H2O was evaporated in the plasma chamber. For the generation of Ca-O-DLC, the gaseous precursor (benzene) together with the CaO-H2O vapor is decomposed due to the direct current discharge under a pressure of between 0.005 and 0.05 Pa. For processing conventional DLC, only benzene is supplied into the plasma chamber. The negative bias of the titanium-substrate attracts ions, loaded particles as well as other decomposed fragments and leads to the coating formation. Conventional and Ca-O-modified DLC of about 5 μm thickness were deposited on the titanium. The Ca-O-modified amorphous carbon fractured cross-sections reveal qualitative differences in comparison to conventional DLC. Fig. 1 presents a fractured cross-section of the Ca-O-modified DLC. The Ca-O-modified amorphous carbon exhibits no smooth and featureless fractured surface like that known for DLC [3], but some topography. The damaged Ca-ODLC cross-section exposes grooves, fluting or stretched hillocks which are perpendicularly orientated to the coated surface. The existence of this topography confirms a less brittle fracture behavior of the amorphous Ca-O-DLC coating and also points to changed

Improved adhesion of diamondlike coatings using shallow carbon implantation

A surface layer of metal carbides provides an excellent interface to achieve a highly adherent diamondlike carbon (DLC) coating. A plasma immersion ion implantation (PIII)-based procedure is described, which delivers a high retained dose of implanted carbon at the surface of aluminum alloys. A shallow implantation profile, followed by argon sputter cleaning and continued until a saturated carbon matrix is brought to the surface, provides an excellent interface for subsequent growth of DLC. At a carbon retained dose above 1018 atoms/cm2 the DLC adhesion exceeds the coating's cohesion strength. Regardless of the silicon content in the aluminum, the coating produced by this method required tensile strengths typically exceeding 140 MPa to separate an epoxy-coated stud from the coating in a standard pull test. Improved DLC adhesion was also observed on chromium and titanium. The reported tensile strength is believed to substantially exceed performance of DLC coatings produced by any other method.

Surface enhancement by shallow carbon implantation for improved adhesion of diamond-like coatings

A surface layer of metal carbides provides an excellent interface to achieve a highly adherent diamond-like carbon (DLC) coating. A plasma immersion ion implantation based procedure is described which delivers a high retained dose of implanted carbon at the surface of aluminum alloys. This proposed implantation procedure employs a low target bias of only 10–12 kV, a pulse repetition rate of around 5 kHz, and a duty cycle of 25%. The resultant shallow implantation profile, followed by an argon sputter cleaning, is continued until a saturated carbon matrix is brought to the surface providing an excellent interface for subsequent growth of DLC. At a carbon retained dose above 1018 atoms/cm2, the DLC adhesion exceeds the coating’s cohesion strength. Regardless of the silicon content in the aluminum, the coating produced by this method required tensile strengths typically exceeding 150 MPa to separate an epoxy coated stud from the coating in a standard pull test. Improved DLC adhesion was also observed on chromium and titanium. The reported tensile strength is believed to meet the majority of industrial applications.