Diamond-like Carbon Thin Films Research Articles

Structural, electrical and mechanical behavior evaluation of palladium doped diamond like carbon thin films

Pure and palladium (Pd) doped Diamond-like carbon (DLC) thin films have been deposited on glass substrates by using KrF Excimer laser having 248 nm wavelength. The doping concentration of Pd in DLC is 0%, 0.5%, 1.0%, 1.5% and 2.0%. Internal structure, surface morphology, mechanical and electrical characteristics have been carried out by Raman spectroscopy, scanning electron microscopy (SEM), Vickers hardening and four point probes, respectively. Using Raman spectra an improved graphitic behavior of DLC has been observed with increase of Pd contents. Some nano rods were observed at the surface of pure and Pd doped DLC thin films. With increase of Pd concentration in DLC, initially there is an accumulation of particles is observed and when the doping concentration is high i.e. at 2%, cracks formation takes place. The electrical resistivity is decreased by adding Pd into DLC thin films. Further, doping of Pd decreased the hardness of films. These characteristics of Pd doped DLC with increased hardness and electrical conductivity make it potential candidate for electronic devices. Also, doping enhance the graphitic behavior, therefore this material can be used for anti-bacterial and anti- cancerous activities.

Accurate estimation of DLC thin film hardness using genetic programming

Abstract In the current research, diamond-like carbon thin films are deposited on silicon substrates by plasma-enhanced chemical vapor deposition. The effect of argon-C2H2 flow rate, hydrogen flow rate and deposition temperature on the thin film hardness is investigated. Morphology of the DLC films is investigated by scanning electron microscopy and atomic force microscopy, while the nano-hardness is investigated using nanoindentation. Raman spectroscopy is used for the characterization of the structural properties of the film. A metamodel of the DLC deposition process with argon- C2H2 flow rate, H2 flow rate and deposition temperature as the regressor variables and coating hardness as the response is built by using a novel symbolic regression approach. A state-of-the-art machine learning approach - genetic programming (GP) - is used for the symbolic regression. By carefully evaluating the performance of the current GP metamodel against a classical RSM (response surface methodology) metamodel, it is seen that the GP significantly outperforms RSM.

Study on Minimally Invasive System of Brain Surgery

The aim of this research was to examine the thermal injury in the brain after a minimally invasive electrosurgery with the chromium nitride (CrN) and diamond-like carbon (DLC) surface modifications. Three-dimensional (3-D) brain models were reconstructed to simulate the electrosurgical procedure. Data indicated that the temperature decreased significantly when minimally electrosurgery with nanostructured CrN and DLC thin films were used, and that it continued to decrease with increasing film thickness. The present study 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 the brain. However, further tests in the clinical trial must be evaluated to confirm the effect and safety of promising findings in the brain electrosurgery.

Diamond-like Carbon Thin Film Coating for Application on Heterojunction Solar Cells by ECR-CVD System

Diamond-like Carbon (DLC) film has the ability to change the refractive index value achieved high transmittance for potential applications of antireflection coating. DLC films were deposited on heterojunction solar cells by the ECR-CVD (Electron Cyclotron Resonance Chemical Vapor Deposition) method using Acetylene (C2H2) and Argon (Ar) gases. DLC coating affects ITO (Indium tin oxide), causing the electrical and resistivity of heterojunction solar cell vary according to the coating time. The surface and thickness of the DLC films was measured with an atomic force microscope. Illuminated I-V characteristic was investigated by photo-I–V measurements. The suitable acetylene anti-reflection deposition time at 0.40 minutes. Therefore, heterojunction solar cell was fabricated on a substrate using the optimized DLC films as an anti-reflection coating and it obtained an increase efficiency of about 1%.

Avaliação de desgaste por perda de massa de sistema extrator de moldes de injeção de termoplásticos revestidos com filme fino de DLC

O presente trabalho tem por objetivo, a deposição de filmes finos de DLC sobre componentes do sistema extrator de moldes de injeção, verificando a influência deste revestimento superficial no desgaste desses componentes, sob diferentes configurações de lubrificação superficial. Para esta avaliação, pinos extratores, atualmente produzidos em aço AISI H13 e nitretados à gás, foram revestidos com um filme fino de DLC (carbono tipo diamante, do inglês Diamond Like Carbon) e buchas extratoras foram confeccionadas em AISI P20 e AISI H13, e, posteriormente, temperadas e revenidas. O filme fino de DLC foi depositado em uma câmara com sistema PECVD (deposição química a vapor assistida por plasma, do inglês Plasma Enhanced Chemical Vapor Deposition) auxiliado por confinamento eletrostático de plasma. Um dispositivo que simula o sistema de extração de um molde de injeção foi utilizado para testar o comportamento ao desgaste dos conjuntos pino-bucha propostos, em função do aumento do número de ciclos. O desgaste nos pinos foi avaliado quantitativamente por perda de massa, após 100.000 ciclos. Os resultados da perda de massa mostram que para as amostras sem utilização de graxa lubrificante, a taxa de desgaste foi consideravelmente menor. Os pinos que menos apresentaram desgaste foram os dos conjuntos PS e HS, ambos sem utilização de graxa, com perda de 5,400 e 5,467 mg, respectivamente. Com isto, ficou evidenciado a possibilidade de utilização de pinos com revestimento de DLC sem a utilização de graxa lubrificante em sistemas extratores de moldes de injeção e que isto ainda propiciou uma redução considerável na taxa de desgaste.

Diamond-Like Carbon for the Fast Timing MPGD

The present generation of Micro-Pattern Gaseous Detectors (MPGDs) are radiation hard detectors, capable of detecting effciently particle rates of several MHz/cm2, while exhibiting good spatial resolution (≤ 50 µm) and modest time resolution of 5-10 ns, which satisfies the current generation of experiments (High Luminosity LHC upgrades of CMS and ATLAS) but it is not sufficient for bunch crossing identification of fast timing systems at FCC-hh. Thanks to the application of thin resistive films such as Diamond-Like Carbon (DLC) a new detector concept was conceived: Fast Timing MPGD (FTM). In the FTM the drift volume of the detector has been divided in several layers each with their own amplification structure. The use of resistive electrodes makes the entire structure transparent for electrical signals. After some first initial encouraging results, progress has been slowed down due to problems with the wet-etching of DLC-coated polyimide foils. To solve these problems a more in-depth knowledge of the internal stress of the DLC together with the DLC-polyimide adhesion is required. We will report on the production of DLC films produced in Italy with Ion Beam Sputtering and Pulsed Laser Deposition, where we are searching to improve the adhesion of the thin DLC films, combined with a very high uniformity of the resistivity values.

Crack evolution in diamond-like carbon films on steel substrates during nano-indentation

Fracture behaviors of thin hard diamond-like carbon (DLC) films were investigated considering the effects of plastic deformation of steel substrates. Nano-indentation tests for DLC films on SUS304 and M50 steels were conducted. The nucleation and propagation of film cracks were analyzed using the extended finite element method (XFEM). The ultimate tensile strength, fracture energy release rate and toughness of the films were evaluated. Results showed that cracks in DLC films on M50 steel substrates nucleated on the top surface of the films during nano-indentation; however, the first crack initiated at the bottom surface of DLC films on SUS304 steel because of its low yield strength. Large plastic deformation of the steel substrate was generated under nano-indentation, leading to consequent high tensile stress that concentrated first at the bottom surface of the films due to the film bending effect.

Barrier coating and plasmonic effect by using diamond-like carbon and silver nanoparticles on quantum dots sensitize solar cells

Effects of diamond-like carbon (DLC) and Ag nanoparticles (Ag NPs) on photoanode of quantum dot sensitized solar cell (QDSSCs) have studied for the first time. Photoanodes include thin films of the TiO2 deposited on the FTO substrate, subsequently, graphene and CdS quantum dots (QDs) added on. Some photoanodes decorate by Ag nanoparticles and DLC thin film. Current density–voltage (J–V) characterization showed that the short-circuit current density (Jsc) and power conversion efficiency (PCE) of QDSSCs with localized surface plasmon resonance (LSPR) of Ag NPs and anti-corrosion, photon and electron barrier properties of DLC thin film increase photon harvesting and improve solar cells performance. Jsc of this configuration increased from about 8.87 to 14.6 mA cm−2, nearly doubled. The Ag NPs scatter photon and increase the photon harvesting in QDs. Results were showing that the presence of a thin film of DLC on TiO2/CdS/G photoanodes increased the efficiency by 97%, short circuit current by 64%, and open circuit voltage by 16%. Also, the efficiency change from 0.8 to 1.58 in the presence of both DLC and Ag NPs in cells in compare with cells without Ag NPs and DLC.

A new method to calculate the laser induced damage threshold of thin film

The traditional method for calculating laser induced damage threshold (LIDT) value of thin films is based on qualitative or semi-quantitative empirical formulas, the results obtained are of low accuracy and credibility. A new method for accurately calculating LIDT values of thin films is presented in this paper, when a thin film is subjected to intense laser irradiation, the distribution models of internal electric field-absorption-temperature field are constructed respectively. In general, when the corresponding temperature value at a certain time and a certain depth is the maximum value in the temperature field distribution of the thin film, the incident laser energy is the damage energy threshold of the thin film at this time, and the depth is the location where the thin film is most prone to damage. Therefore, an expression of the relationship between the damage energy threshold and the maximum temperature can be established, which can be used to combine to the relation expressions of critical electron density with temperature maximum and damage energy threshold respectively, the LIDT values of the thin films can be solved simultaneously. In order to verify the reliability of the method, the LIDT values of single-layer titanium dioxide, silicon dioxide and diamond-like carbon (DLC) thin films were calculated respectively, their experimental values are obtained at the same time, and each film’s theoretical value was compared with the experimental value several times The results show that their theoretical values and experimental values are consistent, indicating that this new method for calculating LIDT of thin film is feasible, and it not only enriches and develops the traditional theoretical calculation methods, but also provides a new judgment basis for evaluating the resistance to laser damage of thin films.

Experiment of frictional vibration performance of the micro-texture of DLC thin film with dry gas seal rings

The frictional vibration performances of textured surface coated with DLC(Diamond-like Carbon)film of dry gas seals ring were investigated. In the meantime, the mechanism of textured surface on interfacial tribological behavior was revealed under dry frictional condition. The acceleration and frictional force were measured by using universal friction and wear tester which type is MMW-1, and the surface topographies were measured by using SEM and ST400 three-dimensional non-contact surface topography instrument. Results show that the textured surface coated with DLC film can significantly improve the tribological behavior of dry gas seal. Textured surface with reasonable size parameters can capture debris and avoid strong impact between the friction pairs, which improves effectively the tribological behavior of interfaces.

The effect of multilayer dielectrics on electrical characteristics of thin film capacitors for high energy density application

Hydrogenated diamond-like carbon and aluminum oxide thin films were used in combination to fabricate capacitors in order to investigate the effect of multiple dielectrics on dielectric constant, breakdown strength, and energy density. It was found that capacitors made by combining the two materials exhibited significantly higher breakdown strength and energy density than capacitors made with either dielectric material alone. In addition, the model for calculating the combined dielectric constant for multiple dielectrics was validated. The highest energy density (U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> = 5.2 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) capacitor made for this investigation had a breakdown strength of 5.3 MV/cm and an effective dielectric constant of 5.3.

Sub-micron structuring/texturing of diamond-like carbon-coated replication masters with a femtosecond laser

Diamond-like carbon (DLC) coatings have very attractive mechanical and tribological properties, i.e. high hardness, low friction and high wear resistance. Therefore, DLC is often used as a solid lubricant in moulds for injection moulding. Laser processing of DLC with ultrashort lasers, i.e. femtosecond lasers, can be performed both at micron and sub-micron scales, namely by producing laser-induced periodic surface structures (LIPSS). In this research, the effects of laser structuring/texturing on DLC properties are investigated. First, the laser-processing parameters were optimised to produce uniform LIPSS without damaging a thin DLC film and then the properties of the textured DLC-coated substrates were studied. It was determined that the tribological properties of the processed surfaces remained unchanged, but the hardness of the structured/textured DLC layers was reduced significantly. Although GAXRD and Raman spectroscopy did not show any significant crystallisation of the DLC coating after the laser irradiation, the analysis indicated that a thin graphitised layer had been formed on the surface as a result of the femtosecond laser processing.

Diamond-Like Carbon Thin Film Electrodes for Microfluidic Bioelectrochemical Sensing Platforms.

This work aims to utilize diamond-like carbon (DLC) thin films for bioreceptor immobilization and amperometric biosensing in a microfluidic platform. A specific RF-PECVD method was employed to prepare DLC thin film electrodes with desirable surface and bulk properties. The films possessed a relatively high sp2 fraction, a moderate electrical conductivity (7.75 × 10-3 S cm-1), and an optical band gap of 1.67 eV. X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy revealed a presence of oxygen-containing functional groups on the DLC surface. The DLC electrodes were integrated into polydimethylsiloxane (PDMS) microfluidic electrochemical cells with the channel volume of 2.24 μL. Glucose oxidase (GOx) was chosen as a model bioreceptor to validate the employment of DLC electrodes for bioelectrochemical sensing. In-channel immobilization of glucose oxidase (GOx) at the DLC surface was realized through carbodiimide covalent linkages. Enzyme bound DLC electrode was confirmed with the redox potential at around -79 mV vs NHE in 0.1 M phosphate buffer pH 7.4. Amperometric flow-injection glucose sensing at a potential of -0.45 V vs Ag in the absence of standard redox mediators showed the increase of current response upon increasing the glucose concentration. The sensing mechanism is based on the reduction process of H2O2 liberated from the enzymatic activity. The proposed model for the catalytic H2O2 reduction to H2O on DLC electrodes was attributed to the dissociation of C-O bonds at the DLC surface.

Effect of Electrolyte Type on Properties of Diamond - like Carbon Films Electrodeposited onto N-Type Si Substrate, Application as Electrode for Supercapacitors

In this work, diamond-like carbon (DLC) thin films were successfully electrodeposited onto n-type Si(100) substrate using three types of organic electrolyte (as carbon precursor) namely dimethylsulfoxide (C2H6OS), acetonitrile (CH3CN) and ethanol (CH2CH2OH). The effect of electrolyte type on morphological, structural and chemical properties was investigated using Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray and X-ray diffraction (XRD). The DLC films Raman spectra show the films are amorphous and the more disorder film is obtained by dimethylsulfoxide (DMSO). These results were confirmed by energy dispersive X-ray and XRD techniques. The SEM observations show that the DLC films were uniformly deposited on the whole Si substrate surface and that it contains of compact and small spherical grains with uniform distribution. Moreover, it was found that the DLC film obtained from a DMSO electrolyte is more conductive, which enables it to be more favorable for the fabrication of a good supercapacitor electrode. The study of electrochemical properties of Si and DLC/Si electrode has shown that the deposition of DLC films from DMSO electrolyte remarkably improves the electrochemical activity of Si electrode and the specific capacitance. Indeed, it allows to get a specific capacitance of 17 mF/cm2 in KOH aqueous solution at scan rate of 5 mV/s with capacitance retention of 95% after 4000 cycles. Thus, the deposition of DLC film from DMSO electrolyte onto silicon substrate can be considered as a simple and economical method to fabricate of a performant electrode of supercapacitors.

Monopolar Resistive Switching in Diamond-Like Carbon Films

Current–voltage characteristics were studied for Pt/diamond-like C/Pt structures based on thin (20 nm) diamond-like carbon films, when the ratio between carbon phases with sp2 and sp3 hybridization was controlled by the film growth conditions at the high-frequency diode sputtering method. The effects of resistive switching from the initial high-resistive state to a low-resistive state at an applied voltage of V ~ 3 V and reverse switching at V ~ 0 are detected. These effects are symmetric with respect to change in voltage polarity and are associated with the change in the hybridization type of local carbon regions, which causes switching from the high- to low-resistive state in strong (~106 V/cm) fields because of sp3 → sp2 transitions and reverse switching in the field absence. The high-to-low resistance ratio reaches ~50.

Structural, morphological, electrical and optical properties of Cu doped DLC thin films

In this research, effect of copper (Cu) doping on the structural, optical, morphological and electrical characteristics of diamond like carbon (DLC) thin films have been investigated. Thin films of DLC and Cu doped DLC (Cu-DLC) have been deposited on glass substrates by pulsed Laser Deposition (PLD) technique. XRD results showed that at 1.5% of Cu doping, Cu form cluster in DLC. Below of this doping ratio, Cu has amorphous form in DLC. AFM reveals that the minimum surface roughness was observed for the 1.0% DLC thin film with the root mean square surface roughness (Rrms) of 2.07. The Rrms values for the 1.5%, 2.0% and 2.5% Cu-DLC thin films are 2.45, 3.14 and 3.89 respectively. The average sheet resistivity of films is decreased by increasing the Cu concentration, according to Four Point Probe technique.

Micrometric Growth Defects of DLC Thin Films

Defects in diamond-like carbon coatings deposited on corrosion sensitive 100Cr6 steel have been studied. Diamond-like carbon (DLC) thin films are promising for corrosion protection due to chemical inertness and low electrical conductivity. Nevertheless, the performance of these coating is highly sensitive to the presence of uncoated areas. These defects represent the primary way of substrate degradation in aggressive environments. An in situ optical microscopy coupled to an electrochemical activation was developed to reveal micrometric growth defects and observe that they were at the origin of corrosion. A square wave voltammetry was applied to increase the sensitivity of electrochemical techniques based on the detection of the dissolution of the bare metal surface triggered by the presence of uncoated spots. This method can be utilized to quantify defect density arising from vapor deposition processes.

Research On Secondary Electron Emission Characteristics of Diamond-Like Carbon Thin Films

In modern particle accelerators, the build-up of electron cloud is a main limiting factor for the achievement of high-quality beam. Among the techniques to mitigate it, coating the internal walls of the beam pipes with a thin film which has a low secondary electron yield (SEY) is considered to be one of the most effective means. From several earlier studies, it was found that diamond-like carbon (DLC) thin films are potential coatings. This paper is mainly about the research on secondary electron emission characteristics of DLC thin films. The secondary electron emission (SEE) tests were done at temperature of 298 K and vacuum pressure of 2 × 10–9 Torr. Here, we obtained the characteristics of the SEE from DLC film coatings with different thickness under ultrahigh-vacuum (UHV) conditions. The maximum secondary electron yield (SEY), δmax, of the DLC thin films under different primary electron doses were also obtained, respectively.

On the adhesion and wear resistance of DLC films deposited on nitrile butadiene rubber: A Ti-C interlayer

To promote the adhesion strength between diamond-like carbon (DLC) films and nitrile butadiene rubber (NBR) substrates, titanium-doped carbon (Ti-C) films prepared by dual-target magnetron sputtering under varied substrate bias voltages were used as an interlayer on the rough NBR. The surface topography and structure of Ti-C films were investigated by atomic force microscopy (AFM) and Raman spectra. Raman analysis indicates that the increase of substrate bias voltage leads to an increase of the number or the size of sp2 clusters in the Ti-C interlayer. The adhesion strength and tribological properties of DLC films coated on NBR substrate were scrutinized by a scratch tester and a ball-on-disk tribometer, respectively. It was found that DLC film with a Ti-C interlayer at a certain bias voltage exhibited superior wear resistance with a low coefficient of friction (CoF) during the sliding of 6000 laps. No clear damages in the coatings were observed from the wear tracks. Besides, the scratch test also revealed a reliable adhesion when the interlayer was prepared at −150 V, as confirmed by a scratch crack width of ~50 μm as compared to that of the pure DLC film increasing to ~ 120 μm. Therefore, a Ti-C interlayer could significantly enhance the adhesion and wear resistance of DLC thin films deposited on NBR.

Adhesion, biological corrosion resistance and biotribological properties of carbon films deposited on MAO coated Ti substrates

A thin diamond-like carbon (DLC) film, a graphite-like carbon (GLC) film and a thick diamond-like carbon (PE-DLC) film are deposited on the micro arc oxidation (MAO) coated pure titanium substrates using a hybrid ion beam deposition system, magnetron sputtering and plasma enhanced chemical vapor deposition, respectively. The microstructure, adhesion, biological corrosion resistance and biotribological properties were determined. The results showed that the three duplex coatings presented uneven surface features and increased binding force. The binding force of the duplex coatings was strongly affected by the bonding strength between the MAO coating and Ti substrate. Although the roughness Ra of the three duplex coatings was high, their friction coefficients were small (under 0.22) in the SBF solution. The MAO/DLC and MAO/GLC coatings showed an excellent tribological behavior and corrosion resistance in the SBF solution.