Diamond-like Films Research Articles

High Temperature Characterization of a MIS Schottky Diode Based on Diamond-Like Carbon Nanocomposite Film

Many kind of materials have been inserted between metals and semiconductors to obtain metal–interlayer–semiconductor (MIS) Schottky diodes with higher barrier height. It is well known that the interlayer materials have to meet some requirements such as hold on the substrate, thermal stability and wear resistance. In this context, the diamond-like carbon (DLC) films seem good candidates as a material that can fulfill these requirements due to their superior properties. In this study, sulfur doped diamond-like carbon (S-DLC) nanocomposite film was deposited electrochemically, and it was used as an interlayer to fabricate an Au/S-DLC/p-Si MIS Schottky diode. An Au/p-Si metal semiconductor diode was also fabricated for comparison. The electrodeposited S-DLC film was characterized by scanning electron microscopy, Raman spectroscopy and x-ray photoelectron spectroscopy. Temperature dependence of the current–voltage (I–V) characteristic of the diodes was studied in the range of 300–700 K. The ideality factors (n) and barrier heights (Φb) were calculated from the forward bias I–V characteristics. It was observed that both parameters showed temperature dependence. Barrier height values were increased with increasing temperature, while ideality factors values were decreased. The observed non-linearity in Richardson plots were explained by Gaussian distributions of inhomogeneities of barrier heights. Modified Richardson plots were used to obtain actual values of barrier height. It was shown that S-DLC film can be a good candidate for the high temperature diode applications.

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%.

Dielectric Losses in Nanosized Ferroelectric and Diamond-Like Films on SHF

The article considers the issues of receiving nanosized Ba0,8Sr0,2TiO3 ferroelectric films and diamond-like films in the range of 10‒60 GHz with various thickness between 0.1‒10 μm and their dielectric properties. Peculiarities of SHF dissipation measuring method in dielectric films are discussed. It shows the influence of structural perfection of films on the value of losses of SHF energy.

Comparison of Transmission Electron Microscopy and X-Ray Reflectometry Data in the Study of the Structure of Silicon-Carbon Nanocomposite Films

Vanadium-doped diamond-like silicon-carbon films have been studied by X-ray reflectometry and transmission electron microscopy. A comparison of the data obtained has shown that the layered structure of the films is retained over an area of about 100 mm2 at a total film thickness of 3–4 µm and layer thicknesses of 10–40 nm. The film surface has been examined by semi-contact probe microscopy. It is demonstrated that the root-mean-square roughness decreases by an order of magnitude (from 2.0 to 0.2 nm) with an increase in the vanadium content in the film from 12 to 17 at %.

An Apparatus for Depositing Carbon Films in Magnetron Sputtering under Conditions of Photoactivation of a Film Surface

An apparatus for depositing thin carbon films in magnetron sputtering under the conditions of photoactivation of the film surface is described. Studies of the phase composition of films that were obtained under different operating conditions of the apparatus revealed the presence of carbon atoms in the sp1 and sp3 hybridized states. A diamond-like film, a film containing carbine, and a graphite film were obtained on this apparatus.

Proposal of a new formation mechanism for hydrogenated diamond-like carbon transfer films: Hydrocarbon-emission-induced transfer

Diamond-like carbon (DLC) is one of the most promising solid lubricants for sliding against other materials, such as steel, alumina, and silicon carbide (SiC). During sliding, a DLC transfer film is usually formed on the counterpart surface, affording a low friction coefficient. It is well known that hydrogen in DLC strongly promotes the formation of the DLC transfer film. To further improve the lubricity of DLC, we investigate the formation mechanisms of the DLC transfer film on amorphous SiC and the influence of hydrogen on transfer film formation using reactive molecular dynamics simulations. In addition to the conventional transfer mechanism induced by surface adhesion, we herein propose the new transfer mechanism of “hydrocarbon-emission-induced transfer”. In the proposed transfer mechanism, hydrocarbon molecules are emitted from the DLC surface and subsequently adsorb on the counterpart surface during the continuous grinding of the sliding interface, ultimately generating the DLC transfer film. Furthermore, the addition of hydrogen atoms to DLC slightly increases the adhesion-induced transfer and greatly accelerates the “hydrocarbon-emission-induced transfer”, collaboratively contributing to substantial DLC transfer film formation. Thus, we suggest that the experimentally observed promotion of DLC transfer film formation by hydrogen is largely attributable to our proposed mechanism of “hydrocarbon-emission-induced transfer”.

Infrared and mechanical properties of the oxygen-doped non-hydrogenated diamond-like carbon film prepared by pulsed laser deposition

The non-hydrogenated diamond-like carbon films were prepared by the femtosecond laser in the oxygen atmosphere, and the influence of the oxygen atmosphere on the microstructural, surface, infrared and mechanical properties of the oxygen-doped diamond-like carbon films were researched. The oxygen atmosphere was propitious to reduce the granules on the surfaces but increase the surface roughness of the diamond-like carbon DLC films. During the pulsed laser deposition, the carbon and oxygen atoms were inclined to form the CO bond, CO bond and CC hybridized bond, when the oxygen pressure was lower than 5 m Torr. Although the CO and CO bonds led one additional absorption band and two additional absorption peaks in the infrared spectra of the oxygen-doped diamond-like carbon films, their transmission in the medium infrared band increased. Nano-hardness of the DLC films was reduced when the oxygen pressure increased dominantly because the CC sp3 bonds with higher atomic binding energy were replaced the CO bonds with lower atomic binding energy.

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.

Electron spectroscopy of various nanostructured carbon films

X-ray photoelectron spectroscopy technique have been used to study carbon films obtained by means of ion-plasma deposition in the plasma of different chemical composition. The detailed analysis of electron spectroscopy data made it possible to determine the structure of the films and the influence of nitrogen and hydrogen admixture in plasma on the structural properties. Diamond-like films are obtained in pure argon plasma, graphite-like and carbon chain structures correspond to nitrogen and hydrogen addition respectively.

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.

Excellent mechanical, tribological and anti-corrosive performance of novel Ti-DLC nanocomposite thin films prepared via magnetron sputtering method

Ti-doped diamond-like carbon nanocomposite thin films with different Ti contents are prepared by closed field unbalanced magnetron sputtering. Designed Ti target current increases from 0.3A to 1.0A. The effect of Ti content on microstructures and properties is investigated. The phases of nano-TiC and amorphous carbon are confirmed. The film (containing less than 50% sp3 C content) deposited with a Ti target current of 0.4A obtains the highest hardness of 44.6 GPa, which is rarely reported. Besides, the film with a Ti target current of 0.3A exhibits the lowest the friction coefficient of 0.02 and 99.10% reduction in wear rate compared with the untreated specimen due to its lubricating effect and the gradient multilayer structure. Moreover, the films have a high open-circuit corrosion potential, a low anodic current density and a wide passivation range, indicating its enhanced corrosion resistance. Most importantly, these inspiring results demonstrated that the excellent mechanical, tribological and anti-corrosion properties can be realized simultaneously by introducing the as-deposited films with the merits of high hardness, self-lubricating and chemical inertness.

Electron Spectroscopy of Thin Nanocarbon Films

This work presents the results of the X-ray photoelectron spectroscopy investigation of carbon films obtained by ion-plasma deposition at various plasma compositions. The detailed analysis of X-ray photoelectron spectra makes it possible to determine the structure of the deposited films and the influence of the presence of nitrogen and hydrogen in the plasma on the structure. Diamond-like films are obtained in pure argon plasma. The addition of nitrogen leads to a dramatic increase in the graphite-like phase while the addition of hydrogen corresponds to the formation of carbon chains.

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 Carbon Nanostructure for a Thermoelectric Generator

We demonstrate that it is technologically possible to obtain graphite-like films which can be used for the creation of a thermoelectric generator. The proposed technology ensures uniformity and rather small thickness of these films and allows them to be formed on a diamond-like film substrate with deposited contacts at acceptable interface. Measurements show that the electron-phonon drag effect in this system ensures thermo-emf values about 100 times as large as those provided by the diffusion process. Arrangement of the graphite-like material on a diamond-like film substrate also favors increase in the thermo-emf, which is a manifestation of the electron–ballistic phonon drag. It is established that conditions necessary for the creation of a thermoelectric generator can be achieved based on the proposed carbon nanostructures.

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.

Improvement of Functional Properties of Medical Stainless Steel Surface by Treatment with Helium, Argon, and Silver Ions

Investigations of the carbon film synthesis on the surface of steel orthopedic structures obtained by ions implantation of argon ions (accelerating voltage Uacc = 40–130 kV and dose range F = (1.25–3.1) × 1016 ion/cm2) in a carbon dioxide medium have been conducted. It is shown that implantation of Ar+ ions in a CO2 environment leads to a significant increase in microhardness of medical steel surface (up to 31 GPa). The method of ion beam modification of the carbon diamond-like film by implantation of silver ions (accelerating voltage 50 kV and dose range 1.2 × 1016–1.8 × 1016 ion/cm2) to impart antimicrobial surface properties has been proposed. The studies in vivo have proved that the steel implants modified by the developed ion beam method efficiently take root in the bone tissue without inflammatory processes in the surrounding biostructures.

Femtosecond laser surface texturing of diamond-like nanocomposite films to improve tribological properties in lubricated sliding

We report on femtosecond laser ablation and surface micropatterning (texturing) of diamond-like nanocomposite (DLN) films (a-C:H:Si:O films), aimed to improve tribological properties of laser-patterned films under lubricated sliding conditions. Femtosecond laser system generating pulses of 320-fs duration at the wavelength 515 nm is applied. Femtosecond laser ablation of 2.7-μm-thick DLN films is studied to determine optimum irradiation parameters for laser surface texturing with the requirements of the minimal spot size, high ablation rate, surface quality and pattern depth less than the film thickness. Periodic microcrater patterns (with 10 μm diameter, 2.2 μm depth, and different area density of microcraters) have been fabricated on the DLN films over the areas of 6 mm × 10 mm size. Tribological tests of the original and laser-patterned DLN films are performed using a ball-on-flat tribometer under linear reciprocating sliding against 100Cr6 steel balls in the presence of oil lubrication (engine oils of low and high viscosity). The ball-on-flat investigations have demonstrated the reduced friction and wear properties of the laser-textured DLN films, depending on the area density of microcraters and lubrication conditions. The obtained results evidence that femtosecond laser surface texturing is an effective technique to improve lubricated sliding performance of the DLN coatings.

Silicon-Doped Diamond-Like Composite Film to Improve the Thermal Dissipated Performance of Light-Emitting Diode

With the progress of light-emitting diodes (LEDs) research deepening, LEDs are gaining more and more widespread. During the use of LED, the excessive temperature of the P-N junction has a bad influence on the life of the LED. In order to reduce the junction temperature of the LED, efficient thermal management has become the key to the popularity of LEDs. The graphite materials are promising thermal conductivity material due to their superior thermal conductivity. In this experiment, Al/AlCX/Diamond-like carbon (DLC) composite film was coated on the surface of the LED substrate by direct current (DC) sputtering and radio frequency (RF) magnetron sputtering. On studying the effect of this composite film on the thermal dissipation performance of LED, the results show that the Al/AlCX/DLC composite film can effectively improve the thermal conductivity of the LED and reduce the thermal resistance. When the LED was driven using a 350-mA drive current, the thermal resistance of the uncoated device was 36.69 K/W and the thermal resistance of the coated device was 30.06 K/W. Compared with the uncoated device, the thermal resistance of the coated device is reduced by 18.1% and the junction temperature is reduced by 4.27 °C.

Углеродная наноструктура для термоэлектрического генератора

AbstractWe demonstrate that it is technologically possible to obtain graphite-like films which can be used for the creation of a thermoelectric generator. The proposed technology ensures uniformity and rather small thickness of these films and allows them to be formed on a diamond-like film substrate with deposited contacts at acceptable interface. Measurements show that the electron-phonon drag effect in this system ensures thermo-emf values about 100 times as large as those provided by the diffusion process. Arrangement of the graphite-like material on a diamond-like film substrate also favors increase in the thermo-emf, which is a manifestation of the electron–ballistic phonon drag. It is established that conditions necessary for the creation of a thermoelectric generator can be achieved based on the proposed carbon nanostructures.

Effects of AFM tip wear on frictional images of laser-patterned diamond-like nanocomposite films

Effects of AFM tip wear on frictional images of laser-patterned diamond-like nanocomposite films