Thick Carbon Films Research Articles

Pulsed laser deposition of high-quality diamond-like carbon films under an inhomogeneous magnetic field

High-quality diamond-like carbon film was deposited on silicon substrate by magnetic field-enhanced pulsed laser deposition. The motion tracks of carbon ions in the inhomogeneous magnetic field were simulated. The thickness and surface morphology of carbon film were characterized by surface profilometer and atomic force microscopy, respectively. Mechanical property was evaluated by an indenter. The results showed that the deposition rate of the carbon film prepared under the magnetic field increased 1.7 times than that of the carbon film without magnetic field. The surface of the carbon films constructed of columnar particle arrays with the size ranging from 20 nm to 30 nm was improved and the roughness was decreased from 3.22 nm to 0.93 nm. The nano-hardness of the carbon film was 53.4 GPa, which increased by 18.1% than that of carbon film deposited without magnetic field. The experiment and simulation on the magnetic field-enhanced pulsed laser deposition proved that the new method of film preparation by magnetic filtration laser plasma deposition is feasibility.

UV fluorescence as a method of high throughput surface cleanliness assessment: A comparison with XPS

UV visible fluorescence (UV–vis) was trialled as a method for the rapid screening of surface cleanliness of metals. By comparing the relative intensity of the fluorescence to the film thickness of the carbonaceous contamination, an evaluation of the effectiveness of UV–vis was made. Surface composition and the thickness of carbon contamination on stainless steel/mineral oil and copper/tallow wax samples was measured with X-ray photoelectron spectroscopy (XPS). After vapour degreasing with trichloroethylene it was found that residual tallow wax was not effectively detected by UV–vis; whereas a commercial mineral oil was readily detected by UV–vis. The reason for the lack of fluorescence is that the tallow wax is largely an unconjugated system, in that it mostly comprises saturated or monounsaturated carbon – carbon bonds, which do not fluoresce. Using imaging XPS an increase in carbon film thickness close to the edge of the sample is observed, a result of solvent residue caused by the interfacial tension that exists between the solvent and the substrate. UK Ministry of Defence © Crown Owned Copyright 2020/AWE.

Synthesis of graphene-like carbon film on SiC substrate

Carbon film is widely used in many fields due to its excellent electronic, mechanical, and chemical properties. In this work, a free-standing graphene-like carbon film was synthesized on SiC substrate by a CVD process with ethylene as the major carbon source. The carbon film can be easily exfoliated from the substrate completely without any residuum. Intensity of the 2D peak of graphene is strong, while the feature peaks of SiC is not observed in the Raman spectra. Meanwhile, no shift of the feature peaks was found in the Raman spectra for the samples with different growth time. Results show that the carbon film is formed by the carbon atoms which come from the decomposition of ethylene rather than the thermal sublimation of SiC substrate. Intensity ratio of 2D to G peak increases with carbon film thickness reduces, which means that few layers of graphene can be synthesized by reducing the thickness of the carbon film. Besides, the sheet resistivity of the sample is as low as 40 Ω/sq. The excellent electrical conductivity of such carbon film can be useful in some special field in the future, such as electricity and energy.

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.

Atomic H diffusion and C etching in multilayer graphene monitored using a Y based optical sensor

In this work, the authors expose transferred multilayer graphene on a yttrium based hydrogen sensor. Using spectroscopic ellipsometry, they show that graphene, as well as amorphous carbon reference films, reduce diffusion of hydrogen to the underlying Y layer. Graphene and C are both etched due to exposure to atomic H, eventually leading to hydrogenation of the Y to YH2 and YH3. Multilayer graphene, even with defects originating from manufacturing and transfer, showed a higher resistance against atomic H etching compared to amorphous carbon films of a similar thickness.

Graphene synthesis on SiO2 using pulsed laser deposition with bilayer predominance

Here we report the low-defect synthesis of bilayer graphene film on SiO2 with a nickel catalyst using pulsed laser deposition combined with rapid thermal annealing. A parametric study was performed with various initial amorphous carbon (a-C) film thicknesses and annealing temperatures and a fixed nickel catalyst film thickness. Raman spectra and mapping over large areas of up to 100 × 100 μm2 were used to investigate the structure and the defects of graphene films. Optimal conditions for graphene growth were an initial a-C film thickness of 2 nm and an annealing temperature of 900 °C. Results showed that 76% of the optimized film contained graphene bilayers, and 18% of the optimized film contained graphene monolayers. A transmittance of 87% at 550 nm is observed without any transfer process from the SiO2 substrate. This paper presents experimental guidelines for optimal synthesis conditions to control graphene growth by pulsed laser deposition.

Determination of Refractive Index and Thickness of Nanosized Amorphous Carbon Films Via Visible Range Reflectance Spectra

The values of thickness and refractive index (1.92 < nf < 2.19) of amorphous nanosized carbon films obtained on a crystalline silicon substrate by a pulsed laser deposition were experimentally determined via an analysis of visible range of reflection spectra. Manufactured films can be used as single-layer anti-reflective coatings for Si and GaAs semiconductors.

Verification Study of Nanostructure Evolution with Heating Treatment between Thin and Thick Fullerene-Like Hydrogen Carbon Films

Fullerene-like hydrogen carbon films with a thin film grown on a NaCl substrate are usually employed to show the nanostructure of films (usually of hundred nanometers thick grown on Si substrates) under high resolution transmission electron microscopy (HRTEM) tests because it is easier floated off, where dependability and reasonability has never been seriously contested. Thus, in this paper, thin and thick hydrogen carbon films have been deposited on NaCl (thin films) and Si (thick films) substrates and annealed under room temperature to 500 °C, of which nanostructures have been investigated by HRTEM, Raman spectroscopy, and X-ray photoelectron spectroscopy, to verify the dependability and reasonability of the NaCl method. The results showed heating induced graphitization but with hydrogen content nearly unchanged. HRTEM results revealed that under annealing of 200, 250, and 300 °C, the curved graphene structures gradually increase in films. However, beyond 400 °C, onions structures are present. However, both Raman and XPS spectra show us that after annealed treatment, for original films, both thin and thick films have the near sp2 bonding content and size, but with the annealing temperature increase, sp2 bonding content increases more quickly for thick FL-C:H films due to the higher internal stress compared to thin films. In one word, the NaCl method used for nanostructure detection for films might be a good choice for an easier and quicker analysis, but it is still insufficient, because the heating effect induced by plasma cannot be ignored.

Role of carbon quantum dots and film thickness on enhanced UV shielding capability of flexible polymer film containing carbon quantum dots/N-doped ZnO nanoparticles

We report a simple method for preparing flexible polymer film containing carbon quantum dots/N-doped ZnO (CQD/N-ZnO) nanoparticles, as UV shielding material. The polymer film showed an enhanced UV shielding capability with increasing of CQD/N-ZnO nanoparticles. The maximum of 47% of UV shielding capability was achieved with 1 wt.% of CQD/N-ZnO nanoparticles and two-order enhancement was achieved by controlling film thickness to 250 μm. It was found that CQDs plays important role to promote compatibility of hydrophilic ZnO into hydrophobic polymer matrix without disturbing the transparency of the film. An excellent UV shielding capability of 85% and 92% was witnessed in 250 μm thick polymer film under a UV lamp and direct daylight, respectively.

Corrosion and wear behaviors of Si-DLC films coated on inner surface of SS304 pipes by hollow cathode PECVD

An integrated technology of hollow cathode plasma enhanced chemical vapor deposition (PECVD) with plasma immersion ion deposition (PIID), promoting the deposition rate ranging from10 to 14 µm h−1, was developed to deposit thick Si-doped diamond-like carbon (Si-DLC) films on the internal surface of 304 stainless steel (SS304) pipes with various inner diameters for corrosion and abrasion protection. After the deposition, the films inside 30 mm and 90 mm diameter pipe have been comprehensively investigated by FESEM, optical 3D profiler, Raman, XPS, nanoindentation, EIS and polarization measurements, salt spray test and friction test. It was found that Si-DLC films were compact and smooth, thick (~11 µm) and hard (~13 GPa). The current density (2.38 × 10−9 A cm−2) of Si-DLC films was 1000 times lower than the uncoated steel pipe through the electrochemical polarization test. The EIS data were analyzed by an equivalent circuit model, which presented a highest charge transfer impedance of ~4.5E7 Ω cm2. Si-DLC films survived 720 h salt spray test without the presence of corrosion pits and exfoliation. The test results confirmed that Si-DLC films possessed superior performances in corrosion resistance, which was not only attributed to the chemical inertness of DLC and Si incorporation, but also to the multilayered film with few defects. Besides, the friction coefficient of Si-DLC films in air, water and oil environments was low at 0.05–0.06, 0.08–0.12 and 0.08–0.09, respectively, in comparison with 0.55, 0.30 and 0.11 for bare steel. The corresponding wear rates of Si-DLC films were much lower than uncoated steel pipe in the three environments as well.

Graphene-based plasmonic waveguide devices for electronic-photonic integrated circuit

Graphene is a one-atom thick carbon film packed in a honeycomb structure, and because it has extraordinary optoelectronic properties, it has attracted a great deal of attention in the field of photonics. Graphene-based plasmonic photonic devices have been developed which are capable of emitting, transmitting, modulating, and detecting light wave signals using a single material. In this paper, we propose the concept of on-chip graphene electronic-photonic integrated circuits (EPICs) architecture, and present developments and perspectives on the essential graphene plasmonic-based photonic components, including the plasmonic waveguide, modulator, and photodetector, which are based on the graphene EPICs. The optical characteristics and design considerations of the graphene-based photonic devices are discussed based on experimental and theoretical investigations at telecommunications wavelengths. In parallel, we provide new device design concepts and a potential solution for further improving their operating characteristics. We also performed a numerical investigation of the characteristics of the photonic devices to explain their operating principles and to predict their operating performances. The proposed photonic components were fabricated on an organic photonic chip using an optimized fabrication process, and their optical characteristics were experimentally demonstrated. Based on these results and demonstrations, we hope to introduce new perspectives on the future direction of graphene-EPICs in graphene plasmonics and the optical telecom field.

Reactive magnetron sputtering of N-doped carbon thin films on quartz glass for transmission photocathode applications

N-doped carbon thin films were deposited on a silicon substrate and quartz glass by RF reactive magnetron sputtering using a carbon target and an Ar+N2 gas mixture. During the magnetron sputtering, the substrate holder temperatures was kept at 800 °C. The carbon film thickness on the silicon substrate was about 70 nm, while on the quartz glass it was in the range 15 nm – 60 nm. The elemental concentration in the films was determined by RBS and ERD. Raman spectroscopy was used to evaluate the intensity ratios ID/IG of the D and G peaks of the carbon films. The transmission photocathodes prepared were placed in the hollow-cathode assembly of a Pierce-structure DC gun to produce photoelectrons. The quantum efficiency (QE) was calculated from the laser energy and cathode charge measured. The properties of the transmission photocathodes based on semitransparent N-doped carbon thin films on quartz glass and their potential for application in DC gun technology are discussed.

Synthesis of New Materials in the Boron–Carbon System

Experimental results from the synthesis of diamond-like BC x compounds with the aid of high-pressure techniques and laser sputtering methods are presented. A combination of unique characteristics in these compounds can be attained by varying the B/C ratio. The possibility of sputtering carbon films of micron or nanosize thickness with high boron content opens up a way to use such materials on industrial scales. Hetero-diamonds with high boron content have high elastic moduli and boron-doped diamond polycrystals possess metallic conductivity.

A study for anticorrosion and tribological behaviors of thin/thick diamond-like carbon films in seawater

The thin and thick diamond-like carbon (DLC) films were prepared by unbalanced magnetron sputtering technique on 304L stainless steels and (100) silicon wafers. Microstructure, mechanical, corrosion and tribological properties were systematically investigated by SEM, Raman, nanoindenter, scratch tester, modulab electrochemical workstation and R-tec multifunctional tribological tester. Results showed that the adhesion force presented a descending trend with the growth in soaking time. The adhesion force of the thin DLC film with high residual compressive stress (−3.72 GPa) was higher than that of the thick DLC film (−2.96 GPa). During the corrosion test, the thick DLC film showed a higher impendence and a lower corrosion current density than the thin DLC film, which is attributed to the barrier action of large thickness. Compared to bare 304L substrate, the friction coefficients and wear rates of DLC films in seawater were obviously decreased. Meanwhile, the thin DLC film with ideal residual compressive stress, super adhesion force and good plastic deformation resistance revealed an excellent anti-wear ability in seawater.

Self-formation of a nanonet of fluorinated carbon nanowires on the Si surface by combined etching in fluorine-containing plasma

In this work, we report a technique of the self-formation of a nanonet of fluorinated carbon nanowires on the Si surface using a combined etching in fluorine-containing C4F8/Ar and SF6 plasmas. Using scanning electron microscopy, atomic force microscopy and x-ray photoelectron spectroscopy, we show that after the etching of Si in the C4F8/Ar plasma, a fluorinated carbon film of nanometer-scale thickness is formed on its surface and its formation accelerates at elevated temperatures. After a subsequent short-term etching in the SF6 plasma, the film is modified into a nanonet of self-formed fluorinated carbon nanowires.

Protective amorphous carbon coatings on glass substrates

Thick amorphous carbon films were deposited by the Magnets-in-Motion (M-M) rf linear hollow cathode at varying acetylene contents in Ar in a hybrid PVD/PE-CVD process directly on glass substrates. The hollow cathode plates manufactured from graphite were used as the PVD target. The measurements show that the films can reach thickness of up to 50 μm at deposition rates of up to 2.5 μm/min. Scratch test measurements confirm that well adhering films several μm thick can be achieved at C2H2 contents of up to 0.5%.

Fast deposition of thick diamond-like carbon films by ion-beam technique

A diamond-like carbon film doped with TiC nanocrystallites (TiC–DLC) with a thickness of 35.8 μm was successfully prepared on a stainless steel substrate by employing a combination of metal vapor vacuum arc and filtered cathode vacuum arc techniques. A maximum deposition rate of 0.25 μm/min was achieved for TiC–DLC films. The structure and properties of the TiC–DLC films were systematically analyzed using different methods such as transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, X-ray diffraction, and friction and wear tests. The results indicated that typical a-C:H films containing nano-sized TiC grains were deposited which exhibit improved mechanical properties such as high cohesive strength, Vickers hardness, and capacity against high temperature. Parameter windows for C2H2 flow rate and solenoid current were also provided for the deposition of TiC–DLC films to meet the requirements for using the material for specific commercial applications.

Growth evolution of carbon film on the hydrocooling copper substrate by DC arc plasma jet

The growth process of carbon film on the surface of hydrocooling copper substrate in high-density direct current (DC) arc plasma was studied. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, nuclear magnetic resonance spectroscopy, and UV confocal Raman spectroscopy were used to analyze the structural constituents of the intermediate products generated at different growth periods. Results show that despite the remarkable heating effect of DC arc plasma to the copper substrate, one layer of cauliflower saturated carbon and double carbon bond as main component loose matter are first formed because of water-cooled copper substrate. With the increase in thickness of carbon film, the surface temperature gradually increases, the etching ability of the atomic hydrogen is enhanced and high concentration reactive units are maintained on the surface of carbon film. The cauliflower structure may effectively reduce the diamond nucleation barrier and promote the generation of nano-diamond. The diamond grains gradually grow up to the micron scale by the continuing influence of carbon-based active group and plasma. The growth pattern of carbon film on the hydrocooling copper substrate in high-density DC arc plasma may provide a new way to prepare large crack-free diamond films.

Effects of modified surfaces produced at plasma-facing surface on hydrogen release behavior in the LHD

In the present study, an additional deuterium (D) ion irradiation was performed against long-term samples mounted on the helical coil can and in the outer private region in the LHD during the 17th experimental campaign. Based on the release behavior of the D and hydrogen (H) retained during the experimental campaign, the difference of release behavior at the top surface and in bulk of modified surfaces is discussed. Almost all samples on the helical coil can were erosion-dominant and some samples were covered with boron or carbon, while a very thick carbon films were formed in the outer private region. In the erosion-dominant area, the D desorbed at much lower temperatures compared to that of H retained during the LHD plasma operation. For the samples covered with boron, the D tended to desorb at lower temperatures compared to H. For the carbon deposition samples, the D desorbed at much higher temperatures compared to no deposition and boron-covered samples, which was very similar to that of H. The D retention capabilities at the top surface of carbon and boron films were 2–3 times higher than no deposition area. The results indicate that the retention and release behavior at the top surface of the modified layer can be different from that of bulk substrate material.

Growth Mechanism for Low Temperature PVD Graphene Synthesis on Copper Using Amorphous Carbon

Growth mechanism for synthesizing PVD based Graphene using Amorphous Carbon, catalyzed by Copper is investigated in this work. Different experiments with respect to Amorphous Carbon film thickness, annealing time and temperature are performed for the investigation. Copper film stress and its effect on hydrogen diffusion through the film grain boundaries are found to be the key factors for the growth mechanism, and supported by our Finite Element Modeling. Low temperature growth of Graphene is achieved and the proposed growth mechanism is found to remain valid at low temperatures.