Magnetron Sputtering Of Graphite Target Research Articles

Fabrication of carbon nanowalls by radio frequency magnetron sputtering of graphite target in argon plasma

Vertical carbon nanowalls have been fabricated by RF magnetron sputtering of a graphite target in an argon plasma without hydrogen presence. The effect of deposition parameters such as substrate temperature, argon pressure, deposition time and RF power on the morphology and the structure of carbon nanowalls was investigated by using Raman spectroscopy and atomic force microscopy. The argon ion bombardment of the substrate is crucial for the nucleation and growth of carbon nanowalls. A specific range of RF power and argon pressure values was established at which nanowalls formation is possible. The height of nanowalls produced at minimal RF power increases non-monotonically with the deposition time. It turned out that the nanowalls growth rate has an extremum, after reaching which the growth rate of the thickness of nanowalls increases.

Superconducting magnesium diboride films for levitation of laser targets

Inertial confinement fusion targets would benefit from being levitated inside hohlraums to avoid capsule support-related implosion perturbations. Levitation inside a magnetic trap requires coating the capsule with a thin film that is superconducting at 20 K. Such non-epitaxial film growth on non-planar substrates is challenging. Here, we study Mg vapor annealing and solid-phase reactive inter-diffusion methods to form superconducting magnesium diboride (MgB2) films on different planar and spherical carbon substrates, evaluating glassy carbon, polycrystalline diamond made by chemical vapor deposition, and carbon deposited by magnetron sputtering of graphite targets. Thin films of B and Mg are produced by magnetron sputtering onto stationary planar or rolling spherical substrates and annealed at either 600 or 850 ∘C in Mg vapor. The films are characterized by a combination of high-energy ion scattering, electron microscopy, and magnetometry. Results show that the critical superconducting temperature of resultant films depends on film microstructure and oxygen impurity content. The formation of MgB2 films is also strongly substrate dependent, even in this case of non-epitaxial growth. Important factors to consider are oxygen outgassing of the substrate during thermal processing, substrate surface roughness, and the matching of thermal expansion coefficients of different layers in the multilayer structure.

Electric properties of carbon films deposited by magnetron sputtering with ion assistance

The paper deals with the study of ion assistance impact on structure and electrophysical properties of the carbon films deposited by magnetron sputtering of graphite targets. The flow of assisting ions was generated in the plasma reactor based on inductive RF discharge located in the external magnetic field. The change of the ionic current density in the range from 0.5 to 1 mA/cm2 was provided. Ion energy was changed by biasing the substrate in the range from 10 to 85 V. Neon, argon and krypton were used as working gases. The electrophysical properties of carbon films are shown to depend non-monotonous on energy of the assisting ions.

Multilayer graphene synthesized using magnetron sputtering for planar supercapacitor application

This study reports the direct preparation of graphene-based films using magnetron sputtering of graphite target. The nanomaterial was deposited at a low temperature of 620 °C on silicon wafers and on metallic foils including aluminum. The films were used in fabrication of supercapacitors with a planar geometry. Electrochemical characterizations demonstrated that the films produced showed nearly ideal electrical capacitive behavior. The maximum capacitance obtained from cyclic voltammetry analysis was 325 F/g for a scan rate of 1 mV/s. The device is capable of delivering an energy density of 13.9 Wh/kg at a very high power density of 50 000 W/kg for ultrafast scan rate of 1000 mV/s. The graphene nanomaterial electrode retains the electrochemical stability over a large number of charge-discharge cycles.

Comparison of the hardness of TiC/a-C coatings obtained by the method of the magnetron sputtering of a graphite target with high- and low-power pulses

TiC/a-C coatings 0.1–2.0 μm thick are deposited onto substrates made of (WC + Ti) hard alloy or stainless steel by the method of the pulsed magnetron sputtering of Ti and graphite targets. The microhardness of coatings obtained by the sputtering of a graphite target by pulses of high (∼1 kW/cm2) and low power (∼25 W/cm2) is compared. The effect of the coating thickness on the measured value of the microhardness is investigated. It is shown that maximum values of coating hardness (35 ± 5 GPa) are attained at a Ti/C ratio of 0.6–0.9.

Formation of a thin film containing α-carbine in the magnetron sputtering of graphite targets and the impact of an external photoactivation source

The possibility of formation of a thin film containing α-carbine in magnetron sputtering of graphite targets and the impact of an external photoactivation source with the spectral density of the radiation flux ∼5 × 108 W/m3 at the wavelength of 300 nm and at the substrate temperature ∼660 K is shown experimentally.

Preparation of diamond-like films in the process of magnetron sputtering of graphite target

Preparation of diamond-like films in the process of magnetron sputtering of graphite target

Tribological Performance of Reactively Sputtered a-C:H Coatings in Ambient air and Aqueous Environment

Amorphous hydrogenated carbon (a-C:H) films, supported by a layer system consisting of substoichiometric chromium nitride and amorphous carbon, were deposited on case-hardened steel disks using reactive magnetron sputtering of graphite targets in an acetylene-containing atmosphere. The a-C:H film hardness was adjusted between 8 and 19 GPa by varying the acetylene gas flow and the bias voltage. To evaluate friction and wear behaviour, pin-on-disk tests were done in ambient air and deionised water. It could be shown that optimised a–C:H films are suitable to protect steel from sliding wear in ambient air but also in aqueous environment eliminating the problem of insufficient heat removal.

Surface and electron emission properties of hydrogen-free diamond-like carbon films investigated by atomic force microscopy

In this study, we have deposited hydrogen-free diamond-like carbon (DLC) films by using DC magnetron sputtering of graphite target at various r.f. bias voltages. Surface and nanoscale emission properties of these DLC films have been investigated using a combination of atomic force microscopy (AFM)-based nanowear tests and conducting-AFM, by simultaneously measuring the topography and the conductivity of the samples. Nanowear tests show that these DLC films are covered with the thin (1.5–2.0 nm) graphite-like layers at surfaces. Compared to the film bulk structure, the graphite-like surface layers are more conductive. The graphite-like surface layers significantly influence the electron emission properties of these films. Low-energy carbon species can be responsible for the formation of graphite-like surface layers. Nanoscale electron emission measurements have revealed the inhomogeneous emission nature of these films. The low-field emission from these films can be attributed to the existence of sp 2-configured nanoclusters inside the films.

Effect of air post contamination on mechanical properties of amorphous carbon nitride thin films

We report in this study the mechanical, structural and compositional characteristics of amorphous carbon nitride films (a-CN x ) deposited on Si(100) using RF magnetron sputtering of graphite targets in pure nitrogen and under different RF powers. The properties of the films were determined in their as deposited state using nuclear reaction analysis (NRA), elastic recoil detection (ERDA), infrared (IR) absorption and Raman spectroscopy. The mechanical properties were obtained combining nanoindentation and residual stress measurements. The presence of various types of C–N bonds, as well as the post-deposition contamination of the deposited films by oxygen and water (voids) is revealed. The measured hardness and Young modulus were 0.9–2.03 and 23–27 GPa, respectively. These results have been analysed in term of the matrix flexibility which results from the nitrogen content and the porous character of the films, which can affect deeply the estimation of the physical–mechanical properties of the films.

Bias-graded deposition of diamond-like carbon for tribological applications

Hydrogen-free diamond-like carbon coatings of thickness 1.5 μm were deposited on 440C stainless steel substrates and silicon wafers via DC magnetron sputtering of graphite target at power density of 10.5 W/cm 2. RF bias voltage was applied in the range of −20 to −150 V in two configurations: constant bias and bias-graded. The structure, surface topography, hardness and tribological behavior of these coatings were investigated. The surface roughness ( R a) of the coating decreased from 5.8 to 3.4 nm as bias voltage increased. Results from nanoindentation showed that the hardness of the coatings deposited at high bias voltage reached at 30 GPa and toughness (plasticity during indentation deformation) from approximately 50 to 60%. The hardness of the coating deposited with bias-graded configuration was comparable to the coatings deposited at high bias voltage but the toughness and adhesion strength were significantly improved. Ball-on-disc tribotests were carried out under dry, water- and oil-lubrication conditions. The result showed that the bias-graded coating had a very low coefficient of friction (down to 0.07 in oil). Furthermore, after 2.5 km sliding against alumina and steel (6 mm in diameter) at a high load of 10 N with and without lubrication, no sign of damage was observed on the wear track. Bias-graded sputtering deposition is an appropriate technique to combine the hardness, toughness and adhesion strength into one coating for demanding tribological applications.

AMORPHOUS CARBON NITRIDE THIN FILM AS A BARRIER AGAINST COPPER DIFFUSION

The application of carbon nitride as a barrier against copper diffusion was investigated. Amorphous carbon nitride (a-CN) thin films were prepared on Si(100) substrates by rf magnetron sputtering of graphite target in N2 plasma. A thin Cu layer was then deposited in-situ atop of the a-CN film. Annealing process was carried out in nitrogen (N2) ambient at the temperature of 400°C and 600°C respectively. The as-deposited and annealed films were characterized by x-ray photoelectron spectroscopy (XPS). The measurements show that both sp2C-N and sp3-N bonds were formed in the as-deposited carbon nitride films. The compositional analyses indicate that the deposited a-CN thin film is able to act as an effective diffusion barrier against copper at annealing temperature up to 400°C.

RAMAN AND PEELS STUDIES ON MAGNETRON SPUTTERED a-C

Amorphous carbon coatings (a-C, a-C:H) of less than 100 nm thick were deposited on KBr pellets and silicon wafer substrate via magnetron sputtering of graphite target in argon, argon/hydrogen and argon/nitrogen atmosphere. Parallel electron energy loss spectroscopy (PEELS) analysis was used to quantify the sp 2/ sp 3 bonding in carbon films. Stand-alone films of amorphous carbon were produced by sputtering onto compressed KBr pellets and then floating off is distilled water for PEELS study. Raman spectroscopy was used to measure the peak intensity ratio of D-band to that of the G-band (IdIg). It shows that higher sp 3 fraction often associates with lower Raman peak ratio (IdIg). At the same time, G-band peak position P g decreases while sp 3 fraction increases.

Planarization of substrate surface by means of ultrathin diamond-like carbon film

The effect of reactive ion etching on surface roughness of diamond-like carbon (DLC) films was investigated. The DLC carbon films were deposited by d.c. magnetron sputtering of graphite target and r.f. plasma-enhanced chemical vapor deposition at room temperature. Plasma etching of DLC films were performed by r.f. reactive ion etching in oxygen. It is shown that the surface roughness of the diamond-like carbon film under reactive ion etching was less than that of the original substrate.

Study of diamond-like carbon films for protective coatings

Interest in investigating thin films of diamond-like carbon (DLC, a-C:H) has been motivated by the unique properties of this material and the demand of modern technologies. The development of low-temperature methods T3 s < 200 °C) for producing DLC films used as protective layers is of practical interest. In this work, a-C:H films were prepared by low-temperature deposition by using three methods: magnetron-sputtering of a graphite target in argon (80%)-hydrogen (20%) atmosphere, magnetron sputtering of graphite target combined with plasma-stimulated, gas-phase deposition from a mixture of gases (10% CH 4 + 90% Ar) and rf decomposition of a mixtures of gases (10% CH 4 + 90% Ar). A comprehensive investigation of the composition, structure, optical and electrical properties of a-C:H films was performed from the standpoint of the requirements that protective coatings for electrophotograhic information carriers and stable protector for Ag-based optics must meet. The investigation of the composition and structure was performed by elastic recoil detection (ERD), resonance nuclear reaction 16O (α, α) 16O and Raman spectroscopy. The optical properties (the transparency over a wide spectral range and the refractive index) were determined by means of IR-spectroscopy and ellipsometric measurements. It was shown that solid, diamond-like a-C:H films (DLC) can be obtained with low-temperature deposition. It was shown that a protective DLC coating increases the storage time in the air and the strength properties of the a-Se (or a-Se alloy) electrophotographic information carriers. It was determined that a protective DLC coating is an effective and stable protector for Ag-based optics from an attack of active sulfide.

Electrical conductivity of amorphous carbon and amorphous hydrogenated carbon

Abstract Amorphous carbon (a-C) thin films have been prepared by r.f. magnetron sputtering of graphite targets in an Ar atmosphere and their d.c. electrical dark conductivity has been measured as a function of temperature. The results are compared with those obtained by earlier workers for a-C and hydrogenated a-C. A detailed analysis leads us to the conclusion that conductivity of amorphous C with or without H is determined mostly by the amount and distribution of sp2 sites in the material. Near room temperature the experimental results suggest hopping between neighbouring sp2 (graphitic) islands embedded in an sp3 (diamond-like) matrix if the sp2:sp3 ratio is below its percolation threshold value and hopping in the band tails if this ratio is above such a threshold. In the temperature region above 500 K hopping in the band tails is shown to be the only effective mechanism.

Surface-defect formation in graphite targets during magnetron sputtering

Magnetron sputtering of graphite targets is frequently marred by the formation of topographic defects. The defects are either soft with a furry appearance or hard with a stalagmite appearance. The soft defects are often found on top of the hard ones, implying a close connection in formation sequence between the two types of defects. The formation mechanism of the hard defects is related to the presence on the surface of low sputtering-yield impurities or other types of lattice imperfections, which suppress the erosion induced locally by sputtering, and to porosity-induced asperities. The emergence of the soft defects is ascribed to a growth phenomenon involving redeposition of carbon from debris and possibly generated in a chemical vapor deposition (CVD) process. The gradual coverage of the target surface by defects causes a steady decrease of the sputtering rate of carbon. Also, the breakup of the soft defects promotes nodular defects in the subsequent growth of the carbon film, thus severely degrading the film quality. Remedial measures are devised for limiting the onset of defect formation.