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Journal ArticleDOI

Synthesis and mechanical properties of amorphous carbon films by closed-field unbalanced magnetron sputtering

01 Mar 2004-Materials Letters (North-Holland)-Vol. 58, Iss: 9, pp 1513-1516
TL;DR: Amorphous hydrogen-free carbon (a-C) films were synthesized by closed-field unbalanced magnetron sputtering (CFUBM), and the deposition rate, structure, and mechanical properties of these films were studied as a function of applied bias voltage on substrate during deposition.
About: This article is published in Materials Letters.The article was published on 2004-03-01. It has received 19 citations till now. The article focuses on the topics: Carbon film & Amorphous carbon.
Citations
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TL;DR: In this article, it was shown that pair hopping through a Kondo singlet gives rise to a negative Josephson coupling, which supports the existence of staggered pair correlations in the strong coupling limit of a one dimensional Kondo lattice.
Abstract: We Show that pair hopping through a Kondo singlet give rise to a negative Josephson coupling. Thus, our calculation supports the existance of staggered pair correlations in the strong coupling limit of a one dimensional Kondo lattice.

82 citations

Journal ArticleDOI
TL;DR: In this article, the authors used micro arc Oxidation (MAO) and closed field unbalance magnetron sputtering (CFUBMS) techniques to deposit duplex MAO/DLC coating on Ti6Al4V (Grade 5) alloy.
Abstract: DLC (Diamond-Like Carbon) coatings feature high hardness, good wear resistance and low friction. Applying DLC coatings to titanium alloys using different coating techniques can improve the surface properties. However, in many cases, this hard coating fails under mechanical loading due to the mechanical incompatibility of the coating and substrate. Therefore, an intermediate layer providing improved load support is necessary to prevent the failure of the DLC film. For this purpose, the Micro Arc Oxidation (MAO) and Closed Field Unbalance Magnetron Sputtering (CFUBMS) coating techniques were used to deposit duplex MAO/DLC coating on Ti6Al4V (Grade 5) alloy. The surface topography, morphology, crystallographic structure and thickness of the duplex coatings were determined using Scanning Electron Microscopy (SEM), XRD and RAMAN. The hardness was measured using a nano-hardness tester. The hardness, adhesion to the substrate and load-bearing capacity of DLC increased due to the intermediate layer of TiO 2 deposited by MAO because it decreased the mechanical incompatibility between the soft substrate and hard coating. The duplex coating using the MAO/CFUBMS process was effective in maintaining a convenient, low, stable coefficient of friction and improving the tribological behaviour of the Ti6Al4V substrate. It was observed that the duplex coatings deposited on the Ti6Al4V substrate indicate a better tribological performance than the DLC or MAO coatings on the Ti6Al4V alloy substrate.

52 citations

Journal ArticleDOI
TL;DR: In this article, a novel strategy for the selective determination of dopamine concentrations based on carbon thin film electrodes is presented in which unbalanced magnetron sputtering is used to measure dopamine levels in situ.
Abstract: For therapeutic purposes, an accurate measurement of dopamine levels in situ would be highly desirable. A novel strategy for the selective determination of dopamine concentrations based on carbon thin film electrodes is presented in this paper. Traditionally, in order to make diamond films conductive, they are doped with different concentration of boron atoms. Here, carbon thin films with varying conductivities were achieved by unbalanced magnetron sputtering. The benefit of the method is that it can be performed at room temperature consequently broadening the selection of suitable substrates. The carbon thin films had a wide potential window, which showed strong dependence on conductivity. The potential window was largest (4.6 V) with the most resistive carbon thin film. On the other hand, the sensitivity of the electrode toward dopamine was not significantly affected by the conductivity. In addition, relatively similar behavior with respect to the dopamine oxidation was observed between various surfaces. The slight differences observed in the electrochemical behavior among the thin films are most likely caused by 1) different conductivities and/or 2) different surface charges and subsequent differences in the chemical properties of the surfaces. In conclusion, it can be stated that a-C thin film is a very potential neural sensing material.

29 citations

Journal ArticleDOI
TL;DR: In this paper, a pin-on-disc tribotester under electrochemical polarisation in NaCl 1.5% solution was used to test the performance of a closed field unbalance magnetron sputtering (CFUBMS).

26 citations

Journal ArticleDOI
TL;DR: In this article, a diamond-like carbon (DLC) film was deposited using plasma-assisted chemical vapour deposition (PACVD) at −350 V and −800 V, respectively.
Abstract: Diamond-like carbon (DLC) film was deposited using plasma-assisted chemical vapour deposition (PACVD) at −350 V and −800 V. DLC strain gauges were integrated in bulk micromachined silicon. Optical bandgaps were found to be 1.2 eV and 1.03 eV at −350 V and −800 V, respectively. Films deposited at −350 V have a higher hydrogen percentage, hardness, sp3 content, resistivity and gauge factor compared to films deposited at −800 V. Piezoresistive gauge factors were measured under longitudinal and transversal strain configurations and in vertical and lateral current injection directions. It was found that the gauge factor was independent of the current injection direction and strain configurations. A model to explain the origin of the piezoresistive effect in DLC films along with parameters which can further enhance the gauge factor value of the films is discussed, which is confirmed experimentally.

24 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the preparation and properties of amorphous carbon and hydrogenated amorphized carbon, often known as diamond-like carbon, have been discussed and models of the electronic structure and mechanical properties are used to relate the physical properties to the atomic structure.
Abstract: This paper revies the preparation and properties of hard forms of amorphous carbon and hydrogenated amorphous carbon, often known as diamond-like carbon. Properties such as the hydrogen content, sp 3 content, optical gap, refractive index, hardness, elastic modulus and friction and their dependence on the deposition conditions are described. Models of the electronic structure and mechanical properties are used to relate the physical properties to the atomic structure.

692 citations

Journal ArticleDOI
TL;DR: A critical review of the pulsed laser deposition (PLD) of amorphous diamond-like carbon (DLC) films is presented in this paper, where a cumulative influence of the laser power density and wavelength on the formation and properties of DLC films is shown.
Abstract: A critical review of the pulsed laser deposition (PLD) of amorphous diamond-like carbon (DLC) films is presented. A short review of the PLD process is followed by a review of various experimental configurations for DLC deposition and a discussion of the influence of process parameters on the composition and energy of ablated carbon plumes. Particular emphasis is given to the relationship between plume properties and film structure and mechanical characteristics. For the first time, a cumulative influence of the laser power density (fluence) and wavelength on the formation and properties of DLC films is shown. The influence of bias, additional auxiliary energy, substrate temperature, and the presence of hydrogen is also discussed. A fluence-wavelength region for DLC formation is proposed and correlated with the kinetic energy of ablated carbon species. It is shown that lower fluences are required to produce DLC films when shorter-wavelength lasers are used. The latest available results on applications of PLD DLC films as protective coatings for reducing friction and wear are also discussed. Methods are proposed to improve film adhesion to steel substrates, so that DLC films can be used in highly loaded friction contacts. Finally, process improvements that are necessary to permit scaling up PLD for growing DLC films are outlined.

340 citations

Journal ArticleDOI
TL;DR: In this article, hydrogen-free amorphous carbon coatings of high hardness (≈30 GPa) and toughness (plasticity from 50 to 60%) were deposited on 440C steel substrates by DC magnetron sputtering at a target power density of 10.5 W/cm2 in the bias range from −20 to −150 V. The surface topography, hardness and tribological behavior of the coatings were investigated.
Abstract: Hydrogen-free amorphous carbon coatings of high hardness (≈30 GPa) and toughness (plasticity from 50 to 60%) were deposited on 440C steel substrates by DC magnetron sputtering at target power density of 10.5 W/cm2 in the bias range from −20 to −150 V. The surface topography, hardness and tribological behavior of the coatings were investigated. With the increase of bias voltage, coating hardness and surface smoothness increased at expense of some adhesion strength and an increase of coefficient of friction. All coatings showed low friction in humid air and graphitization was observed after a high number of rotation cycles. The graphitization adds more benefit aside from reducing friction: the graphite layer can considerably reduce the adhesive wear since it prevents the asperities of the two surfaces to be adhered to each other.

87 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that pair hopping through a Kondo singlet gives rise to a negative Josephson coupling, which supports the existence of staggered pair correlations in the strong-coupling limit of a one-dimensional Kondo lattice.
Abstract: We show that pair hopping through a Kondo singlet gives rise to a negative Josephson coupling. Thus our calculation supports the existence of staggered pair correlations in the strong-coupling limit of a one-dimensional Kondo lattice.

86 citations

Posted Content
TL;DR: In this article, it was shown that pair hopping through a Kondo singlet gives rise to a negative Josephson coupling, which supports the existence of staggered pair correlations in the strong coupling limit of a one dimensional Kondo lattice.
Abstract: We Show that pair hopping through a Kondo singlet give rise to a negative Josephson coupling. Thus, our calculation supports the existance of staggered pair correlations in the strong coupling limit of a one dimensional Kondo lattice.

82 citations