Plasma polymerization of fluorine alloyed amorphous carbon coatings

This article reports on the deposition conditions and characterization of plasma polymerized fluorocarbon coatings grown by an inductively coupled radio frequency plasma source, using CH4 and CF4as precursor gases. SiH4, H2, or Ar were further added to the plasma to investigate their influence on the coating properties. The coatings were characterized by x-ray photoelectron spectroscopy to determine the surface and bulk composition and combined with Fourier-transform infrared spectroscopy to reveal the structure of the coatings. The mechanical properties (hardness and Young's modulus) were measured by nano-indentation. The surface energy was obtained by contact angle measurements with two different liquids. By varying the deposition conditions, it was possible to adjust separately the polar and dispersive part of the surface energy. With the appropriate feed gases and process parameters, we were able to deposit coatings with surface energies as low as 14 mN/m. A low polar component of the surface energy corresponds to a high fluorine, CF3and CF2content at the surface of the coatings. The maximum contact angle achieved was 113°. By adding H2 to the plasma, it is possible to minimize the polar component and maximize the dispersive component of the surface energy to obtain a relatively hard (3 GPa) coating with a hydrophobic nature [contact angle (H2O) = 90°]. © 1999 American Vacuum Society.status: publishe

Physical and tribological properties of a-Si1-xCx : H coatings prepared by r.f. plama-assisted chemical vapour deposition

a-Si1-xCx : H films deposited by r.f. plasma-assisted chemical vapour deposition were studied as a function of their composition. The friction and wear properties were investigated with the help of a conventional ball-on-disc apparatus. These results are correlated with chemical (Si/C atomic ratio) and structural (Raman and infrared spectroscopy) properties. The friction coefficient in a humid ambient atmosphere changes markedly with the carbon fraction and reaches a value as low as 0.05 for coatings with 70 to 90 at.% C. The carbon-rich films consist of diamond-like carbon with silicon

One-dimensional fluid model for an rf methane plasma of interest in deposition of diamond-like carbon layers

A one-dimensional (1D) model for a methane rf plasma consisting of 20 species (neutrals, radicals, ions, and electrons) is presented. The equations solved are the particle balances, assuming a drift-diffusion approximation for the fluxes, and the electron energy balance equation. The self-consistent electric field is obtained from the simultaneous solution of Poisson\u27s equation. The electron-neutral collision rates are expressed as a function of the average electron energy. These expressions are obtained from the solution of the Boltzmann equation using the Lorentz approximation. The results presented in this article are limited to the alpha regime, hence no secondary electrons are considered. In total, 27 electron reactions (vibrational excitation, dissociation, and ionization) have been included in the model, as well as seven ion-neutral reactions and 12 neutral-neutral reactions. The 1D fluid model yields, among others, information about the densities of the different species in the plasma. It is found that in a methane plasma C2H6, C3H8, C2H4, and C2H2 are also present at high densities, together with CH4 and H-2 (inlet gases). The main radical in the plasma is CH3. At low pressure (e.g., 0.14 Torr) the most important ion is found to be CH5+, at higher pressure (e.g., 0.5 Torr) C2H5+ becomes the dominant ion. (C) 2001 American Institute of Physics

Plasma diagnostics of rf discharges used for the deposition of hydrogenated amorphous carbon coatings

The deposition process of amorphous hydrogenated carbon has been studied using optical emission spectroscopy and self-bias measurements. For a given rf power, a transition between two distinct discharge regimes is observed when increasing the pressure. This transition is attributed to different mechanisms by which electrons gain energy in the sheaths and the plasma ($\alpha{-}\gamma$ discharge transition). Ionic species are shown to play an important role in the formation of hard carbon layers

Study of the wear behaviour of diamond-like coatings at elevated temperatures

The wear behaviour of a-C:H coatings in ambient air up to maximum temperatures of 300 degrees C is reported. A simultaneous tribological and thermal load was imposed using a low-amplitude oscillatory sliding test in combination with a heatable specimen holder. The investigation showed that the tribological behaviour of the a-C:H coatings changed considerably at elevated temperatures: the coefficient of friction decreased and the wear scars became larger and deeper, indicating a more severe wear process at elevated temperatures. Under the present test conditions tribological behaviour started to change around 100 degrees C. On previously annealed samples, however, the wear properties at room temperature remained stable up to annealing temperatures of 300 degrees C. The temperature dependent wear behaviour of diamond-like carbon has been linked to the surface properties of these materials which become modified at relatively low temperatures where bulk properties are known to remain unchanged. (C) 1998 Elsevier Science S.A.status: publishe

Application of atmospheric pressure dielectric barrier discharges in deposition, cleaning and activation.

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Study of the wear behaviour of diamond-like coatings at elevated temperatures

The wear behaviour of a-C:H coatings in ambient air up to maximum temperatures of 300 degrees C is reported. A simultaneous tribological and thermal load was imposed using a low-amplitude oscillatory sliding test in combination with a heatable specimen holder. The investigation showed that the tribological behaviour of the a-C:H coatings changed considerably at elevated temperatures: the coefficient of friction decreased and the wear scars became larger and deeper, indicating a more severe wear process at elevated temperatures. Under the present test conditions tribological behaviour started to change around 100 degrees C. On previously annealed samples, however, the wear properties at room temperature remained stable up to annealing temperatures of 300 degrees C. The temperature dependent wear behaviour of diamond-like carbon has been linked to the surface properties of these materials which become modified at relatively low temperatures where bulk properties are known to remain unchanged. (C) 1998 Elsevier Science S.A.status: publishe