Fluorinated Diamond-like Carbon Films Research Articles

STUDY OF FLUORINE ADDITION INFLUENCE IN THE DIELECTRIC CONSTANT OF DIAMOND-LIKE CARBON THIN FILM DEPOSITED BY REACTIVE SPUTTERING

The hydrogenated amorphous carbon films (a-C:H) or DLC (Diamond-Like Carbon) films are well known for exhibiting high electrical resistivity, low dielectric constant, high mechanical hardness, low friction coefficient, low superficial roughness and also for being inert. In this paper, we produced fluorinated DLC films (a-C:F), and studied the effect of adding CF 4 on the above-mentioned properties of DLC films. These films were produced by a reactive RF magnetron sputtering system using a target of pure carbon in stable graphite allotrope. We performed measurements of electrical characteristic curves of capacitance as a function of applied tension (C-V) and current as a function of the applied tension (I-V). We showed the dielectric constant (k) and the resistivity (ρ) as functions of the CF 4 concentration. On films with 65% CF 4, we found that k = 2.7, and on films with 70% CF 4, ρ = 12.3 × 1011 Ω cm. The value of the electrical breakdown field to films with 70% CF 4 is 5.3 × 106 V/cm.

Heat resistance of fluorinated diamond-like carbon films

The heat resistance of fluorinated diamond-like carbon (F-DLC) films produced by Plasma Immersion Ion Processing (PIIP) technique was investigated by annealing F-DLC coatings in a vacuum furnace. The growth rate for the F-DLC films was approximately 0.6 μm/h. In order to see the possible change in the composition and properties of the F-DLC films, Rutherford Backscattering Spectrometry (RBS), nanoindentation and contact angle measurements were performed before and after the heat treatments. The results show that the composition and properties of the F-DLC films were unchanged up to heat treatment at 300°C for up to 30 min. Blistering and film delamination occurred for samples treated at 400°C.

Synthesis of fluorinated diamond-like carbon films by the plasma immersion ion processing technique

The synthesis of fluorinated diamond-like carbon (F-DLC) films was investigated for the first time using the plasma immersion ion processing technique. A pulsed glow discharge plasma was generated at a pressure of 1 Pa from acetylene and hexafluoroethane gas mixtures and the films were deposited on silicon 〈100〉 substrates by applying a pulsed bias to the substrate holder. The film hardness, wear resistance and nonwetting properties were found to be strongly dependent on the fluorine content incorporated into the coatings. With an optimum gas ratio, the deposited F-DLC films were found to have nonwetting properties similar to Teflon®, but were 10 times harder (8 GPa).

Wear-resistant fluorinated diamondlike carbon films

Fluorinated diamondlike carbon (FDLC) films have been deposited on Si wafers by rf plasma-assisted chemical vapor deposition, under a variety of conditions. The films have been characterized by FTIR and index of refraction measurements, RBS and FRES analysis for determination of film composition, and stress measurements from the bending of the wafers by the deposited films. Friction and wear measurements have been performed using pin-on-flat and pin-on-disk testers in ambient air, at maximum Hertzian contact pressures ranging from 320 to 1100 MPa. By adjusting the deposition parameters, the properties of the FDLC films could be changed from soft films, with no significant wear resistance, to films containing more than 20% F and having wear resistance comparable to unfluorinated DLC. The tribological properties of the FDLC films are discussed in relation to their physical properties, as determined by the deposition conditions.