Design Of Hybrid Magnetic Field For The Graphite Cathode Arc Source And Preparation Of Ta-C Film

Tetrahedral amorphous carbon(ta-C) film is a kind of amorphous tetrahedral carbon film with high sp~3 carbon bond content, and it is widely utilized on the field of automobile, electron, biology and so on. And it has also been paid more attention owing to its high hardness, low friction coefficient, wear resistance. ta-C film are frequently fabricated using graphite cathodic arc deposition. However, the low density, high ionization energy and negative temperature coefficient of graphite target result in the combustion instability and easy extinguishment of graphite cathodic arc. Aiming at this issue, a certain magnetic field type was used to make the graphite cathodic arc burn stably in this thesis. The effect of coil current, auxiliary anode, Ar flux, bias voltage, and arc current on discharge characteristics of graphite target was studied under the circumstance of the stable combustion of graphite target. Simultaneously, the effect of substrate bias voltage, Ar flux and deposition time on the structure and properties of ta-C films was also investigated.The magnetic field around the cathodic target was numerically simulated using Ansys software and the results were utilized in designing the structure of magnetic field of the cathodic source. The graphite cathode spot would do rotational motion in a certain region to make graphite cathode arc stable when the magnetic field produced by the coil was opposite to the permanent magnet and the configuration of the magnetic field was appropriate on the surface of target. The utilization ratio of target was improved and the burning of target materials was more uniform when a shielding component was utilized. With the increase of burning time the graphite cathodic arc spot gradually moves close to the edge of target and a circular depression was formed near the rim of the target. This leaded to the instability of graphite cathode.The process parameters had significant influence on discharge characteristics of graphite target. The peak current of the substrate increased with the increase of coil current, auxiliary anode current and target current. However, it decreased with the increase of Ar flux. By the usage of the spectrograph, the characteristics of plasma in front of graphite target were measured, and the results showed that the increase of coil current improved the intensity of Ar(0), Ar~+ and C~+.Bias voltage had a significant effect on the structure and properties of ta-C films. When the bias voltage was-100 V, the film showed that the sp~3 fraction was the highest deduced by Raman spectra, and the film possessed the best corrosion resistance with the corrosion potential of-0.472 V. With the increase of the Ar flux, the sp~3 fraction is lower with higher friction coefficient.