Abstract :
The effect of using a magnetic field to confine and focus the carbon plasma in a filtered cathodic vacuum arc (FCVA)
deposition system was investigated in the preparation of tetrahedrally bonded amorphous carbon (ta-C) thin films. The design of
the magnetic field was such that the plasma can be confined into a high-density focussed spot of 2 cm diameter or de-focussed
into a wide beam of 10 cm diameter. The microstructural, optical, tribological and surface properties of the ta-C films grown in
the high-density magnetic field were subsequently studied in detail.
Under a high-density magnetic field, ta-C thin films were deposited on Si and quartz substrates. Laser-induced surface
acoustic wave (L-SAW) measurements confirmed an increase in the Young’s Modulus and the bulk density of these films as
compared to ta-C films deposited under no or low magnetic field [Phys. Rev. B 48 (1993) 4777; J. Appl. Phys. 79 (1996) 7239].
XPS results showed a high >85% sp3 content on the surface while combined EELS and Raman measurements showed high and
constant sp3 content of >85% in bulk of all deposited films. An increase in optical bandgap was observed, from 3.6 to 3.9 eVas
the density of the plasma (and hence, the films) was increased. In addition, the overall surface free energy was also observed to
decrease from 44 to 40 dyn/cm. This confirms that under a high external magnetic field, the carbon plasma is confined and
focussed, and is thus able to deposit highly densified ta-C thin films with high optical bandgap and low sp2 defect density.
Tribological measurements showed that by comparing the high-density ta-C films with lower density ta-C films, the former have
a better adhesion to the substrate, as well as a better coefficient of friction and wear rate.
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