LOW-ENERGY ION-ASSISTED CARBON-FILM GROWTH - METHODS AND MECHANISMS

Hydrogen-free amorphous carbon films (a-C) prepared by different ion a ssisted methods (i) ion assisted evaporation (IAE), (ii) unbalanced ma gnetron sputtering (MS), (iii) mass separated ion beam deposition (MSI BD) and (iv) filtered vacuum cathodic are evaporation (VA) in the opti mum energy range of about 100 eV were compared. Density data, Raman sp ectra and surface topography images show a different behaviour of the films. The different growth processes were discussed in connection wit h results from ion implantation experiments into IAE a-C and computer calculations of the ion-solid interactions by use of the TRIM-code, Se lf-interstitials in the sub-surface region of the carbon matrix create d due to pure carbon ion beam bombardment (MSIBD and VA) are the key f or the understanding of the densification process. The lower number of self-interstitials created during the noble-gas ion assisted processe s can be compensated by extremely high argon-ion to carbon-neutral arr ival ratios in the case of MS. Furthermore, the sputtered carbon atoms with energies in the range of a few eV should assist this deposition process, Without energetic carbon particles (thermal carbon atoms from the evaporation process) as in the case of neon ion assisted evaporat ion, it is also possible to prepare dense a-C, however with lower dens ity (2.7 g/cm(3)).