Plasma diagnostics during pulsed laser deposition of diamond-like carbon using single crystal graphite and amorphous carbon

Optical emission study of ablation plasma plumes from single crystal graphite (SCG) anti amorphous carbon (a-C) targets during the preparation of diamond-like carbon (DLC) films by KrF excimer pulsed laser deposition (PLD) has been investigated. The C I emission intensity increases with laser energy density (E-L) increase, while the C-2 emission changes drastically with E-L for both ablated plasma plumes. The C-2/C emission intensity ratio for the a-C plum: decreases with E-L increase, while the C-2/C ratio for the SCG plume decreases with E-L increase: up to 3.0 J/cm(2), then increases slightly with further E-L increase. Nanohardness of the DLC film decreases with the C-2/C ratio increase. It is suggested that the C-2 molecule in the plasma plume does not play an important role in producing high quality DLC films, and that the C-2/C ratio is a good parameter to monitor the PLD process.