Diamond-like carbon deposition by laser ablation

The plasma plume generated during laser ablation of a carbon target (graphite 99.99%), is characterized by means of Optical Emission Spectroscopy (OES) and the Langmuir probe technique. Both techniques allow the determination of the mean kinetic energy of ions present in the plasma. Besides that, information about the excited species and the plasma density is obtained. Ablation is carried out using a Nd:YAG laser operated at the fundamental frequency with laser fluences in the range of 2 to 6 J/cm 2 . The main excited specie in the plasma is the C + (299.26 and 426.7 nm). The kinetic energy of these ions can be varied from 100 eV up to 500 eV, as a function of the used fluence. The plasma density varies from 2 x 10 12 cm -3 up to 9 x 10 13 cm -3 , depending on the fluence and on the target-probe distance. Different samples of amorphous carbon thin films were deposited using different plasma parameters. The films show a sp 3 /sp 2 ratio which depend on the plasma conditions: a higher ratio is obtained for high densities and medium ion kinetic energies (about 200 eV). A 60% sp 3 content, in some samples, could be obtained in these experiments. The deposited films were analyzed using Raman spectroscopy and EELS.