Control of the Graphite Femtosecond Ablation Plume Kinetics by Temporal Laser Pulse Shaping: Effects on Pulsed Laser Deposition of Diamond-Like Carbon
Résumé
This study proposes to consider the effect of temporal laser pulse shaping on graphite femtosecond laser ablation plume composition and kinetics, and its potential for depositing diamond-like carbon (DLC) films. Double pulses and long pulses with up to 100-ps delay and 10-ps duration, respectively, are used. The plasma composition and kinetics are investigated by using an optical emission spectroscopy system with a spatial resolution along the ejection axis. Temporal pulse shaping is shown to strongly modify the quantities of the different ejected species in the plume. In particular, it reduces the number of slow C2 or C3 radicals and increases the proportion of monomers, adding ionized species in front of the plume. At the same time, the different components of the multimodal plasma plume maintain their average speed whatever temporal pulse shape is used, thus demonstrating the kinetic modifications. The multiwavelength Raman study of DLC films deposited using different temporal pulse shapes does not reveal significant structural differences between the films. This was found to be in accordance with a prevalence of neutral C atoms and radicals in all the generated plumes, the former being responsible for the subplantation process.