Physics of laser ablation plasma plumes for deposition of diamond-like carbon films under magnetized and field-free conditions

Abstract

Summary form only given. Pulsed laser deposition has been proven to be a useful technique for the synthesis of high quality diamond-like carbon films. In order to understand the mechanisms by which diamond-like carbon films grow, it is necessary to understand the physics of laser ablation plasmas. Quadruple Langmuir probes and optical spectroscopy are used to investigate the plasma created from ultraviolet laser ablation of a carbon target. A KrF excimer laser is used in this experiment with the laser energy varied between 300-1000 mJ. The laser spot sizes on the target were 0.22, 0.26 and 0.29 cm/sup 2/. Electron temperature, ion density, ion flow speed, and plume forward peaking factor are found as functions of laser energy density and spot size at various locations from the target surface. The results are found to be consistent with adiabatic expansion of the plume. Recently, the addition of a magnetic field has been employed to possibly steer the plume to remove macroscopic particulates. The effect of the addition of a 0.4 T magnetic field oriented perpendicular to the flow has been examined with quadruple Langmuir probes, magnetic probes, and optical spectroscopy. The plume behavior is quite different under the influence of the magnetic field. For instance, electron temperatures are found to increase significantly from the field-free case. It is postulated that this is due to magnetic field line diffusion in to the plume. The ion density traces indicate the presence of an instability not seen in the field-free case.