Excimer laser ablation of graphite: The enhancement of carbon dimer formation

Abstract

Carbon plasmas produced by laser ablation can have important applications in the synthesis of nanostructured materials of high current interest (nanotubes, nanowires, graphene) or the deposition of diamond-like thin films. Understanding the fundamental aspects of such transient plasmas in various experimental configurations is useful for optimization of these synthesis/deposition processes. We report here a comprehensive study on the dynamics of an excimer laser produced carbon plasma, including fast photography, space- and time-resolved optical emission spectroscopy, Faraday cup ion current measurements, ablated crater depth profiling. A peculiar V-like shape of the emitting plume is evidenced and explained by the interaction of three plasma structures originating in distinct irradiance areas of the laser spot on the target. The interaction of these structures is also thought to favor an enhanced carbon dimer production, mainly through three-body recombination, at distances significantly higher than previously reported in the literature, which can find technological applications for the efficient deposition of high quality carbon-based nanostructures.