Fullerene C20 synthesis in carbon plasma produced by Nd:YAG laser ablation

Abstract

Intense ns laser pulses can be employed to generate carbon plasma by ablation of carbon vitreous targets in a high vacuum. The high plasma temperature (up to about 80 eV) and density (up to about 0.2 μg/cm³ in the first μs) and the high energy (up to about 2.5 keV C ions) of ablated ions produce carbon vapor, atom nucleation, and the growth of nanostructures. The carbon atoms in plasma may generate aggregates with high molecular weight, bonding energy, and stability, such as nanostructures with high density and ordered configurations. The technique of the laser ablation of carbon vitreous assisted by mass quadrupole spectrometry has permitted the ablation of the target glassy carbon surface and the analysis of the masses of the carbon-aggregated laser plasma generated in vacuum. It has been observed that a high yield is due to the C₂₀ fullerenes synthesis (240 amu), together with different precursors of carbon molecules, such as C₁₇–C₁₉ and C_21–23. The yield of C₂₀ generation is higher with respect to these precursors, indicating higher stability. The conditions to generate these carbon atom aggregates are presented as a function of the laser parameters (pulse energy from 100 mJ up to 500 mJ) and plasma characteristics. The dynamic of the C₂₀ formation is also reported, as well as the possible applications of these carbon-aggregated nanostructures.