Nano-graphene structures deposited by N-IR pulsed laser ablation of graphite on Si |
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Authors: | E. Cappelli S. Orlando C. Scilletta |
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Affiliation: | a CNR-ISC, Montelibretti, Via Salaria Km 29.3, P.O.B. 10, 00016 Monterotondo, Rome, Italy b CNR-IMIP, Potenza, Zona Industriale, 85050 Tito Scalo, Potenza, Italy c CNR-IMM, Bologna, Via P. Gobetti 101, 40129 Bologna, Italy |
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Abstract: | Thin nano-structured carbon films have been deposited in vacuum by pulsed laser ablation, from a rotating polycrystalline graphite target, on Si 〈1 0 0〉 substrates, kept at temperatures ranging from RT to 800 °C. The laser ablation was performed by a Nd:YAG laser, operating in the near IR (λ = 1064 nm).X-ray diffraction analysis, performed at grazing incidence angle, both in-plane (ip-gid) and out-of-plane (op-gid), has shown the growth of oriented nano-sized graphene particles, characterised by high inter-planar stacking distance (d? ∼ 0.39 nm), compared to graphite. The film structure and texturing are strongly related both to laser wavelength and substrate temperature: the low energy associated to the IR laser radiation (1.17 eV) generates activated carbon species of large dimensions that, also at low T (∼400 °C), easy evolve toward more stable sp2 aromatic bonds, in the plume direction. Increasing temperature the nano-structure formation increases, causing a further aggregation of aromatic planes, voids formation, and a related density (by X-ray reflectivity) drop to very low values. SEM and STM show for these samples a strongly increased macroscopic roughness. The whole process, mainly at higher temperatures, is characterised by a fast kinetic mode, far from equilibrium and without any structural or spatial rearrangement. |
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Keywords: | 81.15.Fg 81.07.&minus b 81.05.Uw 61.10.Eq 68.37.Hk 68.55.Jk |
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