ENERGY TRANSFERENCE EFFECTS ON THE MECHANICAL PROPERTIES OF C_(60) FILMS IRRADIATED WITH N IONS

摘要

The nanoindentation technique was used to determine the hardness and Young's modulus of thin C_(60) films irradiated with N ions. The pristine film, with thickness of 170 nm, was grown on a Si (111) substrate, with an intermediary layer of SiO_2 50nm thick. An X-ray analysis reveals a fcc structure for the pristine C_(60) films. The N irradiation was performed with energy of 170 keV (R_p of 380nm) and fluences ranging from 5×10~(11) to 5×lO~(15) ions.cm~(-2). The loads used in the nanoindentation tests were from 0.05 to 16 mN in order to obtain information about the film, the interface and the substrate. The hardness and Young's modulus, for the pristine and irradiated films were compared considering normalised values at tip penetrations of 70 nm. For the C_(60) non-irradiated film, the hardness and the Young's modulus were 0.31 GPa and 23 GPa respectively. After N irradiation at fluences greater than 10~(13) ions.cm~(-2), the hardness and Young's modulus changed drastically, rising to 15 GPa and 170 GPa respectively at fluence of 5×10~(13). These results are discussed in terms of the energy transference mechanisms by the N ions into the C_(60) film.