Graphitization of ultrathin amorphous carbon films on Si(001) by Ar⁺ ion irradiation at ambient temperature

We report the graphitization of ultrathin (8 nm) amorphous carbon films on Si(001) by 2 MeV Ar⁺ ion irradiation at ambient temperature. The resulting graphite films show the 〈001〉 preferred orientation in the film normal direction, but random distribution in the film plane direction. The smooth surface and interface suggest that the activation energy for the graphitization is supplied mostly by the electronic stopping process while Ar⁺ ions travel through the amorphous carbon film.