Effects of high energetic He+ ion irradiation on the structure of polymeric hydrogenated amorphous carbon

Abstract The effects of 2 MeV He + ion irradiation on the structure of polymeric hydrogenated amorphous carbon films were studied. It was found that after the irradiation up to a dose of 1.0×10 16  cm −2 , the carbon network transforms from a polymer-like to a diamond-like structure, as evidenced using Raman spectroscopy. Correspondingly, the optical band gap shrinks from 3.0 to 2.0 eV and the refractive index increases from 1.5 to 1.7. The processes of dehydrogenation and carbon rebonding into hydrogen-free C(sp 3 ) and C(sp 2 ) clusters under the impact of the incident ions are suggested to account for the carbon structural transformation.