Ion-beam-induced conductivity in polymer films

Polymer films darken upon irradiation with energetic ion beams. At high doses (10¹⁶-10¹⁷ cm^{- 2}) of 2-MeV Ar⁺ ions, the resistivity of these insulating films decreases dramatically to 3.5×10^-3 Ω cm. Furthermore, over a wide range of doses (10¹⁴-10 ¹⁵ cm^-2) these films exhibit a temperature-dependent resistivity characteristic of carrier transport via hopping between isolated conducting islands. Rutherford backscattering measurements indicate that while a substantial amount of the carbon is retained in the film, other constituent elements are lost. Raman spectra show that the films are highly disordered at large ion doses.