DOPING OF FULLERENES BY ION-IMPLANTATION

C60 films have been implanted with 30 KeV K+ ions with doses from 1 x 10(14) to 1 x 10(16) cm-2 at target temperatures up to 350-degrees-C. Conductivity measurements performed in situ show a decrease in sheet r esistivity with increasing dose for fullerene samples implanted at ele vated temperatures, whereas implantation at room temperature results i n no change of resistivity. After exposing the samples to air the resi stivity remains constant over weeks. Raman scattering showed that an a morphous surface layer is formed by the implantation process and that the fullerene molecules beyond this layer remain undestroyed. Secondar y ion mass spectrometry and Rutherford backscattering indicate that at elevated implant temperatures K diffuses into deeper regions of the f ilm whereas oxygen is present only in a surface layer about 10 nm thic k.