FORMATION OF AIR-STABLE BURIED K-FULLERIDE LAYERS BY ION-IMPLANTATION

The formation process of buried K-fulleride layers by high dose implan tation of 30 keV K+ at an implant temperature of 300 degrees C has bee n studied as a function of dose. Raman scattering showed a transformat ion of the fullerene molecules to amorphous carbon (a-C) within the ra nge of the implanted ions. At the elevated implant temperatures used m ost of the K diffuses into the depth where a doped layer is formed. Th e buried K-fulleride layer is stable on air due to a passivation by th e a-C. The formation process is discussed on the basis of the K-C-60 p hase diagram and various thermodynamic processes like segregation, pha se formation and diffusion.