SUPERFULLERIDE FORMATION AND ELECTRONIC-PROPERTIES OF C60 ON K/RH(111) SURFACES

Despite the high electron affinity of C60, photoemission and work function measurements of C60 on Rh(111) surfaces containing submonolayer amounts of K show that a low value of the work function is not sufficient to cause extensive charge transfer (> 1 electron) from the substrate to the C60 molecule. However, when appropriate amounts Of C60 are evaporated onto potassium multilayers of controlled thickness at 100 K, interdiffusion occurs and potassium superfullerides, KxC60 with 6 < x < 12, form on the surface. The resulting phases can be purified by annealing the sample to almost-equal-to 325 K for x-->12, or higher temperatures for lower K stoichiometries, to drive out excess K.