X-ray photoemission investigations of binary and ternary C60 fullerides of Na, K, Rb, and Cs.

Core-level photoemission studies of alkali fulleride A x C 60 o thin films indicate alkali bonding configurations that can be associated with octahedral and tetrahedral interstitial sites of the C 60 lattice. For K x C 60 , the K 2p core-level results suggest K 3 C 60 nucleation for K concentration as low as x∼0.1 with occupation of both octahedral and tetrahedral sites. In contrast, the Rb 3d and Cs 4d core-level spectra show filling of only octahedral sites until x∼1, forming A 1 C 60 phases. For intercalation beyond x∼1, the fcc tetrahedral sites of Rb are occupied as Rb 3 C 60 forms