Electrical transport in Na, K, Rb, and Cs fullerides: Phase formation, microstructure, and metallicity.

The electrical properties of the alkali-metal fullerides have been investigated via parallel resistivity measurements and photoelectron spectroscopy. Phase formation associated with the incorporation of Na, K, Rb, and Cs into C 60 films is reflected by the dependence of resistivity on temperature and alkalimetal concentration. Photoemission spectra show the details of the filling of states derived from the lowest unoccupied molecular level and the consequences of electron correlation. For K-C60 and Rb-C 60 films, the resistivity and photoemission results indicate metallic character only for the A 3 C 60 phase