ELECTRICAL-RESISTIVITY AND STOICHIOMETRY OF KXC60, RBXC60 AND CSXC60 FILMS

Electrical resistance measurements as a function of stoichiometry have been carried out on KxC60, RbxC60 and CsxC60 thin films for 0 < x < 6 . The annealed films show global resistance minima at K3C60, rho(min)= 4 X 10(-3) Omega cm (60 degrees C), Rb3C60, rho(min)=4 X 10(-3) Omega cm, and Cs1C60, rho(min)=7 X 10(-2) Omega cm. All of the annealed film s show additional features in the vicinity of x=4, but the manifestati on of the A(4)C(60) phase (A=K, Rb, Cs), in transport studies is depen dent on the metal and the annealing conditions. The A(6)C(60) phase is apparent for all of the metals studied and shows a relatively high re sistivity. The activation energies of the conduction process show well defined stationary points at K3C60 (not activated), Rb3C60 (not activ ated). Cs1C60 (minimum), Cs4C60 (maximum), with less distinct features between 4 < x < 6 in all cases.