Photoemission Evidence for Dilute K-doped Phase K_x C₆₀ with x<0.2

A shift about 0.3eV to higher binding energy is reported in the valence band and Cls core level of K_x C₆₀(x<0.2). Analysis shows that the result could not be interpreted by a mixture of C₆₀ and K₃ C₆₀. A dulite K-doped phase and fermi level pinning near the lowest unoccupied molecular orbital derived band
caused by K-doping are proposed.