CHARGE-TRANSFER AND A NEW IMAGE STATE OF C-60 ON CU(111) SURFACE STUDIED BY INVERSE-PHOTOEMISSION

We have used inverse photoemission to study ultra-thin C-60 films adso rbed on Cu(111) surfaces. Unlike a previous study of C-60 adsorption o n a Au film where the unoccupied states shift rigidly towards the Ferm i level, the spectra here look strongly perturbed and more-like those characteristic of K3C60. This indicates that the interaction of C-60 W ith Cu is much stronger than with Au. Annealing at 350 degrees C resul ts in a well ordered (4 x 4) structure as seen in LEED. An additional broad peak appears below the vacuum level. This new state has a parabo lic dispersion with an effective mass dose to unity. We interpret this state as the image state or resonance on top of the metallized C-60 o verlayer. Copyright (C) 1996 Elsevier Science Ltd