Bulk and surface charge states of K3 C60

Abstract

We detect a significant angle-dependence in the core level and valence line shapes of photoelectron spectra of single crystal K3 C60. This allows the identification of bulk and surface components in the data, and allows us to explain the anomalous line shapes observed for this system. The states near the Fermi level are associated with the bulk of the sample. There is strong evidence of an insulating surface layer, which we ascribe to intermolecular electron correlations. These results simplify the interpretation of previous, apparently conflicting observations. © 2005 The American Physical Society.