K/graphite: Uniform energy shifts of graphite valence states

Ultra-thin graphite overlayers prepared by heating SiC crystals can give highly resolved valence band photoemission spectra. This is exploited to monitor K deposition induced energy shifts of graphite valence band states. States near the corners of the Brillouin zone, responsible for the semimetal character of graphite, are observed to show shifts that are nearly equal to the shifts of the uppermost filled σ state and of an empty state 7.6 eV above EF. The results give credence to the rigid band shift model often used to discuss the electronic structure and charge transfer for graphite ad- and absorption systems.