Charge-Transfer Satellites in K L23 XAS Data for K/Si(111)-(2 × 1): Evidence for Strong Ionic Bonds

We report K L23 edge X-ray absorption spectra (XAS, both normal and grazing incidence) and photoelectron spectra (XPS) for K/Si(111)-(2 X 1) at three different coverages (0.1, 0.3 and 0.5 ML). The data show features which exhibit a very strong variation in both the energy, intensity, and line shape with incidence angle and coverage. Some of these features correspond to charge-transfer satellites and give a measure of the hybridization of the ground state. They indicate very ionic bonding.