Substrate-induced effects in the creation and decay of potassium 2p core excitations in ultrathin films of KCl on copper

Substrate-induced effects on the transport properties in thin KCl films on the Cu(100) surface have been studied using K+ 2p photoelectron, photoabsorption and resonant Auger spectra. The measurements were performed at different KCl coverages ranging from a partial monolayer to a thick bulk-like film. The morphology and layer thickness were estimated from an analysis of the electron energy loss structure of the K+ 2p and Cl- 2p photoelectron peaks, and from the variations in the photoelectron peak fine structure. The resonant Auger spectator decay spectra measured at the photoabsorption resonances show that the significant differences between the spectra of the solid and of thin layers are related to the charge delocalization from the K+ 3d excited state into the metal substrate. The core-hole-clock approach yields an estimate of 1.5 fs for the corresponding charge transfer time at a single monolayer KCl coverage