CRYSTALLOGRAPHIC AND ELECTRONIC-STRUCTURE OF ULTRA THIN AG/CR/AG(100) SANDWICHES

We have investigated the electronic and crystallographic structure of thin Ag/Cr/Ag(100) sandwiches using angle-resolved ultraviolet (ARUPS) and X-ray (ARXPS) photoemission. First an ordered two-dimensional (2D) Cr monolayer is formed by deposition of one layer equivalent (LE) Cr onto a clean Ag(100) single crystal kept at 440 K under UHV conditions. The relevant ARXPS curves for Cr2p1/2 are structureless as expected for a single monolayer. Then Ag films (from the submonolayer range to 5 LE) are deposited at RT onto this Cr monolayer. Even after deposition of 3 LE Ag, the ARUPS spectra show the persistence of Cr3d induced features characteristic of the 2D Cr monolayer. However after Ag deposition the valence band spectra also reveal an additional sharp Cr3d peak at 1.2 eV binding energy, and the Cr2p1/2 ARXPS curves are structured and exhibit strong forward scattering features characteristic of a face-centered cubic environment. It is concluded that only a part of the Cr monolayer is destroyed and dissolves in the deposited Ag which grows in the form of 3D islands.