Low-energy electron diffraction structure determination of an ultrathin CoO film on Ag(0Â 0Â 1)

The atomic structure of a four layer thick film of CoO on a Ag(0 0 1) substrate has been determined by comparing experimental low-energy electron diffraction (LEED) I(V) curves with multiple scattering calculations. The CoO film has been prepared using reactive evaporation of Co in an oxygen atmosphere leading to almost layer-by-layer growth. Contrary to the surface of CoO crystals an outward relaxation of the two outermost CoO layers as well as rumpling in the top layer has been found. The supposed driving force of this relaxation is the in-plane compressive stress, which results from the pseudomorphic growth of the CoO film on the Ag(0 0 1) substrate and the lattice mismatch of the two materials.