Low energy electron diffraction analysis of ultrathin Ag films on W(110)

We have measured low energy electron diffraction data for clean W(110), ult rathin and thick Ag films on W(110). The data are analyzed by full dynamica l multiple scattering calculations to determine the structure of the Ag-fil m/W(110) system. The multiple scattering calculation takes into account the incommensurate scattering between the non-pseudomorphic Ag films and the W (110) substrate. We have examined the effect of dynamical inputs used in th e calculation. We find that for normally incident electrons, the surface ba rrier at the vacuum-film interface and the inelastic damping modify mainly relative intensities of the diffraction peaks while the energy-dependent in ner potential at low energies influences peak positions. After the dynamica l inputs are independently determined, we use the data below 25 eV where th e electron's mean free path is long, to determine the layer spacing at the Ag film - W substrate interface. A major trend we find is that the layer sp acing at the interface decreases as the Ag film's thickness increases.