Growth of Fe on MgO(001) studied by He-atom scattering

With He-atom scattering we studied the epitaxial growth of Fe ultrathin films deposited on in situ cleaved MgO(001). The measurements at Various substrate temperatures (140 less than or equal to T less than or equal to 670 K) start with bare MgO(001) and extend to him thicknesses beyond the complete coverage of the substrate. From the development of specular intensity with Fe deposition we estimate saturation island densities, give a quantitative description of the evolution of their size and shape, and calculate a thickness for coalescence of all islands. The observed three-dimensional metal island growth behavior is suppressed at low temperature (140 K) where a monolayer film almost completely covers the substrate. For increased substrate temperatures a decreased island density and an increased interlayer mass transport from substrate level onto the islands leads to a temperature and thickness dependent change in island shape.