GROWTH OF ULTRATHIN FILMS OF FE ON AU(001)

The crystallographic aspects of the growth of ultrathin films of Fe on Au{001} are studied by means of quantitative low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The first monolayer of Fe is found to be pseudomorphic to the Au{001} substrate with an interlayer spacing of 1.825 angstrom, and to be covered by a monolayer of Au at an interlayer distance of 1.85 angstrom, which acts as a surfactant. Thicker films of Fe [up to 45 layer equivalents (LE)] may be pseudomorphic and hence slightly strained (the lattice misfit is 0.6%) or equilibrium bec with surface relaxation (the present analysis cannot distinguish between the two possibilities), but contain defects and disordered steps. Gold atoms are found to be segregated in the surface region of 45-LE Fe films, but mostly in a disordered arrangement. A comparison between the results obtained with two different computer programs for the calculation of LEED intensities finds that differences of 0.025 angstrom in the values of structural parameters may occur.