STUDY OF INTERFACE ROUGHNESS AND CRYSTALLOGRAPHIC STRUCTURE OF AU/CO/AU SANDWICHES

Polycrystalline texturized Au/Co/Au "sandwiches" are prepared by vacuum deposition on glass substrates. The roughness of the gold base layer has been measured by grazing angle X-ray reflectometry and scanning tunnelling microscopy: similar values were found with both methods. The variation in the free surface roughness was then monitored by soft X-ray reflectometry during the growth of the cobalt film and of the second overlayer of gold. The roughness is found to be constant for thicknesses of gold or cobalt overlayers lower than 3 nm and increases steadily for greater thicknesses. The surface crystallographic structure of the cobalt overlayer has been studied by reflection high energy electron diffraction: a surface lattice expansion of almost 13% is measured for cobalt coverages of one atomic layer that relaxes for cobalt thicknesses greater than 10 monolayers.