Transmission electron microscopy study of Co/Pd and Co/Au multilayers

Abstract

The structure of Co/Pd and Co/Au (111) multilayers is studied using transmission electron microscopy and high resolution electron microscopy. We focused on microstructure, atomic stacking (especially at the interfaces), and coherency, as these are structural properties that have considerable magnetic effects. A columnar structure with a strong curvature of the multilayer influenced by substrate temperature during growth is observed. High resolution imaging shows numerous steps at the interfaces of the multilayer structure and the presence of misfit dislocations. In bright-field images, periodic contrast fringes are observed at these interfaces as the result of moiré interference. These moiré fringes are used to study the misfit relaxation at the interfaces, whereas electron diffraction gives the average relaxation over the whole layer. Both measurements determined that, for Co/Pd as well as Co/Au multilayers, 80–85% of the misfit is relaxed and 20–15% remains in the form of strain, independent of the Co layer thickness in the regime studied.