Interface structures and strain relaxation mechanisms of ferroelectric BaTiO3/SrTiO3 multilayers on (001) MgO substrates

Interface structures and strain relaxation mechanisms of ferroelectric BaTiO3/SrTiO3 multilayers on (001) MgO substrates were systematically studied by electron microscopy. The multilayers are formed in bi-layered structures with different growth morphologies. (i) The lower layer with single crystallinity is an epitaxial layer on the MgO substrate. Defects such as misfit dislocations, anti-phase boundaries, and stacking faults reveal in this layer, acting as a strain relaxation mechanism and (ii) the upper layer is the rest of the multilayer, exhibiting a highly textured columnar structure with small angle boundaries. The columnar grains are formed by local epitaxial growth within individual grains. The strain-relaxation mechanisms are established to understand the growth dynamics of the multilayers.