Lattice strain and lattice expansion of the SrRuO3 layers in SrRuO3/PbZr0.52Ti0.48O3/SrRuO3 multilayer thin films

In ${\mathrm{SrRuO}}_3/{\mathrm{PbZr}}_{\text{0.52}}{\mathrm{Ti}}_{\text{0.48}}{\mathrm{O}}_3/{\mathrm{SrRuO}}_3$ multilayer thin films on ${\mathrm{SrTiO}}_3$ substrates the different lattice distortion behavior of the top and the bottom ${\mathrm{SrRuO}}_3$ film layer is found and characterized by means of transmission electron microscopy. The bottom ${\mathrm{SrRuO}}_3$ layer is compressively strained in the film plane by a constraint of the ${\mathrm{SrTiO}}_3$ substrate. In contrast, in the interface area of the top ${\mathrm{SrRuO}}_3$ layer, a lattice dilatation is measured not only in the film plane but also parallel to the film normal. The misfit strain, the lead interdiffusion and the oxygen concentration in this area are investigated and discussed as possible reasons for the unexpected lattice dilatation along the film normal direction.