Microstructural evolution of [PbZr x Ti1– x O3/PbZr y Ti1– y O3] n epitaxial multilayers (x/y = 0.2/0.4, 0.4/0.6)–dependence on layer thickness

Abstract

The microstructure of ferroelectric [PbZr x Ti1− x O3/PbZr y Ti1− y O3] n epitaxial multilayers (x/y = 0.2/0.4, 0.4/0.6) deposited on SrRuO3-coated SrTiO3 substrates by pulsed-laser deposition with different layer periodicity and layer thickness was characterized by means of transmission electron microscopy. Electron diffraction and contrast analysis revealed a very clear and well-separated layer sequence. The microstructures of PbZr0.2Ti0.8O3/PbZr0.4Ti0.6O3 and PbZr0.4Ti0.6O3/PbZr0.6Ti0.4O3 multilayers show a similar tendency in the dependence on the individual layer thickness. Whereas with thick individual layers, tetragonal a-domains are confined to specific layers of the two types of multilayers, below a certain critical thickness of the individual layers, a-domains extend over the whole film. This indicates a transition into a uniform tetragonal lattice and strain state of the whole multilayer. Increasing the layer periodicity further, the interfaces in PbZr0.4Ti0.6O3/PbZr0.6Ti0.4O3 multilayers become rough, and complex a-domain configurations appear.