Ferroelectricity in epitaxial pulsed laser deposited bismuth-layered perovskite thin films of different crystallographic orientations

Epitaxial thin films of various bismuth-layered perovskites SrBi2Ta2O9, Bi4Ti3O12, BaBi4Ti4O15, and Ba2Bi4Ti5O18 were deposited by pulsed laser deposition onto epitaxial conducting LaNiO3 or SrRuO3 electrodes on single crystalline SrTiO3 substrates with different crystallographic orientations or on top of epitaxial buffer layers on (100) silicon. The conductive perovskite electrodes and the epitaxial ferroelectric films are strongly influenced by the nature of the substrate, and bismuth-layered perovskite ferroelectric films with mixed (100), (110)-and (001)-orientations as well as with uniform (001)-, (116)-and (103)-orientations have been obtained. Structure and morphology investigations performed by X-ray diffraction analysis, scanning probe microscopy, and transmission electron microscopy reveal the different epitaxial relationships between films and substrates. A clear correlation of the crystallographic orientation of the epitaxial films with their ferroelectric properties is illustrated by macroscopic and microscopic measurements of epitaxial bismuth-layered perovskite thin films of different crystallographic orientations.