c -axis oriented epitaxial BaTiO3 films on (001) Si

c -axis oriented epitaxial films of the ferroelectric BaTiO3 have been grown on (001) Si by reactive molecular-beam epitaxy. The orientation relationship between the film and substrate is (001) BaTiO3‖(001) Si and [100] BaTiO3‖[110] Si. The uniqueness of this integration is that the entire epitaxial BaTiO3 film on (001) Si is c-axis oriented, unlike any reported so far in the literature. The thermal expansion incompatibility between BaTiO3 and silicon is overcome by introducing a relaxed buffer layer of BaxSr1−xTiO3 between the BaTiO3 film and silicon substrate. The rocking curve widths of the BaTiO3 films are as narrow as 0.4°. X-ray diffraction and second harmonic generation experiments reveal the out-of-plane c-axis orientation of the epitaxial BaTiO3 film. Piezoresponse atomic force microscopy is used to write ferroelectric domains with a spatial resolution of ∼100nm, corroborating the orientation of the ferroelectric film.