Wedgelike ultrathin epitaxial Ba Ti O 3 films for studies of scaling effectsin ferroelectrics

To study ferroelectric size effects in heteroepitaxial Sr Ru O 3 ∕ Ba Ti O 3 ∕ Sr Ru O 3 capacitors, ultrathin Ba Ti O 3 layers were deposited in wedge form across Sr Ti O 3 substrates. The wedgelike films were fabricated by using either an off-center substrate-target geometry or via a moveable shutter during high-pressure sputter deposition. The crystallinity, composition, and surface roughness along wedgelike Ba Ti O 3 films were verified by x-ray diffraction, Rutherford backscattering spectrometry, and atomic force microscopy, respectively. The electrical measurements performed at 77 K showed that, despite progressive reduction in remanent polarization as the film thickness decreases even the 3.5 - nm -thick Ba Ti O 3 film retains a large remanent polarization of 28 μ C ∕ cm 2 .