Wedgelike ultrathin epitaxial BaTiO3 films for studies of scaling effects in ferroelectrics

Abstract

To study ferroelectric size effects in heteroepitaxial SrRuO3∕BaTiO3∕SrRuO3 capacitors, ultrathin BaTiO3 layers were deposited in wedge form across SrTiO3 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 BaTiO3 films were verified by x-ray diffraction, Rutherford backscattering spectrometry, and atomic force microscopy, respectively. The electrical measurements performed at 77K showed that, despite progressive reduction in remanent polarization as the film thickness decreases even the 3.5-nm-thick BaTiO3 film retains a large remanent polarization of 28μC∕cm2.