Sharp ferroelectric phase transition in strained single-crystalline SrRuO₃/Ba_0.7Sr_0.3TiO₃/SrRuO₃ capacitors

Single-crystalline all-perovskite SrRuO₃/Ba_0.7Sr_0.3TiO₃/SrRuO₃ thin-film capacitors epitaxially grown on SrTiO₃ exhibit a sharp paraelectric-to-ferroelectric phase transition at 350 K with a maximum permittivity of about 6660. This value is comparable to that of bulk ceramics and exceeds by several times the highest values reported for Ba_0.7Sr_0.3TiO₃ thin film capacitors. The observed thickness dependence of the dielectric response is analyzed with the aid of a thermodynamic theory. It is shown that a weak decrease of the permittivity with the Ba_0.7Sr_0.3TiO₃ thickness decreasing from 200 to 10 nm can be explained solely by the thickness-dependent strain relaxation in epitaxial films without assuming the presence of low-permittivity layers at the film/electrode interfaces. © 2003 American Institute of Physics.