Sharp ferroelectric phase transition in strained epitaxial SRO-BST-SRO capacitors

Single-crystalline all-perovskite SrRuO3/Ba0.7Sr0.3TiO3/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 Ba0.7Sr0.3TiO3 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 Ba0.7Sr0.3TiO3 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. (C) 2003 American Institute of Physics