Structural and electrical properties of Ba_0.5Sr_0.5TiO₃ thin films with conductive SrRuO₃ bottom electrodes

Epitaxial Ba_0.5Sr_0.5TiO₃ (BST) thin films were deposited on LaAlO₃ substrates with the conductive metallic oxide SrRuO₃ (SRO) as a bottom electrode by pulsed laser deposition. The BST and SRO films were (h00) and (00l) oriented normal to the substrate surface, respectively. The epitaxial nature of both BST and SRO layers was determined by the measurement of in-plane orientation with respect to the major axes of the substrate. Ion beam channeling with a minimum yield of around 10% from Rutherford backscattering spectrometry demonstrated the films to be of high crystallinity. A dielectric constant around 500 and dielectric loss less than 0.01 at a frequency of 10 kHz were measured on the capacitors with a configuration of Ag/BST/SRO. Electrical measurements on such epitaxial BST films showed a breakdown voltage above 10⁶ V/cm and a leakage current density of less than 5×10^-8 A/cm at a field intensity of 2×10⁵ V/cm. These results prove the BST/SRO heterostructure to be a good combination for microelectronic device applications.