Structure and properties of epitaxial Ba0.5Sr0.5TiO3/SrRuO3/ZrO2 heterostructure on Si grown by off-axis sputtering

Abstract

We report the growth and characterization of epitaxial Ba0.5Sr0.5TiO3/SrRuO3/ZrO2 on Si for potential charge storage applications. Both Ba0.5Sr0.5TiO3 (BST) and SrRuO3 (SRO) are grown (110)-oriented on yttrium-stabilized ZrO2 (YSZ) (100)-buffered Si. These films show a high degree of crystallinity with minimal interdiffusion at the interfaces as evidenced from x-ray diffraction, Rutherford backscattering, and transmission electron microscopy. Studies on the in-plane crystallographic relations between the layers revealed an interesting rectangle-on-cube epitaxy between BST/SRO and YSZ. The dielectric constant and loss tangent of the BST dielectric layer are 360 and 0.01 at 10 kHz, respectively. The leakage current density is lower than 4×10−7 A/cm2 at 1 V. A strong frequency dependence on both dielectric constant and loss tangent is observed in 1–10 MHz frequency range. This is attributed to the effect of a series resistance in the measurement loop, which is likely related to the bottom SrRuO3 electrode.