Heteroepitaxial growth of Ba_0.5Sr_0.5TiO₃/SrRuO₃ on YSZ/Si by off-axis sputtering

We demonstrate an epitaxial heterostructure of Ba_0.5Sr_0.5TiO₃/SrRuO₃/YSZ on Si for potential charge storage applications. The dielectric Ba_0.5Sr_0.5TiO₃ (BST) and conductive oxide SrRuO₃ are both grown (110) oriented on YSZ (100) buffered Si by 90° off-axis sputtering. These films showed a high degree of crystallinity with minimal interdiffusion at the interfaces as examined by X-ray diffraction, Rutherford backscattering spectroscopy, and cross-section transmission electron microscopy. The in-plane epitaxial alignment of the films is BST/SRO 〈111〉 // YSZ 〈110〉 with a four-fold degeneracy. The dielectric constant and loss tangent of the epi-BST films are 360 and 0.01 at 10 kHz. The leakage current density is <4×10^-7 A/cm² at 1 V. The room temperature dielectric constant (ε) of the BST films shows a roll-off in the 1-10 MHz range. This is attributed to the existence of a series resistance in the measurement circuit, which likely arises from the SrRuO₃ electrode.