Structure, dielectrical properties and capacitance properties of Ba0.3Sr0.7Zr0.18Ti0.82O3/BaTiO3 hetero-structure thin films with different BTO layer thicknesses

Abstract

Ba0.3Sr0.7Zr0.18Ti0.82O3/BaTiO3 (BSZT/BTO) films containing 70–640 nm BTO layers and pure BaTiO3 film were deposited on Pt(111)/Ti/SiO2/Si substrate using radio frequency (RF) magnetron sputtering. The effect of the BTO layer thickness on the structure and electrical properties of the resulting BSZT/BTO films was investigated by x-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as dielectrical tests. The BTO layer thickness significantly affected the structure and, as a result, the electrical properties of the corresponding BTO/BSZT thin films. Thin films containing 190 nm BSZT layer and 70–640 nm BTO films demonstrated gradually improved crystallinity as the BTO layer thickness increased. Additionally, the (110) crystalline orientations of these films were more evident as the BTO layer thickness increased, which also resulted in improved electrical properties. When the thickness of BTO film was 640 nm, the dielectric constant, dielectric loss, and leakage current density of the BSZT/BTO composite thin film were 139, 0.00816 at 1 MHz, and 1.36 × 10−6 A cm−2 at 40 V, respectively. The same values for 680 nm thick pure BTO film were 147, 0.02197 at 1 MHz, and 7.63 × 10−6 A cm−2 at 40 V, respectively. Thus, BSZT/BTO hetero-structured film with a 640 nm BTO possessed lower dielectric loss and six times smaller leakage current than pure BTO film. The reduction of dielectric loss and leakage current will improve the quality of the devices containing BTO films, which is advantageous for their wide-spread practical applications. Meanwhile, the relationship between the thickness of BTO layer and capacitance is explored, and the dielectric constant of BSZT buffer layer is calculated.