Effect of SrTiO₃ deposition temperature on the dielectric properties of SrTiO₃/YBa₂Cu₃O_7-δ/LaAlO₃ structures

Abstract

We report on the effect of the deposition temperature of SrTiO₃ on the dielectric properties of SrTiO₃/YBa₂Cu₃O_7-δ/LaAlO₃ thin film multilayer structures. In these structures, the YBa₂Cu₃O_7-δ (YBCO) films were deposited at 800°C by laser ablation, followed by the in-situ deposition of the SrTiO₃ (STO) layer at one of the following temperatures: 750°C, 650°C, 550°C, 450°C, 350°C, and 250°C. Gold (Au) films were deposited and patterned on top of the STO layer to form planar Au/STO/YBCO capacitor structures. The electrical response was studied by measuring the dielectric constant (ε_r) and loss tangent (tanδ) of the ferroelectric film from 300–40 K, at 1.0 MHz, and at electric fields up to 100 kV/cm. Our results show 750°C to be a deposition temperature which allows for large variations of ε_r with applied field, and with limited enhancement of tanδ. Lower deposition temperatures cause a reduction of the induced change in ε_r and an increase in tanδ with applied field.