Effect of SrTiO3 deposition temperature on the dielectric properties of SrTiO3/YBa2Cu3O7-delta/LaAlO3 structures

We report on the effect of the deposition temperature of SrTiO3 on the dielectric properties of SrTiO3/YBa2Cu3O7-delta/LaAlO3 thin film multilayer structures. In these structures, the YBa2Cu3O7-delta (YBCO) films were deposited at 800 degrees C by laser ablation, followed by the in-situ deposition of the SrTiO3 (STO) layer at one of the following temperatures: 750 degrees C, 650 degrees C, 550 degrees C, 450 degrees C, 350 degrees C, and 250 degrees 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 (epsilon(r)) and loss tangent (tan delta) 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 degrees C to be a deposition temperature which allows for large variations of epsilon(r) with applied field, and with limited enhancement of tan delta. Lower deposition temperatures cause a reduction of the induced change in epsilon(r) and an increase in tan delta with applied field.