Structural and dielectric properties of pulsed laser deposited Pb[Yb_1/2Nb_1/2]O₃-PbTiO₃ thin films

Heterostructures consisting of (001) LaAlO₃ or (111) SrTiO₃ substrates, SrRuO₃ metallic oxide bottom electrodes and Pb[Yb_1/2Nb_1/2]O₃-PbTiO₃ ferroelectric films were deposited by pulsed laser deposition. The combination of oxidic perovskite-type materials results in highly 〈001〉- or 〈111〉-heteroepitaxial capacitors with well-defined and homogeneous columnar microstructures. Most of the films show room temperature dielectric constant greater than 1500 associated with low dielectric loss (tgδ < 4%) and exhibit saturated hysteresis loops with remanent polarizations up to P_r ∼ 50μC.cm^-2. It was found that the ferroelectric characteristics and, in particular, the fatigue phenomena greatly depend on the orientation and crystalline quality of the as-grown films. The stabilization of the 〈001〉-orientation enhances the fatigue resistance and a good endurance up to 10¹¹ cycles has been determined for highly 〈001〉-textured samples. In contrast, fatigue tests performed on strongly 〈111〉-oriented capacitors have revealed poor fatigue performances, with a progressive decrease in the switchable polarization by ac voltage cycling.