Microstructure and electrical properties of (120)O-oriented and of (001)O-oriented epitaxial antiferroelectric PbZrO3 thin films on (100) SrTiO3 substrates covered with different oxide bottom electrodes

Abstract

Epitaxial antiferroelectric PbZrO3 (PZO) thin films of two different crystallographic orientations were grown by pulsed laser deposition on (100)-oriented SrTiO3 single crystal substrates. The latter were covered either with SrRuO3 epitaxial bottom electrodes, or with an epitaxial BaZrO3 buffer layer and an epitaxial BaPbO3 bottom electrode, respectively. Their crystal orientation and microstructure were characterized by x-ray diffraction, transmission electron microscopy, and electron diffraction. The orthorhombic (index O) PZO films on SrRuO3∕SrTiO3 were predominantly (120)O oriented and consisted of four azimuthal domains forming 90° and 60° boundaries, whereas those grown on BaPbO3∕BaZrO3∕SrTiO3 were (001)O oriented. All films showed well-defined double P-E hysteresis loops, four distinct switching peaks in the current-voltage characteristics, and piezoelectric double loops recorded by piezoresponse scanning force microscopy. The values of the saturation polarization PS and the critical field EC of the (120)O-oriented PZO films (PS=41μC∕cm2; EC=445kV∕cm) are different from those of the (001)O-oriented films (PS=24μC∕cm2; EC=500kV∕cm). A transition temperature to the paraelectric phase of 260°C has been found, which is 30K higher than the bulk value, probably indicating a stabilization of the antiferroelectric phase by substrate-induced strain.