Nanoscale study of the ferroelectric properties of SrBi2Nb2O9 thin films grown by pulsed laser deposition on epitaxial Pt electrodes using atomic force microscope

SrBi2Nb2O9 (SBN) thin films deposited by laser ablation on epitaxial (100)Pt and (110)Pt have been studied using an atomic force microscope (AFM) in the so-called "piezoresponse" mode. Previous X-ray studies have shown that in the first case two different orientations coexist in the film: a predominant (0 0 1) orientation with a (115) orientation. AFM topographical images reveal the presence of two different kinds of grains of different shape corresponding to each orientation and AFM piezoresponse images are in agreement with the crystallographic orientation of the grains: only the expected (115) oriented grains show a piezoelectric contrast. Moreover, hysteresis loops are obtained over (115) grains and not over (001) regions. Although (115) grains can be in a monodomain state, they also show intragranular ferroelectric domains with nanometric sizes, which orientation can be reversed by applying a dc field between the AFM tip and the grounded conductive bottom electrode of the sample. In the second case, the use of a (110)Pt electrode instead of a (100)Pt electrode leads to preferentially (116) SBN oriented films, inducing far better ferroelectrics properties. In spite of a weak remnant polarization, the surface shows an homogeneous polarization when a 1 mum x 1 mum area is probed after the reversal of the polarization by the AFM tip. (C) 2003 Elsevier Science B.V. All rights reserved.