Self-polarization and migratory polarization in thin lead zirconate-titanate films

Abstract

This paper reports on a study of the electrical properties of 0.7–1-µm-thick textured PZT ferroelectric films prepared by rf magnetron sputtering of a PbZr0.54Ti0.46O3 target which additionally contained 10 mol % lead oxide. Such films are shown to feature a combination of a self-polarized state and migratory polarization. The totality of the data obtained suggest that the films had n-type conduction. As shown by the laser beam modulation technique, the polarization was distributed nonuniformly in depth, with most of the poled state localized near the lower interface of the thin-film ferroelectric capacitor. The mechanism underlying the onset of this self-polarization is related to the charging of the lower interface of the structure by electrons, which occurs during the cooling following the high-temperature treatment of the PZT film, and to poling of the bulk of the film by the charged interface. This mechanism of the self-polarization of ferroelectric films is believed to have a universal character.