CHARACTERIZATION OF FERROELECTRIC LEAD-ZIRCONATE-TITANATE FILMS BY SCANNING FORCE MICROSCOPY

Scanning force microscopy (SFM) has been used for the determination of friction, phase transformation, piezoelectric behavior (in the contac t mode), polarization state, and dielectric constant (in the noncontac t mode) of nanometer regions of lead zirconate titanate (PZT) films. T he use of the SFM tip in the contact mode, to polarize different nanor egions of the PZT film and to apply an oscillating field thereon, led to effective piezoelectric coefficients and piezoelectric loops. The m easured effective piezoelectric coefficient was shown to depend apprec iably on both the tip contact force and the quality of the tip-to-film electrical contact. In the noncontact mode, application of an ac sign al (with a frequency omega) across the tip-PZT film-electrode system p roduced an oscillation of the tip at frequencies omega (fundamental or first harmonic) and 2 omega (second harmonic). The signals at omega a nd 2 omega were related to the state of polarization and the dielectri c constant of the PZT film, respectively. Analysis of the combined con tact, noncontact and friction force microscopic data provided insight into the structure and into the dielectric, ferroelectric, and piezoel ectric properties of distinct nanoregions of the PZT film. (C) 1997 Am erican Institute of Physics.