Characterization of ferroelectric lead zirconate titanate films by scanning force microscopy

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Abstract
Scanning force microscopy (SFM) has been used for the determination of friction, phase transformation, piezoelectric behavior (in the contact mode), polarization state, and dielectric constant (in the noncontact mode) of nanometer regions of lead zirconate titanate (PZT) films. The use of the SFM tip in the contact mode, to polarize different nanoregions of the PZT film and to apply an oscillating field thereon, led to effective piezoelectric coefficients and piezoelectric loops. The measured effective piezoelectric coefficient was shown to depend appreciably on both the tip contact force and the quality of the tip-to-film electrical contact. In the noncontact mode, application of an ac signal (with a frequency ω) across the tip—PZT film—electrode system produced an oscillation of the tip at frequencies ω (fundamental or first harmonic) and 2ω (second harmonic). The signals at ω and 2ω were related to the state of polarization and the dielectric constant of the PZT film, respectively. Analysis of the combined contact, noncontact and friction force microscopic data provided insight into the structure and into the dielectric, ferroelectric, and piezoelectric properties of distinct nanoregions of the PZT film.