High resolution study of domain nucleation and growth during polarization switching in Pb(Zr,Ti)O-3 ferroelectric thin film capacitors

The domain nucleation and growth during polarization switching in Pb(Zr,Ti) O-3 (PZT) ferroelectric thin film capacitors with Pt top (TE) and bottom el ectrodes (BE) were studied by means of atomic force microscopy (AFM). The e xperimental configuration used in this study differs from that conventional ly used (AFM tip/PZT/BE) where the AFM tip acts as a positionable TE. A sma ll ac voltage was applied between the electrodes with a step by step increa sing dc bias voltage. The induced piezoelectric vibration was detected by t he AFM tip, its amplitude and phase determined with the lock-in amplifier. The phase difference between the applied ac voltage and the piezoelectric s ignal as a function of the x-y position was nearly locked at 0 or 180, repr esenting film regions with parallel (in-phase) and antiparallel (antiphase) polarization direction, respectively. The polarization reversal was induce d by application of a step by step increasing dc bias field opposite to the polarization of the prepoled sample. At each bias step 10 mu mx10 mu m ima ges of the amplitude and the phase were collected. By approaching the coerc ive field (E-c), a rapid decrease of the amplitude with a small change in p hase was observed, first in preferential sites for reversed nucleation, the n over the whole studied area. The first regions with reversed polarization were observed at about 3.2 MV/m and the switching was completed at 5.5 MV/ m. The results were interpreted using both the forward and the sideways dom ain growth models that are named by their rate-limiting kinetics. It was co ncluded that under the assumption of a sufficient resolution of domain imag ing in our study, the forward domain growth being the rate limiting mechani sm prevails in our PZT thin film. (C) 1999 American Institute of Physics. [ S0021-8979(99)03513-6].