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Here we introduce angle-resolved piezoresponse force microscopy (AR-PFM), whereby the sample is rotated by 30° increments around the surface normal vector and the in-plane PFM phase signals are collected at each angle. We obtained the AR-PFM images of BaTiO3 single crystal and cube-on-cube epitaxial (001) BiFeO3 (BFO) thin film on SrRuO3/SrTiO3 substrate, and confirmed that the AR-PFM provides more unambiguous information on the in-plane polarization directions than the conventional PFM method. Moreover, we found eight additional in-plane polarization variants in epitaxial BFO thin films, which are formed to mitigate highly unstable charged domain boundaries. [ABSTRACT FROM AUTHOR]

Systematic studies are presented on the effects of cantilever buckling in vector piezoresponse force microscopy (V-PFM) imaging of polarization domains in thin-film based (001)-oriented BiFeO3 nanostructures, as observed through the coupling of out-of-plane and in-plane PFM images. This effect is a strong function of the laser spot position on the cantilever, being strongest at the free end, and insignificant at 60% of the cantilever length from the pivot point. This finding provides a unique approach to V-PFM imaging of ferroelectric polarization domains, yielding three dimensional PFM images without sample rotation in the plane. [ABSTRACT FROM AUTHOR]

We studied polarization switching of 295 nm thick 〈111〉-oriented-Pb(Zr[SUB0.45]Ti[SUB0.55])O[SUB3] (PZT) thin-film capacitors through a polarization hysteresis loop and piezoelectric force microscopy (PFM) on top of the Pt electrode. Positive voltage pulses of 450 kV/cm and 2.5 ms were applied to the top as a poling pulse. Negative pulses ranging from -45 to -60 kV/cm at an interval of 3 kV/cm were applied to the top electrode. After each pulse, we performed PFM imaging by applying 17 kHz ac voltage of 1 V peak to peak to the bottom electrode while grounding the top one and the tip. The first-harmonic amplitude and phase of the tip vibration signal were mapped over the scanned area of 10 × 10μm[SUP2]. Subsequently, we measured the polarization hysteresis curve at 100 Hz after each domain image acquisition to estimate the volume fraction of switched polarization induced by the positive voltage pulses. We analyzed the areal fraction of switched domains as a function of pulse voltage from phase images and compared it with the volume fraction obtained from the hysteresis loops. Based on the evolution of domain images and the comparison plots of the areal and volume fractions of switched domains, we conclude that forward domain growth is a rate-limiting step during polarization reversal in 〈111〉-oriented-PZT thin-film capacitors. [ABSTRACT FROM AUTHOR]

We introduce a method to investigate the domain stability issue based on piezoresponse microscopy. The switching and back-switching processes of sol-gel derived (Pb[sub 0.76]Ca[sub 0.24])TiO[sub 3] thin films were investigated by comparing the local piezoelectric hysteresis loops in continuous mode and pulse mode. It was found that the local hysteresis loops acquired by the pulse mode in shorter pulse width were dominated by the back-switching process while the continuous mode piezoelectric hysteresis loop provides information on the domain switching process. [ABSTRACT FROM AUTHOR]

Direct observation of polarization distribution at nanoscale by scanning force microscopy across partially etched Pb(Zr, Ti)O[sub 3] film ferroelectric capacitors with size 2 × 3 µm and preferential orientation (111) has revealed an anomalous polarization pattern characterized by polarization inversion in the center of the capacitor. This self-structured pattern is reproducible and independent on the spontaneous polarization orientation, but strongly influenced by the film texture and capacitor size. In particular, capacitors of the same texture with size 0.5 × 0.5 µm as well as capacitors with (100) preferential orientation of any size did not exhibit such anomalous polarization distribution. A tentative explanation consistent with the essential features of the observed polarization behavior in terms of strain-induced phase transition is discussed. [ABSTRACT FROM AUTHOR]

The size, shape, and polarization orientation of fatigued areas formed during the suppression of the switchable polarization (P[sub r][sup s]) (fatigue) in Pt–PZT–Pt ferroelectric capacitors (FECAPs), were observed by means of atomic force microscopy and by imaging the phase of the piezoelectric vibration induced by a low ac field applied between the top and bottom electrodes. In the virgin state (FECAP as prepared), the pattern of the polarization domains with opposite orientation was randomly distributed with typical sizes of 1–3 μm. The application of a dc field larger than the coercive field (E[sub c]) enabled to fully orient the polarization of the regions in either directions. During the initial fatigue (<35% of suppressed P[sub r][sup s]), polarized regions with frozen orientation and size ranging between 100 nm and 1 μm became visible. In the fatigued state (>65% of suppressed P[sub r][sup s]), two main configurations of the frozen polarization domains were distinguished. One was characterized by a strong preferential direction (top to bottom electrode) and the other by randomly distributed regions of opposite oriented frozen polarization. The degrees of fatigue obtained by analyzing the vibration phase images are in good agreement with those obtained by standard polarization measurements. It is concluded that the P[sub r][sup s] suppression (fatigue) is due to “region by region” or “grain by grain” freezing of P[sub r][sup s] and that the frozen P[sub r][sup s] can have a preferential orientation. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]