The contrast mechanism of the scanning capacitance microscopy (SCM) to exhibit the ferroelectric domain structures is demonstrated. An image, developed by the mapping of differential capacitance in a virgin SrBi_2Ta_2O_9 (SET) thin film, was observed and three sharp contrast states of white, black, and gray were revealed. A hysteresis loop depicting the opposing polarities at zero bias was obtained by local measurement and, subsequently, the hysteretic capacitance-voltage curves, as the characteristic of domain switching, were acquired by integrating the calibrated differentiation capacitance. It is concluded that the white and black contrast in SCM images are due to the antiparallel 180 deg domains whereas the gray contrast is due to the trivial differential capacitance variation. These results strongly suggest that the local capacitance variation can be correlated well with the polarities of polarizations in nanoscale domains.
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