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Electrostatic force microscopy and scanning surface potential microscopy are applied to study force gradient and surface potential on BaTiO₃ (100) surface. Surface potential evolution during a ferroelectric/paraelectric phase transition and the potential distribution near moving domain walls allow the relationship between potential polarity and polarization orientation. Results indicate that polarization bound charge is completely screened on this surface and domain potential is reverse to that expected from domain polarity. Surface potential is attributed to the formation of double layer due to the complete screening of polarization charge. The absolute value of the measured potential difference between domains of opposite polarity suggests that surface adsorbates play a governing role in potential formation mechanism, though intrinsic screening by free carriers is not completely excluded.
Kalinin et al. (Tue,) studied this question.