Quantitative study of domain structure of BaTiO3 single crystal by UHV-sanning probe microscopy

The nanoscopic properties of the clean, free surface of a BaTiO₃ single crystal in an ultra-high vacuum is examined. Atomic force microscopy, piezoelectric force microscopy and Kelvin force microscopy measurements show that the potential difference between upward and downward 180deg domain is approx 100 mV. This value is 100 times smaller than the value estimated by using the standard 180deg domain theory. Furthermore, our experiments show that this result cannot be explained only by the conventional explanations (that is, a decrease in the depolarization field by closure domains, the compensation of polarization bound charge by contamination or by oxygen excess and deficiency, or ion transport). The results suggest a possibility that an intrinsic electrostatic shielding mechanism exists in the ferroelectrics and is essential for 180deg domains.