Conduction at SrTiO3/LaAlO31 is intensively studied. Before this, conduction at clean surface of fully oxygenated BaTiO3 in UHV (ultrahigh vacuum) was reported.2 This verified conduction at charged domain-boundaries and ferroelectric interfaces.2 These conductances are too small for electronics but are fundamental for domains, because they screens depolarization field.3 Using nm-scale and macroscopic probes, we’ll clarify static and dynamic properties of natural domains of unpolished atomically flat surface of fully oxygenated stoichiometric BaTiO3 single crystal in UHV, air, and acid, which are explained by DFT/GL calculations: The electrostatic domain patterns agree excellently with piezoelectric force response images (PFM) with nearly complete screening of electric field from domains of atomically cleaned surface in UHV without extraneous screening. Both +PS and -PS surface show conduction: The location of each conduction is titanium of one unitcell deeper than top surface and the outermost oxygen, respectively. The domain patterns in UHV, air and acid are mutually very similar. In particular, we find a perfect agreement of domain patterns obtained by etching and PFM for the first time and invariance of domains of air in acid. The domain size/width in UHV, air, and acid was the same despite 100-times difference of permittivity (screening efficiency) between UHV and acid. These results verify intrinsic screening of depolarization field is inside ferroelectric, consistently with the evidence by conduction.2 This screening explains the absence of natural vortex domains on free surface and nano-ferroelectrics such as compulsory nano-domain.
1Ohtomo-Hwang, Nature427(2004), 2Watanabe et al, PRL86(2001), 3Watanabe, PRB57(1998).