Examination of consistency of intrinsic 2D conduction layer on BaTiO ₃ in extreme clean limit with ferroelectric basics

The present article shows that various contradictions with experiments appear if ferroelectrics are always intrinsically insulating. Conventionally, these contradictions have been thought due to extrinsic effects such impurities, defects and surface-dirtiness. On the other hand, as these extrinsic effects are more reduced, the semiconductivity of ferroelectrics as seen in the conduction layer at polarization discontinuity, e.g. at surface, becomes more evident. We discuss the implications to the ferroelectrics basics and the Slater-like origin of the ferroelectricity.