Identification of conduction due to the spontaneous electron layer on the clean free surface of ferroelectric

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The large size effect of ferroelectric is probably due to its unique surface rather than to an intrinsic/essential limitation. The present study clarifies the fundamental properties of a possible new two dimensional electron phase coupled strongly with lattice that is expected to exist on the top surface of the ferroelectric and determine its minimum size limit. This electron phase is expected to exhibit novel phenomena such as unusual electron conduction.We have suggested that the large size effect of ferroelectric and the limitations of FET-type ferroelectric non-volatile memories are probably due to its unique surface rather than to an intrinsic limitation. The present study have attempted to clarify the fundamental properties of a possible new two dimensional electron phase coupled strongly with lattice that is expected to exist on the top surface of the ferroelectric and determine its minimum size limit. This electron phase is expected to exhibit novel phenomena such as unusual electron conduction as well as the response to UV light and the possibility of UV emission and electron emission, leading to a new research area of ferroelectrics. The existence of this hypothetic electron layer and some of these properties are experimentally confirmed by measuring the surface conduction of pure BaTiO_3 single crystals in ultrahigh vacuum. Moreover, we found a new atomic force microscopy to observe 180° domains utilizing the properties of surface electron layer.