Band-gap states and ferroelectric restoration in strontium bismuth tantalate

By means of photoluminescence (PL) and sub-band-gap (sub-E-g) optical illumination, the degradation and restoration of ferroelectric properties in strontium bismuth tantalate thin films have been investigated, and the existence of band-gap states is demonstrated. It is shown that the suppression and recovery of ferroelectricity are closely correlated with the change of PL intensity, since both switchable polarization and PL are related to Ta5+ ions in the TaO6 octahedron. Furthermore, the electric-field-induced restoration increases dramatically by the aid of sub-band-gap light (2.5 eV less than or equal toh nu less than or equal toE(g)) illumination absorbed in band-gap states. (C) 2001 American Institute of Physics.