Voltage offsets and imprint mechanism in SrBi2Ta2O9 thin films

It is shown that voltage shifts in the hysteresis response of SrBi2Ta2O9 (SET) thin-film capacitors can be induced using both thermal and optical methods. These voltage shifts are important since they can lead to imprint failure in ferroelectric memory devices. It is suggested that the voltage shifts in the hysteresis curve of SET are caused by trapping of electronic charge carriers near the film/electrode interfaces, as has been previously reported for the Pb(Zr,Ti)O-3 (PZT) system. In addition, a direct correlation is established between the magnitude and sign of remanent polarization (P-r) and the thermally induced voltage shifts (V-i), where V-i = alpha P-r + beta. It is also found that, unlike the PZT system, the thermally induced voltage shifts in SET are smaller than those optically induced. One. possible implication of this result is that the contribution of defect-dipole complexes to the voltage shifts in SET is negligible. We suggest that the smaller contribution of defect-dipole complexes to the voltage shifts in SET may be related to a smaller oxygen vacancy concentration in the perovskite sublattice of SET as compared to that of PZT. (C) 1996 American Institute of Physics.