VOLTAGE OFFSETS AND IMPRINT MECHANISM IN SRBI2TA2O9 THIN-FILMS

It is shown that voltage shifts in the hysteresis response of SrBi2Ta2 O9 (SET) thin-film capacitors can be induced using both thermal and op tical methods. These voltage shifts are important since they can lead to imprint failure in ferroelectric memory devices. It is suggested th at the voltage shifts in the hysteresis curve of SET are caused by tra pping of electronic charge carriers near the film/electrode interfaces , as has been previously reported for the Pb(Zr,Ti)O-3 (PZT) system. I n addition, a direct correlation is established between the magnitude and sign of remanent polarization (P-r) and the thermally induced volt age 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 ar e smaller than those optically induced. One. possible implication of t his result is that the contribution of defect-dipole complexes to the voltage shifts in SET is negligible. We suggest that the smaller contr ibution of defect-dipole complexes to the voltage shifts in SET may be related to a smaller oxygen vacancy concentration in the perovskite s ublattice of SET as compared to that of PZT. (C) 1996 American Institu te of Physics.