Variation in ferroelectric polarization direction of epitaxial (001) SrBi2Ta2O9 thin film induced by oxygen vacancy

We report the enhancement of c-axis ferroelectric properties in an epitaxial (001) SrBi2Ta2O9 (SBT) thin film originating from the oxygen vacancy. We controlled the oxygen vacancy in the SBT thin film by using the electrical stress process triggering the polarization fatigue. As a result of the fatigue test for the Pt/SBT/Nb:STO capacitor, we observed the gradual increase in the ferroelectric polarization up to 1012 fatigue cycles and then subsequently rapid decrease over 1012 cycles. Based on piezoresponse force microscopy (PFM) measurements, we demonstrated the increase in the polarization and PFM signal resulting from the creation of oxygen vacancy.