Memory effect of charge injection induced by polarization reversal in Pt/SrBi2Ta2O9/Pt thin-film capacitors identified from fast capacitance–voltage sweeping curves

The history of partial reversed domains in Pt/SrBi2Ta2O9/Pt thin-film capacitor arouses the splitting of the peak in one branch of butterfly capacitance–voltage (C–V) loops swept in a fast speed of 10 V/s. Nevertheless, the doublet emerges together, once the sweeping speed is slow enough. This is due to time-related imprint effect induced by the opposite trapped charges within the film thickness to compensate for the previous reversed domains. The previous volume fraction of switched domains under various dc voltages can be estimated from the intensity of the double peaks. Besides the memory effect due to the polarization reversal, one additional shoulder can also appear in the C–V loop under a stressing field at position equal to the applied voltage. This reflects the previous charge injection into the film under an arbitrary field. It is believed that the injected charge distribution within the film thickness facilitates the formation of a p–n junction with junction voltage equal to the applied voltage.