Electrode size effect on switching time of SrBi₂Ta₂O₉thin films

The polarization switching properties of SrBi2Ta2O9(SBT) thin-film capacitors with different areas of the top electrode in a range of 7.85×10-5- 7.85×10-3cm2were studied by traditional integration method. The switching time of the SBT thin films increases rapidly with increasing top electrode area. To clarify its origin, the capacitance of the samples was measured and various external loads of the measuring circuit were tested. It is found that the switching time increasing is proportional to the capacitance increasing as the top electrode area increases. During the switching measurement the "real" capacitance of the thin film is much larger because of the polarization reversal and causes a larger delay of charge delivery from the voltage source to the thin film. Thus in the case of large top electrode area, the real characteristic time is dominant, leading to a significant size effect on switching time.