Improved fatigue endurance in Mn-doped Bi3.25La0.75Ti3O12 thin films

Mn-doped Bi3.25La0.75Ti3O12 (BLT) thin films are fabricated by depositing sol-gel solutions on Pt/Ti/ SiO2/ Si〈100〉 substrate. Mn-doping in BLT films influences the ferroelectric properties, structural orientation, as well as the surface morphology of the films, even if the Mn concentration is low. Mn-doping at 1% of Ti-sites in BLT films enhances the remanent polarization and reduces the coercive field by approximately 25%. However, polarization decreases gradually by Mn-doping more than 1%, which may be due to the trapping of charged particles (holes or electrons) at defects located at the interface or grain boundaries generated by excess Mn-doping. The reduced polarization due to the Mn-doping recovers during switching cycles higher than 107-104 for the x value of 0.05-0.2 in Bi3.25La0.75Ti3−xMnxO12. Under the high switching field, the probability of field-assisted unpinning of domains is expected to be high and this may be the main cause for increase in polarization. Mn-doping significantly improves the fatigue endurance in BLT films because of de-trapping of charges from defects under high switching field.