Effect of zirconium doping on ferroelectric properties and leakage‐current mechanism in Bi3.25La0.75Ti3O12 (BLT) thin films

Leakage-current mechanism in BLT films after Zr doping was studied as a function of Zr doping. The ferroelectric properties improved with doping. With appropriate Zr-doping concentration, such as x = 0.025, the remnant polarization (2P(r)) increases by 36% and saturates afterwards. Different mechanisms for leakage-current conduction were fitted with the observed current density-voltage (J-V) plots, and interplay between the electrode and bulk-limited conduction was sought. Depending upon the field, the importance of a particular charge-conduction mechanism (under the coexistance of multiple mechanisms) was studied. Three different regions, i.e., Ohmic, trap-filled limited, Child's law were explicitly observed in J-V characteristics. Trap density was found to vary with Zr-doping concentration. The measured V-TFL was observed to reduce with increase in the temperature. The J-V behavior of BLT and Zr-doped BLT thin films were found to follow Lampert's theory of space-charge-limited conduction in an insulator with traps. The observed increase in low-field insulation was correlated with the space-charge conduction taking into account the modification of dielectric constant with the Zr doping. Like in BLT thin films, the charge transport in Zr-doped BLT thin films is well controlled by the space-charge-limited mechanism. (c) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim