Analysis of leakage current conduction phenomenon in thin SrBi₂Ta₂O₉ films grown by excimer laser ablation

Abstract

The dc conduction behavior of thin films of SrBi₂Ta₂O₉ (SBT) has been investigated on the basis of space-charge limited current theory. The theory was generalized to account for the traps, which were inevitably present in this case. The relative percentage of trapped injected charge and the free injected charge was seen to follow a dynamical equilibrium instead of the true thermal equilibrium as the temperature of the sample was raised during the measurement. The onset voltage of the trap filled region (V_TFL) showed a decreasing trend with the increase of temperature. This reduction of V_TFL was ascribed to the appearance of some excess charge in the conduction band. It was seen that the thermodynamically stable distribution of charges among the energy levels could not be taken to explain such a situation. A dynamic model was proposed to explain this kind of a nonequilibrium distribution of trapped and free charges.