Compositional dependence of electrical characteristics of SrBi2(Ta1-xNbx)2O9 thin-film capacitors

Ferroelectric capacitors using SrBi2(Ta1-xNbx)(2)O-9 (SBTN) were compositionally altered varying Nb concentration from 0 to 1, the corresponding I - V and P - E electrical characteristics evaluated from room temperature to 145 degrees C. These temperature evaluations reveal that the leakage current will increase with larger Nb concentration and the dominant conduction mechanism changes from Schottky to Frenkel-Poole emission. The ferroelectric hysteresis curve shifts in the direction of negative polarization as the temperature or the concentration of Nb increases. Concentration increases in Nb reduces the temperature dependence of remnant polarization and coercive field. Film resistance to imprint and degradation from elevated temperature improves. Substituting b-site Nb for Ta allows imprinted capacitors to recover by application of either bipolar fatigue pulses at room temperature (RT) or, cycling P - E measurement pulses at elevated temperature. Due to this asymmetrical tradeoff of film ferroelectric properties, there is an optimum identifiable range of Nb concentrations (0.25-0.5) capable of achieving memory performance. Optimized SBTN ferroelectric films will suitably perform in integrated circuit memory function applications provided that the leakage current incurred at higher Nb concentrations can be reduced. (C) 1998 American Institute of Physics. [S0021-8979(98)05724-7].