Compositional dependence of electrical characteristics of SrBi2(Ta1-xNbx)(2)O-9 thin-film capacitors

Ferroelectric capacitors using SrBi2(Ta1-xNbx)(2)O-9 (SBTN) were compositio nally altered varying Nb concentration from 0 to 1, the corresponding I - V and P - E electrical characteristics evaluated from room temperature to 14 5 degrees C. These temperature evaluations reveal that the leakage current will increase with larger Nb concentration and the dominant conduction mech anism changes from Schottky to Frenkel-Poole emission. The ferroelectric hy steresis curve shifts in the direction of negative polarization as the temp erature or the concentration of Nb increases. Concentration increases in Nb reduces the temperature dependence of remnant polarization and coercive fi eld. Film resistance to imprint and degradation from elevated temperature i mproves. Substituting b-site Nb for Ta allows imprinted capacitors to recov er 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 me mory performance. Optimized SBTN ferroelectric films will suitably perform in integrated circuit memory function applications provided that the leakag e current incurred at higher Nb concentrations can be reduced. (C) 1998 Ame rican Institute of Physics. [S0021-8979(98)05724-7].