Phase formation and ferroelectric characteristics of nonfatigue barium bismuth tantalate thin films

The phase formation and ferroelectric properties of new nonfatigue BaBi2Ta2 O9 thin films prepared by the metal-organic decomposition method on Pt/Ti/S iO2/Si substrates have been investigated. After annealing at 700 degrees C, BaBi2Ta2O9 films become fully crystallized. On further higher temperatures , an unknown phase is formed by the interaction between the coated films an d titanium species diffusing outward from the underlying substrates. A seri es equivalent-circuit model is successfully applied to analyze the dielectr ic properties of the unknown phase and BaBi2Ta2O9 films. The intrinsic diel ectric constant of BaBi2Ta2O9 thin films is calculated to be 198. In the po larization-electric analysis, BaBi2Ta2O9 thin films exhibit saturated polar ization hysteresis curves, which demonstrates their ferroelectric character istics. The remnant polarization of BaBi2Ta2O9 thin films increases with in creasing annealing temperatures. Adding excess amount of bismuth contents ( 10 mol %) in BaBi2Ta2O9 thin films substantially further improves their fer roelectric properties. However, adding bismuth species more than 10 mol % l eads to the formation of Bi2O3, thereby inducing high leakage current. Addi ng 10 mol % excess bismuth in BaBi2Ta2O9 thin films, the resultant films ex hibit a high remnant polarization (2P(r) = 14 mu C/cm(2)), a low coercive f ield (2E(c) = 45 kV/cm), and a fatigue-free characteristic up to 10(9) swit ching cycles. (C) 1999 American Institute of Physics. [S0021-8979(99)04523- 5].