Role of excess Bi in SrBi2Ta2O9 thin film prepared using chemical liquid deposition and sol-gel method

We studied the role of excess Bi, added to improve ferroelectirc properties of SrBi2Ta2O9 (SBT) thin him whose Bi-layered structure is fatigue-free characteristics for Nonvolatile memory. The lost of Bi by annealing process was not observed even after annealing at 850 degrees C in chemical liquid deposition (mixed alkoxide solution system). In SBT films composed of fluorite and Bi-layered structure grains, Bi-layered structure grains had a higher Bi content than that in fluorite grains. Excess Bi was added to promote crystallization of fluorite to the Bi-layered structure easy. SET film close to stoichimometric composition formed by a hydrolyzed, condensed solution (sol-gel method) had superior ferroelectric properties despite its closely stoichiometric Sr0.9Bi2.1Ta2O9 composition. Closely stoichiometric Sr0.9Bi2.1Ta2O9 SET film shows no fatigue even after 3x10(12) switching cycles. The improved SET formation solution that is hydrolyzed, condensed solution makes excess Bi unnecessary.