Effect of Forming Gas on Properties of SrBi_2Ta_2O_9 Ferroelectric Thin Film and Powder

SrBi2Ta2O9 (SBT) ferroelectric thin film and powder samples were fabricated by using metal-organic decomposition (MOD) method. XRD and SEM results show that SBT powders still remain polycrystalline perovskite structure and amounts of Bi and δ-Bi2O3 are reduced from SBT annealed in the forming gas at 400℃. Spherical and needle structures form on the surface of SBT thin films annealed in the forming gas at 500℃. Bi element in powders is more easily reduced at lower temperature compared with that of thin films and form needle structures on SBT surface. Bi deficiency derived from forming gas annealing causes serious ferroelectricity degradation on the SBT capacitors. Annealed in the forming gas ambient at 400℃ for 5.5min,the remnant polarization of SBT films drop about 43%. If annealing time is longer than 8.5min,films are breakdown and ferroelectricity disappears totally. However,no obvious polarization fatigue with 109 electric field cycling could be observed.