The structure and degradation mechanism of SrBi2Ta2O9 thin films

SrB2Ta2O9 thin films were grown on Pt/Ti/SiO2/Si substrate by the pulsed la ser ablation deposition method. The crystalline fluorite phase was maintain in the annealing temperature from 540 to 750 degrees C and SET phase appea red at 750 degrees C, crystallized at 800 degrees C, which was observed in the xray diffraction patterns and scanning electron microscopy images. The grains, which were spherical-like, increased from about 50 to 325 nm in dia meter with increasing annealing temperature from 540 degrees C to 800 degre es C. The SBT film annealed at 800 degrees C showed P-r = 6.1 mu C/cm(2), E -c = 65 kV/cm at applied voltage of 5 V, and the hysteresis loops became sa turated at 3 V. The fatigue characteristics of SET thin films with various applied voltage and frequency have also been investigated. It revealed that the polarization fatigue occurred with decreasing switching voltage and fr equency. This significant polarization fatigue is originated due to partial switching when the switching voltage is lower than saturation voltage (sim ilar to 3 V). The signal/noise ratio had maximum value of 5 at 3 V, which i s capable of low-voltage operation in NVFRAM device.