Impact of surface properties on the dielectric breakdown for polycrystalline and multilayered BaTiO3 thin films

The dielectric reliability for polycrystalline and multilayered BaTiO3 thin films has been evaluated using time-zero and time-dependent dielectric breakdown techniques. The histogram of dielectric breakdown for multilayered BaTiO3 thin films showed a typical Weibull distribution in contrast to a random distribution when compared with polycrystalline BaTiO3 thin films. The measurement resulted in that the 400 nm-thick multilayered BaTiO3 thin film sustained about 105 hour-long operation at 1 MV/cm, showing superior properties when compared with polycrystalline. The smaller leakage current level was obtained for a multilayered BaTiO3 film having a relatively thick underlayer of polycrystalline BaTiO3 film. The value of the breakdown field was smaller at the thicker multilayered BaTiO3 while the distribution of the breakdown widened for thicker film. Analysis of the roughness for the films confirmed that the field breakdown mechanism (e.g., lowering and spreading) is related to the surface roughness of the topmost layer which varies with the thickness of underlying polycrystalline BaTiO3. The reduced leakage current at the thick multilayered BaTiO3 was due to the presence of a wide transition layer between polycrystalline and amorphous BaTiO3.