Ferroelectric properties of laser-ablated Sr1-xAxBi2Ta2O9 thin films (where A=Ba, Ca)

Bismuth-layered ferroelectric thin films of Sr(1-x)A(x)Bi(2)Ta(2)O(9), with composition x=0 and 0.2, were fabricated by using the pulsed-laser deposition technique. Structural characterization of the films by x-ray diffraction and atomic force microscopy, revealed that the films are polycrystalline in nature with average grain size of 180 nm. The films displayed spherical grains with a surface roughness of 12 nm. The ferroelectric measurements of Sr0.8Ba0.2Bi2Ta2O9, SrBi2Ta2O9, and Sr0.8Ca0.2Bi2Ta2O9 showed saturated hysteretic behavior with remanent polarization (2P(r)) of 23.5, 17.9, 14 muC/cm(2) and coercive field (E-c) of 31.06, 74.2, 86.3 kV/cm for a maximum applied electric field of 360 kV/cm. Films exhibited minimal (less than or equal to17%) degradation of polarization for up to 10(10) switching cycles. It was observed that the coercive field decreased with increase in the ionic size of partially substituted cations. The leakage current density of films were found to be of the order of similar to10(-8) A/cm(2) for up to a breakdown field of about 75 kV/cm. (C) 2002 American Institute of Physics.