Slow relaxation of the polarization in pulsed laser ablated highly oriented ferroelectric thin films

The relaxation of the polarization (as determined by the pyroelectric effect) of high quality laser ablated films of PbZr _0.52Ti _0.48O ₃ has been measured after saturation with an applied electric field. The decay is observed to be quasilogrithmic over four decades in time Analysis of measurements of the remanent polarization and the depolarization remanence are consistent with the depolarization field providing a polarization-state-dependent field of the correct direction to drive the decay. Also, the quasilogrithmic time dependence is consistent with a model for slow relaxation or creep with the depolarization field the driving field for the decay.These observations along with our AFM measurements imply that for maximum polarization stability a ferroelectric film should consist of decoupled grains. The optimum grain size should be the maximum grain size which does not support domain walls.