Polarization relaxation induced by a depolarization field in ultrathin ferroelectric BaTiO3 capacitors

Time-dependent polarization relaxation behavior induced by a depolarization field Ed was investigated on high-quality ultrathin SrRuO3/BaTiO3/SrRuO3 capacitors. The Ed values were determined experimentally from an applied external field to stop the net polarization relaxation. These values agree with those from the electrostatic calculations, demonstrating that a large Ed inside the ultrathin ferroelectric layer could cause severe polarization relaxation. For numerous ferroelectric devices of capacitor configuration, this effect will set a stricter size limit than the critical thickness issue.