Asymmetry in fatigue and recovery in ferroelectric Pb(Zr,Ti)O3 thin-film   capacitors
  We investigate the fatigue and refreshment by dc-electrical field of the electrical properties of Pt/Pb(Ti,Zr)O$_3$/Pt ferroelectric capacitors. We find an asymmetry in the refreshment, that is, the fatigued state can be refreshed by application of negative high dc-voltage to the top electrode, but no refreshment is measured by positive dc-voltage application. We also find that the fatigue can be prevented by driving the capacitor asymmetrically. 
B. G. Chae, C. H. Park, Y. S. Yang, and M. S. Jang