Acceptor dopant effects on endurance of PZT thin films

The effect of acceptor (Na, Mg, Fe) and donor (Nb,Ta) dopants on the switching properties of Pb(Zr0.53Ti0.47)O-3 (PZT) thin films with Pt electrodes was investigated for broad dopant concentration ranges. The effect of dopants on endurance was found to be characteristic to type of doping (donor or acceptor) and independent of individual dopant element, microstructural features, or site of doping. All acceptor dopants studied were found to strongly improve the endurance characteristics of PZT thin films. Increasing the acceptor dopant concentration was found to shift the onset of polarization suppression (electrical fatigue) toward a higher number of switching cycles. It is proposed that the origin of endurance degradation in PZT thin films with Pt electrodes is the transition from p to n type stoichiometry with AC-switching, which leads to the formation of Ti3+ defects. Acceptor dopants shift the p to n transition to higher number of switching cycles, thus postponing the formation of Ti3+ defects, which results in improvement of endurance. It is shown, that PZT compositions (away from the morphotropic phase boundary) in which Ti3+ defects are less stable have better endurance characteristics. Guidelines for optimization of endurance characteristics of PZT thin films with Pt electrodes were developed.