Ultrafast polarization switching of lead zirconate titanate thin films

An experimental setup for ultrafast switching measurements is described. The instrumental time resolution was measured to be ⩽100 ps. An analysis of the test circuit showed that it could be considered as an LRC network having a nonlinear ferroelectric capacitor. The switching and the nonswitching ferroelectric charges were shown to determine the RC and LC network time constants, respectively, and the overall experimental resolution. Experiments on PZT (lead zirconate titanate) films demonstrated switching within 360 ps as well as switching time distributions extending to more than 2 μm. It is argued that the extended switching times can be related to a ceramic-like morphology of the films and that they are caused by the time needed for charge redistribution within the films. The fast switching is observed in films with an epitaxial relationship within columnar grains. It can be explained by 180° and 90° domain configurations needing only charge redistribution at the film-electrode interphases during switching. Two switching mechanisms might explain the fast switching. One is based on a high nucleation rate and propagation of domains across the film thickness. The other assumes a simultaneous reorientation of the ferroelectric dipoles (bulk switching)