Ferroelectric domain switching dynamics with combined 20 nm and 10 ns resolution

Abstract

High speed piezo force microscopy (HSPFM) is employed to investigate ferroelectric domain nucleation and growth of an exposed PZT film. Twenty nanometer spatial and 10 ns temporal resolution is achieved using a pump:probe methodology, allowing area switching and individual domain dynamics to be monitored. Two complementary investigations are performed, mapping switching in either a single 2 μm × 2 μm area for 4.2 V pulses with durations ranging from 20 to 60 ns, or for 10 ns pulses with amplitudes varying from −4 to −4.7 V. In this manner, nascent domains, as well as long-term growth, are efficiently quantified with substantial statistical significance due to the hundreds of images that can reasonably be acquired in a practical experimental session. The switching mechanism, areal switching rate, domain nucleation time, and domain wall velocity are each clearly independent of pulse width. In contrast, these parameters are strongly influenced by increasing pulse heights, including a faster switching rate, shorter nucleation times, and additional nucleation sites. This suggests a spatially and energetically heterogeneous landscape of activation energies for domain reversal sites, only some of which can therefore participate in switching with weak pulses but many of which are activated for strong pulses. These quantitative results, and the spatial, temporal, and statistical benefits provided by HSPFM combined with pump:probe techniques, have important implications for determining ultimate switching speeds, ideal device geometries, and optimal materials selection and processing.