Unusually large PFM-written domains at cryogenic temperatures in PZT films

Abstract

This study investigates the temperature dependence of ferroelectric domain wall motion in epitaxial PbZr0.3Ti0.7O3 (PZT) thin films (60 nm) using piezoresponse force microscopy (PFM) from 5 to 300 K. Contrary to thermal activation models, domain radii (and inferred domain wall velocities) exhibit minimal reduction at cryogenic temperatures (down to 5 K) compared to room temperature. Suggesting non-thermal mechanisms govern domain dynamics in PZT at low temperatures. Additional studies exclude surface charge accumulation and adsorbed water layers as primary factors, confirmed via destructive 3D polarization mapping showing domain stability throughout the film depth. It is shown that AFM probe tip geometry critically influences domain sizes: Tip blunting or contamination during scanning causes significant artifacts in field distribution, explaining apparent size discrepancies between high- and low-temperature datasets acquired with different probes. However, this effect cannot account for the persistent domain growth kinetics observed at low temperatures. We propose that the formation of a domain wall in a high-magnitude electric field affects its further movement in low-magnitude fields. Our findings highlight probe-geometry control as essential for reliable PFM measurements. The overall conclusion is that in experiments investigating domain wall motion in thin films, when a nonuniform electric field of the AFM probe is used to switch the polarization, it is difficult to obtain results for reliable qualitative and quantitative conclusions due to the large number of unknown parameters.