The effects of domain wall thickness on the nanoscale piezoresponse of ferroelectric domains

The effects of domain wall thickness on the nanoscale piezoresponse of ferroelectric domains, including typical 180°, uncharged 90°, and charged 90° domains, are investigated via treating the domain wall as a piezoelectric medium, which possesses distinct piezoelectric coefficients from the adjacent domains. It is found that increasing the domain thickness can result in enhanced lateral piezoresponse force microscopy response of uncharged 90° domains and vertical piezoresponse force microscopy (VPFM) response of charged 90° domains, while it would reduce VPFM response of uncharged 90° domains. Good agreements with experiments are observed. The different enhancement behaviors maybe result from the distinction of average polarization orientation of those domain walls. These insights point to a new pathway to enhance nanoscale piezoresponse in ferroelectric materials.