Ferroelastically protected polarization switching pathways to control electrical conductivity in strain-graded ferroelectric nanoplates

Controllable local electronic conduction in otherwise insulating materials can be created by arranging two opponent ferroelectric polarizations in a head to head (or tail to tail) configuration. Using an effective trailing field of dc biased tip motion, charged domain walls have been artificially created in the context of tip-based nanolithography. However, the charged domain wall formed by a trailing field is unstable because of elastic interaction at the boundary between poling and nonpoling regions, finally resulting in ferroelastic back-switching. Here, we report that nanoscale plate structures under strain relaxation can provide a promising opportunity for stabilization and manipulation of a charged domain wall using a highly anisotropic mechanical boundary condition that restricts the unique ferroelastic domain configuration. We demonstrate that a ferroelectric BiFeO3 nanoplate subjected to compressive misfit strain at the bottom but less external stress on the side walls exhibits radial-quadrant in-plane ferroelectric domain structures. Electronic conduction is significantly enhanced near the side walls and the magnitude of electrostatic conductivity is adjustable up to about 20 times by 180° ferroelectric switching that is protected by the clamped ferroelastic domain. Our findings provide a pathway to controllable nanoelectronic logic devices by tuning a charged ferroelectric domain wall.