No abstract

Domain walls in ferroelectric materials have tantalizing potential in disruptive memory and reconfigurable nanoelectronics technologies. Here, we demonstrate a ferroelectric domain wall switch with three distinct addressable resistance states. The device operation hinges on fully-controllable and reversible conformational changes of the domain wall. As validated by atomistic simulations consistent with the experiments, using electric field, we alter the shape -and hence the charge state -of the domain wall, and ultimately its conduction. Sequential nanoscale transitions of the walls are visualized directly using stroboscopic-piezoresponse force microscopy and Kelvin probe microscopy. Anisotropic head-to-head domain wall injection, stabilized by the majority carrier type of the ferroelectric, BiFeO 3 , is identified as the key factor that enables conformational control.

In light of directives around the world to eliminate toxic materials in various technologies, finding lead-free materials with high piezoelectric responses constitutes an important current scientific goal. As such, the recent discovery of a large electromechanical conversion near room temperature in (1−x)Ba(Zr0.2Ti0.8)O3−x(Ba0.7Ca0.3)TiO3 compounds has directed attention to understanding its origin. Here, we report the development of a large-scale atomistic scheme providing a microscopic insight into this technologically promising material. We find that its high piezoelectricity originates from the existence of large fluctuations of polarization in the orthorhombic state arising from the combination of a flat free-energy landscape, a fragmented local structure, and the narrow temperature window around room temperature at which this orthorhombic phase is the equilibrium state. In addition to deepening the current knowledge on piezoelectricity, these findings have the potential to guide the design of other lead-free materials with large electromechanical responses.