Charge carriers in dynamic ferroelectric domain walls

Ferroelectric domain walls (DWs) are the subject of intense research at present in the search for high dielectric, gigahertz responsive materials with novel functionalities[1]. Crucial to the integration of DWs into nanoelectronics is a proper understanding of the local electronic landscape around the wall and the influence this has on the behaviour of the DW under variable electric fields. A high degree of mobility under small electric fields is especially desirable for low power applications which escape from the critical current thresholds required to move magnetic domain walls[2]. Perovskite oxides are prime candidates for tuning the thermodynamic variables affecting the energy landscape of DWs and thus controlling their orientation/charge state[3]. Here we present an investigation into the behaviour of ferroelectric DWs under dynamic fields and the specific charge carriers present at DWs

Probing the dynamics of topologically protected charged ferroelectric domain walls with the electron beam at the atomic scale

Dynamic charged ferroelectric domain walls (CDWs) overturn the classical idea that our electronic circuits need to consist of fixed components of hardware.[1,2] With their own unique electronic properties and exotic functional behaviours all confined to their nanoscale width, DWs represent a completely new 2D material phase.[3-5] The most exciting aspect of CDWs in single crystals is that they can be easily created, destroyed and moved simply by an applied stimulus. The dynamic nature of CDWs gives them the edge over other novel systems and may lead to them being the next promising disruptive quantum technology. This is an area of research at its very early stages with endless possible applications. However, to harness their true potential there is a great deal of the fundamental physics yet to uncover. As the region of interest (CDW) is atomically thin and dynamic, it is essential for the physical characterisation to be at this scale spatially and time-resolved

Charged domain wall and polar vortex topologies in a room temperature magnetoelectric multiferroic thin

Multiferroic topologies are an emerging solution for future low-power magnetic nanoelectronics due to their combined tuneable functionality and mobility. Here, we show that in addition to being magnetoelectric multiferroic at room temperature, thin-film Aurivillius phase Bi6TixFeyMnzO18 is an ideal material platform for both domain wall and vortex topology based nanoelectronic devices. Utilizing atomic-resolution electron microscopy, we reveal the presence and structure of 180°-type charged head-to-head and tail-to-tail domain walls passing throughout the thin film. Theoretical calculations confirm the subunit cell cation site preference and charged domain wall energetics for Bi6TixFeyMnzO18. Finally, we show that polar vortex-type topologies also form at out-of-phase boundaries of stacking faults when internal strain and electrostatic energy gradients are altered. This study could pave the way for controlled polar vortex topology formation via strain engineering in other multiferroic thin films. Moreover, these results confirm that the subunit cell topological features play an important role in controlling the charge and spin state of Aurivillius phase films and other multiferroic heterostructures