Room 128, Science Centre North, University College Dublin, Belfield, Dublin, Ireland
Dr Amit Kumar
School of Mathematics and Physics, Queen's University, Belfast
Domain walls in ferroelectrics are interfaces that separate volumes of differently oriented electrical polarization and their structural, functional and transport properties have long been expected to differ from domain interiors. Recently, enhanced functionality at the walls has catalysed researchers to look at domain walls afresh. In particular, enhanced domain wall conductivity reported in a range of ferroelectric materials has projected them as distinct pseudo 2D functional materials. Since the domains themselves are comparatively insulating, domain walls represent isolated conducting channels which confine currents into narrow sheets. The walls themselves can be created, destroyed or moved upon application of external stimuli and thus could be actively and dynamically deployed for nano-circuitry, memristors and reconfigurable domain-wall based nanoelectronics devices such as 'ephemeral transistors'. However, mechanisms associated with domain wall conduction are not yet fully understood. Key carrier information and transport mechanisms are matters of open debate. In addition, a large number of the ferroelectrics where charged domain walls showing significant conduction have been reported are improper ferroelectrics where precise injection and controlled motion of long conductive walls presents another significant challenge. This talk will focus on addressing these key challenges related to domain wall conduction in ferroelectrics. A novel approach employing Kelvin probe force microscopy based Hall effect in charged conducting ferroelectric domain walls to detect carrier type and densities in YbMnO3 (Rare earth manganite) single crystals and thus gain fundamental insight into origin of domain wall conductivity in this system will be discussed. The observation, mechanical injection and controlled movement of charged conducting domain walls in the improper ferroelastic-ferroelectric Cu3B7O13Cl will also be discussed. It will be shown that site-specific injection of conducting walls of up to hundreds of microns in length can be achieved through locally applied point-stress and, once created, that they can be moved and repositioned using applied electric fields, thus satisfying key requirements for domain wall-based nanoelectronics. Recent results on domain wall based p-n junctions will be discussed in the context of the outlined vision of reconfigurable domain wall-based nanoelectronics.