Vivasha Govinden, PhD student, UNSW
Nanoscale ferroelectric topologies, such as polar skyrmions, flux-closures, vortices, antivortices, and bubble domains, have received significant attention recently. In these topological structures, polarization vectors can be arranged in a complex manner, often with polarization curls. Such enforced rotation of the polarization leads to changes in the local electrostatics and strain which can thus affect functional properties such as enhanced conductivity, negative capacitance,chirality and enhanced magnetism.
These exciting properties potentially allow such topological defects to be exploited for the next generation electronic devices. Further, to enable these ferroelectric topology-based devices, it becomes essential to manipulate the topological defects and modulate the resultant functional property.
We have earlier shown the deterministic and reversible manipulation of nanoscale bubble domains via a mechanical-electrical dual-pass using scanning probe microcopy technique. The as-grown bubble domains can be completely erased under an external mechanical force and be created again using a critical DC pulsed bias. Here, we report the dynamic conductivity of nanoscale bubble domains in ultrathin ferroelectric PbZr0.2Ti0.8O3 (PZT) sandwich-structured films. Conductive atomic force microscopy (CAFM) reveals a robust electrical conductivity in as-grown bubble domains, larger in magnitude compared to their surrounding matrix. When the bubble domains are electrically and mechanically erased, their loci show reduced conductivity as compared to as-grown ones. Repeat scanning of the same region under DC bias drives an evolution of the bubbles into labyrinthine which is accompanied first by a peak in the conduction.
Further scanning continues the transition to a single domain state with a gradual reduction in the conduction. These results show that a thorough understanding of the interplay between structure and electronic behavior is necessary to precisely manipulate non-trivial ferroelectric topologies for nanoelectronic functionalities. Currently, theoretical computations and further experiments are being carried out to unravel the origin of the observed dynamic conductivity of the bubbles.
About the presenter
Vivasha Govinden is a PhD student working with Prof Nagy Valanoor at UNSW to investigate ferroelectric coupling with the introduction of a spacer between ferroelectric thin films, leading to exotic ferroelectric domains that can contribute to a giant electromechanical response. An enhanced electromechanical response is key to applications in nanoelectronic sensors, memory and logic devices and electromechanical systems. The work falls under FLEET’s Research Theme 1, topological materials.