Manipulation of Conductive Domain Walls in Confined Ferroelectric Nano-islands

TL;DR

This study demonstrates the visualization and electrical manipulation of various conductive domain walls within confined BiFeO3 nano-islands, revealing their potential for high-density, multilevel ferroelectric memory applications.

Contribution

It provides the first direct observation and electrical control of different conductive domain walls in small ferroelectric nano-islands, expanding understanding for nano-scale domain wall electronics.

Findings

Charged domain walls exhibit ~10^4 times higher conductivity than domain interiors.

Multiple distinct conduction states can be electrically written in individual nano-islands.

Conductive domain walls can be manipulated in confined nano-islands for memory device applications.

Abstract

Conductive ferroelectric domain walls--ultra-narrow and configurable conduction paths, have been considered as essential building blocks for future programmable domain wall electronics. For applications in high density devices, it is imperative to explore the conductive domain walls in small confined systems while earlier investigations have hitherto focused on thin films or bulk single crystals, noting that the size-confined effects will certainly modulate seriously the domain structure and wall transport. Here, we demonstrate an observation and manipulation of conductive domain walls confined within small BiFeO3 nano-islands aligned in high density arrays. Using conductive atomic force microscopy (CAFM), we are able to distinctly visualize various types of conductive domain walls, including the head-to-head charged walls (CDWs), zigzag walls (zigzag-DWs), and typical 71{\deg} head-to-tail neutral walls (NDWs). The CDWs exhibit remarkably enhanced metallic conductivity with current of ~ nA order in magnitude and 104 times larger than that inside domains (0.01 ~ 0.1 pA), while the semiconducting NDWs allow also much smaller current ~ 10 pA than the CDWs. The substantially difference in conductivity for dissimilar walls enables additional manipulations of various wall conduction states for individual addressable nano-islands via electrically tuning of their domain structures. A controllable writing of four distinctive states by applying various scanning bias voltages is achieved, offering opportunities for developing multilevel high density memories.