Tuning the domain wall conductivity in bulk lithium niobate by uniaxial stress

TL;DR

This study demonstrates how uniaxial stress can significantly modulate the conductivity of domain walls in lithium niobate, revealing asymmetrical behavior and potential for strain-controlled electronic applications.

Contribution

It provides the first experimental evidence of stress-induced tuning of domain wall conductivity in bulk lithium niobate, supported by a theoretical model.

Findings

Negatively screened walls become more conductive under stress

Positively screened walls decrease in conductivity with stress

Conductivity can be increased by an order of magnitude with 100 MPa stress

Abstract

Conductive domain walls (CDWs) in insulating ferroelectrics have recently attracted considerable attention due to their unique topological, optical, and electronic properties, and offer potential applications such as in memory devices or re-writable circuitry. The electronic properties of domain walls (DWs) can be tuned by the application of strain, hence controlling the charge carrier density at DWs. In this work, we study the influence of uniaxial stress on the conductivity of DWs in the bulk single crystal lithium niobate (LiNbO$_3$). Using conductive atomic force microscopy (cAFM), we observe a large asymmetry in the conductivity of DWs, where only negatively screened walls, so called head-to-head DWs, are becoming increasingly conductive, while positively screened, tail-to-tails DWs, show a decrease in conductivity. This asymmetry of DW conductivity agrees with our theoretical model based on the piezoelectric effect. In addition, we observed that the current in the DW increases up to an order of magnitude for smaller compressive stresses of 100 MPa. This response of DWs remained intact for multiple stress cycles over 2 months, opening a path for future applications.