Large Hall electron mobilities in head-to-head BaTiO$_3$-domain walls

TL;DR

This study demonstrates that head-to-head domain walls in BaTiO$_3$ exhibit high electron mobility around 400 cm$^2$(Vs)$^{-1}$, and introduces a practical Hall-transport measurement method for characterizing conducting ferroelectric domain walls.

Contribution

It provides the first quantitative Hall-transport measurements of H2H BaTiO$_3$ domain walls, revealing their high mobility and proposing a new measurement approach.

Findings

Electron mobility reaches ~400 cm$^2$(Vs)$^{-1}$.

2D charge density is approximately 7×10$^3$ cm$^{-2}$.

Method effectively characterizes ferroic conducting domain walls.

Abstract

Strongly charged head-to-head (H2H) domain walls (DWs) that are purposely engineered along the [110] crystallographic orientation into ferroelectric BaTiO$_3$ single crystals have been proposed as novel 2-dimensional electron gases (2DEGs) due to their significant domain wall conductivity (DWC). Here, we quantify these 2DEG properties through dedicated Hall-transport measurements in van-der-Pauw 4-point geometry at room temperature, finding the electron mobility to reach around 400~cm$^2$(Vs)$^{-1}$, while the 2-dimensional charge density amounts to ~7$\times$10$^3$cm$^{-2}$. We underline the necessity to take account of thermal and geometrical-misalignment offset voltages by evaluating the Hall resistance under magnetic-field sweeps, since otherwise dramatic errors of several hundred percent in the derived mobility and charge density values can occur. Apart from the specific characterization of the conducting BaTiO$_3$ DW, we propose the method as an easy and fast way to quantitatively characterize ferroic conducting DWs, complementary to previously proposed scanning-probe-based Hall-potential analyses.