Current-induced nonuniform enhancement of sheet resistance in Ar+ irradiated SrTiO3

TL;DR

This study investigates how high currents cause nonuniform increases in sheet resistance in Ar+ irradiated SrTiO3, revealing local irreversible changes linked to vacancy dynamics and ferroelectric domain boundaries below 40 K.

Contribution

It uncovers the current-induced nonuniform resistance enhancement mechanism involving vacancy attraction and ferroelectric boundary polarization in SrTiO3.

Findings

Resistance increases significantly below 40 K with high current

Local irreversible changes in current distribution observed via SQUID microscopy

Recovery of resistance linked to vacancy diffusion energy barriers

Abstract

The sheet resistance Rs of Ar+ irradiated SrTiO3 in patterns with a length scale of several microns increases significantly below 40 K in connection with driving currents exceeding a certain threshold. The initial lower Rs is recovered upon warming with accelerated recovery around 70 and 160 K. Scanning superconducting quantum interference device microscopy shows local irreversible changes in the spatial distribution of the current with a length scale of several microns. We attribute the observed nonuniform enhancement of Rs to the attraction of the charged single-oxygen and dioxygen vacancies by the crystallographic domain boundaries in SrTiO3. The boundaries, which are nearly ferroelectric below 40 K, are polarized by the local electrical field associated with the driven current and the clustered vacancies which suppress conductivity in their vicinity and yield a noticeable enhancement in the device resistance when the current path width is on the order of the boundary extension. The temperatures of accelerated conductivity recovery are associated with the energy barriers for the diffusion of the two types of vacancies.