# Electrochemical Oxygen Intercalation into Sr$_2$IrO$_4$

## TL;DR

This study demonstrates electrochemical oxygen intercalation into Sr$_2$IrO$_4$, revealing limited oxygen incorporation and minimal impact on resistivity, suggesting challenges in doping efficiency and potential for ionic liquid gating applications.

## Contribution

First detailed investigation of electrochemical oxygen intercalation in Sr$_2$IrO$_4$, quantifying diffusion and doping levels, and exploring implications for electronic properties.

## Key findings

- Oxygen intercalation concentration is approximately 0.01.
- Diffusion length is estimated to be a few micrometers.
- Minimal change in resistivity indicates poor charge transfer.

## Abstract

Oxygen was electrochemically intercalated into Sr$_2$IrO$_4$ sintered samples, single crystals and a thin film. We estimate the diffusion length to a few $\mu$m and the concentration of the intercalated oxygen to $\delta$ $\simeq$ 0.01. The latter is thus much smaller than for the cuprate and nickelate parent compounds, for which $\delta$ $>$ 0.1 is obtained, which could be a consequence of larger steric effects. The influence of the oxygen doping state on resistivity is small, indicating also a poor charge transfer to the conduction band. It is shown that electrochemical intercalation of oxygen may also contribute to doping, when gating thin films with ionic liquid in the presence of water.