Selective formation of apical oxygen vacancies in La$_{2-x}$Sr$_{x}$CuO$_{4}$

TL;DR

This study uses low-temperature annealing and Raman spectroscopy to selectively create apical oxygen vacancies in La$_{2-x}$Sr$_{x}$CuO$_{4}$ thin films, revealing their impact on local structure and potential influence on superconductivity.

Contribution

It demonstrates that apical sites are preferred for oxygen vacancies under low-temperature conditions and explores their effects on the local environment in overdoped cuprate films.

Findings

Apical oxygen vacancies are favored during low-temperature annealing.

Oxygen vacancies significantly deform the copper-oxygen environment.

Results align with defect-chemical studies, prompting further research.

Abstract

The superconducting properties of high-\tc\ materials are functions of carriers concentration, which is controlled by the concentration of defects including heterovalent cations, interstitial oxygen ions, and oxygen vacancies. Here we combine low-temperature thermal treatment of La$_{2-x}$Sr$_{x}$CuO$_{4}$ epitaxial thin films and confocal Raman spectroscopy to control and investigate oxygen vacancies. We demonstrate that the apical site is the most favorable position to accommodate oxygen vacancies under low-temperature annealing conditions. Additionally we show that in high-quality films of overdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$, oxygen vacancies strongly deform the oxygen environment around the copper ions. This observation is consistent with previous defect-chemical studies, and calls for further investigation of the defect induced properties in the overdoped regime of the hole-doped lanthanum cuprates.