Pushing the Study of Point Defects in Thin Film Ferrites to Low Temperatures Using In Situ Ellipsometry

TL;DR

This paper introduces a novel in situ ellipsometry method to analyze point defect chemistry in La1-xSrxFeO3-d thin films at low temperatures, providing new insights into defect behavior relevant for device applications.

Contribution

The study presents the first systematic defect chemistry analysis of La1-xSrxFeO3-d thin films at intermediate-to-low temperatures using in situ spectroscopic ellipsometry.

Findings

Correlated hole concentration with optical properties.

Mapped defect evolution with temperature and oxygen pressure.

Enhanced understanding of defect chemistry in LSF thin films.

Abstract

Unveiling point defects concentration in transition metal oxide thin films is essential to understand and eventually control their functional properties, employed in an increasing number of applications and devices. Despite this unquestionable interest, there is a lack of available experimental techniques able to estimate the defect chemistry and equilibrium constants in such oxides at intermediate-to-low temperatures. In this study, the defect chemistry of a relevant material such as La1-xSrxFeO3-d (LSF) with (x = 0.2, 0.4 and 0.5 (LSF20, LSF40 and LSF50 respectively) is obtained by using a novel in situ spectroscopic ellipsometry approach applied to thin films. Through this technique, the concentration of holes in LSF is correlated to measured optical properties and its evolution with temperature and oxygen partial pressure is determined. In this way, a systematic description of defect chemistry in LSF thin films in the temperature range from 350dC to 500dC is obtained for the first time, which represents a step forward in the understanding of LSF20, LSF40 and LSF50 for emerging low temperature applications.