Imaging Oxygen Defects and their Motion at a Manganite Surface

TL;DR

This study presents the first atomic resolution images of oxygen defects on a manganite surface, revealing defect dynamics and providing insights into oxygen migration crucial for catalytic and electroresistive properties.

Contribution

It demonstrates the use of scanning tunnelling microscopy to directly image oxygen defects and their motion on manganite surfaces, a novel achievement in this field.

Findings

First atomic resolution images of oxygen defects on manganite surface

Observation of defect dynamics including migration and recombination

Explanation for STM challenges in layered manganites

Abstract

Manganites are technologically important materials, used widely as solid oxide fuel cell cathodes: they have also been shown to exhibit electroresistance. Oxygen bulk diffusion and surface exchange processes are critical for catalytic action, and numerous studies of manganites have linked electroresistance to electrochemical oxygen migration. Direct imaging of individual oxygen defects is needed to underpin understanding of these important processes. It is not currently possible to collect the required images in the bulk, but scanning tunnelling microscopy could provide such data for surfaces. Here we show the first atomic resolution images of oxygen defects at a manganite surface. Our experiments also reveal defect dynamics, including oxygen adatom migration, vacancy-adatom recombination and adatom bistability. Beyond providing an experimental basis for testing models describing the microscopics of oxygen migration at transition metal oxide interfaces, our work resolves the long-standing puzzle of why scanning tunnelling microscopy is more challenging for layered manganites than for cuprates.