Femtosecond visualization of oxygen vacancies in metal oxides.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32181341.
- Also identified by DOI 10.1126/sciadv.aax9427 and PMC identifier 7060066.
- Licence recorded as CC BY-NC.
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Abstract
Oxygen vacancies often determine the electronic structure of metal oxides, but existing techniques cannot distinguish the oxygen-vacancy sites in the crystal structure. We report here that time-resolved optical spectroscopy can solve this challenge and determine the spatial locations of oxygen vacancies. Using tungsten oxides as examples, we identified the true oxygen-vacancy sites in WO<sub>2.9</sub> and WO<sub>2.72</sub>, typical derivatives of WO<sub>3</sub> and determined their fingerprint optoelectronic features. We find that a metastable band with a three-stage evolution dynamics of the excited states is present in WO<sub>2.9</sub> but is absent in WO<sub>2.72</sub>. By comparison with model bandstructure calculations, this enables determination of the most closely neighbored oxygen-vacancy pairs in the crystal structure of WO<sub>2.72</sub>, for which two oxygen vacancies are ortho-positioned to a single W atom as a sole configuration among all O─W bonds. These findings verify the existence of preference rules of oxygen vacancies in metal oxides.