Wavelength-Selective Control of Visible Light Absorption through Capping-Assisted Oxygen Migration in Oxide Heterostructures.

Chen, Jingxin; Oh, Jin Young; Li, Boyu; Qiao, Zhihan; Zhang, Haiyang; Li, Deyang; Men, Enyang; Wang, Hangtian et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Oxygen concentration critically determines the physical properties of transition metal oxides. In this work, we realized a subtle modulation of the oxygen concentration in heterostructures composed of perovskite SrTiO<sub>3</sub> (STO) and brownmillerite SrCoO<sub>2.5</sub> (BM-SCO) by deliberately promoting oxygen migration from the oxygen reservoir to BM-SCO with the assistance of STO capping. A small increase in the oxygen concentration was demonstrated to exclusively change the interorbital transition that is mostly related to the O 2p states in BM-SCO. The independent tuning of interorbital transition facilitates a wavelength-selective control of visible-light absorption. This results in a rich colorful appearance of the heterostructures, which depends on the thickness of the STO capping layer. The capping-assisted oxygen migration is expected to facilitate the designing and tailoring of emergent phenomena in oxygen-deficient oxides, even in the absence of a full topotactic phase transition.