Tuning oxygen vacancies in complex oxides using 2D layered materials

Abstract

The hybrid interface between 2D materials and complex oxides offers a rich platform to explore fascinating physical phenomena like helical edge states, broken-symmetry phases, and giant magnetoresistance. While current research primarily focuses on the influence of complex oxides on layered 2D materials, the reverse—how layered 2D materials affect complex oxides—remains largely unexplored. Here, we examined the impact of graphene layers on the formation of oxygen vacancies in SrTiO3 (STO) during high-temperature annealing. Our findings, supported by Raman spectroscopy and x-ray photoelectron spectroscopy, indicate that increasing the number of graphene layers progressively leads to a reduced oxygen vacancy content in STO, demonstrating the efficacy of graphene in modulating oxygen vacancy formation in bulk STO. Additionally, using photoluminescence, we showed that graphene layers can tune the in-gap states induced by oxygen vacancies in STO. Our first principal calculations further revealed that graphene layers increase the energy barrier for the outward diffusion of oxygen atoms, thereby inhibiting the formation of oxygen vacancies in STO. These results highlight a new route for tailoring the physical properties of complex oxides by engineering the interface with layered 2D materials.