Electron–electron interaction-driven semiconducting ground state of oxygen-terminated zigzag graphene nanoribbons

Edge engineering of graphene nanoribbons introduces additional correlation effects, and oxygen-terminated edges offer excellent ambient stability. However, oxygen-terminated ribbons are extremely difficult to fabricate within the width of 3 nm, and theoretical predictions for their magnetic and electronic ground states remain conflicting. Here, we report the fabrication of oxygen-terminated zigzag graphene nanoribbons with widths below 3 nm. Using scanning tunneling spectroscopy, we observe an edge state splitting evolving from 0.17 to 0.24 eV as the ribbon width reduced from 3.8 to 2.2 nm. For a 1.8 nm ribbon, we measure a bandgap of 1.04 eV, which opens above the Dirac energy, and an energy shift of phonon modes at K points is also observed in the same region. These measurements experimentally validate hybrid density functional theory predictions for oxygen terminated ribbons and extend the width range for gapped oxygen-terminated ribbons from theoretically 0.8 to 1.8 nm. These findings establish oxygen-terminated nanoribbons as a robust platform for studying correlation and edge physics, and they suggest new opportunities for device applications based on chemically stable, narrow graphene ribbons.