Metal-to-Semiconductor Transition in Edge-Passivated C ₃ N Nanoribbons: A First-Principles Study

The magnetic and electronic characteristics of C 3 N nanoribbons with armchair and zigzag edge configurations were systematically investigated using density functional theory (DFT) calculations. Pristine C 3 N nanoribbons exhibit metallic behavior with antiferromagnetic ground states which originate from unsaturated edge atoms. To tailor their electronic and magnetic properties, edge passivation was performed using H, O, and F atoms. The results demonstrate that H and F passivation completely quenche the edge magnetism and induce a metal-to-semiconductor transition in armchair nanoribbons with PBE band gaps of 0.48–0.50 eV, whereas the corresponding zigzag nanoribbons retain their metallic character while becoming nonmagnetic. In contrast, O passivation preserves the metallic behavior and stabilizes a ferromagnetic ground state. Additional HSE06 calculations for the representative semiconducting structures predict band gaps of 0.85 and 1.02 eV for H- and F-passivated armchair nanoribbons, respectively, confirming the reliability of the electronic trends obtained from PBE. Partial density of states, local density of states, spin-density distribution, and Hirshfeld charge analyses reveal that the distinct electronic and magnetic behaviors originate from the different orbital contributions and charge redistribution induced by the passivating atoms. Furthermore, the calculated edge energies indicate that the energetic stability strongly depends on both the ribbon geometry and the passivating species. These findings provide valuable theoretical guidance for the future design of C 3 N-based spintronic and nanoelectronic materials.