Strain Effect on Optical and Magnetic Properties of Zigzag Two-Dimensional Passivated GaN Nanoribbons: An Ab Initio Study

In this work, systematic studies are conducted to investigate the electronic, magnetic, and optical properties of oxygen- and sulfur-passivated zigzag GaN nanoribbons (Z-GaNNRs) using first-principles density-functional theory. Simulation investigations pertaining to Z-GaNNRs of 0.9−5 nm width reveal that edge passivation increases GaNNR stability, whereby O-Z-GaNNRs are more stable than S-Z-GaNNRs and bare Z-GaNNRs. We demonstrate that the stability increases with the GaNNR width. Spin-polarized band structure analyses further show that bare Z-GaNNRs of all widths exhibit metallic properties with an antiferromagnetic (AFM) phase. In contrast, owing to their half-metallic and semiconducting nature, oxygen-passivated NRs (O-Z-GaNNRs) are characterized by ferromagnetic (FM) and AFM phases, respectively. Finally, S-passivated NRs exhibit ferromagnetic metal properties irrespective of their width. We found that the strain significantly affects the entire band structure of Z-GaNNR compared to bulk GaN, allowing the optical and magnetic properties of the material to be modulated. When the effect of strain on the electronic structure of all three GaNNR materials was investigated, at -4% applied strain, metal-to-semiconductor abrupt transitions were observed in bare Z-GaNNR. For O-Z-GaNNR, the applied -4% and -6% strains allow a transition of the magnetic properties from AFM to FM, showing a metal characteristic band structure. In contrast, no change in the electronic and magnetic properties of S-Z-GaNNR with strain is observed. The optical investigations and electron energy loss (EELS) analysis predict that these NRs have weak absorption potential but exhibit plasmonic vibrations in the 10−11 eV range. Although the refractive index of the bare Z-GaNNRs is equal to that of the bulk GaN, the applied strain and chemical passivation modulate its refractive index value. Thus, our results pave the way for novel one-dimensional GaNNR-based optical, magnetic, and photonic applications.