Effects of electronic correlation, physical structure, and surface termination on the electronic structure of V2O3 nanowires

We report on a density functional theory (DFT) study of the electronic structure of vanadium sesquioxide (V2O3) in both bulk and nanowire form. In particular, our study focuses on the role of spin polarization and electronic correlations, as computed within the local (spin) density approximation (L(S)DA) and the LDA + U formalism. As expected for a mean-field approach such as DFT, our optimized bulk V2O3 structure is shown to be metallic in nature, while an adequate choice of the Hubbard U parameter (U = 4 eV) is enough to open the band gap, making the system insulating. However, this formalism predicts a nonmagnetic insulator, as opposed to the experimentally observed antiferromagnetic structure, to be the ground state. The electronic structure of the V2O3 nanowire system is more complex, and it strongly depends on the surface termination of the structures. Our results showthat non-spin-polarized LDAcalculations of < 001 >-grown nanowires are metallic in nature. However, LSDA predicts that some surface terminations are half-metals, with a large band gap opening for one of the spins. When LSDA + U was used to study the nanowire model with a closed-shell oxygen surface termination, we observe insulating behavior with no net magnetic moment, with a 104 meV band gap. This is consistent with the experimentally observed gap recently reported in the literature for similar wires. To experimentally address the surface structure of these nanowires, we perform surface specific nano-Auger electron spectroscopy on as-synthesized V2O3 nanowires. Our experimental results show a higher O:V peak ratio (1.93:1) than expected for pure V2O3, thereby suggesting higher oxygen content at the surface of the nanowires. From our results, we conclude that oxygen termination is likely the termination for our as-synthesized V2O3 nanowires.