Metal-insulator transition of c-axis-controlled V₂O₃ thin film

We prepared c-axis-controlled V₂O₃ thin films by RF magnetron sputtering and proved their metal-insulator transition (MIT) in terms of electronic structure. The lattice constant of the c-axis depends on the film thickness and the lattice mismatch of the substrate and V₂O₃. MIT is observed at a temperature of ∼150 K in the V₂O₃ thin films with the lattice constants of c = 13.942 and 13.992 Å, although the V₂O₃ thin film with c = 13.915 Å exhibits metallic conductivity without MIT. The electron correlation energy, which corresponds to the energy difference between the lower Hubbard band and the upper Hubbard band, increases with increasing lattice constant of the c-axis. Bandwidths also depend on the lattice constant of the c-axis. The intensity of the a1g orbital around the Fermi level decreases with increasing lattice constant of the c-axis. These results suggest that the electron correlation interaction and bandwidths play important roles in the MIT of c-axis-controlled V₂O₃ thin films.