Optical constants of e-beam evaporated and annealed Nb2O5 thin films with varying thickness.

Niobium pentoxide (Nb₂O₅) films with different thicknesses were prepared using the electron beam evaporation method and then annealed at temperatures from 300 °C to 800 °C before being characterized by variable-angle spectroscopic ellipsometry, x-ray diffraction, etc. The results showed that the optical constants and microstructures of Nb₂O₅ films exhibit a strong dependence on the annealing temperature. In the visible light region, the refractive indices show a positive correlation with the annealing temperature from 300 °C to 600 °C, but a negative correlation from 600 °C to 800 °C. The amorphous Nb₂O₅ film converts into TT- Nb₂O₅ (pseudo-hexagonal) after annealing at 500–600 °C, and into T-Nb₂O₅ (orthorhombic) after annealing at 700–800 °C. [ABSTRACT FROM AUTHOR]