Spectroscopic ellipsometry study of CVD molybdenum oxide films: effect of temperature

The optical properties of CVD MoO3 films were studied by ellipsometry in the spectral range 280–820 nm. The films were deposited on silicon substrates by pyrolytic decomposition at atmospheric pressure of Mo(CO)6 at 150 and 200 °C. To optimize the film structure, annealing was performed at temperatures of 300 and 400 °C. The refractive index for as-deposited MoO3 films varies within 1.8–2.2 and the optical band gap energies in the range 2.87–2.98 eV. After annealing, the latter values slightly increase to 2.85–3.05 eV, depending on the annealing temperature. The band gap energies are typical for a polycrystalline material. Peaks in the spectral dependence of the absorption coefficient were observed. Their position and intensity are found to be affected by the process temperature.