Optical Properties and Color‐Center Formation in Thin Films of Molybdenum Trioxide

The optical absorption spectrum of thin films of MoO3 has been measured over the temperature range from 77° to 290°K. The fundamental absorption edge occurs at 3300 A with an absorption coefficient of 105 cm−1. A stoichiometric film of MoO3 shows three absorption peaks at 3350, 2880, and 2700 A, respectively, and these are suggested to be due either to exciton formation or to transitions involving a split valence band.Values for the refractive index have been measured in the wavelength range 0.42–1.2μ. The low‐frequency dielectric constant (18.0±1) has been measured and the comparison with the high‐frequency dielectric constant (5.70) indicates that the bonding is predominantly ionic.The electrical conductivity has been measured on a polycrystalline sample in the temperature range 298° to 900°K and the activation energies of conduction found to be 1.83 eV (intrinsic) and 0.56 eV (impurity).On irradiating a thin film (0.2μ) of MoO3 with light of wavelength shorter than 3300 A, three color‐center bands havi...