Enhanced photocatalytic activity of amorphous MoO3 thin films deposited by RF reactive magnetron sputtering

The photocatalytic activity of molybdenum trioxide (MoO3) thin films was studied. The MoO3 thin films were deposited on Corning glass substrates by radio frequency reactive magnetron sputtering using a metallic Mo target. The dependence of the physical properties of the metal oxides on the sputtering power and working pressure was investigated. X-ray diffraction patterns of the films revealed the formation of amorphous structures. From optical absorption spectra, the band-gap energy was obtained in the range 2.8?3.0 eV for most compounds, while this parameter decreased down to 1.64 eV for samples deposited at 4.5?mTorr and 80?W. X-ray photoelectron spectra disclosed signals associated with the Mo6+, Mo5+, and Mo4+ oxidation states, which correspond to MoO3 and other substoichiometric molybdenum oxides. The photodegradation of a methylene blue (MB) aqueous solution was chosen to evaluate the photocatalytic performance of the thin films. There was found a dependence of the photocatalytic activity on the working pressure, with the samples deposited at 8.0 mTorr and 40?W displaying the highest MB removal.