Effects of substrate temperature and sputtering gas composition on physical properties and photocatalytic activities of WO x thin films deposited via radiofrequency sputtering

Tungsten oxide (WO x ) is expected to act as a photocatalytic material under visible light. We have deposited WO x thin films using radiofrequency sputtering and evaluated the photocatalytic activities of the films via degradation of methylene blue solution. The optical absorbance, crystallization, and surface morphology of the WO x thin films were also investigated. The absorption edge of the WO x thin films was shifted to the long-wavelength region when the substrate temperature was high and the O 2 gas flow rate was low. Crystallization proceeded when the substrate temperature was high and additional WO x diffraction peaks were appearing with low O 2 gas flow during growth. Furthermore, the grain size of the WO x thin films was smaller when the O 2 gas flow was high. The photocatalytic activity was higher when the substrate temperature and O 2 gas flow rate were low.