Anatase TiO2 Films Crystallized by RF Plasma Treatment

Anatase-phase TiO2 films were prepared from amorphous TiO2 films with using a novel crystallization technology in which 13.56 MHz rf (radio frequency) plasma is applied to the film samples for few minutes without heating. The obtained anatase TiO2 films have almost the same photocatalytic degradation activity as that of the thermally-crystallized anatase TiO2 films. Although the key parameter of this plasma crystallization process is the plasma gas pressure, the best plasma gas pressure depends on the plasma gas species and applied rf power and is independent to film materials nor substrate materials. Experimental results strongly suggest that the plasma crystallization is realized by the application of alternating rf electric field into the film materials. Easiness of plasma crystallization of TiO2 films is found to depend on the film preparation conditions and this relation between crystallization easiness and preparation condition is different from the relation in the heat crystallization.