X-ray diffraction area mapping of preferred orientation and phase change in TiO2 thin films deposited by chemical vapor deposition

This paper reports on an investigation into the formation of TiO2 thin films, whereby X-ray diffraction is used to map systematic changes in preferred orientation and phase observed throughout the films. The key to this strategy is the recording of X-ray diffraction patterns of specific and isolated areas of a substrate, ensuring this specificity by the use of a small X-ray sample illumination area (approximately 3-5 mm(2)). A map of the variation in film composition can then be built up by recording such diffraction patterns at regular intervals over the whole substrate. Two titania films will be presented, grown using atmospheric pressure chemical vapor deposition, at 450 and 600 degrees C, from TiCl4 and ethyl-acetate precursors. The film grown at 450 degrees C showed a systematic change in preferred orientation, while the film grown at 600 degrees C was composed of a mixture of the rutile and anatase phases of TiO2 with the ratio of these phases altering with position on the substrate. The results of physical property measurements and electron microscopy carried out on the films are also reported, conducted at locations identified by the X-ray diffraction mapping procedure as having different compositions, and hence different physical responses. We found that the photocatalytic activity and hydrophobicity were dependent on the rutile: anatase ratio at any given location on the film.