CONTRIBUTION OF THE X-RAY-ABSORPTION SPECTROSCOPY TO STUDY TIO2 THIN-FILMS PREPARED BY ION-BEAM-INDUCED CHEMICAL-VAPOR-DEPOSITION

TiO2 thin films have been prepared and their structure analyzed by XRD at grazing angles and x-ray absorption spectroscopies (EXAFS/XANES). The deposition method is an ion beam induced chemical vapor deposition procedure (IBICVD) consisting of the bombardment of a substrate with accelerated O +2 ions while the vapor of a volatile metallic precursor is directed on its surface. The structure of the films was dependent on the type of substrate (glass, fused quartz, and sapphire) and on the conditions used for their preparation (temperature of substrate and beam energy of 1 or 10 keV). Thus, while on glass and silica/sapphire, an amorphous structure is formed when the substrate is at 300 K during preparation, a rutile-rich structure is obtained if the substrate is at 573 K during deposition or, even to a larger degree, when using ions of 10 keV. The amorphous structure of the films grown on glass yield 100% anatase after calcining at 773 K. On sapphire, the crystallization was less perfect and besides anatase, rutile and amorphous phases were detected after calcination at that temperature. The films prepared at 573 K or with O+2 ions of 10 keV yield after calcining a well ordered structure of rutile. A detailed analysis of the EXAFS and XANES spectra has permitted a better characterization of the amorphous and crystalline phases in the films and provided a better understanding of the crystallization processes during calcination. The contribution of the different factors controlling the crystallization of the films is discussed. © 1995 American Institute of Physics.