Photo-CVD deposited TiO₂ films studied by Raman and XPS spectroscopy

We report the deposition of thin titanium oxide films on Si (100) and quartz at low temperatures between 100-350°C by photo-induced chemical vapour deposition (photo-CVD) with 222 nm radiation using an injection liquid source. The thickness of the films grown, from several nanometres to micrometres can be accurately controlled by changing the number of drops injected. Under optimum deposition conditions, refractive index values as high as 2.5, optical transmittance of between 85-90% in the visible region of the spectrum and leakage current densities as low as 10^-6 A/cm² can be obtained. XPS analysis has shown that the composition of titanium oxide was TiO₂ and that the carbon content was very low (<5%). The nanostructure of the films deposited on Si wafers was examined by atomic force microscopy (AFM). Raman spectroscopy showed that crystalline TiO₂ layers could be formed at deposition temperatures as low as 210°C with characteristic peaks of anatase-TiO₂ being found at 142, 395 and 638 cm^-1, respectively. Details of the leakage current density and other electrical properties of the TiO₂ films are also discussed.