The effect of type and concentration of modifier in supercritical carbon dioxide on crystallization of nanocrystalline titania thin films

Abstract Nanostructured TiO 2 anatase thin films were directly prepared using supercritical carbon dioxide (scCO 2 ) modified by organic solvent and water in two step processing. Organic solvent used as scCO 2 modifier at 30 MPa and 40 °C in the first step of processing was in the second step changed to water with simultaneous temperature increase to 150 °C which caused anatase thin films crystallization. The effect of the type of modifier (water, methanol, ethanol and acetone), concentration of modifier (5–40 wt.%) in scCO 2 and the amount of scCO 2 (50–200 g) passed through the high pressure column as well as the type of substrate (soda-lime glass and monocrystalline Si) on microstructure and purity of TiO 2 thin films were examined in both steps of processing. The prepared thin films were characterized with respect to their (micro)structural properties by Raman spectroscopy as well as X-ray diffraction, to their wettability by contact angle measurements and to their morphology by high resolution transmission electron microscopy.