Synthesis of titanium dioxide nanocrystalline layers using hexaprismatic shaped μ-oxo Ti(IV) alkoxo carboxylates as precursors

The reaction between Ti(OR)₄ (R = ⁿBu, ⁱBu, SiMe₃) and 2,2-dimethylpropionic acid lead to the formation of hexanuclear μ-oxo titanium(IV) alkoxo carboxylato complexes of the general formula Ti₆O₆(OR)₆(OOC^tBu)₆]. Thermal decomposition pathways of these compounds and their potential application in the preparation of TiO₂ nanolayers using chemical vapor deposition (CVD) methods have been discussed. The type of the alkoxide ligands causes differences in the thermolysis pathway, and the type of the volatile decomposition products. Among the examined complexes only Ti₆O₆(OR)₆(OOC^tBu)₆] (R = ⁱBu, SiMe₃) show promising properties for their application as precursors in CVD methods. The TiO₂ films were grown in a wide range of substrate temperatures (653–873 °K), under the total reactor pressure 2.0–3.0 mbar. The crystallinity and the composition of layers were analyzed by X-ray diffraction (XRD). It was found that the formation of TiO₂ amorphous, anatase or rutile films depends on the deposition temperature and gas phase composition.