Thermal behaviour of hexanuclear titanium(IV) oxo isopropoxide carboxylates,and their usability as a single-source TiO2 CVD precursors

Hexanuclear oxo titanium(IV) isopropoxide carboxylates, of the general formula Ti₆O₆(OPrⁱ)₆(O₂CR)₆] (R = Bu^t (1), CH₂Bu^t (2)) and Ti₆O₆(OPrⁱ)₆(O₂CC(CH₃)₂Et)₆] · 0.5(C₇H₈) (3), have been synthesized as polycrystalline powders in order to study their thermal properties and usability as TiO₂ CVD precursors. Analysis of thermogravimetric and variable temperature (VT-IR) data shows that the thermal stability of the synthesized complexes decreases as follows 3 > 2 > 1. The composition of the vapors formed during the thermolysis of 1–3 were qualitatively analysed with VT-IR methods and mass spectrometry (MS-EI). According to obtained results, the decomposition of 1 and 2 proceeds with a partial decomposition and the formation of a volatile and stable titanium species, sufficient for their transport in vapors. The formation of volatile titanium-containing derivatives is an important factor that decides the application of 1 and 2 as precursors in CVD experiments. The high stability of 3 causes the thermal decomposition of this complex to be observed just above 573 K, and volatile titanium-containing derivatives were not detected in vapors. These results indicate that 3 could not be used as a precursor in CVD processes.