Thermal stability, sublimation pressures and diffusion coefficients of some metal acetylacetonates

Metal acetylacetonates are often used as precursors for the deposition of oxides in CVD or ALE experiments. The thermal stability and the vapour/sublimation pressures of such compounds are of fundamental importance for reproducible depositions. We have started a program to study the long term thermal stability, sublimation pressures and the diffusion coefficients of organometallic compounds. The latter are needed for the calculation of the Sherwood and Lewis numbers used to describe mass transfer process. In a recent publication [M. A. Siddiqi, B. Atakan, Thermochim. Acta 452 (2007) 128.] we demonstrated a method for the evaluation of diffusion coefficients of less volatile substances in gas mixtures by combining the experimental thermogravimetric measurements with accurate sublimation pressure data (e.g. from Knudsen effusion method). In the present communication the results for aluminium(III) acetylacetonate, chromium(III) acetylacetonate, iron(III) acetylacetonate, manganese(III) acetylacetonate and nickel(II) acetylacetonate are presented. The last three of these show decomposition at low temperatures. Aluminium(III) acetylacetonate and chromium(III) acetylacetonate evaporate without residuals and hence their sublimation pressures and binary diffusion coefficients at various temperatures are reported for the first time.