J. Phys. IV France 11 (2001) Pr3-995-Pr3-1003
In situ mass spectrometry during thermal CVD of the tris-acetylacetonates of 3-d transition metalsP.P. Semyannikov, I.K. Igumenov, S.V. Trubin and I.P. Asanov
Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Lavrentiev 3, Novosibirsk 630090, Russia
The processes of thermal decomposition of 3-d metal acetylacetonates (ScL3, VL3, CrL3, MnL3, FeL3, CoL3) and HL were investigated within the 370-870 K temperature range using a high-temperature molecular beam source with mass spectrometric sampling of the gas phase composition directly at the outlet from the reaction zone. A scheme of thermal decomposition of complexes vapour is suggested. According to the scheme, at the first reaction stage the β-diketone HLgas and [LM(L - H)ads and [L4M2(L - H)]ads intermediate species are formed on the surface in the "low-temperature" stage of decomposition processes. In the next "high-temperature" stage these intermediate species are decomposed to produce ML2, ML and (C5H6O), (C5H6O)2 gas species and metal oxides on the surface. The effective values of kinetic parameters in Arrhenius equation are calculated from temperature curves of ML3 complexes for the first order reaction. The saturated vapour pressure of these chelates was determined as a function of temperatures according to the Knudsen effusion method. From temperature dependence of vapour pressure the thermodynamic parameters of the chelate sublimation processes are calculated. It is shown that the volatility of complexes decreases in the row from Sc to Co compounds. The mechanisms of thermal decomposition of complexes in vapour phase and their conversion into the metal oxide on surface are discussed.
© EDP Sciences 2001