In situ mass spectrometry during thermal CVD of the tris-acetylacetonates of 3-d transition metals

The processes of thermal decomposition of 3-d metal acetylacetonates (ScL3, VL3, CrL3, MuL(3), FeL3, CoL3) and HL were investigated within the 370-870 K temperature range using a high-temperature molecular beam source with ma ss spectrometric sampling of the gas phase composition directly at the outl et from the reaction zone. A scheme of thermal decomposition of complexes v apour is suggested. According to the scheme, at the first reaction stage th e beta -diketone HLgas, and [LM(L - H)](ads), and [L4M2(L - H)](ads) interm ediate species are formed on the surface in the "low-temperature" stage of decomposition processes. In the next "high-temperature" stage these interme diate species are decomposed to produce ML2, NIL and (C5H6O), (C5H6O)(2) ga s 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 o f 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 calc ulated. It is shown that the volatility of complexes decreases in the row f rom Se to Co compounds. The mechanisms of thermal decomposition of complexe s in vapour phase and their conversion into the metal oxide on surface are discussed.