A study by GC-MS of the decomposition of precursors for the MOCVD of high temperature superconductors

Abstract
This paper describes a study by gas chromatography/mass spectrometry (GC-MS) of the gas phase thermal decomposition of HTMHD (where HTMHD is 2,2,6,6-tetramethylheptane-3,5-dione), [Y(TMHD)3] and [Y(TMHD)3-hydrate] in the presence and absence of oxygen over the temperature range 200-600 °C. The gas phase at the outlet of the reactor was condensed in a liquid nitrogen trap and analysed by GC-MS to try to elucidate the composition of the gas mixture in the reactor. On the basis of the identified decomposition products, decomposition processes of the various compounds are suggested. The results show that the compounds are, not unexpectedly, less thermally stable in oxygen and the mechanism of their thermal decomposition is changed. It is also shown that the residence time of the precursors in the reactor has significant effect of decomposition chemistry.