REPRODUCIBLE MOCVD OF BARIUM FLUORIDE - STUDIES OF THE EFFECT OF THE DEGREE OF PRECURSOR CRYSTALLINITY AND PURITY

The previously reported varying CVD deposition rates obtained when using the new precursor [Ba(TDFND)(2)] have been investigated using a range of techniques for analysing hydrated and anhydrous forms of the precursor before and after use for deposition. It is shown that, apart from water loss from the hydrate, there are no significant molecular structural changes to the precursor in use. X-Ray powder diffractograms do show, though, that there is the possibility of crystalline growth, and the implications of this are discussed. A simple model of spherical crystallites coalescing is considered, and it is shown that the range of behaviour observed in practice with solid precursors can be satisfactorily explained by the model. When full cognisance is taken of the effects of precursor purity and degree of crystallinity it is found to be possible to grow reproducibly high-quality BaF2 and superconducting YBCO. The precursor [Ba(TDFND)(2)] is thus a potentially useful new material for MOCVD of YBCO and other barium-containing films.