COORDINATION-COMPOUNDS OF ALUMINUM AS PRECURSORS TO ALUMINUM NITRIDE

Two different systems have been examined as potential sources of aluminum nitride, an important electronic and structural ceramic material. Cyclic organoaluminum amides obtained as intermediates in the thermolysis of trialkylaluminum: ammonia Lewis acid-base complexes have been used to obtain AlN powder and as precursors for the chemical vapor deposition of AlN films. The structures of two of these intermediates were determined by single-crystal XRD and the kinetics and thermodynamics of their formation and thermal decomposition reactions were also studied. The second system employs ethylenediamine as the Lewis base in combination with the R3Al (R = Me, Et) compounds. A 2:1 ratio of Et3Al with en yields a hydrocarbon-soluble, polymeric amide on thermolysis, which can be used to prepare AlN films by solution coating followed by pyrolysis in NH3. Lower proportions of R3Al to en, on thermolysis, lead to the formation of R(m)Al(en-2H)n cluster species that contain 5- and 6-coordinated Al atoms chelated and bridged by en-2H ligands. On further heating, these cluster species apparently go on to form cross-linked, insoluble, polymeric networks through condensation reactions involving the multiple N-H and R-Al groups on the periphery of the cluster molecules. The structures of two of these novel Al-en cluster compounds were determined by single-crystal XRD.