Synthesis and characterization of fluorinated aminoalkoxide and iminoalkoxide gallium complexes:: Application in chemical vapor deposition of Ga2O3 thin films

Gallium trichloride, GaCl3, reacts with the in situ prepared sodium salt of an aminoalkoxide or iminoalkoxide, denoted as NaL, to give the disubstituted compounds GaL2Cl, where L = OC(CF3)(2)CH2NMe2 (1), OC(CF3)(2)CH2C(Me)=NMe (2). Single-crystal X-ray diffraction studies on 1 and 2 indicated the formation of a trigonal-bipyramidal structure with chloride and alkoxy groups occupying the equatorial sites and the nitrogen donors located at the axial positions. For the related trimethylgallium reagent GaMe3, addition of an equal amount of amino alcohol LH induced the elimination of methane to afford the complexes GaMe2L, where L = OC(CF3)(2)CH2NHMe (3), OC(CF3)(2)CH(2)NHBut (4), OC(CF3)(2)CH2NMe2 (5), in high yields. The crystal structure of 5 was determined by X-ray diffraction, showing a distorted-tetrahedral framework which differs greatly from that observed in the trigonal-bipyramidal Ga complexes 1 and 2. Variable-temperature H-1 NMR studies on 3 and 4 indicated the occurrence of rapid N-->Ga bond scission, followed by recoordination with a change of the absolute configuration. A lower activation barrier was observed for the But complex 4 upon changing solvents from CDCl3 to more polar media such as deuterated toluene and THF. Complexes 1 and 4 were then evaluated as potential precursor molecules for the chemical vapor deposition of Ga2O3, and the as-deposited films were analyzed using scanning electron micrographs (SEM), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering (RBS).