Structural and Dynamic Properties of Gallium Alkoxides

A comparison of chlorido-gallium functionalized alkoxides as precursors for aerosol-assisted chemical vapor deposition (AACVD) was carried out. Variable-temperature (VT)-NMR studies were used to probe the fluxional behavior of these alkoxides in solution, and hence their utility as precursors. The synthesis involved the initial isolation of the dimer [GaCl(NMe 2 ) 2 ] 2 via a salt metathesis route from GaCl 3 and 2 equiv of LiNMe 2 . This dimer was then reacted with 4 equiv of HOCH 2 CH 2 CH 2 NEt 2 , resulting in the formation of Ga[μ-(OCH 2 CH 2 CH 2 NEt 2 ) 2 GaCl 2 ] 3 ( 1 ). Mass spectrometry and VT-NMR confirmed the oligomeric structure of 1 . Tuning of the ligand properties, namely, the chain length and substituents on N, resulted in formation of the monomers [GaCl(OR) 2 ] (R = CH 2 CH 2 NEt 2 , ( 2 ); CH 2 CH 2 CH 2 NMe 2 , ( 3 )). VT-NMR studies, supported by density functional theory calculations, confirmed that the ligands in both 2 and 3 possess a hemilabile coordination to the gallium center, owing to either a shorter carbon backbone ( 2 ) or less steric hindrance ( 3 ). Both 2 and 3 were selected for use as precursors for AACVD: deposition at 450 °C gave thin films of amorphous Ga 2 O 3 , which were subsequently annealed at 1000 °C to afford crystalline Ga 2 O 3 material. The films were fully characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-visible spectroscopy, and energy dispersive X-ray analysis.