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)] via a salt metathesis route from GaCl and 2 equiv of LiNMe. This dimer was then reacted with 4 equiv of HOCHCHCHNEt, resulting in the formation of Ga[μ-(OCHCHCHNEt)GaCl] (). Mass spectrometry and VT-NMR confirmed the oligomeric structure of . Tuning of the ligand properties, namely, the chain length and substituents on N, resulted in formation of the monomers [GaCl(OR)] (R = CHCHNEt, (); CHCHCHNMe, ()). VT-NMR studies, supported by density functional theory calculations, confirmed that the ligands in both and possess a hemilabile coordination to the gallium center, owing to either a shorter carbon backbone () or less steric hindrance (). Both and were selected for use as precursors for AACVD: deposition at 450 °C gave thin films of amorphous GaO, which were subsequently annealed at 1000 °C to afford crystalline GaO 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.