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(NMe2)2]2 via a salt metathesis route from GaCl3 and 2 equiv of LiNMe2. This dimer was then reacted
with 4 equiv of HOCH2CH2CH2NEt2, resulting in the formation of Ga[μ-(OCH2CH2CH2NEt2)2GaCl2]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 = CH2CH2NEt2,
(2); CH2CH2CH2NMe2, (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 Ga2O3, which were subsequently annealed at 1000 °C to
afford crystalline Ga2O3 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.