Abstract
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.
Highlights
Others include βketoiminates,13,19−21 of the general formula [4-[2-(R)imino]2-pentanone] gallium(III), (R = CH2CH2CH2OCH2CH3, CH(CH3)2, CH2CH2OCH3, CH2CH2CH2OCH3, and CH2CH2OCH2CH3),13,21 and further contributions (Figure 1) have recently detailed the synthesis of oxygen-rich gallium complexes with dimethylmalonate and cyclopropane-1,1dimethylester ligands for use in catalysis22 and di(tert-butyl)gallium species with β-diketonato ligands, which were further functionalized with molecular oxygen to form metal-stabilized peroxides
We extend the study through the synthesis of chloro-gallium bis(alkoxides): Ga[μ
The fluxionality due to the hemilabile coordination of the donor-functionalized alkoxide ligands can cause the nitrogen and gallium atoms to dissociate−associate in a dynamic fashion, producing the broad spectrum observed at 296 K (Figure 4)
Summary
The research surrounding metal oxide thin films, those containing group 13 elements, has expanded greatly due to these materials having properties crucial to the function and performance of a wide variety of electronic, optical, and chemically active devices, including photovoltaic cells, gas sensors, transparent conducting oxides (TCOs), as well as screen displays. Gallium oxide (Ga2O3) is a material that exists in various forms, with two prevailing due to their increased thermodynamic stability, α-Ga2O3 and β-Ga2O3 being metastable band and gap stable, respectively. of 4̃ .7 eV5 and. The reaction of [GaCl(NMe2)2]2 with 4 mol equiv of the corresponding donor-functionalized alcohol in dry Et2O at −78 °C was allowed to warm to room temperature and stirred for 24 h This solution was reduced in vacuo and stored in a freezer at −18 °C, affording a pale viscous oil in the case of 1 and colorless single crystals of 2 and 3. The fluxionality due to the hemilabile coordination of the donor-functionalized alkoxide ligands can cause the nitrogen and gallium atoms to dissociate−associate in a dynamic fashion, producing the broad spectrum observed at 296 K (Figure 4) This fluxionality displayed by compounds 2 and 3 is not surprising; five-coordinate trigonal bipyramidal systems are capable of polytopal rearrangements in the coordination sphere, classically including portrayed by PF5, titanium, cobalt, iron, with and more modern examples antimony complexes.−. The X-ray photoelectron spectroscopy (XPS) for a Ga2O3 thin film deposited from compound 3 (Figure 8c) confirmed the presence of gallium in the thin films
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