Group 13 β-Ketoiminate Compounds: Gallium Hydride Derivatives As Molecular Precursors to Thin Films of Ga2O3

Bis­(β-ketoimine) ligands, [R­{N­(H)­C­(Me)-CHC­(Me)O}2] (L1H2, R = (CH2)2; L2H2, R = (CH2)3), linked by ethylene (L1) and propylene (L2) bridges have been used to form aluminum, gallium, and indium chloride complexes [Al­(L1)­Cl] (3), [Ga­(Ln)­Cl] (4, n = 1; 6, n = 2) and [In­(Ln)­Cl] (5, n = 1; 7, n = 2). Ligand L1 has also been used to form a gallium hydride derivative [Ga­(L1)­H] (8), but indium analogues could not be made. β-ketoimine ligands, [Me2N­(CH2)3N­(H)­C­(R′)-CHC­(R′)O] (L3H, R′ = Me; L4H, R′ = Ph), with a donor-functionalized Lewis base have also been synthesized and used to form gallium and indium alkyl complexes, [Ga­(L3)­Me2] (9) and [In­(L3)­Me2] (10), which were isolated as oils. The related gallium hydride complexes, [Ga­(Ln)­H2] (11, n = 3; 12, n = 4), were also prepared, but again no indium hydride species could be made. The complexes were characterized mainly by NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction. The β-ketoiminate gallium hydride compounds (8 and 11) have been used as single-source precursors for the deposition of Ga2O3 by aerosol-assisted (AA)­CVD with toluene as the solvent. The quality of the films varied according to the precursor used, with the complex [Ga­(L1)­H] (8) giving by far the best quality films. Although the films were amorphous as deposited, they could be annealed at 1000 °C to form crystalline Ga2O3. The films were analyzed by powder XRD, SEM, and EDX.