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

Abstract

Bis(β-ketoimine) ligands, [R{N(H)C(Me)-CHC(Me)═O}(2)] (L(1)H(2), R = (CH(2))(2); L(2)H(2), R = (CH(2))(3)), linked by ethylene (L(1)) and propylene (L(2)) bridges have been used to form aluminum, gallium, and indium chloride complexes [Al(L(1))Cl] (3), [Ga(L(n))Cl] (4, n = 1; 6, n = 2) and [In(L(n))Cl] (5, n = 1; 7, n = 2). Ligand L(1) has also been used to form a gallium hydride derivative [Ga(L(1))H] (8), but indium analogues could not be made. β-ketoimine ligands, [Me(2)N(CH(2))(3)N(H)C(R')-CHC(R')═O] (L(3)H, R' = Me; L(4)H, R' = Ph), with a donor-functionalized Lewis base have also been synthesized and used to form gallium and indium alkyl complexes, [Ga(L(3))Me(2)] (9) and [In(L(3))Me(2)] (10), which were isolated as oils. The related gallium hydride complexes, [Ga(L(n))H(2)] (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 Ga(2)O(3) 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(L(1))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 Ga(2)O(3). The films were analyzed by powder XRD, SEM, and EDX.

Synthesis and Characterization of (pyNO−)2GaCl: A Redox-Active Gallium Complex

“…The Ga-Cl bond is in the range of other non-bridging Ga-Cl bonds reported for structurally characterized five-coordinate gallium(III) complexes. For example, the bis(o-iminosemiquinonate) gallium(III) chloride complex reported by Piskunov et al has a Ga-Cl of 2.1875(5) Å [23] and the gallium salen complex reported by the Dagorne group has a Ga-Cl distance of 2.2255(6) Å [24] The bis(β-ketoiminate) gallium(III) chloride complex prepared by the Carmalt group has a Ga-Cl bond length of distance 2.231(7) Å [25]. The Ga-N py bond distances are also similar to other Ga-N distances reported for gallium complexes supporting pyridine ligands: The pyGaX 3 (X = Cl and Br) complexes have an average Ga-N distance of 1.98 Å [26] while the {pyGaCl 2 H} 2 dimer has Ga-N distances of 2.000(2) and 1.998(2) Å [27].…”

Advances in Deposition of Main‐Group Metal Oxides and Rare‐Earth Oxides from Metal Enolates

“…Carmalt and coworkers discussed the synthesis, characterization, and deposition properties of aluminum, gallium, as well as indium hydride β-ketoiminate (15) and hydride β-diketonate metallorganic complexes [48][49][50] . The synthesis of metal hydride β-ketoiminate (15) complexes is depicted in Scheme 2.…”

“…The synthesis of metal hydride β-ketoiminate (15) complexes is depicted in Scheme 2. Formation of complex 15 from ligand 12 via the "logical" intermediate steps 13 and 14 is precluded by the failure of the latter chloride β-ketoiminate complex to undergo exchange with a series of hydride reagents (LiH, NaH, NaBH 4 , LiAlH 4 , NaBEt 3 H); reaction of 12 with the metal hydride complex [MH 3 (NMe 3 )] was successful 48,49 . The penta-coordinated gallium complex 15 (M = Ga, n = 2) was successfully applied as a single-source precursor for the aerosol-assisted chemical vapor deposition (AA-CVD) of Ga 2 O 3 48 .…”

“…Formation of complex 15 from ligand 12 via the "logical" intermediate steps 13 and 14 is precluded by the failure of the latter chloride β-ketoiminate complex to undergo exchange with a series of hydride reagents (LiH, NaH, NaBH 4 , LiAlH 4 , NaBEt 3 H); reaction of 12 with the metal hydride complex [MH 3 (NMe 3 )] was successful 48,49 . The penta-coordinated gallium complex 15 (M = Ga, n = 2) was successfully applied as a single-source precursor for the aerosol-assisted chemical vapor deposition (AA-CVD) of Ga 2 O 3 48 . The as-deposited amorphous transparent films could be converted to crystalline gallium oxide layers by annealing at 1000 ∘ C. The optimal deposition conditions were as follows: substrate temperature of 450 ∘ C, a carrier gas flow rate of 1 L min -1 , and toluene as solvent.…”

“…The as-deposited amorphous transparent films could be converted to crystalline gallium oxide layers by annealing at 1000 ∘ C. The optimal deposition conditions were as follows: substrate temperature of 450 ∘ C, a carrier gas flow rate of 1 L min -1 , and toluene as solvent. The film composition and morphology were determined by EDX and XRPD, whereas UV-vis spectroscopy confirmed its high transparency (80-90%) and low reflectivity 48 . Gallium complexes of the type [Ga 2 Me 4 (L 13 )] and [GaH(L 13 )] (15, M = Ga, n = 2, 3) served as precursors for the AA-CVD of stoichiometric and oxygen-deficient Ga 2 O 3 thin films on glass 49 .…”