Gallium acetylacetonate Ga(acac)3 has been studied by mass spectrometry. The main decomposition pathways of the complexes Ga(acac)3 involve loss of ligand radicals from the molecular ion [Ga(acac)3]+ and lead to the ions [Ga(acac)2]+ and [Ga]+. The formation of the ions [Ga(acac)]+ and [Ga]+, and the fragmentation behaviour of [Ga(acac)]+ were explained in terms of the stability of gallium oxidation state +I. The complexes also exhibit reactions involving elimination of ligand fragments, such as CH3•, CH2CO and CH3COCHCO. [475]
Gallium acetylacetonate Ga(acac)3 dissolved in deionized water (with added small quantitiy of HCl) has been applied as Ga precursor for the epitaxial growth of Ga2O3 thin films by mist chemical vapor deposition (CVD) at low temperatures of 430–470 °C. Trigonal α-Ga2O3 thin films could be obtained on sapphire (α-Al2O3) substrates (despite strong tendency of Ga2O3 to obtain monoclinic β-gallia structure on sapphire). The grown α-Ga2O3 films had narrow FWHMs (~60 arcsec) in their XRD rocking curves. Almost completely transparent in the near-UV and visible regions Ga2O3 films having RMS roughness ≤1 nm and optical band gap energy 5.3 eV were obtained. [[i]]
[i] Daisuke Shinohara and Shizuo Fujita, Jpn. J. Appl. Phys. 47 (2008) pp. 7311-7313, “Heteroepitaxy of Corundum-Structured α-Ga2O3 Thin Films on α-Al2O3 Substrates by Ultrasonic Mist Chemical Vapor Deposition”
Ga(acac)3, and either water or ozone as oxygen sources were applied for the deposition of amorphous uniform gallium oxide thin films on Si(100), soda lime, corning glass substrates by ALE. The films deposited with H2O contained a considerable amount of carbon as an impurity whereas O3 as an oxidizer gave stoichiometric Ga2O3 films.The optimal choice of the pulse duration, growth and source temperatures allowed to obtain a self-controlled growth at 370°C.[476]
Ga(acac)3 was used as source material (with H2O as oxygen source) for the preparation of amorphous Ga2O3 thin films by the ultrasonic spray pyrolysis. Annealing at 850°C/1h resulted in crystalline β-Ga2O3, both as-deposited and annealed films have stoichiometric chemical composition without carbon contamination by RBS. No incorporation of O-H and Ga-OH radicals was oserved by IR spectroscopy; amorphous films have broad absorption band from 400 to 900 cm–1, typical for some amorphous metallic oxides. The annealed films show well-defined peaks the IR spectra located at 450 and 670 cm–1 and related to the beta-phase of Ga2O3. Amorphous films change upon annealing the refractive index and optical bandgap from 1.846 and 4.94 eV to 1.935 and 4.99 eV
Gallium acetylacetonate Ga(acac)3 in combination with zinc acetylacetonate Zn(acac)2 have been used as precursor for LPCVD of spinel-structure ZnGa2O4:Mn thin films as the emitting layer in thin‐film electroluminescent (TFEL) devices. TFEL devices using as‐deposited ZnGa2O4:Mn films had max luminance of green EL emission 0.7-7.6 cd/m2 , postannealing of the layers at ~1000°C increased maximum luminance >600 cd/m2 , what was attributed to the emitting layer crystallinity improvement. Details are described under Zn(acac)2[307]
Ga(acac)3 has been used for the two-step MOCVD growth of β-Ga2O3/ZnO core−shell nanowires on Au-precoated sapphire (0001) substrates, which were converted to well-aligned single-crystalline ZnGa2O4 nanowires by annealing. ZnGa2O4 nanowires presented a strong CL emission band centered at 360 nm and a small tail at 680 nm at room temperature [478]
Ga(acac)3 for GaPO4 by ALE
Ga(acac)3 in combination with tributylphosphate, both dissolved in organic solution, were used as precursors for the aerosol CVD (‘pyrosol’) growth of amorphous gallium phosphate thin films on Si substrates, films had large range of chemical compositions. Ga atoms in both tetrahedral and octahedral sites were present according to X-ray absorption measurement. Film electrical and dielectric characteristics (resistivity and permittivity) are different from the crystallized gallium phosphate. [479]
Ga(acac)3 for LaGaO3 by ALE
Ga(acac)3 in combination with La(thd)3 and O3 as precursors, was applied for the growth of lanthanum gallate thin films by atomic layer epitaxy (ALE) at 325–425°C on soda lime glass, Si(100), MgO-buffered Si(100), sapphire, MgO(100), SrTiO3(100) and LaAlO3(100) substrates. Good control of film stoichiometry was obtained by adjusting the La(thd)3/O3 to Ga(acac)3/O3 pulsing ratio. Transparent uniform stoichiometric LaGaO3 films were obtained, with only 0.4 at.% C and <0.2 at.% H as impurities. Film thickness could be accurately controlled by the number of deposition cycles. The as-deposited films were amorphous, after annealing films grown on sapphire and MgO(100) substrates became polycrystalline LaGaO3, whereas films grown on Si(100) and MgO-buffered Si(100) composed of La4Ga2O9 phase. Smooth epitaxial LaGaO3 thin films were obtained on LaAlO3(100) after annealing at 850 °C, verified by X-ray rocking curve of the (200) reflection and AFM surface roughness. [480]
Ga(acac)3 for ErGaO3 by ALE
Ga(acac)3 has bee applied for the growth for ErGaO3 by ALE (and compared with Ga(NMe2)3 precursor.
Ga(acac)3, in combination with Fe(acac)3 as iron source, has been applied for the growth of highly crystalline corundum-structured α-(Ga1-xFex)2O3 alloy thin films on c-plane sapphire substrates by mist CVD; the FWHM of XRD rocking curves were <100 arcsec for the entire range of x from 0 to 1. α-(Ga1-xFex)2O3 (x = 0.24) thin films at 110 K possessed ferromagnetic properties according to magnetic measurements. By changing the Fe content x in the films the optical band gaps were tuned to a value between α-Ga2O3 and α-Fe2O3 (between 2.2 eV and 5.3 eV). [[i]]
Ga(acac)3 was applied as Ga source for the growth of highly conductive and transparent Ga-doped ZnO films by atmospheric pressure CVD on glass substrates at temperatures 375-475°C. According to XRD, films were polycrystalline with (002) preferred orientation. The resistivity of the films (in the range of 10−1 to 10−3 Ω cm) strongly depended on doping level. Ga-doped films deposited at 425°C temperature had the lowest resistivity of 2.0×10−3 Ω cm, n-doping level 5.9×1019 cm−3 and Hall mobility 31 cm2 /Vs. [[i]]
[i] K. Haga, P. S. Wijesena and H. Watanabe, Applied Surface Science, Vol. 169-170, 15 January 2001, Pages 504-507
Ga(acac)3 has been applied as precursor for the growth of GaN nanowires (at 900 °C) and InGaN nanowires (at 550 °C) by horizontal furnace chemical vapour deposition (HF-CVD) on Si (100) substrates coated by 2 nm Au thin film as the catalyst. Comparing the growth mechanisms of GaN-NWs and InxGa1-xN-NWs, the vapour-solid (VS) mechanism is dominant in GaN nanowires, except with a low ammonium flow rate, and the vapour-liquid-solid (VLS) mechanism is dominant in InxGa1-xN nanowires. [[i]]
[i] Liang-Yih Chen, Cheng-I Liao, Hsuan-Ying Peng, physica status solidi (c), Special Issue: E-MRS 2009 Spring Meeting, Symposium J: Group III Nitride Semiconductors, Vol. 7, Iss. 1, p.40–43, 2010 , “Influence of gas flow rates on the formation of III-nitride nanowires”
Mass spectra of gallium(III) trifluoroacetylacetonate Ga(tfac)3 have been investigated. The molecular ion [M(tfac)3]+ is fragmenting mainly by ligand radical elimination producing ion [M(tfac)2]+ whose subsequent fragmentation proceeds via reactions involving loss of ligand fragments. [475]
The molecular structure of Ga(hfac)3 (hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) has been determined by gas-phase electron diffraction (GED) combined with ab initio computations. The structure has D3 symmetry with a distorted octahedral arrangement of oxygen atoms about the central atom with E (hfac) planes oriented at ca. 82° to one another. Structure similar to that found experimentally but with less distorted EO6 octahedra, ca. 89° were predicted by theoretical computations at the SCF and DFT levels. [[i]]
[i] Paul T. Brain, Michael Bühl, Heather E. Robertson, Andrew D. Jackson, Paul D. Lickiss, Donald MacKerracher, David W. H. Rankin, Dipti Shah and Walter Thiel, J. Chem. Soc., Dalton Trans., 1998, 545-552
Gallium tris-hexafluoroacetylacetonate Ga(hfac)3 , with O2 as oxidant, has been applied as precursor for the deposition of Ga2O3 thin films on Al2O3 and TiO2 substrates by MOCVD, at 470°C growth temperature and 2.6 kPa growth pressure , resulting in a growth rate of 0.7 μm/h. As-grown films were black, smooth and well adherent to the substrates. The layers consisted of stoichiometric Ga2O3 with C content <5% and almost undetectable F, according to XPS studies. As-deposited Ga2O3 films were X-ray amorphous, but the start of crystallization process was observed after annealing in dry air at 700 °C. After thermal treatment, the films became carbon free and transparent. Thermal treatment at 600 to 1000 °C converted layers from amorphous to polycrystalline Ga2O3. Al diffusion into Ga2O3 films was detected by SIMS in the films annealing at 1000 °C grown on pure Al2O3 substrates; Al diffusion was completely inhibited by using a thick TiO2 buffer layer (≥4 μm) [[i] ]
[i] G. A. Battiston, R. Gerbasi, M. Porchia, R. Bertoncello and F. Caccavale, Thin Solid Films, Volume 279, Issues 1-2, June 1996, Pages 115-118 Chemical vapour deposition and characterization of gallium oxide thin films
The melting point, vapour pressure and heat of sublimation Ga(2,2,6,6-tetramethyl-3,5-heptanedionate)3 has been determined for the temperature range below the melting point of 40°C to 250°C and pressures from 10 to 10 -2 torr. The measurements were made with a Knudsen effusion cell in conjunction with a Mettler thermobalance [[i]]
[i] H. R. Brunner, B. J. Curtis, Journal of Thermal Analysis, Vol. 5 (1973) 111--115
Gallium tris (2,2,6,6-tetramethyl-3,5-heptanedionate) Ga(thd)3, in combination with Ca(thd)2 and Ce(thd)4, has been applied as precursor for the growth of Ga2S3, and CaGa2S4:Ce thin films by liquid delivery MOCVD. The growth of Ga2S3 is limited by the deposition kinetics; however, CaGa2S4:Ce deposition system growth behaviour is independent of its components (Ga2S3 and CaS): slight presence of Ga in the form of CaGa2S4:Ce or Ga2S3 on the surface catalyzes Ca incorporation from Ca(tmhd)2 to the growing film. The layers were characterized using XRF and electroluminescence measurements of the color and brightness. [[i]]
[i]Moss, T S , Dye, R C , Smith, D C , Samuels, J A , DelaRosa, M J , Schaus, C F, “Metal-organic chemical vapor deposition of electronic ceramics II; Proceedings of the Symposium, Boston, MA; UNITED STATES; 27-29 Nov. 1995. pp. 21-29. 1996, “MOCVD of the blue electro-luminescent phosphor CaGa2S4:Ce from a liquid reagent delivery system”