Aerosol-Assisted Chemical Vapour Deposition of a Copper Gallium Oxide Spinel

Copper-based spinel oxide CuGa₂ O₄ films have been deposited by means of a simple one-pot solution-based chemical vapour deposition (CVD) method. Aerosol-assisted (AA) CVD of copper(II) 2,2,6,6,-tetramethylheptan-3,5-dionate (thd), Cu(thd)₂ and gallium(III) acetylacetonate, Ga(acac)₃ , in toluene resulted in the formation of transparent films with a slight yellow tinge at 300-500 °C. Scanning electron microscopy (SEM) indicated that the films had grown by means of an island growth mechanism. Energy-dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS) showed that CuGa₂ O₄ had formed along with copper(I) oxide and gallium(III) oxide was observed at the surface of the film. Annealing the films under a range of conditions (air, N₂ , vacuum) resulted in oxidation and the formation of CuGa₂ O₄ and copper(II) oxide, as shown by powder X-ray diffraction (XRD). The films were further analysed by UV/Vis spectroscopy and atomic force microscopy. Similar AACVD depositions using copper(II) acetylacetonate, Cu(acac)₂ , and Ga(acac)₃ in a range of solvents only resulted in the formation of gallium oxide owing to the lower solubility of the copper precursor than the gallium complex. AACVD is dependent on the precursor solubility hence Cu(thd)₂ is a superior precursor to Cu(acac)₂ owing to its increased solubility.