Synthesis and characterization of transparent conducting oxide cobalt–nickel spinel films

Cobalt–nickel oxide films of nominal 100 nm thickness, and resistivity on the order of 10−2 Ω cm have been deposited by spin casting from both aqueous and organic precursor solutions followed by annealing at 450 °C in air. Films deposited on sapphire substrates exhibit a refractive index of about 1.7 and are relatively transparent in the wavelength region from 0.6 to 10.0 μm. They are also magnetic. The electrical and spectroscopic properties of the oxides have been studied as a function of the x=Co/(Co+Ni) ratio. An increase in film resistivity was found upon substitution of other cations (Zn2+, Al3+,…) for Ni in the spinel structure. However, some improvement in the mechanical properties of the films resulted. A combination of x-ray diffraction, x-ray photoelectron spectroscopy, UV/Vis, and Raman spectroscopy indicated that NiCo2O4 is the primary conducting component and that the conductivity reaches a maximum at this stoichiometry. When x 0....