Synthesis and Optoelectronic Properties of CuFeO2 Semiconductor Thin Films

This paper explored the influence of structural transformations on the optical and electrical properties of the p-type semiconductor CuFeO2 thin film. In the Cu-Fe-O phase change process, monoclinic CuO and spinel CuFe2O4 are low-temperature phase structures. With the increase in temperature, the copper, iron, and oxygen atoms had higher energy, sufficient to be stacked and arranged as delafossite, CuFeO2, where CuFeO2 is a high-temperature stable phase. As the annealing temperature increased from 600°C to 850°C, a cell-like microstructure grew on the surface of the CuFeO2, the surface root mean square roughness gradually increased from 3.10 nm to 10.40 nm. The structural transformation dominantly affected the absorption coefficient of the Cu-Fe-O thin film. The CuFeO2 thin film mainly absorbs photons with wavelengths less than 400 nm. Photon energies of high effective excitation were identified, with values ranging over 3.63-3.87 eV. The CuFeO2 film annealed at 700°C had better electrical properties; the bandgap, Hall coefficient, and electrical resistivity of the film were 3.16 eV, 139.2 cm3/C, and 1.19 Ωcm, respectively. The nano-scale structure and characteristics of CuFeO2 were analyzed. Furthermore, this study also compared the microstructure and optoelectronic properties of CuFeO2, CuAlO2, and CuCrO2.