Structure, surface morphology and optical properties of post-annealed delafossite CuFeO2 thin films

Delafossite CuFeO2 (TCO) thin films have been successfully deposited onto quartz substrate by low-cost chemical spray pyrolysis at 450 °C and post-annealed at 800 °C for 2 h. The XRD results for as deposited and post-annealed films show polycrystalline structure with Hexagonal (Rhombohedral) phase. The CuFe2O4 phase appeared as the film deposited and post-annealed. The preferred orientation was along (0 1 2) plane and the crystallite size increased from 20.89 nm to 22.588 nm after annealing process. The surface morphology of CuFeO2 thin film seems relatively smooth and plated regularly; the EDX spectra confirm the stoichiometry of the prepared films. The average roughness values obtained from AFM measurements have been decreases from and from (19.7 to 14.4 nm) respectively after annealing process. The optical transmission of these films has been studied in the wavelength range 400–800 nm and found to be more than 62%. The direct optical band gap of the CuFeO2 films was 2.66 eV and decreased to 2.63 eV after annealing process. The Urbach's energy was found to be increase from 0.247 eV for as deposited film at 450 °C to 0.2857 eV after annealing process.