Band gap determination in multi-band-gap CuFeO2 delafossite epitaxial thin film by photoconductivity

The photoconductivity within a wavelength range of 450–1100 nm was determined for a sample of epitaxial delafossite CuFeO 2 film grown by pulsed laser deposition. The film thickness was estimated to be 75 nm. The resistance of the films was determined with four-contact van der Pauw’s method and using monochromatic illumination of the film. The most significant change in resistance resulted in three rapid lineal conductivity increases at photon energies of ~ 1.5 eV (gap-1), ~ 2.1 eV (gap-2) and ~ 2.5 eV (gap-3). The conductivity properties are well correlated with prior optical absorption results obtained in the NIR-VIS region using transmittance spectroscopy.