Characterization of amorphous p-type transparent CuFeO2 thin films prepared by radio frequency magnetron sputtering method at room temperature

Amorphous CuFeO2 thin films were prepared on Al2O3 (001) substrates by radio-frequency magnetron sputtering method at room temperature. Various oxygen partial pressures PO in the sputtering gas ambient (9.1%, 11.1% and 13.0%) were used in the deposition experiments. X-ray photoelectron spectroscopy analysis convinced the chemical state of Cu+ and Fe3 + in the films, and the chemical compositions of the thin films are close to the stoichiometry of CuFeO2. The content of oxygen composition increased systematically with increasing PO. From the optical transmission spectra, only one absorption edge could be observed during 200–1200 nm for all the films with a band gap around 3.25 eV. This result is different from the polycrystalline CuFeO2 films which have 3 absorption edges in the range of 200–1200 nm. This interesting result indicates that amorphous CuFeO2 thin films have much different electronic energy band with polycrystalline ones. The resistivity of the films first decreases and then increases with increasing PO. The minimum resistivity of 4.2 Ω cm with optical transmittance of 47% at 600 nm is obtained for the film deposited in PO = 11.1%.