Modification of The Chemisorption Properties of Epitaxial Delafossite CuFeO₂ thin films by substituting Fe for Ga in the Crystal Structure

Films of CuFe_0.75Ga_0.25O₂ were grown over sapphire substrates in high vacuum using a pulsed laser deposition technique. The films were made alternating deposition of CuFeO₂ and CuGaO₂ in a ratio 3/1 and the films are terminated in CuFeO₂. Surface of the films were inspected with X-ray and UV photoelectron spectroscopy. Adsorption of CO₂ and H₂O was studied by a thermal program desorption technique (TPD).
X-ray photoelectron data showed that Ga is not present on the surface.TPD showed that CO₂ adsorbs
with better afinity on this sample containing Ga rather than on the pure CuFeO2 film. UV photoelectron spectroscopy showed that the valence band of the CuFeO₂ delafossite oxides is modified with the
substitution of Fe by Ga in this sample. The semiconductor band gap of CuFeO₂ delafossite oxides also increased from 1.2 eV to 1.5 eV due to the substitution of Fe by Ga in the crystal lattice.