Delafossite CuFeO2 thin films electrochemically grown from a DMSO based solution

Abstract

This study shows the results obtained in the direct electrodeposition of CuFeO2 thin films from a DMSO based solution. First, a detailed electrochemical study was carried out in order to determinate the best condition for the CuFeO2 electrodeposition. The films were obtained potentiostatically from a 0.01M CuCl2+0.005M Fe(ClO4)3+0.1M LiClO4 solution in the presence of molecular oxygen at 50°C onto FTO/glass substrates. In all cases, the time of electrodeposition was 1000s. The grown films presented a yellow-reddish color and exhibit an homogeneous aspect. Analyses of composition carried out through EDS, shown that a stoichiometric composition (atomic relation Cu:Fe=1:1) is obtained at a potential of –0.6V. However, as-grown films analyzed through XRD experiences did not evidence the presence of CuFeO2 compound presumably because it is amorphous. An annealing treatment at 650° C for 30minutes in an argon atmosphere was necessary to transform the solid phase of the as grown films in crystalline CuFeO2. Furthermore, the presence of CuFeO2 has been confirmed through XPS analyses. UV-vis analyzes shown a ladder-like appearance due to the presence of several absorption edges from the IR to the UV spectrum region. The most clearly determined were a direct-like edge at the IR: Eg(IR)=1.64eV. However, several absorption edges in the visible (Egdir(vis)=2.35eV, and Egind(vis)=2.03eV) and UV beginning (Egind(UV)=3.37eV) spectrum region also were observed.