Thin films preparation by rf-sputtering of copper/iron ceramic targets with Cu/Fe=1: From nanocomposites to delafossite compounds

Abstract

In the Cu–Fe–O phase diagram, delafossite CuFeO2 is obtained for the CuI oxidation state and for the Cu/Fe=1 ratio. By decreasing the oxygen content, copper/spinel oxide composite can be obtained because of the reduction and the disproponation of cuprous ions. Many physical properties as for instance, electrical, optical, catalytic properties can then be affected by the control of the oxygen stoichiometry. In rf-sputtering technique, the bombardment energies on the substrate can be controlled by the deposition conditions leading to different oxygen stoichiometry in the growing layers. By this technique, thin films have been prepared from two ceramic targets: CuFeO2 and CuO+CuFe2O4. We thus synthesized either Cu0/ CuxFe1−xO4 nanocomposites thin films with various Cu0 quantities or CuFeO2-based thin films. Two-probes conductivity measurements were permitted to comparatively evaluate the Cu0 content, while optical microscopy evidenced a selfassembly phenomenon during thermal annealing.