Influence of chemical composition on phase transformation and optoelectronic properties of Cu–Cr–O thin films by reactive magnetron sputtering

Abstract Cu–Cr–O films were co-sputtered from Cu and Cr targets on fused silica substrates. Then, these films were annealed at 700 °C for 2 h under controlled Ar atmosphere. [Cu]/[Cr] ratio was increased from 0.59 to 2.02 by increasing the Cu-target power from 10 W to 52 W. When the film was prepared at Cu-target power of 10 W, a pure spinel CuCr 2 O 4 phase was formed in the film. As the Cu-target power increased to 22 W, the phase transformed gradually from spinel CuCr 2 O 4 to delafossite CuCrO 2 . Further increase of Cu-target power resulted in the appearance of an additional monoclinic CuO phase. The [Cu]/[Cr] ratio was approximately 1 at Cu-target power of 22 W, which caused the film to exhibit pure delafossite CuCrO 2 phase and high crystallinity. Accordingly, optimum electrical conductivity and visible transparency were achieved for the pure CuCrO 2 film prepared at Cu-target power of 22 W with a figure of merit of 1.51 × 10 −8  Ω −1 . The formation of the CuO and CuCr 2 O 4 phase was confirmed to deteriorated optoelectronic properties of films.