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 CuCr2O4 phase was formed in the film. As the Cu-target power increased to 22 W, the phase transformed gradually from spinel CuCr2O4 to delafossite CuCrO2. 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 CuCrO2 phase and high crystallinity. Accordingly, optimum electrical conductivity and visible transparency were achieved for the pure CuCrO2 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 CuCr2O4 phase was confirmed to deteriorated optoelectronic properties of films. Keywords: Sputtering, Ceramic coating, Phase change, Coating process