Towards delafossite structure of Cu–Cr–O thin films deposited by reactive magnetron sputtering: Influence of substrate temperature on optoelectronics properties

Abstract

Cu–Cr–O thin films were co-sputtered from metallic Cu and Cr targets in the presence of a reactive argon–oxygen gas mixture. Evolution of the coatings composition as a function of the discharge current dissipated on each target allowed to obtain convenient composition. The films deposited at ambient temperature (without intentional heating of substrate) were initially amorphous and need to be annealed at different temperature under vacuum to achieve delafossite structure. In this case, the delafossite structure presented a thermal instability to the annealing temperature. CuCr2O4 and CuO as the secondary phases were clearly detected by XRD analysis, and could evidently affect the CuCrO2 films optoelectronic properties. Cu–Cr–O thin films were also deposited at high temperatures (substrate temperature varied from 923 to 1083 K) to investigate the influence of substrate temperature on the structure, morphology and optoelectronic properties of the films. Relatively, raising the substrate temperature up to 1033 K was better to obtain CuCrO2 delafossite phase and improved their optoelectronic properties. The optimum conductivity and transparency were achieved for the film deposited at about 1033 K with figure of merit of 6.18 × 10−13 Ω−1 (σ ≈ 1.34 × 10−2 S cm−1 and the maximum visible transmittance up to 43%).