Observable color change of Cu₂O-Mo-Zr composite films based on rapid oxidation at room temperature and thin film interference behavior

In this paper, the Cu2O-Mo-Zr composite films with multiple structural colors on a flexible substrate polyimide (PI) were prepared by magnetron sputtering without introducing O-2 and N-2. Results show that the color of composite films changes rapidly when exposed to air at room temperature. Moreover, the color of composite films has a thickness dependence under the interference of the PI substrate and composite films. Analysis indicates that the addition of Zr and Mo in the composite films affected the microstructure and adsorption capacity of composite films to O-2, causing the rapid oxidation and color change of the composite films when they were exposed to air. Furthermore, composite films sputtered at different vacuum conditions exhibited different structural colors, and the Mie scattering caused by Cu particles on films' surface after annealing changed the optical properties of films. The Mie scattering intensity of Cu particles was simulated using finite difference time domain to further illustrate the effect of Cu particles on the optical properties. The present work provides a simple and cost-effective method to prepare Cu2O composite films with multiple structural colors on different substrates.