Optical properties of sputter deposited nanocrystalline CuO thin films

Black copper oxide thin films with high solar absorptance (α), high thermal emittance (ε), low diffused reflectance and moderate electrical conductivity are required for various light absorption applications and are conventionally prepared using processes involving carcinogen chemicals. Therefore, there is a need to develop these coatings using eco-friendly processes. In this paper, CuO thin films have been deposited on copper, glass and Si substrates using reactive direct current magnetron sputtering of Cu target. The structural, chemical and morphological characterization of the coatings was carried out using X-ray diffraction, micro-Raman spectroscopy, X-ray photoelectron spectroscopy and field emission scanning electron microscopy techniques. The results showed that both oxygen flow rate and sputtering time have a significant effect on the optical properties of the films. The optimized films were found to be of the composition CuO with α and ε of 0.955 and 0.52, respectively. The emissivity could be further increased to 0.78 after sandblasting of the substrate.