Effect of sputtering pressure and oxygen content on the electrochromic properties of NiO films by DC magnetron sputtering

In this study, NiO films were fabricated using DC magnetron sputtering under various conditions of sputtering pressures and oxygen contents. The effects of the sputtering pressure and oxygen content on the structure, morphology, optical properties, and electrochromic performance of the NiO films were analyzed using X-ray diffraction, scanning electron microscopy, atomic force microscopy, UV spectrophotometry, and electrochemical workstation. The grain size, thickness, and roughness of the NiO films showed decreasing trends with increasing sputtering pressure; however, these factors showed significant variations with increasing oxygen content. The results demonstrated that when the sputtering pressure was 0.8 Pa, the prepared films were characterized by loose and porous surfaces, high roughness, crystallinity, and excellent electrochromic properties. The optical contrast was 75.34 % (at 550 nm), coloration efficiency was 14.86 cm2/C, coloring time was 2.09 s, and bleaching time was 2.05 s. Furthermore, good cycling stability was achieved.