Optical and mechanical characterization of novel cobalt-based metal oxide thin films synthesized using sol-gel dip-coating method

摘要

New cobalt-based metal oxide thin films (M _xCo _yO _z with M=Mn, Cu, Ni) have been deposited on commercial aluminum and glass substrates using sol-gel dip-coating method. The as-deposited films were characterized by a wide range of complementary techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), spectrophotometry and nanoindentation techniques. A light absorption study for coatings on glass substrates within a wavelength range of 300-1100nm was also conducted. Topographical and morphological investigations showed the presence of nano-sized, grain-like particles in the copper-cobalt oxide coatings, which consequently had the roughest surface among the three coatings. All coatings on glass substrate exhibited higher absorption of ultraviolet (UV) light compared to visible light, while coatings on aluminum substrate generally had low reflectance (<50%) of UV light, moderate reflectance (<80%) of visible light and high reflectance (up to 100%) of infrared light. Implications of optical properties as a function of film thickness controlled by dip-heating cycles were discussed. The elastic modulus (E) and hardness (H) of thin film samples compared with stand-alone commercial aluminum substrate were also measured.