Low reflective CoO coatings are processed by chemical vapor deposition from Co2(CO)8at temperatures between 120◦C and 190◦C without additional oxygen source. The optical reflectivity in the visible and near infrared regions stems from 2 to 35% depending on deposition temperature. The combination of specific microstructural features of the coatings, namely a fractal “cauliflower” morphology and a grain size distribution more or less covering the near UV and IR wavelength ranges enhance light scattering and gives rise to a low reflectivity. In addition, the columnar morphology results in a density gradient in the vertical direction that we interpret as a refractive index gradient lowering reflectivity further down.The coating formed at 180◦C shows the lowest average reflectivity (2.9%), and presents an interesting deep black diffuse aspect.
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