Spectrally selective surfaces of Co-pigmented anodic Al2O3

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Abstract
The multilayer model of Al anodized selective surfaces has been revised by taking into account surface defects and incident angle of of illumination. This theory has been applied to Co-pigmented surfaces. Emphasis was put on extended experimental determination of all parameters used in the theory. With a detailed scanning and transmission electron microscope study of the structure, the size of the pores and their aerial density have been determined. Moreover, the surface roughness has been measured. This has permitted the calculation of the dielectric permeability for each layer. The permeabilities have then been used to compute spectral reflectance curves using the Bruggeman theory. Computer calculated reflectance curves based solely on experimental data agree well with experimental results for λ≥2 μm. At shorter wavelengths, interference peaks that were predicted, but not observed, were minimized by considering surface roughness.