Optical properties of passivated metal slanted columnar thin films from cobalt within the visible spectral region are reported. Glancing angle deposition is utilized to grow slanted nano-columns which have been conformally coated with Al2O3 by a subsequent atomic layer deposition process. A generalized anisotropic Bruggeman effective medium approximation has been employed to analyze spectroscopic generalized ellipsometry data. The modified homogenization approach allows for determination of biaxial (monoclinic) optical and structural properties as well as fractions of three film constituents. The conformal alumina passivation layer preserves the pristine metal character of the nano-structures and prevents oxidation and aging effects.
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