A detailed characterization of the optical, microstructural, and electrical properties of thin (5–50 nm) Al films grown by thermal evaporation, magnetron sputtering, and ion‐assisted sputtering (IAS), is reported. Dielectric‐function measurements were carried out by using grating coupling to surface plasma waves (SPW) and, for comparison, ellipsometric measurements were also performed. Scanning electron microscope (SEM) studies of film microstructure as well as dc electrical resistivity measurements were carried out and correlated with the optical data. Using the Bruggeman effective media approximation, good agreement was obtained for thicker films (30–50 nm), but not for thinner films (<30 nm). SEM and resistivity measurements suggest that conditions of film growth influence the behavior of individual grains, resulting in increased electron reflectance at the grain boundaries with increasing energy delivered to the substrate during deposition. This resulted in lower electrical resistivities for evaporated films than for IAS films. Finally, the influence of 5–20 A˚ Al2O3on thick Al films was investigated: Both SPW and resistivity measurements suggest that the oxide film was not confined to film surface, but had penetrated inside the film leading to much higher electrical resistivities than would be otherwise expected.
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