Grain-size effects in the parallel-band absorption spectrum of aluminum

The near irvisible"near uv dielectric functions of polycrystalline Al films whose grain sizes have been decreased by codepositing the metal with small amounts of Si are interpreted by effective-medium theory. The damping of the 1.5-eV Al parallel-band absorption peak with increasing Si content is shown to be due to the decrease of the relaxation time with grain size of the electrons involved in the Al parallel-band absorption process by scattering from the boundaries of the metal grains.