Investigations of aluminum films with synchrotron radiation of wavelengths 500 to 1000 Å

Abstract

Measurements of the transmittance and reflectance of Al films as a function of wavelength, polarization, angle of incidence, and film thickness have been carried out using synchrotron radiation together with a normal-incidence monochromator for the vacuum ultraviolet spectral region. A pronounced difference in the measurements for “s” and “p” polarized light was found near the Al plasma wavelength (λ _p=835 Å). We measured a dip in thin film transmittance for “p” light atλ _p which is due to the excitation of plasmons. The “p” reflectance exhibits a Brewster minimum belowλ _p. For “s” light there is no structure for very thin films. With films thicker than about 500Å interference effects appear, especially in reflection, for both “p” and “s” light at wavelengths less thanλ _p where Al becomes transparent. The transmittance and reflectance of Al films of various thicknesses, both with and without substrate materials and oxide layers, have been computed assuming optical constants based upon previous experiments. The calculations explain the structure exhibited in the experimental curves. Our measurements show that the vacuum ultraviolet synchrotron radiation is highly polarized even after passing through our monochromator.