FAR-ULTRAVIOLET REFLECTANCE MEASUREMENTS AND OPTICAL-CONSTANTS OF UNOXIDIZED ALUMINUM FILMS

The far-UV reflectance of thin unoxidized aluminum films prepared and maintained in ultra-high-vacuum conditions was measured versus the ang le of incidence, and the complex refractive index was obtained from th ose measurements on several wavelengths from 82.6 to 113.5 nm. Measure ments were made on two perpendicular planes of incidence to deal with the unknown of the polarization state of the radiation beam. The surfa ce roughness was characterized by atomic force microscopy. The refract ive index is obtained for the first time, to our knowledge, from direc t optical measurements in this spectral range. Current results match w ell the former values in the literature that were calculated through t he Kramers-Kronig analysis by using in the above interval reflectances estimated from electron-energy-loss spectra and from optical measurem ents on surfaces of unstated roughness.