Wavelength dependence of angle-resolved scattering in the extreme-ultraviolet-visible region.
The wavelength dependence of p-polarized, angle-resolved scattering has been thoroughly investigated on 12 aluminum films at wavelengths of 160, 325, and 633 nm. The isotropic samples were made by evaporating aluminum films in ultrahigh vacuum onto supersmooth silicon wafers at different temperatures. By further annealing in ultrahigh vacuum, surface roughnesses of ˜ 5-70 Å rms were obtained, as measured by total integrated scattering. The experimental measurements were carried out in a dedicated angle-resolved scattering system with provisions for operation in vacuum and for illuminationof the same spot on the sample at all three wavelengths. The theoretically expected 1/λ(4) dependence was in reasonable agreement with measured values for the average of all 12 samples, but large variations were found for the individual samples. In particular the wavelength dependence was far from a constant ratio when plotted versus the surface spatial frequency. Hillocks on some of the aluminum films produced additional scattering. It was not possible to explain this additional scattering with the Twersky model of conducting hemispheres on an infinitely conducting plane.
Mattsson
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Ingers
J
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Bennett
J M
JM