This paper presents a method of controlling the ellipsometric parameters (ψ,Δ), pseudo-optical constants (n,k), and reflectance (R) of freshly deposited aluminum films. By use of this method, values of Δ, n, and R can be predicted from measurements of the terminal pressure/terminal deposition rate (terminal p /r ratio) prevailing during deposition of the surface region. The pseudo-optical constants and reflectances were calculated using the ψ,Δ values. The highest-purity aluminum (99.9999%) was used and ellipsometric measurements were made immediately after removal of the films from the vacuum system. A review of existing literature on ellipsometric parameters, optical constants, and reflectance of aluminum films in the ultraviolet, visible, and infrared regions of the spectrum supports the theory that volume-oxide contamination is a primary factor affecting optical properties.
J. H. Halford, F. K. Chin, and J. E. Norman, "Effects of vacuum deposition conditions on ellipsometric parameters, optical constants, and reflectance of ultrapure aluminum films," J. Opt. Soc. Am. 63, 786-792 (1973)