Optical constants of bulk and thin-film aluminum at 6328 Å

Publisher Website
Google Scholar
Abstract
The optical constants of bulk and thin-film aluminum were determined at 6328 Å by use of ellipsometry. The samples were measured immersed in a liquid whose refractive index was within ±0.02 of that of oxide films. In addition, the effect of the oxide film on the optical constants of evaporated aluminum was eliminated by making measurements at the metal-glass interface of a strain-free glass prism of known refractive index, and by making measurements in situ at pressures of 2×10-10 torr. Electropolishing of bulk polycrystalline and single-crystal aluminum yielded n’s ranging from 1.63 to 1.72 and k’s ranging from 7.56 to 7.77. The Drude model for 2.6 free electrons yields n = 1.55, k = 7.60; the Kramers-Kronig relationship yields n = 1.40, k = 7.50. In order to determine the effect of evaporation pressure on n and k, aluminum was evaporated at rates of 25 to 30 Å/s onto optically polished fused silica at pressures of l×10-5, 5×l0-8, and 5×10-9 torr; the results were n = 1.70, k = 6.60; n = 1.62, k = 7.29, and n = 1.57, k = 7.52, respectively. The average values for aluminum evaporated at 1×10-9 torr of n and k that agree most closely with both the Drude and Kramers-Kronig relationship were 1.60 and 7.53, respectively. These values were used successfully to monitor the uniformity of samples used in all anodization experiments.

This publication has 6 references indexed in Scilit: