Optical constants of transition metals: Ti, V, Cr, Mn, Fe, Co, Ni, and Pd

TLDR

Transition metals oxidize rapidly, so measurements were performed in a nitrogen atmosphere to avoid surface oxidation. The study examines how film thickness and evaporation rate influence the optical constants n and k. Optical constants were extracted from reflection and transmission of vacuum‑evaporated polycrystalline thin films (200–500 Å) in the 0.5–6.5 eV range by inverting three optical measurements to determine film thickness, n, and k. The constants were determined with ±2 Å thickness error and <±2 % error in n and k, oxidation had a negligible effect, and the results agree with recent theoretical calculations and other experiments for V, Cr, and Ni.

Abstract

The optical constants $n$ and $k$ were determined for some transition metals (Ti, V, Cr, Mn, Fe, Co, Ni, Pd) from reflection and transmission measurements on vacuum-evaporated polycrystalline thin films at room temperature, in the spectral range 0.5-6.5 eV. Three optical measurements were inverted to determine the film thickness $d$ as well as $n$ and $k$. The estimated error in $d$ was \ifmmode\pm\else\textpm\fi{}2 \AA{} and that in $n$, $k$ was less than \ifmmode\pm\else\textpm\fi{}2% over most of the spectral range. Transmission measurements were made on films in the thickness range 200-500 \AA{}. Many transition metals oxidize rapidly in the air and so measurements on those samples were performed in a nitrogen atmosphere. A detailed analysis of the effect of oxidation on the measured quantities indicates that it is small. The effects on the optical constants of the film thickness and the evaporation rate are discussed. Some recent theoretical calculations of the interband optical conductivity are compared with the results for V, Cr, and Ni. In addition, some other recent experiments are compared with our results.