Optical Constants of Single-Crystal Gray Tin in the Infrared

Reflectance measurements were made on grown, gray tin single crystals by the Avery method. The measurements were done at 300°K and in the 1- to 25-μ region of the spectrum. An analysis of the data yielded the index of refraction, extinction coefficient, and other related constants. The absorption coefficient was characterized by two regions of strong absorption separated by an absorption minimum at 0.075 eV and a weaker minimum at 0.14 eV. The long-wave absorption was shown to be due to free carriers as evidenced by the behavior of $n^2-k^2$ versus ${\lambda }^2$ according to the Drude-Zener theory of the free-carrier electrical susceptibility. Correlation of information from the ($n^2-k^2$) curves with Hall effect data then led to estimates of the hole effective mass.