Optical Constants of Gray Tin Single Crystals from 1.18 to 4.95 eV

The optical constants of gray tin single crystals, i.e. , the real ( ε 1 ) and imaginary ( ε 2 ) parts of the dielectric constant, were obtained in the region from 1.18 to 4.95 eV from measurements of the ratio R p / R s for two different angles of incidence. Measurements were made on the surfaces of growth at 278 K. Structure in ε 2 (ω) was observed at 1.25, 1.65, 2.25, 3.02, and 4.2 eV. The empirical pseudopotential method was used to compute electronic band structure. The resulting energy bands were then used calculate the imaginary part of the dielectric constant as a function of photon energy. Comparison between experimental results and theory is discussed and optical interband transitions are examined.