Optical characterization of rocksalt Pb1–xSnx Te alloys

Abstract

The optical properties in terms of dielectric function ϵ (ħω) = ϵ1(ħω) + iϵ2(ħω) of rocksalt Pb1–xSnx Te alloys (0 ≤ x ≤ 1) are investigated experimentally by spectroscopic ellipsometry and theoretically by first-principles electronic band structure calculation. We find a strong optical response in the 0.5–2.0 eV region arising from optical absorption around the LW-line of the Brillouin zone. The response peak of the imaginary part of the dielectric functions at E = 1.6–1.8 eV shifts towards lower energies for high Sn compositions as a consequence of narrower W-point band-gap Eg(W) for the Sn-rich alloys.