Ellipsometric studies of (Cu₆PS₅Br)₁₋ₓ(Cu₇PS₆)ₓ and (Cu₆PS₅Br)₁₋ₓ(Cu₇PS₆)ₓ mixed crystals

Abstract

(Cu₆PS₅Br)₁₋ₓ(Cu₇PS₆)ₓ and (Cu₆PS₅Br)₁₋ₓ(Cu₇PS₆)ₓ mixed crystals were grown using a direct crystallization technique from the melt. Refractive indices and extinction coefficients for mixed crystals were obtained from the spectral ellipsometry measurements. A nonlinear increase in the refractive indices is revealed with the increase of Cu₇PS₆ content. The dispersion of refractive indices is described in the framework of the Wemple–DiDomenico model. The compositional dependences of optical parameters for (Cu₆PS₅Br)₁₋ₓ(Cu₇PS₆)ₓ and (Cu₆PS₅Br)₁₋ₓ(Cu₇PS₆)ₓ mixed crystals are analyzed.