Optical Properties of Cation-Substituted (Cu1 – xAgx)7GeSe5I Mixed Crystals
Keywords:mixed crystal, spectral ellipsometry, refractive index, diffuse reflection, energy pseudogap
(Cu1−xAgx)7GeSe5I mixed crystals were grown by the vertical zone crystallization method and are shown to crystallize in a cubic structure (F43m). The diff use reflection spectra for the powders of (Cu1−xAgx)7GeSe5I mixed crystals were measured at room temperature. The refractive indices and extinction coefficients for (Cu1−xAgx)7GeSe5I mixed crystals were obtained from spectral ellipsometry measurements. Two anomalies of the refractive index in the spectral region from 440 nm to 1000 nm are observed. One of them corresponds to the band-to-band optical transition, while another one to the interband Van Hove–Phillips singularity. A nonlinear decrease of the energy pseudogap is revealed with an increase in the Ag content in (Cu1−xAgx)7GeSe5I mixed crystals.
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