Dielectric functions and optical parameters of AgGaS2 and AgGaSe2

We report the dielectric functions, ε _∥ and ε_⊥, of AgGaS₂ and AgGaSe₂ in the range 1.6 - 4.9 eV measured by spectroscopic ellipsometry, and the refractive indices and absorption coefficients calculated from these data. The electronic transitions with highest oscillatory strength are found at 4.30 - 4.55 eV, for AgGaS₂, and 3.47 - 3.55 eV, for AgGaSe₂ and are associated to the E₁ transitions in the corresponding II-VI analogs.