Abstract

Spectroscopic ellipsometry measurements were done at room temperature on samples of the system Cu(In1¡xGax)5Se8. They allowed to determine the real and imaginary parts of the complex refractive index N(hº), the real and imaginary parts of the complex dielectric function "(hº), the absorption coefficient ®(hº) and the re°ectivity R(hº). The value of the energy gap Eg for each composition was obtained from fitting the numerically obtained second derivative d2"(hº)=d(hº)2 of the experimental data "(hº) to analytic critical-point line shapes. The energy gap values of the edges, measured by ellipsometry, are in good agreement with those reported. The value of the high frequency dielectric constant "1 for each composition was determined ¯tting the real refractive index n to the Sellmeier dispersion formula.