Optical properties of GeSeTl thin films

Using the usual melt-quenching technique, glasses with composition Ge₁₄Se_86−xTl_x (x = 20%, 22%, 23.5%, 25%, 26.5% and 28%) have been obtained to prepare thin films with different thicknesses (d = 15, 30, 60, 90, 120 and 180 nm) using electron-beam evaporation. The optical gap E_g was found to decrease with increasing thallium content, x. It is found also that thicker films are accompanied with larger optical gaps. The refractive index n was found to increase with increasing Tl ratio and to decrease with increasing thickness of the films.