Ellipsometric Spectroscopy of Liquid Selenium–Thallium Mixtures

Abstract

Complex dielectric function for liquid Se–Tl mixtures has been obtained by ellipsometric measurements at temperatures between 300 and 500 °C. The optical gap decreases rapidly with increasing Tl-concentration in the low concentration region less than 15 at. % Tl, while it remains nearly constant for higher concentrations up to 40 at. % Tl. A long-standing problem of the discrepancy between the activation energies of the electrical conductivity and thermopower can be resolved by considering the temperature dependence of the energy gap precisely.