RuS₂and RuSe₂single crystals: a study of phonons, optical absorption and electronic properties

Abstract

Optical and electrical measurements on RuS2 and RuSe2 single crystals are presented. The experimental effectivity spectra are discussed in terms of a dielectric function containing contributions from the valence electrons, the polar optical phonons and the free carriers. The optical absorption measurements indicate that RuS2 and RuSe2 are indirect semiconductors. The energy gaps have been determined at 1.22 eV for RuS2 and 0.76 eV for RuSe2. Unusual transport properties characterise these compounds. The electrical resistivity and Hall effect measurements have shown n-type semiconducting-like behaviour for RuS2 and RuSe2.