CsHgInS3: a New Quaternary Semiconductor for γ‑ray Detection

The new layered compound CsHgInS3 was synthesized using solid state and flux synthesis techniques. The compound is a semiconductor and shows promising properties for X-ray and γ-ray detection. It features a layered structure that crystallizes in the monoclinic space group C2/c with cell parameters: a = 11.2499(7) Ǻ, b = 11.2565(6) Ǻ, c = 22.146(1) Ǻ, β = 97.30(5)°, V = 2781.8(4) Ǻ3, and Z = 8. CsHgInS3 is isostructural to Rb2Cu2Sn2S6, where the Hg, In, and Cs atoms occupy the Cu, Sn, and Rb sites, respectively. Large single crystals with dimension up to 5 mm were grown with a vertical Bridgman method as well as a horizontal traveling heater method. CsHgInS3 has a γ-ray attenuation length comparable to commercial Cd1–xZnxTe and a band gap value of 2.30 eV. The electrical resistivity of CsHgInS3 is anisotropic with values of 98 GΩ cm and 0.33 GΩ cm perpendicular and parallel to the (001) plane, respectively. The mobility-lifetime product (μτ) of electrons and holes estimated from photoconductivity measurements on the as-grown crystals were (μτ)e = 3.6 × 10–5 cm2 V–1 and (μτ)h = 2.9 × 10–5 cm2 V–1, respectively. Electronic structure calculations at the Density Functional Theory level were performed based on the refined crystal structure of CsHgInS3 and show a direct gap with the conduction band near the Fermi level being highly dispersive, suggesting a relatively small carrier effective mass for electrons.