TlSbS2: a Semiconductor for Hard Radiation Detection

We report the quasi-2D semiconductor compound TlSbS2 as a new hard radiation detection material. This compound crystallizes in the triclinic P-1 space group, with a direct bandgap of 1.67 eV and high chemical stability. Thanks to its congruent melting at 484 °C, 1 cm-sized single crystals were grown from stoichiometric melts by the Bridgman method. The device exhibits a high resistivity of >1010 Ω·cm, and responds to 22.4 keV Ag X-rays and 5.5 MeV a-particles from 241Am at room temperature. Power-dependent photoluminescence spectra at 17 K reveal that the near-band emission bands peaked at 1.61 and 1.53 eV can be ascribed to donor–acceptor pair recombination. The mobility-lifetime product for electrons along the perpendicular direction with respect to the (0k0) cleavage planes was estimated as 2.4 × 10–6 cm2·V–1, based on spectral response against a-particles. Drift mobility measurements based on a time-of-flight technique using a-particle response reveals an electron mobility of 13.2 ± 2.6 cm2·V–1·s–1. Electronic band structure calculations based on the density functional theory indicate that the lowest effective mass and, thus, the best charge transport are along the (0k0) planes.