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.