Direct thermal neutron detection by the 2D semiconductor ⁶LiInP₂Se₆

Highly efficient neutron detectors are critical in many sectors, including national security^1,2, medicine³, crystallography⁴ and astronomy⁵. The main neutron detection technologies currently used involve ³He-gas-filled proportional counters⁶ and light scintillators⁷ for thermalized neutrons. Semiconductors could provide the next generation of neutron detectors because their advantages could make them competitive with or superior to existing detectors. In particular, solids with a high concentration of high-neutron-capture nuclides (such as ⁶Li, ¹⁰B) could be used to develop smaller detectors with high intrinsic efficiencies. However, no promising materials have been reported so far for the construction of direct-conversion semiconductor detectors. Here we report on the semiconductor LiInP₂Se₆ and demonstrate its potential as a candidate material for the direct detection of thermal neutrons at room temperature. This compound has a good thermal-neutron-capture cross-section, a suitable bandgap (2.06 electronvolts) and a favourable electronic band structure for efficient electron charge transport. We used α particles from an ²⁴¹Am source as a proxy for the neutron-capture reaction and determined that the compact two-dimensional (2D) LiInP₂Se₆ detectors resolved the full-energy peak with an energy resolution of 13.9 per cent. Direct neutron detection from a moderated Pu-Be source was achieved using ⁶Li-enriched (95 per cent) LiInP₂Se₆ detectors with full-peak resolution. We anticipate that these results will spark interest in this field and enable the replacement of ³He counters by semiconductor-based neutron detectors.