Robust Thermal Neutron Detection by LiInP2Se6 Bulk Single Crystals

Direct neutron detection based on semiconductor crystals holds promise to transform current neutron detector technologies and further boosts their widespread applications. It is, however, long impeded by the dearth of suitable materials in the form of sizeable bulk crystals. Here, high-quality centimeter-sized LiInP2Se6 single crystals are developed using the Bridgman method and their structure and property characteristics are systematically investigated. The prototype detectors fabricated from the crystals demonstrate an energy resolution of 53.7% in response to alpha-particles generated from an Am-241 source and robust, well-defined response spectra to thermal neutrons that exhibit no polarization or degradation effects under prolonged neutron/gamma-ray irradiation. The primary mechanisms of Se-vacancy and In-Li antisite defects in the carrier trapping process are also identified. Such insights are critical for further enhancing the energy resolution of LiInP2Se6 bulk crystals toward the intrinsic level (approximate to 8.6% as indicated by the chemical vapor transport-grown thin crystals). These results pave the way for practically adopting LiInP2Se6 single crystals in new-generation solid-state neutron detectors.