Lithium-containing semiconductor crystals for radiation detection

Abstract

ABSTRACTSemiconductor materials have shown promise as ionizing radiation detection devices; however, to be used as a neutron detector, these materials require the addition of a nucleus with a large neutron absorption cross section (such as 10B or 6Li) to capture thermal neutrons and convert them into directly detectable particles. A semiconducting material that contains the neutron absorber within its regular stoichiometry has the potential to be more efficient than a layered or heterogeneous device at transferring the kinetic energy of the charged particle into the semiconducting material. One class of materials that has shown promise is Li-containing AIBIIIXVI2 compounds such as LiGaTe2, LiGaSe2, and LiInSe2. These materials have band gaps (2-3.5 eV) appropriate for room-temperature detection of thermal neutrons and would be the first detection material that is simultaneously, exquisitely sensitive to thermal neutrons; is insensitive to gammas; and acts as a direct conversion device. A vacuum distillation process provided high-purity lithium metal for AIBIIIXVI2 synthesis. Single crystals of sufficient bulk resistivity (grown for LiGaSe2 and LiInSe2LiInSe2) showed a distinct photo response as well as a clear response to alpha particles. Additional radiation measurements indicated that a 6 mm x 7 mm x 1.33 mm crystal of LiInSe2 detected gamma rays, and despite being composed of natural abundance lithium, responded to thermal neutrons as well.