Device fabrication, characterization, and thermal neutron detection response of LiZnP and LiZnAs semiconductor devices

摘要

Nowotny-Juza compounds continue to be explored as candidates for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled ~3He and ~(10)BF_3 detectors. The ~6Li(n,t)~4He reaction yields a total Q-value of 4.78 MeV, larger than ~(10)B, an energy easily identified above background radiations. Hence, devices fabricated from semiconductor compounds having either natural Li (nominally 7.5% ~6Li) or enriched ~6Li (usually 95% ~6Li) as constituent atoms may provide a material for compact high efficiency neutron detectors. Starting material was synthesized by preparing equimolar portions of Li, Zn, and As sealed under vacuum (10~(16) Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace . The raw synthesized material indicated the presence high impurity levels (material and electrical property characterizations). A static vacuum sublimation in quartz was performed to help purify the synthesized material. Bulk crystalline samples were grown from the purified material. Samples were cut using a diamond wire saw, and processed into devices. Bulk resistivity was determined from I-V curve measurements, ranging from 10~6-10~(11) cm. Devices were characterized for sensitivity to 5.48 MeV alpha particles, 337 nm laser light, and neutron sensitivity in a thermal neutron diffracted beam at the Kansas State University TRIGA Mark Ⅱ nuclear reactor. Thermal neutron reaction product charge induction was measured with a LiZnP device, and the reaction product spectral response was observed.