Materials Development for Nuclear Security

Abstract:
BiI3 has been investigated for its unique properties as a layered compound semiconductor for many decades. Among these are several qualities that make it an attractive candidate for a room temperature gamma ray sensor. However, despite the exceptional atomic, physical, and electronic properties of this material, good resolution gamma ray spectra had never been reported for BiI3. The shortcomings that have previously prevented BiI3 from reaching success as a gamma ray sensor are herein identified and suppressed to unlock the performance of this promising compound. Included in this work are studies on a number of methods which have, for the first time, enabled BiI3 to exhibit spectral performance rivaling many other candidate semiconductors for room temperature gamma ray sensors. New approaches to crystal growth are explored that allow BiI3 spectrometers to be fabricated with up to 2.2% spectral resolution at 662 keV. Fundamental studies on trap states, dopant incorporation, and polarization are performed to enhance performance of this compound. Additionally, advanced detection techniques are applied to showcase the capability of high quality BiI3 spectrometers. Overall, through this work, BiI3 is revealed as a potentially transformative material for nuclear security and radiation detection sciences.
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