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Proceedings Paper

Probing the gamma-scintillation process in semiconductor nanomaterials using ultrafast transient cathodoluminescence
Author(s): Jeffrey M. Pietryga; Lazaro A. Padilha; Wan Ki Bae; Victor I. Klimov; Richard D. Schaller
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Paper Abstract

Energy-resolving gamma-ray detectors are of particular interest for the detection of illicit radioactive materials at border crossings and other portals because they offer fast, contactless screening that can discriminate between dangerous and benign materials. Among detector classes, scintillators offer an intriguing balance between cost and performance, but current technologies rely on single-crystal materials that are not scalable to portal-relevant detector sizes. Thus, there is a recognized need for novel, processible, high-performance scintillating materials or composites. Composites based on semiconductor nanocrystal quantum dots (QDs) are of interest because of their potentially high gamma-stopping power, high emission quantum yields, and low-cost solution synthesis and processing. Yet the performance of these and other granular nanomaterials has not met expectations. We suggest that this is due to the general lack of insight into the gamma-to-photons transduction process within these inherently more complex materials, which reduces the development and refinement of candidates to simple trial-and-error. Here, we describe the development of ultrafast transient cathodoluminescence as a unique spectroscopic tool for probing the population of excited states formed within a material during scintillation, and thus determining the major sources of energy loss. Our analysis shows that in the case of CdSe/ZnS core/shell QDs, any efficiency loss due to previously blamed factors of low-stopping power and high reabsorptive losses are likely dwarfed by the losses attributable to efficient, non-radiative Auger recombination. We examine how we reached this conclusion, and how this insight defines the characteristics needed in the next generation of scintillating QD composites.

Paper Details

Date Published: 29 May 2013
PDF: 10 pages
Proc. SPIE 8710, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIV, 87101G (29 May 2013); doi: 10.1117/12.2015495
Show Author Affiliations
Jeffrey M. Pietryga, Los Alamos National Lab. (United States)
Lazaro A. Padilha, Los Alamos National Lab. (United States)
Wan Ki Bae, Los Alamos National Lab. (United States)
Victor I. Klimov, Los Alamos National Lab. (United States)
Richard D. Schaller, Argonne National Lab. (United States)
Northwestern Univ. (United States)

Published in SPIE Proceedings Vol. 8710:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIV
Augustus Way Fountain, Editor(s)

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