Efficient, low-cost, high resolution imaging of hard x-rays using PbTe nanosemiconductor-based composites

This SBIR Phase I project will demonstrate that high sensitivity, radiation-resistance, and resolution can be elicited from nanostructured media composed of semiconducting nanoparticles derived from size-governed PbTe. In order to transform x-ray imaging instruments, nanocrystalline semiconductors provide an attractive material basis because they present a means of: 1) decreasing the underlying material cost by utilizing a solution-based fabrication methodology, 2) increasing the range of candidate materials by including the narrow-gap semiconductors, 3) increasing the exciton multiplicity upon the impingement of ionizing radiation by utilizing multi-exciton generation, and 4) increasing the radiation resistance because the introduction of a high density of nanoparticles can convey pronounced improvement in the radiation hardness of the material. In order to realize these properties, several experimental challenges must be overcome, the surmounting of which is one of the objects of the proposed research, during which we will: 1) utilize self-assembly to realize close-packed quantum-dot colloidal solids where the charge transport is optimized, and 2) extend the size of those domains to macroscopic size.  The research is designed to not only deliver a high-performance x-ray sensor that can be commercialized but it will also advance basic physics by studying the interactions between energetic particles and strongly-confined charge carriers. By finding general material-design methods to suppress both radiation-induced damage and the stochastic thermal loss component in semiconductor materials, one can greatly increase the charge-conversion efficiency, which impacts the resolution of sensing devices, such as the extreme photon counting application targeted.